Trouble with a 1986 IROC.....

[trapin]

Not sure where this falls in the forums, it's kinda general so I'll post it here.



My friend has this 1986 IROC Camaro that is his pride and joy. It has a 305 with TPI on it (yes, I know...I've already discussed the whole LS1 swap thing with him). He has been struggling for a few years now to get it fixed. The car is in mint condition (30K miles garage kept). He says he can park that thing for a couple months, get in, and it runs fine. However, as soon as he gets up to speed (45+mph) it starts hesitating and the rpms start going erratic. Soon after it starts running terrible. He has taken it to 6 different people and they all say they know what the problem is. They fix it and then as soon as he leaves the shop it starts acting up again. It just happened to him again today. He took it to an auto electric shop and they replaced some modules and the computer and as soon as he left it started hesitating again. He's actually thinking about selling it now because he's so discouraged with it all. I got to thinking about this....do you think it might be his catalytic convertor that's causing the problem? I also thought maybe his convertor lockup module for the transmission is not unlocking the convertor. I don't know.

Any insight would be greatly appreciated. I'd hate to see the guy sell the car.

Thanks

T.

[Damn True]

Does it have Optispark?

[BonzoHansen]

Does it have Optispark?

No. That is an LT1 thing.


It won't go over 45? No codes?

[6'9"Witha69]

Sounds like a timing issue, perhaps vacuum interrelated.

Also, check fuel pressure and injector pulse. Sometimes the connectors just get old and come a little loose, causing erratic connections not noticeable at lower engine/vehicle speeds.

[trapin]

I talked with him just before I left work and he elaborated some on what the problem is. He says that the car runs fine at idle and even runs smooth with no problems as he is accelerating up to speed. However, once he gets up to 45+mph the rpms start decelerating, almost like it's going to stall. That's what's making me think it might be the lockup convertor.

[HILROD]

I worked on my buddies 85 Trans Am. Same symptoms. Chased it all over hell. It ended up being a weak GM fuel pump. He or I changed out half the car, including the fuel pressure regulator. The problem was it had fine pressure at idle, it was going lean higher up. It was running rich, according to the computer which would lean it out more. His problems were almost the same as yours, low miles, not a lot of use, we couldn't find it till it got worse.

[70 Chevelle]

Check the fuel filter also, clogged fuel filters will give you the impression that the fuel pump is fine because pressure stays adequate, but there is very little volume you would be surprised how many shops miss it. having a clogged filter will give the symptoms your describing.It also destroys the pump do to drawing so much amperage to overcome the clogged filter. The other problem I
've had with stored TPI engines, or any gm for that matter, is pull the ignition cap and check the pickup coil wiring where it goes into the ignition module check to see if those terminals have turned green from corrosion, just look for any powdery stufff around the pickup coil or the module. If you see any corrosion replace both.

[Vegas69]

Sounds like a fuel delivery problem to me as well. Probably a bad pump or clogged fuel filter due to bad gas and sitting so much. Once you accelerate the pump can't keep up anymore. Back when I was a line tech I would put a long hose on a pressure gauge and tape it to the windshield and go for a drive.

[z65mm6]

Fuel filter and weak pump sound like likely culprits as others have stated, but this sounds more like the fuel strainer on the end of the pump. Varnish from sitting, and any silt in the tank, work to form a cement like coating that makes it nearly impossible to pass fuel. It's simple enough to do, remove and replace. But it is a pain since the tank probably has to come out. However you might want to pull a book and check since some cars have an access panel if you pull the carpet back. Tell your friend to do himself a favor and get a new seal and locking retainer for the pump.

[MrQuick]

I agree it sound fuel related. Another thing is to check the gas cap. Run without it. Don't forget about the catalytic converter, they weren't the best.

[Bow Tie 67]

Sounds like a fuel delivery problem to me as well. Probably a bad pump or clogged fuel filter due to bad gas and sitting so much. Once you accelerate the pump can't keep up anymore. Back when I was a line tech I would put a long hose on a pressure gauge and tape it to the windshield and go for a drive.

This is a great way to Troubleshoot it instead of just replacing parts. To many parts changers these days and not enough brain power put into diagnosing the problem. And of course other drivers look at you like your nuts.

[Jim Nilsen]

I had an 89 Camaro that would do the same thing you describe. You take off it runs and then it loads up and stumbles like it has the choke on. Putting a new cat on it won't hurt it a bit since there have been milestone improvements to them since the eighties.

I wouldn't rule out the fuel pump either or the other filters on a car that age with such low miles.

Goodluck and start by replacing the stuff that should be replaced anyway just because it is the right thing to do so you have a reliable car. Sounds like a good time to change all of the fluids too!

[scogin918]

See if it's throwing code "NEM" - Not enough Mullet. Usually there's a sensor in the headrest that recognizes a certain length of mullet.

[68nate]

We had a camaro in the shop just last week doing the exact same thing. Ended up being a faulty pick up coil in the distributor. BUT THE FIRST THING YOU SHOULD DO IS DRIVE IT WITH A FUEL PRESSURE GUAGE HOOKED UP- PRESSURE SHOULD RISE A COUPLE PSI UNDER ACCELERATION-SHOULD NOT DROP. Always test drive with a guage on when you have a driveability issue like this. If fuel pressure looks good while acting up, the next step would be to test drive with a scan tool hooked and see what's happening when running poor. Usually if catalytic converter is so plugged it causes a condition like you describe, you will hear a very loud whistle the harder you accelerate. A locked up torque converter would try to stall the engine on deceleration.

[David Pozzi]

I'd start with the fuel pressure test for sure.
Also I've seen the EGR valve fail and open way too far it pluggs up internally, the stem is hollow with exhaust pressure inside. Pull the vac hose off the EGR valve and see if it runs better. It can cause a very low vaccum condition if it opens too much.

It will ping if you get on it without the EGR so ignore that, also the knock sensor will kick in if it pings retarding timing. Just drive it around easy and if it's normal, replace the EGR valve. I wouldn't expect the EGR to be bad at that low a mileage however.

[trapin]

Would a 305 TPI motor have knock sensors and an EGR on it?

I believe this motor is a gen1. It's a 1986 car.

[HILROD]

The EGR is under the upper plenum. The knock sensors are next to the oil pan rails. Some have one some have two

[trapin]

Ah, I see.

Thanks everyone for your input by the way. It's greatly appreciated.