I've done quite a few parts upgrades on my GN. I'm running about 16lbs of boost on a new turbo. 42# inj w/ I believe a thrasher chip. Car runs strong, no complaints, but my scan master shows 19 degrees of retardation at WOT. My car goes way into the red line...I'm pretty sure all my RPM lights go on. Also, I get some retardation while just idling down the road at about 25mph and such. Nothing big, something like 2-6 degrees. I'm just wondering if this is characteristic of the chip (I've heard some chips have retardation programmed in to compensate blah blah blah...), or if there is some problem. Thanks fellas.
19 degrees is bad, no matter who's chip you've got. If it is a Thrasher, then I think you need to replace it. I thought they were only available for the stock and 36# injectors. Although I thought I heard something about a test version was available for some other size injectors. What does it say on the chip? Is there a label?
Brian
I agree with Brian ... something else is going on there. It should NEVER show retard at cruise or idle.
I'd look for some mechanical noise in the motor fooling the knock sensor or possibly a wiring problem that is forcing the ECM to be in ALDL mode (which will return erroneous data to the ScanMaster).
Well, I think my driver header is cracked. I get a fairly loud ticking from that general area. Is retardation and knock the same thing? I though retardation was determined by the chip, whereas knock was sensed by a microphone type sensor. Am I incorrect in my understanding?
Friend of mine had a simular problem turned out
the knock sensor not there. Check to see if it's
connected or there.
What does one of these look like, and where on the engine should I look?
It's at the rear of the motor somewhere under the rear of the coilpack in the center and it has 1 wire going to it.
So is the spark retardation controlled by the knock sensor or by something else?
This morning I nailed it and got an o2 reading of like 706 with retard@ 19.9.
you're too lean. You need more fuel before your headgaskets go poof. Thats why you're retarding. I'd question the fuel pump or a seriously clogged fuel filter if you're retarding while cruising.
The ECM retards timing when the knock sensor detects knock.
You have 36# injectors so you've got the capacity for it - you need to go through your entire fuel delivery system before you beat on that car again! 706 is wayyy to low at WOT
sorry - i meant 42# injectors.
Will that infamous header-crack really be loud enough to trigger the knock sensor and retard his timing at cruise? If not the header crack - check for some exhaust interference that may be smacking against something and trigger the knock sensor. Try the crossover pipe/cat area as well while you're checking out the exhaust manifold.
Well, I have 42# inj - don't think it makes a difference, but what static fuel pressure should I be running? I've been told lately that between 45-47lbs is good. Seemed a bit high to me, but I'm a newbie. I believe I'm running about 42# static right now.
How likely is it that the knock sensor is just picking up my ticking header and that is why I'm getting the knock at cruise? The ticking is fairly loud at cruise, but I don't hear the slightest thing under moderate to full throttle.
Hey, I want to say thanks everyone for your input. I know this is off topic, but I've made tech question posts in Porsche groups about my Turbo Porsche, and those guys only want to talk about how their $120,000 car beat a vette, they are pure jugheads (if I may use such language on the board
) and know nothing about the cars. You guys are all great, and I thank you for your continued education of the buick population.
Jay is absolutely correct. Go through your fuel system, before you are going through your motor, or worse your crank goes through the oil pan. If you plan on still driving the car while you are trouble shooting, then I would suggest that you turn the boost way down, and work your way up as you get it running better. As for the knock while cruising, I've had this problem twice before. The first time it was the tranny input shaft. I didn't figure it out until I was stuck on the side of the highway with a pretty black paper weight. The shaft broke. The second time was after a hard day at the track. I had a bad FP regulator, that caused a couple of other problems, and I detonated too much(couldn't get a handle on it) I drove the 3 hours home, with the knock registering the whole way home. By the time I pulled into my driveway, the engine was making so much noise it sounded like a sewing machine. I pulled the motor, and a few months later I yanked the caps. I had two broken mains and a useless crank. I'm pretty sure that was the noise. ;-)
So you see the importance of eliminating the knock before you hammer on it. Good Luck, and keep us updated with your progress.
Brian
One last question before I begin my experimenting. I have a 60GPH/70PSI in tank fuel pump. I do not have a hot wire kit on it. What are your feelings on the necessity of this kit?
Regarding the hot wire kit, it is a necessity. You have to have the correct voltage, at idle and at WOT.
For example, most car audio amps are "rated" at a higher voltage. For example, I have an amp that is "rated" 100watts at 14.4 volts, and 75 watts at 12 volts.
I know a fuel pump is not an amp, but I am sure that the output will be different if the pump is seeing 11 or 13 volts.
After I added my hot wire kit, the voltage to the fuel pump went up 1.5 volts at idle.
I used the DIY article from this site. Except I used two relays instead of one, just to be safe. I also used a toggle switch for the ground wire. I use this for security reasons.
Good luck.
As long as you NEVER go into boost and drive like grandma, the hot wite kit is not necessary.
Now if you plan on getting on the throttle now and then, yes it is ABSOLUTELY necessary.
(Unless you like spending money on things like blown head gaskets, burnt pistons, hammered rod bearings, etc.)
The fuel delivery on these cars can make the difference in a blown engine or not. The hot wire kit is part of that system. Factory wiring was marginal when new. Personally I wont even drive my car without a scan tool running to keep track of any knock, as well as a visible hood mounted fuel pressure gauge to verify enough fuel pressure under WOT conditions. As Jay said, verify your fuel system before turning it up and beating on it again. Make sure the filter isnt clogged, and the lines arent pinched. Make sure the fuel pump keeps up with the boost index. (Example-- if you have 45# FP static and 15# boost you should see 60# on the fuel pressure gauge when at WOT.) A few more 19* retards at wot with low o2s will have you learning how to change head gaskets soon. Until you get things sorted out either turn the boost down, richen the fuel pressure, or both. You mention the RPM going well into the red. I hope you aren't going by the factory boost gauge. The factory tach and boost gauge are as usless as pearls on a pig.
Also if you are running a true 16# of boost by a good gauge, the local gas you are running may not have enough octane for your car. All cars arent the same, nor is gas. I can run anywhere from only 15 to as much as 19# of boost on the same brand gas, depending on time of year I bought it, weather conditions, and other factors. So called "premium" today isn't very consistant from season to season what with all the reformulating/jerking around they do now to please the smog nazis.
Good luck, and be safe tuning.
Dwight
Yeah, I don't drive like grandma (course if I drove like my grandma I would have blown my gaskets
) Thanks for the advice. I'll chill till my hotwire kit comes in.
Even with all the great help you've gotten, they didn't mention something you might be curious about and it's something to shoot for. You want your O2s somewhere around 800, NOT 700. I'd say get it in the 850 range since every car is different, then you can tune from there. That can kind of tells you how far off your car is tuned(you-700, good-800-850). Do you have a new pump on the car too?
I have a new pump on the car. Actually, I'm going to be installing the hot wire kit tonight. I increased the fuel pressure yesterday to about 46lb. Car seems a bit more sluggish, and I can still get about 17 degrees of knock. Shouldn't I be able to hear something in the engine if I'm getting this much detonation?
What are your O2 readings when you get that much knock? I'm not sure about actually hearing it, I'd think so, but you should definitely feel it, the car should feel like it's getting the crap beat out of it, sputtering and jerking. Since you're putting the hot wire kit in tonight, you'll probably be doing some testing later? Check your readings then and let us know, give us the O2s and KR. Try to get your O2s just under 800, maybe 790 or so. I've got my static pressure(vacuum line off) at about 44-45psi. Good luck and watch out for the nice officers in your area while testing.
OK. Hot wire kit installed. Running 45lbs static. Took it out for a spin. Running about 15lbs of boost, I power braked it up to like 3lbs of boost then launched. Car accelerates good, but it feels like the trans isn't locking. I'm used to driving manual transmisions, so I'm used to feeling the car's acceleration directly corrolating with the increase in RPM. Anywho...car goes well into the red line 02 reads about 810 and the knock went up to 15.5. The car has never really jerked or sputtered or anything while accelerating. I've had the scanmaster reading 19.9 degrees of retard and the felt just fine...actually it felt very strong. I'm beginning to doubt the accuracy of these readings. When I got 19.9 degrees of retard, I was running about 42lbs static, now I'm running 45lbs and I haven't gotten much more than 15 degrees. I haven't been working on these cars very long, so I'm not sure if 45lbs of pressure is starting to get kind of high or not. I don't know what other people out there are running. Let me know what ya'll think, or if there is anything else I should look at.
ok - O2's are better now
At least you're safe for testing as far as fuel delivery is concerned. Besides false knock and a bad knock sensor..i'd change your plugs and/or check them at least. The wires might be nasty as well and the stock boots dont fit on real well..check that passenger rear wire/boot for sure. It's hard to get on good.
They should be gapped at .035, and if you buy a new set i would go for the AC Delco R43TS available at tons of auto parts stores. Pull the plug wires off of the coil one at a time, and check for rust - mine dumped a ton when i first bought it! I put Accel 150-ohm Racewires on mine, and with new plugs it cured a ton of problems, and the car just ran great after that. Check those wires, and replace them if they're stock.
Measure the resistance of each wire with an ohmmeter. My stock wires were in the 6K-7K-Ohm range and the car had 12K miles on it. Wires were in good shape, but the Accel 150-ohm racewires actually made a difference you could feel. There are over the counter "performance wires"..yeah right. Take the box up to the counter and have them measure resistance...Bosch, Accel, MSD..they all were just like stock wires. The "Hi-Perf" Accel's were actually HIGHER than stock at 11K ohms!
Just my suggestion..dont be fooled by claims labeled on a box. Have someone measure the resistance of any wires you buy - you'll be surprised how adequate the stock buick wires really are compared to what else is out there...but from 7K ohm to 150 ohm..there's a HUGE difference.
Start simple and cheap
6 plugs..about $7. Good luck
Just to give everyone a little more history on the car...I had a bad turbo on it for about a year. Was blowing oil pretty bad. Since I was new to turbo cars, I didn't realize that the oil was coming from the turbo. I figured it was rings, valve guides...blah blah blah. My plugs are fairly new, I'm not sure what kind, but I will double check them to see what I'm running, and what the gap is like. I remember when I did a compression test a few months ago, the pugs looked good.
The wires that I have are new as well. I have 8.5 MM Magnecore Plug Wires that I bought from ESP, as well as a brand new ESP coil pack. I've been warned about ESP brand parts, and from my experience, the guys there work there don't seem on the level either. I had to dispute my credit card to get the credits for some parts they never sent me and admitted to me that they never sent. (Sorry about off topic complaining, but I feel it helps establish a little history of the vehicle and parts quality).
The O2 sensor on the car is a 4 wire heated O2 that I put on last summer (2001) along with new plugs. Keep in mind I replaced my turbo in May 2002 along with coil pack, wires and the zillion other things I did to the car.
The big thing that confuses me is that my O2 readings seem ok, but my knock counts are high and I don't feel it at all. Another thing I'll mention is that when I start my car cold, jump into Drive and take it up to 35mph, the car seems to surge a lot and have a hard time. I have two 87 turbo porsches that do that (and they are professionally maintained by a superb shop), so I wasn't too woried about my GN surging. Also, when the car is at operating temp (ie - I've been driving it for well over 20 minutes), sometimes I get some surging when just cruising at like 25 with very light throttle.
Well, that'll give you gurus something to mull over while I check my plugs. By the way, if any of you GN hot shots are in the Norwalk, Ohio area, if you want to meet at the track some night I would be very willing to do that. I live about 3 miles from the strip. Let me know
This is definitely interesting.With O2s in that range you shouldn't be getting any knock. Also with my car, one time I was out testing and got some pretty bad knock(don't know the #s, didn't have TL yet) and the car took off strong but then started sputtering and basically fell flat on it's face. Actually it was more like fall on it's face, stand back up, fall on it's face, stand back up. When the computer starts taking over, you can usually feel the car fall on it's face. Turn the boost down to like 12psi and see what happens. If you were feeling the car lose power, then I would say to check for something hitting, like the downpipe hitting the car, that can sometimes introduce false knock. But you said it seems fine. That just seems odd to me that the scanmaster is showing knock and 15 degrees of retard, but you said the car feels strong. Maybe there is something wrong with the scanmaster or wiring??
If I power brake the car and get a good take off, the car seems cool with no retard. If I hit the gas in high gear, I usually don't get any retard (maybe a degree or two). I seem to get the retard when, for instance, the other day I was just screwing around and I stopped in front of a friend of mine on the road. I power braked it to get the tires to spin a little, then floored it and lifted off the brake. The car lit the tires like it was on ice. I got about 15 degrees of retardation. Couldn't tell by the feel of the engine that anything was wrong, but the scanmaster was screaming at me 15 degrees. I believe the O2 counts was like 810 or something like that. The other times when I get the most retardation is when it seems like the transmision is slipping. I know absolutely nothing about automatics, but I know how a transmision feels like in a manual when you only let the clutch out slightly. That's how my car feels when I get the detonation. The revs are going up, but the car really isn't accelerating that much. Maybe I need to rebuild the trans or get a shift kit or something. It seems like when I go about half throttle to 2/3 throttle, the trans locks up good, but if I'm idling along and then floor it, that is when it seems like the trans doesn't lock up all the way. I've got a orange stripe 3000 rpm stall converter in the car.
Regarding the stumbling and eratic behavior above 15 lbs...Check your volts output from the alternator when under boost. I had a faulty alternator that could not supply enough "juice" when under boost. Fixed the alt and now run 22-23 lbs no problem. Just a thought...
Rob Green
RobGreen@att.net
86 GN 11.55 @119
72 455 Stage 1 Skylark
hmmmm...
Still confused. (that is OK, I have ADD).
Are you saying that you get KR at WOT and high RPM's? What RPM's? Do you have a fuel gauge taped to the windsheild so you can see what the FP is? When you do a burnout, the RPM's climb way high; could be the same thing during a WOT run...
I think that we have the same problem. I posted it about two-three months ago. I am going the valve spring route. I also just bought a fuel gauge to tape to my windsheild...
Hope I didn't mix anything up...
Well, I've been thinking over this a bit more, and I have a better way of stating the problem.
If I run WOT / High RPM, with very little load on the motor (such as just lighting the tires at high rpm - the car will just sit there, smoke the tires and rev really high), I get detonation.
If I run WOT / High RPM, but with normal load (such as running down a drag strip with transmission locked up and good traction), I get no detonation, or maybe a degree of retard.
I'm probably going to replace the spark plugs tonight - and as I stated earlier, I'm not really confident about my coil pack, but I'm not sure if either of these will cause the retardation I'm experiencing. I've read a little bit about block learn and stuff like that - how the chip is responsible for regulating fuel based on engine load, so maybe there is something with the chip that needs fixed. I seem to remember the chip saying 38# on it, when I know I have 42# injectors. I'll have to check that out tonight. Course that'll be another thing I have to beat ESP over the head about, since they sold me them as a package.
Anyway, those are what I'm looking at as far as my options to fix this problem - if someone out there will let me know some of their experiences, maybe I can figure out which route is more probable - although I'm going to replace the plugs tonight no matter what.
Another thing to mention - on my way home on the back country roads, I'll stop at a stop sign, then take off WOT till 60 mph, then let out of the gas and just give maintence throttle, the car sort of bucks a little and I get some retard then. After doing a hard acceleration like that, the car will buck slightly while cruising at 60mph for quite some time. I thought it was weird that I didn't get retard during acceleration, just after I let off the gas and was giving just maintenance throttle to keep the speed constant. That was why I'm leaning towards plugs or coil pack.
Just a little note. You mentioned high rpms, I hope you aren't going by the factory tach they are known to be very inaccurate. Mine reads 6000+(all lights lit up) if I'm at WOT anywhere above about 3000....used to scare the crap out of me when I thought it was correct.
So it sounds like during what would be a normal 1/4 mile, the car is fine with maybe a degree or two of knock retard? On the highway do you get the buck before or after the retard? Hopefully somebody who knows about this problem will jump in but I remember hearing about a bucking problem before and I think it had to do with the torque converter lockup, not sure though. The other retard you get, your tach may be more accurate than most and if it's really spinning that high in the rpms, maybe you're getting something like vale float that's causing it. I always try to keep my rpms around 3000 when I spin the tires. I'm sure somebody else will jump in here with their ideas. Good luck,
When I said high rpm, I'm just meaning that it is more than 4000 rpm. I've done some comparison between my scanmaster and rpm, and my rpm gauge on my car isn't too bad. It's maybe 500 rpm or so off, so when I say high rpm, just realize that the car is reving pretty high. Non necessarily red lining, but it is running pretty high.
Well gents, I put new plugs in, the R43TS gapped at .035. The old plugs were R44TS gapped at like .040. I've got the fuel pressure at 45#, and am getting retard of like 4 degrees, but it is retardation that you can feel - seat of your pants. The times when I get those high numbers like 6 degrees and above I feel nothing and the car seems to be running just fine. I'll probably increase fuel pressure back up to 50# tomorrow. That seems to be working good for me, despite people telling me that it is too high.
Everyone, what is the likelihood that my scanmaster is bad? I can't figure out why I would get these readings. I'm getting retard under no engine load, or very light load. Usually while deccelerating after a quick zero-to-sixty, or just idling down my street at 25mph right after I turn my car on cold.
Also, my O2s are weird. Sitting in park at idle, the O2s read like this....035....125....303....679....275. Is my O2 sensor bad? I have a fairly new 4 wire O2 sensor, but I just got my scanmaster and I dunno what I should be expecting to get. If I mash the petal to the floor, it takes about 2 seconds or so, and then the O2s sort of lock in....usually at about 820 when I'm running 50# of static fuel pressure. I'm plum out of ideas. Just about every part on this car is new.
Also, I'm not supremely confident that I didn't maybe get the wrong chip with these injectors. What kind of problems would I get if they sent me the wrong chip?
Thanks to everyone....
Also, I'm getting alternator voltage fluxuation from 12.9 volts - 13.9 volts while driving. Is that bad? Typically at full throttle I get 13.2 volts.
Your ECM is stuck in ALDL mode. This will affect exactly the readings that you are describing...
Look for a bad connection to the serial data line or the ground connection is in the wrong place or wrong pin.
What is ALDL mode? Will this cause some of the other things I have been experiencing?
ALDL mode is a diagnostic mode for the ECM (usually commanded by either shorting the diag pin to ground or putting a 10K or 3K resistor in between diag and ground).
This could cause alot of what you describe. If you have another scan tool, you can check the ECM mode.
Hm...well, I found out that when I installed my scanmaster, I installed the black wire as a negative wired into my gauges, instead of as a ground. I have fixed this problem. Car seems to run better, but I'm still getting these weird retardation numbers. With my boost set at 17lbs max, at 780+ O2 I'm getting up to 4 degrees of retardation in third gear. Car seems a little underperforming, I'm wondering if you have any ideas what I can check next to start getting these problems worked out.
Tom,
Whats the story so far? Get anything worked out?
I just re-read your posts and one thing comes into mind...timing.
It sounds like your timing or chip is way off. Are you using the factory chip in your car, or is it a performance chip? The only reason I ask is because i had similar problems with odd detonation and it was a combination of 2 things:
1) Chip was programmed for 8lb injectors when i actually had 28# (stock) injectors. Talk about detonation! It was just an error in the chip programming...lots of tables, values..but man - does that wreak HAVOC on trying to tune a car!
2) One injector was bad.
I upgraded to new 009's (43#) instead of replacing stock injectors....and different chip...problem solved. Looking back - now im burning my own chips, and found the error on the chip i had bought. It wasn't the only error on the chip either.
Just keep in mind..if you're running a performance chip...the possibility for error exists. I'd have never known it if i didn't see the chips .bin file for myself.
Anyway - see if you can verify operation of your injectors by holding a wood stick or some automotive "stethoscope" on each injector, and listen for them ticking..make sure they all tick evenly. You might be able to get away with just pressing your finger on each injector while the car is running to get an idea. You'll know if one isn't working.
Other than that - chip/timing seems to be a problem. What is your spark advance at WOT and cruising?
Hope you got it worked out already - but if not - i'd really like to see your issue resolved. I know how frustrating it is...i wanted to sell my car i got so frustrated. Thanks to this site, and my buddies - they kept me in-line and all worked out for the best... after all that troubleshooting, and finally finding the problem, now i got me a hauler! :P
I've tried calling ESP to get some information on this chip and injectors, but they won't talk to me. I really don't have the money to buy a new chip just to drop in and see how it goes.
One thing that was goofy with my car was that I had my scanmaster black wire hooked to negative instead of ground. Got that fixed, and now I'm not getting those strange retardation number, but I do get retardation on high rpm, that I believe is actual detonation because you can actually feel the motor "pull out" so to say.
Another thing about my car, my intercooler has no scoop. I should have a new shroud/scoop monday, but after that, no more money to invest in my car for a little while.
The injectors all feel good, I already checked that stuff out. I'm only running about 17lbs of boost now, and I believe my static fp is about 45#. I know it's high, but if I turn it down I'll have worse detonation. Right now I'm pretty much limited to doing no more than half throttle accelaration. Thanks for the checkup, and let me know if you have any ideas.
I'd like to start burning my own chips some day. What kind of equipment is needed. I'm a computer programmer, so that kind of stuff is my bag
Well gang, thanks to Jayster, I've tried a new chip in my car. Some of the problems seem better, but some still exist.
Thanks to Jay's chip, I've been able to drop my FP to 38#. Hooray. That's a biggie. Car seems to be doing going - going up to about 16# boost.
2 problems that still exist:
1) I'm cruising down the road - doing about 35 - I mash the throttle to the floor - car downshifts 2 gears, seems to just rev within the redline range, then upshift. Retardation today went up to 38 degrees. Wow huh?
2) Car seems to hit its peak performance in the gear (close to redline), but continues way into the redline. Basically, the engine RPMs increase, but since there is little power in that range, no acceleration is there.
I'm thinking tranny problems, but I don't know how my tranny is supposed to act, and whether or not some of the tranny shifting is programmable. I know when I had a stock setup, I switched chips and it switched what RPM my car shited at.
Well, I'm going to bed. Tomorrows another day
Oh, before I forget...I'm still trying to tune my fuel pressure. I know 780-790 is my target value, but what exactly does that mean. When should it be at 780-790? What RPM, what gear? Sometimes I can get it to read 780, but I'm having a hard time making it consistent. I can have it tuned for 780, then turn around and get a reading of 820. What is the technique for locking this stuff in?
I tune for those numbers in third gear. Usually(as per my minimum experience) your O2s are usually higher in the lower gears(not by much) and the spot you really start to lean out is in third gear when the car is really working hard to move the air. I generally look at my O2s on TL right before I let off the gas, so at the end of the 1/4. Sometimes they can actually drop pretty good towards the end. From what I remember though my car is good to about the 760 range, usually closer to 770.
"I switched chips and it switched what RPM my car shited at."
Did you notice any Ford parts in the pile? lol. I know it's just a typo especially since you wrote it right before bed, but it's still funny.
Good luck.
Tom...I see you got the chip
Well..dont get discouraged...this was a chip that worked wonders on my car,
and you're not far off. Did you run better times at the track?
The O2 "curve" is programmed into the chip for my setup - I could only guess to what yours would do. I can edit it as well if you send me a graph of your O2's and any other data you have. I'll be happy to help you translate your logged data, and reprogram the chip again now that you've tried it..but if you got 38 degrees retard on that chip..it's not the chip thats causing it. Keep in mind I could run 29lbs boost on that chip with basically the same setup you have - with NO knock at 100 octane. Anybody could run 22-24psi safely with that chip - as long as their cars were running okay prior. Yours doesnt appear to be...and you put the scoop on?
Your 38 degrees reatardation...any wheelhop? Was it audible? What RPM did it start knocking? No way you should knock with that chip..if your O2's are within range, you have a different problem. That chip only has 18-20 degrees timing in it max. Thats lower than the stock chip! If you get knock/retard with that chip - something is definitely causing it...and it's mechanical/electrical because it's definitely not in the chip at that point. I'd torque your knock sensor to be sure..14lbs it says on the list thanks to our helpful pro's here
try to post as much data as possible.
Dont worry - this is just the first step...baby steps...;)
..so what were your times?
Jay
87GN
I went to the track, and they had some pontiac race day going on, so I didn't get any runs in. I've been fiddling with it on the road. Nevermind about that retardation. I haven't seen any of it lately, cept a tenth a degree or so. The scanmaster just displays O2s and such, it doesn't allow me to graph and record them. I want to get a turbolink or something of that nature so that I can record. I'll wait till I get out to the track to post more. At least this gives me a heads up. I'm going to try putting the chip in that came with the injectors and give that a go. I'm running 18lbs of boost and about 37-38 psi fuel pressure. Things feel much better now. I'll keep ya'll posted. Hopefully I'll get out to the track Wednesday. If not then, Friday. Thanks Jay for the chip, and thanks to everyone else for your great advice.
I just bought a modified car with Kenne Bell '87 Buick GN V6 turbo. I'm not familiar with the GN turbo engine, which only has about 1,700 miles. The car has been sitting idle for at least 5 years. I just pulled the spark plugs and they are a dark black color. The previous owner was using Bosch HR88P plugs with a gap setting is 0.032. I just bought some Autolites AP25s. The car has T&D roller rockers set at a 1.65 ratio with a Stage 3 camshaft. My questions are, which gap setting should I use, and also any concerns regarding the deposits on the old plugs?
Thanks
The specialists on this board have told me .032-.035" seems to work the best and platinums aren't recommended. Your dark black plugs might be from oil seeping past the valve guide seals (?).