Please read my previous post - "Engine Backfire and hard to start - help"
Now, the engine will not start AT ALL, and when I crank it it backfires. I really need some help here, I dont think there is anything mechanically wrong with the engine, but Im not sure. Is it the cam sensor/ crank sensor? Is there a way to test those to see if they are working?? Or is it my ignition module?? Obviously spark is way off if it's firing when the exhaust valves are open.
Please let me know what you think it could be.
thanks
I can't be much help here, but I was under the impression that your plugs are supposed to fire on the exhaust stroke. What? you say.
You have 2 plug wires on each coil. When the coils fires, it fires the cylinder on compression AND the cylinder on exhaust. Take the last half of the firing order and write it under the first half of the firing order. That will show you which wires are paired for each coil.
Make sure you have the right wires on the right plugs, and check your grounds on the back of the pass side head.
I'd also take a look at the crank sensor. I had my car quit on me one night coming home and when I tried to restart it, it would just crank and crank then all of a sudden POW!, backfire. It kept doing this so I just left it there for the night. After a few days and a few parts later, I finally looked at the crank sensor and it was broken/cracked. I'm guessing a rock flew up and hit it. I also guessed that it was hitting something or somehow getting close enough together that would cause it to yell "SPARK!" and then the backfire. Good luck.
Get a compression tester and check compression,
should be around 150 psi. to 120psi.. If it's not
you have a timing chain that jumped 1 or 2 teeth.
Quite common and easy to change.
Ok, well, I tried to start the car yesterday, (been sitting for a day) and it started right up. This is really getting annoying, how can it just be fine now? It seems when the engine gets hot is when all the problems happen. I am going to do a compression test, and I will check the wires today and make sure they are in order.
Now the crank sensor, is there any way I can check that with a meter or something? Or is it very easy and cheap to replace??
thanks for all your input.
A lot of the electrical parts will break down with heat, crank sensors included. If it's the old design and had hot coolant on it from a prior water pump failure it may well be your problem. There is no electronic test for it but sometimes you can cause the engine to stall if you tap on it lightly. It's difficult to do this and some what risky. I use a long 1/4 drive extention. The current design requires a new mounting bracket and retaining screw.
Ok, that definately makes sense, the car only has 35,000 miles on it, so it probably has the original crank sensor, and I blew a rad cap and it blew hot coolent all over, this happened recently, actually right before I started having problems. Definately seems logical that this is the problem then. Should I get a new crank sensor from GM? or somewheres else? Will it come with this new mounting bracket and anything else I would need to install it?
Caspers Electronics PN 107111
$69.00. You'll have it in a couple of days.
casperselectronics.com
Ok, Now the car was fine for awhile, and I decided to do a little tune up.. oil change, new fuel filter, new plugs and wires, and I did get a new crank sensor, and the car seemed fine. Now I just went down to my dads, car was fine, and on the way back it starting doing it again. Car just starts bucking, and then backfiring like crazy. If i give it gas it will come out of it, and be ok for a few mins. Then it stalled, luckily got it started again, and I barely made it home. Every so often it would start bucking a bit, and if I would give it some gas it would be ok. Made it home, and car seems fine now. What in gods name could this be?!?! I am pulling my hair out, I got a scanmaster, NO codes, everything is running great! And now that I have eliminated the crank sensor I am stumped! The coil tower has 11.9K resistance between each pair of contacts too. Like how can the car be running so badly one minute, and the next be fine? Its not like its ALWAYS when it gets hot,.. just sometimes.. so I think that pretty much rules out anything mechanical, or else the car wouldnt run so good sometimes. HELP ME!!!
This is a guess and maybe somebody else can either verify or deny this but what about the MAF? You said you blew the rad cap and got coolant all over the place. I remember hearing or reading that if you ever go to wash your engine compartment that you should either take the MAF off and place it in the car or wrap it up in a garbage bag to keep it from getting wet. Have you done the tap test on it? I think you just get the car running and tap on it and see what happens. Or you could maybe disconnect it and see what happens. I'm not really "up" on all the MAF tests, I've been lucky enough not to have problems.....yet.;) Another thing is to make sure you have the crank sensor tight, both on the block and in its holder, it could have vibrated loose and maybe got close to the ring again. Good luck, keep us informed.
Well, I've done the tap test many a times... and with my scanmaster I can see it responding properly. I didnt really get coolant over that far, and a bad maf wouldnt make the engine backfire, right? I appreciate the help.. any more ideas guys?? Oh, and I forgot to mention this, but the first two times this happened, it was shortly after I put the cruise control on, I dont see how this would have anything to do with it, but I thought I'd mention that, and the most recent time it happened, I had JUST switched on the A/C. Maybe just coincidence. I immediately switched the cruise and a/c off though, and the car would continue to backfire and run like crap.
I have gone over almost everything on the car. The thing that stumps me is how its just so intermittent.
bad MAF wouldn't backfire with tapping, but change idle a bit and stumble. Seems the problem surfaces under load on your engine. My guess is MAF as well and/or some sort of timing issue.? This is really a tough one to diagnose, but the intermittency is almost always electrical in nature. Fuel pump relay? Man..the guessing could go on and on, but guessing costs $$. We need Superman. :\
yeah, I did the tapping, and engine continues to run fine.. maf is good. I know it is, its giving me good readings with my scanmaster.
hmmm..re-reading got me curious..what do you get on the MAF readings at idle, and WOT when it's running right, and then NOT running right? Are they the same?
Have you kept an eye on the voltage? I'm not sure if a scanmaster gives you regular voltage, but maybe it's the alternator? You could take the car to any auto parts store and they should be able to check it for you, or you could take it off the car and bring it in.
just thought I'd post a follow-up. Still havent figured out the problem. I got a new chip, thinking that was possibly the problem, and the car was fine for days. I drove for like 20 mins on the highway, even went on a trip to the drags, car was fine. Then lastnight, on my way home on the highway, I feel the surge again, car starts bucking. I've narrowed it down to it only seems to happen when going a steady cruising speed over 60mph. (i.e. Highway) As soon the car starts doing it, if I put it to the floor, the car will take off, and come out of it, and run normal for a bit. but then it will start again a few minutes later. As long as I keep playing with the gas, and taking off, it wont do it. This is really frustrating, and annoying, as Im afraid to take the car anywheres for fear of being stranded. The Maf values go from 5-6 at idle, up to 235-240 or so at WOT. I just dont understand how the car can be fine for days, and miles of driving, and then just decide to act up when it feels like it.
I cant even take it to someone, because I wont even know if we've fixed the problem! and the things left to replace (cam sensor, ecm,) are rather expensive to replace just on speculation.
Help!
This happened to me also. I fixed it (I hope) by making a ground wire from the bottom of one of the module mounting bolts to the firewall. I have heard of the Type II modules having grounding problems so it's possible that OEMs could as well. If you have a couple of ring connectors and some wire, you can do this for a free test anyhow.