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        General >> OBD Advice >> Short term fuel trims.
        
(Message started by: twinturbo on Oct 14^th, 2006, 7:33pm)

Title: Short term fuel trims.
Post by twinturbo on Oct 14^th, 2006, 7:33pm

Right, still trying to get to the bottom of my lumpy idle..

I swapped over the MAF today for another one ( no history ) and the car ran exactly the same. If I desconect the maf the car pics up a bit but then still struggles.

I monitored the fule trims, and the STFT on Bank two was more often in the -% often hanging around -14% . It would rise above ZERO when the throttle was depressed.

Now is a negative % Week mixture or rich Mixture?

Bank 1 was generaly + but dipping ocasionaly negative.

TT

Title: Re: Short term fuel trims.
Post by Havinga on Oct 14^th, 2006, 11:06pm

Hi,
Firstly id have a good look for an air leak and disconect the EGR
spray carb cleaner round the inlet manifold, one joint at a time and see if the idle speed increases.
Check the vacuum tees and inlet o'rings are fav for leaks.
Check the vacuum, shoud read about 20-22 with a gauge.
I'd be tempted to ignore stft and watch the Long term trims and o2 sensors (pre cat) along with TPS and MaF.
What are they doing?
As i understand it if a trim shows neg, it's trying to lean the mixture off, Dont take my word for it I could be wrong!
Best of Luck.

Title: Re: Short term fuel trims.
Post by twinturbo on Oct 15^th, 2006, 8:28am

If I had a leak the mixture would be week so surely the trim woul be trying to enrich?

I do think I have a leav on the back passenger plenum joint ( the sleved one..

TT