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warm/hot start HIGH rev idle/ sticking throttle??

R

rschap1

New member
Since our recent heat wave here in Michigan...my 2000 Grand Prix GT 3800 with 200,000 miles has been acting strange:(
I drive 60 miles after work each afternoon to the gym I hit on the way home.
Trip is all highway from work to gym.
I park the car, work out, and return to start the car and head home about an hour later.
When I start the car to head home. It starts hard, takes a bit longer than usual to fire, chugs, bogs, then idles slowly for 5-10 seconds. Stumbling clears then engine REVS way too high. Gets up to 3,000 rpms. I try to give a little throttle and RPMs just increase and stay there.
The more I add throttle the higher it reves and stays/sticks.
Shut down 2 or 3 times and slowly starts to get better and return to normal.
???
Air temps have recently went from 30s and 40s to 80s this time of day.
I am GUESSING that fuel/timing maps/curves maybe out of wack with air temps and going from an hour at 80mph to a cold/warm start situation...???? I guess.
I was formerly informed that the backside of the throttle blade usually gets a carbon build up.
I have had a sticky gas pedal for a few years. 1st time you step on the gas it took alot of effort then was OK. So...last weekend I pulled the throttle body and did clean a TON of build up off the inside of the bore, off the blade, and pulled what I am calling an idle by pass valve (I guess too). I had hopes that cleaning this mess would help the starting revving after the gym, but no luck...
Wondering if any help, advice, or similar situations that may be passed along.
APPRECIATE IT !!!
 


Well, I’m thinking the problem might still be associated with the throttle body. I would start by cleaning/inspecting the TB bore again. The most important surface to keep clean is the interface area between the plate/blade and the bore. Then after cleaning it take a light oil (for heavens sake NOT WD-40) and put 1-2 drops on each end of the pivot shaft. For this application I personally use gun oil. Next clean then lube the throttle cable itself. Check for a good connection/damage/routing issues. During this whole evolution I’d be looking for vacuum leaks also. Next, disconnect your battery for about 20-30 minutes then take it for an easy long-ish drive. Like go visit your grandma on the weekend.:) By doing this it will/should tune your PCM right in.

Another path is sensor related. The MAF is a culprit for a lot of GP drivability issues. I’d start disconnecting the MAF sensor, and see how it performs. If the problem goes away or is much less severe usually indicates you need a replacement. But I would start by very gently cleaning it with MAF/electrical contact cleaner. It is very to easy clean just don’t touch/bump/even breath on the wires.

If you do this stuff and you’re still having issues we’ll go from there. Also, have you scanned for codes?

Good luck.
 
First off, THANKS!!
Sounds like a lot of the same stuff I did while I had the throttle body off.
I used a little stainless steel brush to clean the bore, especially where you mentioned, contact areas. This did remedy my sticky pedal when I first start driving each trip. I used a drop of white lithium grease at the pivot points and for linkage cables.
I had a much better day yesterday after the gym visit.
It ran much better.
Started a lil' bit better, and I waited a lil' bit longer before touching the gas pedal.
It stumbled just for a second or two, searched between 600-800 rpms for just another second or two and seemed OK. I let it idle for 45 seconds, a minute before revving it slightly and no troubles.

The MAF sensor is probably about 6 months old- a year now. Went through a cheapie off Ebay and now a Cardone from Autozone. It was turning the SES light on. It seemed good since I installed that until this past week and the temp changes here. The drastic weather change is what I would like to blame it on and hope that it is just adjusting...I hope.
I did use a blast of MAF cleaner on the sensor last weekend too. I had a can since I was advised to try that prior to replacement. Hopefully it is learning to handle our record breaking temps here. Probably just in time for March to return to Michigan...

APPRECIATE THE HELP, THANKS ! ! !
 
Well it got even worse yesterday.
Previous little stumble and high rev as I left the gym again. Let it "search", waited, shut off and re-started a couple times then was able to drive home.
Drive went OK and ran well.
When I got home and pulled into the drive 20 minutes, 15 miles later...car stalled and died as I parked.
Chugged and stumbled as I restarted. High rev and temp gauge rose to 195-198.
Checked coolant and it looked like same level as usual.
Radiator full, looked good, bottle at hot level and seemed good.
I added about a pint of water just to be sure.
???
Autozone says that they won't scan w/o a SES light on.
I am sure a scan would help, but I have been too cheap to buy a scanner.
See how things go today...
Fingers crossed, THANKS again!!
 
Temps here dropped back to normal Michigan range for March.
Now that we have went back to 50s and 60 instead of mid 80s the car has been fine.
wtf.gif

It seems to be high temp related.
Maybe I will start looking closer at stat or water pump maybe...?
An known issues or method to check flow on a water pump w/o tear off?
Or any other ideas I may be missing??
Thanks for the help this far.
 


With the lower temps here, I noticed the car not even getting as warm as it should now.
Running less than 180 while driving and then gets a lil' warmer when setting at a light or just idling.
Think the stat may be doing a lousy job.
Going to see about replacing that soon.
I am wondering if it was overheating before and getting a real rich mix???
Anyone know if these motors do the extra fuel wash down cylinders when temps get too high?
I didn't think that was the case according to the gage before, but maybe just too hot and going into a limp/safe or some kinda extra rich mode ? ? ? THANKS again!!!
 
Car had seemed to be running cooler than normal when air temps cooled now.
Too hot when air temps are wam, too cool when air temps are cold.
Figured thermostat...put in a new one (195 degrees).
Been running OK since.
Drove it hard to Detroit and home this past weekend, 300 mile round trip w/o any trouble.
But air temps were still mid 50s, guess I will have to wait until temps warm up to know for sure now.
Fingers crossed.
 
Is that the mechanism right above the throttle blade?
Spring loaded with a tapered cone seat?
Looked like it let air by pass even if throttle was fully closed and sealed??
That was just caked with carbon and greasy build up a couple weeks ago. I was hoping that cleaning it up would have freed it up and fixed things, but I did have a big high revving occurence afterwards once.
If this continues and it acts up again maybe I will try replacing the whole IAC unit then.
THANKS!!!
 
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