sl2 wont stay running, driving me nuts

[spare_change]

Hi everyone, I have a 94 sl2 sohc (~130k) that wont stay running and its driving me nuts...!

The car will start when cold and idle at about 1500 for a minute or two, then drop to about 800. I expect that is normal. After idling at 800 for a few minutes, it will stumble for about 10 seconds, then die. The car will not start again until it sits for awhile, and when it does the problem will quickly reoccur.

What I have noticed is this:
-When the car reaches the point of stumbling, the coolant temp. has begun to climb, but only to the point of reaching the first mark. While this is nowhere near normal operating temp., the car does not stay running long enough to expect that it should warm up completely.
-Additionally, the exhaust starts out clean, then progressively emits more and more condensation (white steam) until the car stops running.
-When the car stops running, the fuel pump can be heard operating for a few moments (as it should I believe).
-Finally, the stumbling symptom cannot be overcome using the throttle.

I have replaced the ECTS (the two wire one), EGR valve, PCV and fuel filter. None of these have had any effect. I believe that the problem is fuel or emissions related but I am starting to feel as though Im just throwing parts at it. Can anyone help diagnose this problem??

[westwind999]

Is it SL2 or SOHC? SL2 is DOHC and SL or SL1 is SOHC.

Anyway, is the check engine light on? What are the codes?

It might be the CPS giving up.

When it dies will it restart or does it need to cool down? It might also be the idle air control.

Good Luck.

[fdryer]

Try removing the O2 sensor, the hole will allow exhaust to escape if the catalytic coverter is blocked. If the engine breathes and allows you to drive then the catcon needs replacement.

[ssicarman]

When it is not starting for you have you checked for spark?
Fuel pressure?
When it is running are you abel to rev it high?
Will it rev high freely and stay high without wanting to bog down?

[spare_change]

Thanks for your help guys, I'll try to answer all three of your replies at once.

westwind999 - My apologies, it must be an sl1 in that case. It is absolutely the sohc motor with tbi. The check engine light did come on at one point, but only breifly. I also lack an obd1 reader. I'll take a look at the CPS and particularly the IAC. If that's related to the egr/emissions setup, I can say for certain that things looked pretty cruddy in there when I removed the EGR valve.

fdryer- That's a good point. The car did receive a completely new exhaust system very recently, but it's possible. I'll give it a try.

ssicarman- Yes, I do have spark when the car does not start, it will run fine with a squirt of starting fluid. Fuel pressure is also present, though I dont have a gauge. I have tested (released and recovered) the pressure in the system multiple times using the schrader valve on the fuel line. I am able to rev it high freely, I've brought it up to ~5k but haven't bothered to go as far as the redline. The motor will also return to idle fairly quickly and without resistance. Once it has returned to idle after revving high, however, then it will bog and stall.

Thanks again for your comments, I'll try them out and post another update today.

[ssicarman]

So with the 94 SL1 you are able to see if there is fuel spray from the injector when the engine is cranking. Check for that. If there is none then you may have a power or ground problem to/from the injector. When the car will not start cherck for power to the injector and a pulsing ground signal. Noid light is the best way to go to check this. You may be able to rent, borrow or buy one from a parts store.
Being able to rev high tends to rule out a completely plugged converter. Pulling the O2 sensor, if you can without damaging it or the threaded hole for it, may be worth while just to rule an exhaust problem out.

[Ponchoguy]

Autozone, among others has "free tool rental".

That is, you place a deposit for the tool with a credit card, use it, bring it back in good condition and get your deposit back. I think other chains have similar programs.

[spare_change]

Hi guys, thanks for the two additional responses, hopefully I can pick up the noid light at autozone. I'll check the injector for spray first thing in the morning, that sounds promising.

What I've found since everyones posts earlier is this:
- CPS has the correct resistance, so that checks out.

- The oxygen sensor refused to budge. Perhaps if the car would stay running long enough to heat up the exhaust, it might come out. For now though, I'm willing to rule out a plugged cat. The entire exhaust system is too new and there really is no resistance when revving. The throttle is very responsive.

- Removed the IAC and it turned out to be very cruddy. Cleaned the pintle and the bore in the throttle body, then reinstalled. This time it ran for maybe a minute longer (I didnt bring my stopwatch), stumbled once and recovered for a few moments, then stumbled and died again. Looks like that may be the problem, so I've ordered another one.
The odd thing is that the Haynes states the voltage at the plug (ignition on) should fluctuate between 1.5 and 10.5 volts. I got a completely steady reading of 11.2 volts.
I double checked the Haynes, and all it says that if it's outside the parameters of 1.5 and 10.5 to check the PCM. Typical..
I think I'll throw this one last part at it anyway and see how it goes.

Once the new AIC arrives and I've checked out the injector and PCM Ill be back with an update. Hopefully a positive one.

Thanks again for all of your responses!

[fdryer]

With the O2 experiment and lack of an engine run to heat up the exhaust enough to help loosen it perhaps a propane torch on high will have enough heat to warm the area? I'm presuming you're still using the old catalytic converter? If not, forget this test.

When you replaced the two-wire coolant sensor did you examine the connector for corrosion that would interfere with signal/voltage flow? The corrosion would act the same as the sensor being cracked - a high resistance circuit is read by the PCM as a cold engine, possibly flooding or keeping the mixtures too rich. Check on it to be sure otherwise replacement may be necessary, with either a junk yard air temperature connector or pc connector and all weather sealant.

[spare_change]

Hi guys, I dont know if anyone is following this thread anymore because it was on the second page when I got back around to it, but problem solved!

It turned out to be the IAC valve, and the car ran fine once a new one was installed. I even went so far as to rent out a set of noid lights from autozone, but I guess I wont get to use them.. too bad

Thanks again for all of your posts, they were a big help!