Hi

Fast idle from cold 1200+ but drops to 800 then picks back up does this starting at about 25 second intervals but as it warms up it drops more frequently own to every 7 seconds then goes back up
no codes set
customer says some one looked a few day earlier an the was a can code which he said was irrelavant and he wiped it
once driving seems tpo be ok but did not have much time to look as he was going away he did a 400 hunred mile journey an says was ok apart from the idle
i had a quick look at live data and i did not get chance to look for long but i did notice what i think was strange (not an expert ) but trying to learn
was that the STFT AT IDLE WAS 48 WHICH DID FALL AS I INCREASE THE RPM SLOWLY UP TO 2500 WHERE IF LEVELED AT ABOUT 12
LTFT HOWER THIS IS THE PART I DONNT UNDER STAND REMAINED AT ZERO
I DID NOT HAVE TIME TO DO ANY THING ELSE untill he returns next week
i read some where that some ecus will if they see a LTFT value maxed out for a prolonged period set the figure at zero
the only reason i ask is i know that this vehicle ha fuel pressure problems last year an both pumps where changed so was wondering if maybe ecu had seen low pressure for an extended period an reset LTFT value at zero
just a thought and a bit of history i realise cannt do much till i get it back just wondered did anyone have any thoughts thanks brian

they do suffer with timing chain problems it could have stretched or some times jump giving low vacuum at idle

hi thanks for that Paul as i said did not have a good look at the car due to time but hope to this week also not an expert but my main reason for the early post was the fact that i had high STFT and Zero LTFT which i would not expect and was trying to understand I understand that a vacum leak at idle would give a high STFT but i would have expected to see a high LTFT but perhaps im wrong

any way thanks for the reply will keep you informed when i get the car back and then post some more results may be get a better idea or maybe others could sujest what other tests i need to do brian

Hi Brian,

My initial approach to this would be a DTC check, exhaust emissions check (suspect you will see a fluctuating 02 reading) and then conduct a check for an inlet manifold leak. This can be done with a "sniff" test if you don't have a smoke machine thingy. Might be worth to clean out the throttle body if its easily accessible.

Regards

Pete M

un-resolved car has not returned it will in a few weeks so i will re posr then