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Will not idle - any advice?

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When my car gets normally hot (90c), there are times it will not idle.

Embarrashing at times when I'm in the traffic light. I have to press my brake pedal + my accelerator just to get to idle.

It will die if I don't rig it this way.

When its cold, there is no problem idling. I don't have CELL either.

Some said, could be my AIT, or my coolant temp. sensor and some said could be my idle valve.

My AIT is new.

Any thought?

Thank you

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I wonder why you have to be on the brake-pedal ?! Is there an hardened or loose hose-connection to the plenum chamber, causing an air leak with the brake assist-servo line? the hose does have several hose-clamps: one on the servo, one on the rear of the frame -heading to the top of the engine, and one on the plenum port.

But from my impression additional air would mean 'high idle' ? Instable idle on a hot engine -any problems with fuel-pressure ?!


to name the things if I see them, that's what I call integrity..


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Thanks people.

My problem is more of a low idle. It will not idle at all when very hot say (90c).

Never experience a hi-idle.

Anything below 90c, there is no problem or cold start in the morning or cruising.

I have problem at stop sign when hot weather. I have to press the brake + the accelerator in order to idle.

This low idle is not all the time though but very embarrashing. There is no CEL.

It will not hut to replace the idle valve (except spending money). I will try this first. Also, since I'm in the plenum area,

I'm contemplating to replace a better injectors. Any recommendation in aftermarket injectors? (just a bit more flow)

I have a red race ecu - intercooler & upgrade GTO transmission.

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do you really mean *brake* ..or just 'have to press the *clutch*' -as for the additional power needed to hold the engine on idle, if the gearbox shaft has to spin with the crank. So if your fuel-pressure is not stable under 'heat-soak' situations in the engine bay , I could imagine that the engine dies very easylie for every additional power needed on the crank [for example turning the steering wile engine is on low idle, and causing high loads on the pump if the wheels do not turn on a parket car... .]

Can you monitor what your fuel pumps are doing [add a fuel-pressure tester on the fuel port, turn it towards the window in your back ...and watch the needle dancing in traffic stopps..]


to name the things if I see them, that's what I call integrity..


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Thanks Gunther.

The road a bit stiff inclined (at the traffic light)one foot at the clutch and another in the brake + accelerator.

Otherwise, car will backup in inclined position.

I will try to find a way to monitor the fuel pump when hot. I don't know where I can view it.

You gave me a hint though, "heat soak".

Maybe the AIT is reading is very hot and the ECU will adjust.

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  • 3 weeks later...

After switching to the Red Race ECU on my car I had all sorts of idle issues. I am told the original mapping for learning idle was crude. (Perhaps since it was an early tune for racing and did not benefit from improvements along the way.) Anyway, I also replaced the idle valve a couple times. In fairness I had a crack in the EGR tube that I think was shortening the live of the valve through allowing excessive heat to build up under the plenum. I tried all the other options as well: clearing the memory and 'retraining idle' replacing temperature switches. Monitored duty cycle on my laptop etc etc... Stalling is very embarrassing. Theoretically, the cars should idle with the idle valve fully closed. Finally, I just went for the 'cheater' option and made a slight adjustment to that little set screw on the throttle body. This can be done without taking anything apart, but it is tricky to get at the jamnut and fit the right screwdriver. About 3/4 turns and the car has never stalled since. Basically, I needed the car to be able to run at a minimum of 650 rpm when the ECU has the idle valve fully closed. It is a cheater fix, but it worked.


Rod Wiggins


98 Esprit V8

Dynamic Racing Turbos

Water Injection

Factory Red ECU

3 bar MAP piggyback

Straight-through exhaust

TurboXS BOVs

Blitz I-color boost control + Wide-band AFR

Porsche/Getrag G50/52 Transmission (...coming soon someday)

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I wonder if your idle valve is a bit erratic. I suggest you get the engine up to temperature and, assuming it decides to idle. clamp the hose to the valve so it's not feeding any air to the engine and see if the idle speed drops. If the valve is sometimes sticking open and sometimes closing and your idle speed was set with the valve slightly open (or the engine not fully hot) then, when it does shut, the engine would stall.

Do you still have the base ECU and injectors to re-fit and see if that fixes the problem? If so, I would try them before spending money on parts.

S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE


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  • 1 month later...

I currently have the same problem, but it occurs at 85'C, suggest if possible you swap ecu with someone with the same ecu, just to confirm that its not the ecu, before you start disturbing and replacing parts.

mine has been identified as an ECU problem with the AIC driver

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