Just went on the first drive on my '87 Porsche 944 Turbo/951 LS1 swap. Things did not go well!

The car is just not runnign worth a damn. The wiring harness is aftermarket, so not much on the wiring to screw up (a few +/-'s), and i'm sure i got all those right. I've put new o2's in it, and replaced the MAF, both of which helped. Before it was running lean...now i'm getting pops out the exhaust which seem to indicate rich! The car really feels like it's running on 4 cylinders. Under a load (driving) the car just loads up at about 3000rpms and won't go any higher. The only code i was getting before was MAF low voltage, but with the new MAF i think it's cleared up.

My scanner shows basic data and so far there's been nothing out of the ordinary. My last guess was a vacuum leak, but now that it's popping out the exhaust i'm not sure it's even worth checking!

Off the top of my head, these are the only things strange: I don't have the VSS hooked up, and it's still enabled in the computer. The motor has a mild cam in it: 224/.565 lift, and is not tuned for it. I have no exhaust on the car right now, just some 3"-2.5" reducers with o2 bungs welded in (not sure if this could be affecting my o2 readings).

Any thoughts? Suggestions? Get my brain working again?

 

if the O2 are close to the end of the exhaust outlet the extra O2 will play havoc with the fuel trimming...driving untuned aint helping much either

 

Thanks for the response!
The o2 is about 1" from the tip of the exhaust, so i guess i'll start there! The cam is pretty mild, do you really think i'll need a tune before it's driveable?

 

defintley need to move the O2 sensors...it wont be perfect without a tune but that small cam should be pretty driveable untuned...

 

Yeah definately move the 02s but also you can unplug the MAF if you think thats the problem. I ran for a couple weeks each with my MAF unhooked in my two LT1s (one fans wouldnt turn on so i just put the engine in limp mode to enable the fans, other was waiting on tune for MAF). I had the same thing happen to the lincoln town car limo i used to own. It wouldnt rev above 2500rpm idled perfect but wouldnt stumble and miss horribly. Unplugged the MAF idled a little rougher cold but ran perfect. Just use some electric parts cleaner to clean the MAF. They make MAF cleaner but its the same thing. Just spray it down and see if that helps too.

 

My mechanic friend said you need at least a foot of exhaust after your o2 in order to get a good reading, I'd definately start there as well.