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Missing and chugging before and after recent tune up


tornado_735

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Well, I recently changed the plugs, wires, EVAP solenoid and air filter on my 1996 GP 3100 to try and improve some of the drivability issues I'd been having. They usually only happen when the engine is up to operating temp. First thing in the morning, it's usually fine.

 

The problem isn't really that serious, just extremely annoying.

 

While cruising on the freeway, the engine will feel like it's 'chugging'. You can ever so slightly feel yourself swaying front and rear as the engine chugs. Another way to describe it would be surging, although the tach doesn't budge.

 

Last night coming from a friends house, I noticed it surging so I put my foot to the floor. It had no power and had what felt like a random misfire the whole time.

 

Anything below anywhere below 3k RPM is fine, but get above that and I hear what sounds like light pinging, and the engine doesn't make any power.

 

Could this be a fuel issue? Could it be a weak coil or failing ICM? I'm not sure where to start, and I'm really annoyed by it.

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Solved this exact issue in my 95 GP SE by replacing a coil pack, new plug wires might not hurt either, but sounds like the exact symptoms my car had. It was always the worst towards the lower end of overdrive(50mph) while going up a slight incline.

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Almost sounds like a fuel delivery issue. You needs to check fuel pressure and try to replicate it. A fuel filter change could help.

 

Other though is glogged convertor or dirty/failing MAF.

 

Oh crap, check your cam and crank sensor wiring, they love to melt.

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Solved this exact issue in my 95 GP SE by replacing a coil pack, new plug wires might not hurt either, but sounds like the exact symptoms my car had. It was always the worst towards the lower end of overdrive(50mph) while going up a slight incline.

 

Inclines seem the worst. I have good coils and an ICM from my '94, maybe I'll swap the bastards.

 

Almost sounds like a fuel delivery issue. You needs to check fuel pressure and try to replicate it. A fuel filter change could help.

 

Other though is glogged convertor or dirty/failing MAF.

 

Oh crap, check your cam and crank sensor wiring, they love to melt.

 

All the wiring that I can see is in good shape, so I'm not sure it's that. When it's cold, the thing runs like a rape date...it'll pull all the way to redline without problem.

 

I will definitely check the fuel pressure. What should it run on a '96 L82?

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Minus the pinging, can't give any input on that. I will say my misfire wasn't enough to trigger a code.

 

Well, I have an inherent SES light for a bad rear O2, and the old EVAP code.

 

I'm willing to bet that when I get the codes out of it, one of them is going to be a P0300 Random/multiple misfire. We shall see...

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runs awesome cold, but when hot, reduced power, "chugging", can hear pinging when under load?

 

sounds like knock IMO.

 

You mean like spark knock? I was wondering about that, but since my knowledge on that is somewhat limited, I didn't want to mention it.

 

Could the ECM be picking up what it sees as knock, and be retarding the timing causing my 'missing' and chugging? I could be wrong here, I'm just throwing out ideas.

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I didn't even bother with the fuel pressure test, I just got a new fuel filter, and I'm going to try and throw it on without fucking too much stuff up...I hate screwing with stuff like this.

 

I reckon it's probably original seeing as the rest of this car was held together with a shoe string.

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Sounds similar to the symptoms I'm having in my Lumina. Have you checked the TPS? Also, the MAP sensor could be cause. I know there's a TSB out for an issue like this, with the TPS and MAF being the culprits...not sure if it is your issue or not, but could be. So far I've had no luck tracking my issue down either, but it sounds very similar. Chugging at speed (around 50) but I never once had an issue in the winter...

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I didn't even bother with the fuel pressure test, I just got a new fuel filter, and I'm going to try and throw it on without fucking too much stuff up...I hate screwing with stuff like this.

 

I reckon it's probably original seeing as the rest of this car was held together with a shoe string.

 

everything_went_better_than_expected_RE_Few_Memes_To_Make_You_Smile-s509x385-155629.jpg

 

 

We'll see if this corrects any problems.

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Well, the fuel filter seems to have taken care of most if not all of the hesitation under WOT. I'm almost positive the filter that was on it was original. Surprisingly, it only took about 5 minutes to change. I spent more time looking for my 15mm wrench.

 

It could just be my imagination, but every once in a while, under WOT, it still seems to hesitate. But nowhere nearly as bad as it did. I'll check it again today and see.

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i had a similar problem last year on my 90 regal. after checking a whole bunch of other things first, it turned out to be the MAF sensor. i bought a 8$ can of MAF cleaner, sprayed the wire, put it back together, and everything ran fine.

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post-2339-14368906935_thumb.jpg

 

It's not in my imagination. The problem remains. Tonight on the way home, I turned after a stop sign, and the car had no power, and refused to shift from first gear. I let off the gas and it dropped into third. Then it proceeded to miss and chug. FFFFFUUUUUU.....

 

I guess the next course of action is going to be a fuel pressure test to make sure my fuel pump isn't about to take a dump. Which leads me to my next question...

 

I seem to remember someone saying that dropping the tank wasn't necessary to replace the fuel pump in a Grand Prix because of an access panel in the trunk...please someone tell me this is true and not a figment of my imagination.

 

Also, my next course of action is also going to be to check codes and ignition hardware.

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Nope, on Gen 1 and Gen 1.5s, you gotta drop the tank.

 

FFFFUUUUUCCCCKKKK.....I guess I should thank God this car isn't too rusty then.

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Well, things have taken a turn for the worse although I know where to start at least. Got codes, and the only one I had that wasn't new was a p0306, cylinder 6 misfire.

 

I'm guessing that the NEW wire on that plug is bad, and causing the misfire.

 

If I still have chugging after that, I'm going to change the TPS because it only seems to chug under load with more than 1/3 throttle.

 

To take a line from Bxx....Lord give me the strength...

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I'd double check everything in the delivery and ignition system of cylinder 6; Dirty Injector? Bad spark caused by faulty ignition pack, plug or plugwire? Proper plug gap, etc. Might help to pull that plug and at least 1 other to compare carbon buildup.

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Fixed the Cylinder 6 misfire. It was a bad spark plug wire. Chugging is still there though.

 

Moving onto ignition now. Over the last couple of days, I've noticed that it pulls like a little 3100 freight train when cold, but chugs under WOT when up to operating temp. So I'm wondering if the coils are getting weak. Luckily, I have good spares, so we'll see what I can eff up next!

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