L67 Idle rises to 1800rpm for 30 seconds then returns to normal every minute?

[L67 Calais]

Hi all,

My VS has been playing silly buggers on me the last few days and when stationary the idle will sit on 800rpm for about 30 seconds, Then it will go up to 1800rpm for about 30 seconds and keeps going round over and over.

I am currently doing live tuning with The1 and he can see that the TPS is putting out 700mv @ 0% Throttle with spikes of 750mv.

This voltage increase is consistent throughout the rev range too, So it is fudging with my tuning figures.

Normal TPS voltage @ 0% throttle should be 500mv.

I have replaced it with a known good second hand unit & a brand new one but it is still the same, If not slightly worse.

So, If the TPS voltage is out, But replacing the TPS does nothing, Where does that leave me?

Also i have cleaned around the butterfly with some TB cleaner and a toothbrush so i'm pretty sure it's closing completely.

Thought i should mention that while the revs are up at 1800, All of my dash lights flicker...???

Thoughts?

[L67 Calais]

Anyone????

[L67 Calais]

Nevermind, It was the Idle Stop Screw. Seems it got knocked when i removed the TB.

[L67 Calais]

Hmmm maybe not completely fixed........... Now it only does it when the thermokicks in??????? IAC Maybe???

[TI3VOM]

I would say clean out the IAC and see how that goes, as it's very easy to do.

[L67 Calais]

Yep, Gonna do it now. Post up soon how it went

[L67 Calais]

Ok Cleaned it all spotless (Man it was gummed up)

Still the same????

Revs go up to 1800 when the thermo kicks in and stay there till its off.

TPS voltage is at .53 and the IAC Steps are 32 without thermo, They then step to 110 with thermo on and stay there until it's off......?

Baffled

[L67 Calais]

Any ideas.....?

[aussie4life11]

fuel pump maybe? or altenator?

[L67 Calais]

fuel pump maybe? or altenator?

Nah, But cheers anyway.

[creastyle]

I know you said you checked the throttle screw, but I had this same issue. Its like the IAC is trying to reset the idle speed. What I did was back the screw right off so the IAC does all the work. This worked for me anyway.......

Hope it helps.....

[Brett_jjj]

If the TPS voltage is flunctuating at idle when the TPS percentage is reading 0 ,and the TPS has been replaced, then Id be trying another ECU in the vehicle just to be 100% sure the original one is not faulty. A faulty ECU is pretty rare, but not totally unheard of.

[The1]

tps issue is fixed the stop screw needed adjustment, iac was maxed out and couldnt keep idle down along with tps reading high, now sits on 500mv 0% and sending a tune down to fix thermo fan high idle, fixed an error. so wel see next week if its all fixed.

[The1]

also sent another pcm down to test as there is a qdm2 fault

[scvs6]

Clean the MAF Sensor, mine was doing the same thing, cleaned it and it runs perfect now.