Just bought 1987 GN 4 weeks ago. Car ran well, only had occassional "sputter". Owner said it needed a MAF. Drove car less than 100 miles and it got worse. Now have put on 5 different MAF's, none fixing problem. Changed faulty (?) ECM and stock chips (Poston). Now getting codes 51, 34, & 13. Now car will not run, not even idle. Black smoke. Help before I make t-top car a boat anchor!
sucks to hear you bought somone elses problem that they couldn't figure out. Good news is, it's probably a cheap fix.
#1) Can you start the car?
#2) Is your SES light on and/or flashing when you start it..and it runs really rough?
#3) Pull the chip out. Does it start and/or run the same way?
#4) Replace the MAP sensor.
the major sensors on the car are the crank, MAF, & MAP. Since you are getting O2 and MAF failure codes, I believe it's the MAP that is causing errant readings on these other sensors. The MAP is basically an electronic vaccuum gauge, and if it's failing, but still in range of what the ECM expects, it will not set a code. But our computers aren't very advanced and can be easily fooled.
You can do other basic troubleshooting such as spark and touch/listen to the fuel injectors and feel for them pulsing on/off. If you dont feel one pulsing, or more - it's probably a wiring problem since youve had the ecm replaced.
My money's on the MAP though. Tap the MAF (if the car runs) with the handle of a screwdriver and see if the motor stumbles or not. You gotta whack the MAF pretty good, but not enough to break it or anything. If it stumbles, the MAF or it's wiring s suspect.
Follow some of the steps and post back with results. I say MAP still.
WHat sucks is a bad MAF, crank, or MAP sensor can provide the same symptoms. Im curious to know if it starts and flashes the SES light as if in limp home mode. Then take the chip out and start it again and see if it acts the same way. If it does, the chip or ECM is bad. Keep trying, man..we'll get ya fixed. Good luck!
Jay, it really sounds like you know these cars...There seems to be so much to check and do! I found that the plugs were fouled. I went to my local parts store, picked up new plugs and a MAP sensor. Haven't had time to try them out yet. I've got a few more questions, if you would be willing to drop me an email or email me your number and a good time to call you, I sure would appreciate your knowledge. It would save me alot of time--I'd like to take it to BOP this weekend (Bristol). Here's my email: 71gs455@bellsouth.net. I'm in Asheville, NC...
FWIW,
The MAP only runs the digital boost guage. Will still run the same without it.
DOH! I gotta keep my nose out of other cars.
Rob's right, Stephen - the MAP on our cars has no input to the ECM and therefore it couldn't care less about what it does. On other cars, it's very important and could prevent it from running - but not on the GN's. Hope ya didn't install it because you dont need it. I dunno why I did that..the troubleshooting steps make sense until i mentioned the MAP which doesn't make sense..maybe it's because im working on my Ford truck and have similar issues. Total Brain fart. :\
Anyway, did you go through steps 1-3? Eliminate the obvious like vaccuum hoses, wiring, etc.
Sorry for the confusion...geez. I need more sleep.
Tracked down previous owner for some more information. Turns out that it is an electrical problem-not the MAF like he originally said. Here's some more info I found out: has a crate GM GN motor (not the original). It has the TE44; upgraded injectors (53? I think), so the chips the ECM weren't stock chips and that explains why the new "stock" chips wouldn't work...DUH! Now I just need to track down the ground problem. Does anyone want to buy a stock ECM and chips? I have to put my "old ones" back on since I have a modified car and find the ground problem... Geez, if the dude would have just told me he could have saved me alot of wasted time and $$$!
Steve,
How much do you want for the ECM? I live in Albemarle, NC and will be at Bristol late Sat morning for about an hour. See you there? Call me Sat on my cell phone if you go to Bristol...704-467-1310.
Conrad
you should find out for sure what the injectors are. there are 55's and 50's but 53 doesn't sound right. The thing is if they are 55's they won't work with the stock ecm and may have blown it up already. If they are 50's then you are fine and can keep it as a spare. You can measure them with an ohm meter 10-15 ohms and they are 50's or below (high imoedance) and work with stock ecm. 3-6 ohms and they are 55's or bigger (low impedance) and need a modified ecm.
Common spot for ground problems is on the back of the passenger cyl. head.
good luck