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88 dies at idle, need suggestions


KDirk
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Aw here we go again. A few days ago the 88 started dying at idle while in gear after heating up (i.e. at a stop sign or light). Is also dying in park after engine is up to temperature (closed loop mode). It will restart immediately with no difficulty, and runs fine under acceleration but will die almost every time I am stopped unless I put it in neutral and give it some gas to keep the RPM's up. No codes set, so I started looking at the obvious stuff.

- Idle air control motor, pulled it and cleaned it, but had minimal "soot" in the cavity and on the pintle of the IAC. Idle was very slightly smoother, but still dies after doing this. I hate to replace it on speculation, as it is not the cheapest part to buy.

- MAF; pulled and cleaned. Readouts in diagnostics look to be OK.

- Tested fuel pressure, was 40 lbs. with the fuel rail primed, engine off, and about 32-33 lbs. with the engine running. Seems to be within spec. Also checked the vacuum port on the FPR, and no fuel leakage noted on the vacuum side.

- PCV valve and grommet, both replaced though neither looked too bad. No change noted after doing this.

- Vacuum lines, replaced several sections that were looking dry rotted with new hose. No change from this.

- Going into diagnostics, using the IAC override, I can up the idle while in park to prevent it from stalling out. Cannot used the override in gear (is locked out by the computer).

Now, I do have minor oil leaks from both valve covers (will be doing gaskets/grommets shortly) but cannot tell if the intake manifold gasket is perhaps leaking also. I suspect I would need a pretty bad leak in the intake manifold gasket to cause this problem, and cannot see or hear evidence of one. Wondering if I should suspect it anyway.

So, I am wondering if anyone has any brilliant suggestions to offer. This problem came on with no warning, and I don't note any other drivability or performance issues along with it.

KDirk

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Dave,

I might do that, but I should also point out that the 88 has already been converted to a Delco ignition setup; I trashed the Magnavox ICM and coils many months ago now, as it was dying of green slime disease.

KDirk

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Didn't mention checking the TPS for proper response in diagnostics.

I would put my money on either the ICM as Dave suggested or the MAF.

A quick swap of each would tell the tale.

If you still have the problem try to get a snapshot when its stumbling.

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I don't know if this is even possibly related, but..... when I replaced my R & P I was confused over why the rack had a switch attached to the pressure system on the rack. It was explained the switch was installed as a permanent fix for the low speed stalling, as in parking, with the A/C on. The underpowered engine would stall if the power steering and A/C were both being used. This is a shot in the dark, but maybe you might check that switch, that kills the A/C.

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Throttle body is a good idea. I took the snap ring off, removed the screen, cleaned both the screen and the throttle body with a toothbrush, rag and carb cleaner followed up by Seafoam thru the plenum trick.

Idles better and accelerates much better...

One other thing check your MAF sensor for the O Ring. I have seen missing and two O Rings. That could do it as well.

Edited by DAVES89 (see edit history)
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I don't know if this is even possibly related, but..... when I replaced my R & P I was confused over why the rack had a switch attached to the pressure system on the rack. It was explained the switch was installed as a permanent fix for the low speed stalling, as in parking, with the A/C on. The underpowered engine would stall if the power steering and A/C were both being used. This is a shot in the dark, but maybe you might check that switch, that kills the A/C.

Lots of cars have a 'power steering pressure sensor switch'. It isn't for keeping the engine from stalling, it is for ensuring that the idle is high enough to keep adequate pressure in the power steering system. I am actually about to replace the one in my '90 Regal, like this coming weekend, because it will sometimes lose power assist at idle. Am hoping it is just the switch.

I'm thinking fuel pressure of 30-32 psi is a bit low. Should be high 30s to low 40s. (3 bar pressure regulator. 3 bars = 43.5 psi.) Sounds like the FPR is ok. Maybe the fuel pump is getting weak? (Had the same issue in my '90 Regal a year ago...)

Edited by wws944 (see edit history)
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Hmmm,

Ok, swapped the ICM this afternoon and no change, so I think that can be ruled out. It has been raining off and on, so I don't want to get into anything that I may have to run for cover if another downpour happens. May check the throttle body yet tonight, and will double check the TPS - which I think was showing normal in diagnostics. MAF has one O-ring, verified that when it was off for cleaning.

Will report back either tonight (weather permitting) or tomorrow.

Thanks for the suggestions so far!

KDirk

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Ok, an update to the saga:

Pulled MAF housing and exposed the throttle body. Cleaned generously with carb/choke cleaner and let sit for a bit. Put it all back together, and had a very hard time starting (all that cleaner in the intake) after which it smoked like a BBQ cook-off down South; though it didn't smell nearly as good. After it settled down, it seems to be running ok, and will stay running most of the time. It may take a bit yet for it to smooth out completely I guess.

The strange thing is, I could not really see that much buildup inside the throttle body on close inspection with a flashlight. In any case, I will be driving it tonight and tomorrow to see if it is fixed, or if it is just faking me out right now.

KDirk

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  • 2 weeks later...
When you set the IAC manually, where did it need to be set to idle smoothly ? Bit of a long shot but could also be plugs and plug wires. Any smoke from the exhaust ?

Funny, I had the same problem several weeks ago. Would stall if it wasn't rolling. Replaced the IAC, TPS. It turned out to be bad wires. Purrs like a kitten now. Stay away from the $19 Pep Boys wires. One yr is the most you'll get.

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I guess I should post an update again, as I did get the problem solved per my previous post above. Appears to have been entirely the result of a dirty throttle body. After a thorough cleaning, it has continued to run great the past two weeks and the idle is smoother as well (as should be expected).

KDirk

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Hello. Try replacing the fuel pressure regulator. this repair was stumbled upon after 11 tries. It never had any trouble codes. It is right on top of the engine between the horseshoe shaped fuel rail and the gas line. I have been a Buick sales rep since 1984. All 3586 spot welds were still done by hand on the Reatta.

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