Im in the midst of troubleshooting and figured it wouldn't hurt to get some other opinions

Temp gauge at 195 = perfect idle.

Randomly car will overheat to what looks to be about 225/230. It randomly heats up after 15 or so minutes of driving OR if I shut car off and restart it before it cools completely off.. It will usually kick back down to about 200 as soon as I turn the car on, but then it heats back up and can't get back down to 195, and it will go back up to 225/230 It alternates between 210-230 once it's hot and will not cool down to 195 or lower until the car is shut off, and sits there until it's completely cold.

Here's the kicker... when at 195, it idles perfect. The more the temp creeps up, the more the idle drops. It's a smooth transition comparing temp to idle. Once at about 225/230 my car is idling at 400-450 RPMs. It's cammed, so has a slightly rougher idle, so at 400 it's really struggling to stay running.

I replaced the thermostat approx 200 miles ago, back when it was in storage cause it overheated up into the red (I took it out and was in a dangerous spot to pull over, hence the reason I let it run that high). Got a thermostat from GM & that seemed to fix it until I brought it out of storage.. it still overheats a little. I don't understand why the @!#$ is it idling like @!#$ once it heats up a little bit. Back when it overheated into the red before, it idled fine then. Nothing motor-wise has changed.

I got another thermostat to throw in just to see if it effects anything. Maybe mine is sticking, but that still doesn't explain the idle.

Is there something that could be intermitantly failing that would cause maybe, not enough power, to run the engine & maybe causes the water pump to not circulate the coolant properly?

Maybe my fans failed and arent aiding in cooling properly?

It's hard to tell if both problems are caused by the same thing, or two different things that are in relation to eachother. Any input will help.

I can't check my tune right now cause I don't have a working laptop but my tune is basically stock, when I went back to a stock tune I don't think I fudged anything up that would effect the idle. My file was identical when compared to the stock file, other than injector constant for my SS injectors.





Edited 1 time(s). Last edited Monday, May 10, 2010 8:23 AM

My rpms would pulse and at the same time my temp guage would normally drop and raise back up. For me changing plugs and wires seemed to fix the pulsing and then I changed the ECT sensorand my temp guage has acted fine since

My plugs are brand new and gapped properly so those should be fine.. I changed the wires when I turbo'd it at about 50k miles (it has 59k now)... so unless the turbo/turbo heat strained my wires they should be ok I would imagine. Might be worth changing though.. I don't get any misfires or anything. Even while driving while hot the car drives smooth, it just can't idle for @!#$. It's as if it's being commanded to idle low at those heat ranges. I know the stock tune changes idle slightly varying on temp, but I don't know why my car wants to change it so drasticly.

There could be air lock in your cooling system that needs to be bled out, could try another radiator cap also. The ecm will sense the overheating then may send more or less fuel in reaction causing rough idle, that could explain it's perfect idle at 195.

Bump - With picture

I have burped the coolant system and got a teeny bit of air out but this effected nothing.

As posted in another thread, compression test revealed 180's across the board, so deff not a HG issue..

Even once I stop the overheating, anyone have any other ideas as to what would cause the idle to fluctuate so dramatically to the point it stalls itself out?

Soon to be replacing thermostat, possibly waterpump, complete coolant flush, and possibly replacing my cooling fan as well.. seems like it might be being tempermental... doesn't really seem like its entirely the cause, cause driving on the highway doesn't cool the car off at all, and if the fan was the only thing letting it heat up, you would think that driving on the highway would simulate the same thing.. but my fan doesnt seem to want to kick on all the time. Idk.




Edited 1 time(s). Last edited Thursday, June 10, 2010 7:08 AM

Attachments

0407101259-00.JPG (247k)

Bump again - issue still present.

Here's the funny thing... it seems to be a little better since I swapped bumpers. There must be better airflow with the stock bumper versus the RK Sunfighter. Anyways, now, as long as Im driving consistantly, without stopping, it doesn't overheat at all and going onto the highway or on a road where I can cruise, if it had been just overheating, it cools it off fine. It still drives fine from the cold start up, for atleast 15 minutes of driving or so before It might start stumbling, in traffic specifically.

I've driven it an hour away on the hwy and it didn't go a hair over the 195 mark, until I got off the hwy, lol.

I did notice once, when I was working on it (turned the car on to prevent battery from draining too much from radio) it had JUST started to heat up and stumble, and the fan kicked on and cooled it right off.... lil bit later, it started to stumble and heat up and the fan never came on and it just caused it to run rougher and rougher, as it does.

So that leads me to my question. When a cooling fan/motor goes bad, will it work intermitantly?.. generally speaking, only for the first 15 minutes (give or take) of the car being driven, from a cold start up. Could the motor be heating up and then it gives up until it has sufficient time to cool off? Or do they generally just up and go bad. I don't want to make unnecsary purchases like I already have with an unneeded head gasket and head studs. lol.


Edited 2 time(s). Last edited Wednesday, August 04, 2010 7:09 AM

Now I don't really consider it a "problem" but my car gets right near where your gauge is reading in the pic, and it will idle rougher and rougher (more and more vibes) then the fan kicks on and all is fine. I could see the fan not kicking on causing most of what you're describing.....
I don't know much about cooling fans, the only ones I have seen fail, seized up and would smoke/blow fuses if they didn't/couldn't run.

That temp is fine and i think your cam is enhancing a common 2200 quark.


I <3 JGM
I think bigfoot is blurry,
that's the problem. It's not the photographer's fault. Bigfoot is blurry. And that's extra
scary to me. There's a large, out-of-focus monster, roaming the countryside.
"Run! He's fuzzy!" "Get outta here!"

In Loving Memory of Phil Martin December 14 2005

Thanks for your input Richard K. I wouldn't consider it a problem either, but my idle drops down lower and lower, idling rougher and rougher (cause it's purely trying to stay running while idling so low) but then it starts to stall out, so Ill be in traffic and I have to keep my revs up or it will just stall (sitting in neutral) or turn my car on after a quick stop, and try to back out of a parking space and the car will stall or try to stall.

Notice in that picture, where my RPMs are at, when it's at that temperature. At the 195 degree mark, the idle is nice and smooth at about 900 RPMs.

Jeffie - That's possible, and something I've considered and might just be the case... however as long as the fan kicks on it keeps it in a nice range, but it seems the fan isn't kicking on 90% of the time. So if it was the cam id imagine it'd be a more consistant problem as well.. Also, when it's idling and sitting at that temperature, the fan is completely stationary. I just wasnt sure if they'd work intermittantly or if it was a bad fan if it would just seize up and not work at all.

I wish my laptop screen would work so I could run HPT and set my fan settings to come on at 200 and just see if that fixes it.



Edited 1 time(s). Last edited Friday, August 06, 2010 8:04 AM