High Idle When Hot

[Hughes]

So on a hot day car runs about 195degrees with no problem. When I park it temp goes up "naturally" water isn't flowing anymore, but is hard to start, when it finally starts the idle surges to like 2000 rpm then drops and stalls, I have to feather the pedal to keep it going and after a minute or so its back to running normal. Is this normal for a highly modified naturally asperated 95gt. Well be here all day if u ask me what's in my car.

 

[toyman]

Are we to assume it's the stock ECU or has a tuning chip been installed? Have you pulled the DTCs (trouble codes and what are they)? Are you reading the actual temperature from an aftermarket gauge (195*F seems pretty specific)? And how high is high?

 

[Hughes]

Stock ecu, no codes, aftermarket gauge, high temp around 220 max. I know this isn't a bad temp the car just don't like being this hot.

 

[toyman]

I guess you need to define "highly modified" as it relates to the engine. There are limits to which the stock ECU can adjust for. No codes, not even the 111 pass? At what temperature do you see the rad fan coming if at all. Depending on the reference source the low fan comes on between 208 and 220*F and once on will stay on until the temperature cools to about 205*F.

 

[Hughes]

Your killing me, of course I got a pass code take that out of the conversation. My fan works perfect its aftermarket and its hardwired to run all the time when the ignition is on. Motor trickflow heads, trickflow upper and lower intake, comp cam, 6:1 roller rocker, scat crank, bored 60 over which causes a lot of heat, kieth black 10.5/1 compression pistons, msd ign, 24lb inj matching maf sensor, adjustable fpr, cold air intake, bbk 75mm throttle body, headers, x-pipe, pypes exhaust, no cats, no smog pump, no ac compressor. Think that about sums it up. stock ecu, fuel pressure about 40. 295hp 320tq to the wheels on dyno.

 

[toyman]

You would be surprised how many try to pull codes from the under dash port then say they have no codes or say the coolant temperature is 200* because the dash gauge it pointing to the R. You have the particulars, so unless you tell your audience what you have, they are at best wild guesses. How would we know about the fan if you hadn't mentioned it is hard wired. Is this something that just started or? Any parts recently changed? Trying to narrow down the possible causes.

 

[Noobz347]

I saw headers, high compression, and no mention of a HT starter or starter blanket.

Have there been any upgrades to the battery wiring or ground straps? More heat in the engine bay can affect these items as well.

When was the last time your AFR was checked? If you're running a little lean, that can account for some things as well (hot headers are hot).


That's all the spitballing I have for now. Maybe one of them will help.

 

[Hughes]

Ya sorry for being frustrated the car has always acted up during the summer months only, runs great the rest of the year because it stays below 185degrees. I have header wrap on the headers, stock starter it seems to crank just fine and no blanket on it. I just don't understand why it can't run normal from 200 degrees up to 220 sounds like normal operating temp for a v8. So I'm constantly trying to fine ways to get my operating temp as low as possible hense the aftermarket fan running all the time. A guy told me once that since my bore is 60 over my cylinder walls are too thin to dissipate the heat causing a hot engine. And the temps I'm giving are from a coolant hole on the lower intake I could be getting hotter spots somewhere else where it could be affecting sensors. Idono u got me.

 

[Noobz347]

Post a pic of the front of the car when you have the chance.

Do you still have the OEM air dam?

Also... Do your fans stay on for any time at all after the motor is shutdown? A delay timer could help quite a bit too. Keep those fans running while the headers cool and keep them from heat soaking the starter.

Either way.... I'd try replacing that starter. How old is it? Are you running long tube headers or shorties?

 

[Hughes]

Oh sorry in my original post I said it was hard to start when hot I should have been more specific, it turns over just fine it just won't fire I have to pump the gas pedal like its a carb and then when it fires the rmps jump up and down for about 5 sec till it cools down. I like the fan timmer idea I though of the myself once almost like a turbo timmer. Not sure about the air dam I'll have to check in the morning, but I'm definitely heat soaking something just not sure what, maybe the fuel is evaporating not sure.

 

[toyman]

I have to pump the gas pedal like its a carb and then when it fires the rmps jump up and down for about 5 sec till it cools down.

Pumping the gas pedal does a couple of things. Firstly, you move the TPS outside the expected idle start range. Secondly, if the TPS signal is WOT while cranking the ECU shuts off the injectors, as this is a "clear flood" signal. The engine should start without touching the gas pedal. Maintaining the idle is another matter. Has the coil been replaced and are you using an ignition box? These are often high temperature sensitive components.

 

[Hughes]

Ya I use msd digital 6 plus ignition. Though about getting rid of it doesn't seem like r cars need them. I like the rev limiter thou.