Official Vauxhall/Opel/Holden Calibra Technical Community

Calibra Modifications & Calibra Maintenance => Technical Troubleshooting & Servicing => Topic started by: Jacobpm1234 on October 01, 2019, 04:45:01 AM

Title: C20LET idle problems and more
Post by: Jacobpm1234 on October 01, 2019, 04:45:01 AM
I own a C20LET and I have some problems with it.:

1. On cold starts the engine seems to run fine in idle but stutters a lot in 1st gear.

2. Cold start: I can drive for 1 minute and then the idle is really rough, going from 1000 rpm to 1500 rpm back to 1000 rpm and fighting for its life to stay on, almost dies (but never has died on idle).

3. When downshifting and then putting the clutch back down the engine sometimes just dies.

4. When accelerating there is a loud whistle noise coming from the engine, sound like a turbo leak.

I have checked for turbo leaks everywhere, but can't find any. I have now ordered new gaskets for the intake manifold and the throttle housing, maybe it loses pressure to the blow-off valve there. The previous owner adjusted the turbo to 1.5 bar and got a chip, but I think it's a pretty bad one. Looking at installing a completely new racing ECU and getting it proberly tuned, maybe this can fix it. Well, my actual question was if anyone on here knows about anything I should check for that can prevent this from happening as I'm now looking at thousand pounds fixes, which I was hoping it not to be.
Title: Re: C20LET idle problems and more
Post by: TURBOHEAD on October 01, 2019, 11:43:19 AM

My advice from the problems you are experiencing is to remove the "Idle Control Valve" from under the inlet manifold and give it a good clean with Carb Cleaner.

From time to time these get gummed up......causing it to stick and work poorly.   There is a thread on Cc on how to clean it.

Also there is a thread on re locating the I.C.V so it is easier to access......well worth doing.      After cleaning etc check the wiring harness for breaks.....damage etc....and fix if needed.

Fineally Vacume leaks will produce a whistling sound  as you suspect .....but also the turbo can also whistle if worn etc and the best way forward on checking is with a vacume gauge or sqiuirting soapy water from a plastic bottle and watch for any bubbles.  Try cleaning it first before anything I am sure your engine will run better.
Title: Re: C20LET idle problems and more
Post by: CalibraTurbo666 on October 09, 2019, 12:15:13 PM
Check the one way valve in small rear cam cover tube, they jam open or break inside and whistle under acceleration , also cause the problems you list when they pressurise the cam cover.
Is the hot start valve still plummed in, best to do away with its tubes but leave electric plugged in, can also cause some of these problems
Title: Re: C20LET idle problems and more
Post by: Jacobpm1234 on November 27, 2019, 08:31:02 AM
I did try and clean the idle control valve, nothing happened. I also tried removing the vacuum hoses to it and leave the electric wire to it in, but still, nothing happened. I've heard from a mate that the temperature sensor could cause these issues as well because the ECU thinks the engine is cold when it's warm giving bad mpg and bad idle etc. All the vacuum hoses seem good, checked them twice, but will again when I get the car out of the garage in April.