[ds968]

When I started the car after work today the idle needle dropped a bar, then two, then came up again, then dropped again by about 400 rpm, .. you know, the "it's going to stall if I let it" symptom. I rev'd it up a bit, the engine seemed to hesitate somewhat but I still decided to drive it out of the parking lot. Stopped at the traffic light which is about a minute away where the idle was still acting up so I kept the rpm above 1600 and then when the light turned, I just took off.. stepped on it, no problem whatsoever - smooth power on demand, no hesitation at all. When I put it in neutral to see what might happen, the idle was just fine - back to normal. This was about four or five minutes later. Entered the highway, and the car ran as smoothly as it always does. When I reached the bumper to bumper segment where I had it in neutral off and on for a couple of miles.. .nooo problem. <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" />



Anyway, as soon as it stumbled when I started the car I thought it could either be the dme relay, ( no worries since I keep a "spare" one in the glove box <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> ) or the idle stabilizer valve. The dme relay is only a year old, so that being the culprit seemed a bit unlikely, and I'm thinking IF it was the stabilizer valve the problem would continue, right ? May be the fuel filter is a bit clogged ? But it only stumbled for a minute or two and after that ... ran as if this problem never happened <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" /> .



Got home about 45min. later, I let it idle and all was well. Turned it off, went in had a beer, came back, started it up.. well again.



I had filled the car up in the morning - same gas I always use ( Chevron 91) - with which I never had problems, but now I wonder: would some impurities in the gas that slipped trough somehow cause those type of symptoms...momentarily ?



I guess I'll see what happens in the morning when I start it, but was curious what you guys think in the meantime..

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[mitch968]

Maybe wet weather or condensation caused some electrical gremlins that went away when the moisture cooked off? How are your plug wires, distributor, etc? Just a thought.

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[whakiewes]

Same problem here! No solution yet - Fuel pressure is fine at startup, but stumbles for the first little bit, then fires right up and runs perfect. I ordered a new fuel filter to see if that helps, and I may run some injector cleaner through.



Wes

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[Etnier]

What's the procedure for changing a fuel filter, BTW?

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[ds968]

distributor, wires, etc.. no more than 9 or 10 months old so those should be ok.



trapped moisture.. hmmm...I washed the engine last weekend, but had no problems Mon ot Tue, so it would be odd to act up three days later, but who knows ?



I'll check into the fuel filter situation if it does this again today.

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[ds968]

WORSE this morning. Engine hesitating and stumbling quite a bit, as soon as I took off ( and actually anything below 2000 rpm ) for the first five minutes was.. ugly. Above 2k, no problem.





Further thoughts ?

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[flash]

since you washed the engine, i would pop the distributor cap and look for water for sure

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[ds968]

will do that for sure ( with hair dryer on stand by <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> )



also will be checking the temp sensor connections ( assuming I'll find where the sensor is ) and provided it's accessible



doing the blink test as well to see if any fault codes appear



here's a weird thought - any chance whatsoever the racer X chip could suddenly develop a glitch and send the wrong signal to a sensor ?

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[flash]

extremely unlikely, unless the DME got wet

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[ds968]

oh, did I forget to mention that I washed the DME - too dusty behind all that carpeting and the floor board, so I figured while I still had 2 quarters in the autowash, why waste good money and all that water left over <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" />

ok, I know - too many comedians out of work and I'm not helping the situation



yes, I realize there could have been a leak getting to the dme, but absent that I'm glad to hear the chip is not likely to suddenly develop gremlins .. unprovoked that is.. <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

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[ds968]

did the blink test: 1-5 ( no faults )



made sure all plug wires and other connections are tight



changed the dme relay with a new one - no difference





the mystery continues..

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[ds968]

update : a more specific description of the symptom as of this morning..may be this is a clue..



On start, the idle is ok for approximately 30 seconds to 45 sec. Then it starts to fluctuate ( rough idle, hesitating..) with the needle moving with a 50 to 100 rpm deviation. It does not seem that should be a lot, but it sure feels pronounced. Especially if I give it gas slowly between 850 rpm to 1400 rpm it really hesitates and stumbles, WHETHER in neutral OR driving it. Once it gets past 1400 it seems to be ok.

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[Mark]

Have you tried putting your stock chip back in?

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[ds968]

[quote name='Mark' date='May 19 2006, 07:37 AM']Have you tried putting your stock chip back in?

[right][post="21274"]<{POST_SNAPBACK}>[/post][/right][/quote]



Yeah, thought about it but dreading having to do that... might have to, if the rest of the troubleshooting things come up empty.



Removing the dme box and trying to put it back in with the fit and brackets the way things are positioned was a friggin' nightmare - I swore if I had to do that again I'd hire a contortionist from Cirque Du Soleil for the job.

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[Mark]

LOL That's why I payed to have mine done at the same time as a bunch of other stuff. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> I figured it was worth a shot since nothing else seems to have done it.

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[S_Cal968]

Unfortunately what you've described could be a few things. And I doubt a code would be stored if the condition only existed for a few minutes, [warm-up?]. I know domestic ECM's require the condition for 15mins before a code is stored. This allows time for the ECM to go from open loop to closed loop mode. I would guess the DME is similar. Typically during the warm-up period the a/f mix is slightly richer, however the DME looks at air temp, water temp, rpm and vacuum. So the issue may be with any of the components that monitor these parameters.



If this issue came up after washing your engine - I'd suspect a connector has moisture infuktion. [tech term] <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" /> If so, you'd have to inspect every sensor plug for moisture and used wd-40 [or contact cleaner] to disperse the H2O. I never spray water on my engine for that reason.



If I had to guess, I'd say it's a water temp sensor that's open. I'm not sure if the resistive values are in the shop manual, but the sensors would be worth checking...



I doubt it would be the idle stabilizer, typically it'll idle rough all the time.



Another thought... a long shot, the dme chip may have been damaged during installation due to ESD [electro-static discharge] damage. The chip may work fine initially, but can fail anytime thereafter. If you grounded yourself while handling the chip this shouldn't be an issue. If we knew the check-sum for the firmware we could verify it with a chip reader.



Good Luck...

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[ds968]

Thanks,



re: chip - yup, was grounded when handling / installing it.



though I am as technically inept as it gets <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" /> I'm thinking if it was the chip gone bad, there would be a heck of a lot more symptoms than just that single problem and only b/w 900 and 1400 rpm, in the first five minutes.. but that's nothing more than speculation - I have no clue of the dynamics of the chip and what it controls or if it's compartimentalized to the point where only a single element can fail..



as for this issue coming up after the wash - would it make much sense ( if there was any moisture infuktion <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" /> ) for the car to run perfectly after the wash for two and a half days, and then be suddenly affected ?



he, if I knew where the water sensor was I'd check the plug ( provided it's accessible ). for that matter, if I knew where the other sensors are - BTW, just

how many are there ? - I'd do the same. Am told temp sensor # 2 should be under the intake manifold, on the block.

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[mitch968]

Yes, the temp sensor #2 (the one that sends to the DME) is under the intake manifold. Looking from the front of the car, I believe it's the one closest to you with the blue connector. I think the next one in is the one for the temp gauge.

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[ds968]

thx for confirming. will look into it, hope I can reach it fairly easy..

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[mitch968]

No problem. It's very easy to reach and replace if necessary. I replaced mine a while ago as a troubleshooting step. You may lose a tiny bit of coolant when you swap, but not too bad at all.

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