Ok, it's only happened the last two times driving her but here are the symptoms...

1. After the engine is at operating temp...AFR runs very rich (12's-11's) as soon as I touch the throttle from idle to cruise.

2. Idle is rough.

3. Vacuum and fuel pressures are normal.

4. After driving a few more miles, AFR and idle goes back to normal.

Not sure what would cause an intermittent rich condition??

 

What are u using to measure it ?

 

Wideband O2

 

Leaky diaphragm on a regulator or dampner? MAF starting to go out?

 

Yes figured that as you gave out numbers, some r more unstable and also tend to flux a bit. I'm using an Innovate LC-1 w/ digital read out.

I'm guessing that yours was working correctly and this is a new issue, so yep what AO said, as something is over reacting.

 

Darien-

Changed anything recently? Is this condition new?

A wimpy connection to either of the temp-II channels would do it. Generally, fuel pressure issues don't come and go, and the LH box compensates for minor changes while you are in closed-loop mode anyway. The temp-II sensor may be telling the controllers that the engine is still cold, and it is purposefully enriching the mixture some based on that false signal. The sensors themselves are pretty durable, but the ground connection between the switch body and the water manifold is critical, the ground between the water manifold and the block and on to the chassis just as critical, and of course the wiring and connections from the business end of the sensor to the two brains is important too. I know that your engine-bay wiring is immaculate, so 'd start with the easy step of removing the sensor and buffing up all the metal there where it hits the water bridge. An ohm meter check between the water bridge and chassis might be a good idea too. A little resistance will wreak havoc on lots of things.

 

It is caused by too much HP. I recommend you de-tune to around 400 rwhp...

 

Thanks guys...

Andrew, my first thought was the FPR but when the diaphram failed before, it was hard failure...Bill reminded me that I'd see a Lean condition if the MAF fails.

Bob haven't changed anything...I'll check out the sensor.

Shane, glad you're still kicking.

Damn intermittent problems are always the worst to t-shoot

 

Short in the WOT switch signal? would cause a rough idle, and running on the WOT map would cause a rich cruise condition as you would be open loop.

 

Hey Stranger ! Hows things going on the right coast? Not to jack your thread, but some of us are going over to the Third Coast gathering in Nov. Why dont you run over and meet us..

 

I thought about that too...I'll check it along with the MAF and Temp sensor