Hey guys. I was driving around yesterday morning and the car (87 GTA 350/auto) was running great, when all of a sudden it starting kind of surging. At a stop, the idle was lower than usual and running very rough - the whole car shakes. The exhaust smells very rich - what a stink.

I let it sit over night then fired it up this morning, and it shook big time when I was backing out of the garage, then it suddenly smoothed out, then rough again.

I have not put any new gas in for a long time (don't drive it too much), so I can't believe it would be fuel. There are no codes, and there is a smell of gas in the oil. I haven't pulled any plugs yet because it is major pain with the headers - I will wait to hear other thoughts.

Can anyone shed some light on what might have happened so suddenly? Some of the things I had thought of:

1) Fuel filter - not too likely to cause a "missing" feeling at idle
2) Ignition module - don't know if this would affect idle or not. I know it will cause surging at road speed if it is on it's way out.
3) Bad injector - rebuilt about 3 years ago
4) Bad plug - not very old
5) Bad plug wire - Accel wires - almost brand new and no burns
6) Cap/rotor - again, almost new

Thanks for any help

Eric

 

I just had the same problem. Mine was a bad MAF. Just unplug it and see if your problem goes away. If it does, then get another one.
FBird

 

If this was an office pool, I'd take the "burnt spark plug wire" square.

 

Well, I might buy into the "bad spark plug" and "distributor cap problem" squares, too.

 

Well if something is wrong, the ECM should detect it and pop the SES light. Have you checked it for codes?

One thing that's happened to mine a couple times. It was running great and then all of a sudden it starts running like dog poop. The ECM itself took a crap. Replaced the ECM and it cured it's ills. On these cars, whenever something wierd like that happens, the first thing you should do is sheck for trouble codes. Get out the paper clip!!
Count the flashes!

 

This is so funny... The exact same thing happend to me on Saturday morning. 10 to 1 odds your headers burnt through one of the spark plug wires. Thats what was wrong with mine. I just bought a replacement coil wire for $7 and made it long enough to clear all of the headers. That will work till I get the $$ to have my headers ceramic coated.

Also, I would check cylinder #8 first. It has the wire that has to run closest to the headers & and its the hardest to get to!! Thats gota be it!! hahaha (It was the one that was bad on mine.) Plus remember that it may not look "burnt." My plug wires were only 1-2months old and the header heat caused the #8 wire to crack. That crack allowed the spark to jump out of the wire. Now what really sucked.. The plug wire went when i was trying to impress some girls with my car/exhaust. I guess I should learn a lesson here... NAAAAAAA!!!

And just to let you know.. my car didnt throw a code either.


Good luck
Mark B

 

Make sure all your wires are actually tightly connected at both ends - distributor end, and spark plug end.

That happened to me once... started missing and running rough just outta nowhere when I was sitting at a light. Drove to a parking lot, I popped the hood, all the wires looked fine, then I started pushing them all on, to see if they were loose... one was loose. Popped it back on, and all was cool again.

 

i remember that my car was shaking and i knew it was missing. wires were all in tact, cap and rotor were fine, i really didnt know what was wrong. then the thought came into my head that the car was probably running too rich so i should check out my plugs to see if that was the answer... maybe one of my plugs fouled out. when i checked them, the first three seemed to be perfect. when i took off the fourth one, i found it to be COMPLETELY black. talk about having a plug foul out on you. it so happens that when i put the plug in, i accidently cracked the ceramic part of the plug without noticing. it didn't come off, it just cracked and wouldnt let the spark reach the end of the plug. replaced the plug and it worked fine. maybe it's your plugs... check them out just to be sure. i would check the plugs, wires, cap and rotor. if it's happening for no reason, it should be one of those. oh.. and also, the other day i noticed a miss and a strong smell of gas... popped the valve cover and guess what i found? rocker came loose because the lock wasnt tightened all the way and wasn't able to push down the valve.

 

If it was MY office pool, I'd bet on the EGR valve flopping open and sticking from carbon....

 

OK, here is an update...

I checked all the plugs/wires/cap/rotor and all look good. Now, I cannot get to the damned #3 plug because of the header. I did pull all the others and the burn looks good. I suppose I could have the worst luck in the world and #3 would be the bad one, but I am not convinced.

We scanned using Datamaster and everything appears to be just fine, as far as the ECM is concerned - no readings out of the ordinary.

I pulled the distributor and took it apart and found the pickup coil was pretty much disintegrated! I replaced that and put it back together. I quickly timed it by ear (when the idle got best) and it now seems to run a lot better. However, I still have rich-smelling exhaust, and it isn't running perfect.

My buddy called to tell me that he was looking through the data logs and found that the ECM set a 32 twice while we were driving (curious no SES light). That brings me back to EGR, which I have investigated previously. The EGR solenoid has been replaced, and we pulled the EGR valve off and it SEEMS to be working OK. Put the old lip vacuum on it and it holds the diaphram. I suppose it could be sticking - I think that would account for some stinky gas and a stumble. I hate to replace the EGR valve ($$$$) and find out that it is not the problem.

So I am still working on it. At least I can drive it. I do have a question about timing, but I will start a new thread.

Thanks for all the replies.