The story: I was DD'ing it for a while, and I had noticed that it started having a little miss here and there at Idle. Then it started getting worse, I thought it could be the plugs, so I checked them out and they seemed to be fine. I cleaned them up with a wire brush and it didn't change anything.

Continued driving it and it just kept getting worse, lean AFR's at cruise and at Idle causing hesitation and miss fires.

The one thing I can think of that could have adverse effects was that I premixed it a little heavy once about 12 oz to about 9-10 gallons. But I did go back and put in a few gallons after I had drove it a little bit. I also installed Solid Tranny mounts and it's kinda vibraty, maybe somthing rattled loose?

I took it out to a meet and I went out and tore up some backroads and it boosted great, but then it got even worse, serious lean/hesitation/missing and I was/am scared to boost it now.

Symptoms: Lean 14-15 AFR's (PLX Wideband), missing at idle & revs & cruise.

I just don't see/notice/smell/hear anything out of the ordinary. It seems to get worse as it warms up. The temps(coolant, AFM, AIT) seem to read normal & I can't find any vacuum leaks.

I am using S4 NA 680cc Primaries (not sure how old they are) and 1000cc RC Secondaries.
I have replaced the fuel filter and plugs. No errors per the RTEK. The n326 AFM has been replaced with a N318 AFM(although I had the problem before swapping AFMs). TPS checks out per the RTEK.

Here is a video, it runs ok when I first fire it up for a little bit, then goes to crap after it warms up a little. It seems to have ok AFR's when I rev it sometimes, other times it's sluggish and lean.

<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid272.photobucket.co m%2Falbums%2Fjj169%2Fnick_d_123%2FP1018284.mp4">

I have had suggestions for the ECU ground which I will be checking soon (gotta pull the carpet and the ecu cover), and vacuum leaks (intake manifold gaskets). I have checked the variable resistor setting and if I turn it up it seems to get worse (set a 0 like it has been for a while & it has ran great). I will check the fuel maps(again it has been running great and no changes were made to the RTEK) and see if I crank up the correction if I can get it richer.

Any and all suggestions/information is greatly appreciated.

 

Try cleaning the connection to your AFM, a lot of times that one piece wire clip that holds the harness to the AFM doesn't always make a great connection. Let the car idle then move it around and see if the car responds to it, if it does then that may be a source of the problem.

 

I did check the AFM connection and lightly wirebrushed the contacts on the plug and socket. But I will check it out again.

 

Maybe this one will work...


Not much luck searching the forums...

Fuel pump is a rewired(bypassed fuel pump resistor) ebay walbro, but seems to have plenty of pressure would assume it has to be flowing plenty for idle.

Emissions stuff is all removed. The symptoms started, and then got gradually worse... Maybe a clogged/gunked primary injector?

Will try and check for vacuum leaks(intake mani gaskets) with propane tonight.

 

Thanks for All the Help everyone!~ Turns out there was a bolt or something in the back of the SSQV BOV and it is gone, creating a vacuum leak...



Question is, do I just stuff a bolt in there or should I do a bolt with lock nut?

 

S4 n/a has 460cc injectors....