v8power4life1

Hi, I did a 4 valve swap to my 98 gt. I used the gt's wiring and pcm. Everything runs great for the most part. I did this swap about 3 months ago. I have a problem that is driving me nuts. Here is the problem, when I decelerate for a red light or stop sign, the motor will randomly stall. So from say 25mph and under. The crappy part about it is when it does i loose power brakes and steering! I didnt do this before the swap. The motor is out of a 93 lincoln mark 8 with 60k miles. I did a 98 cobra intake swap with the deleted runner control. I deleted the egr as well. I put on a new idle control valve and it helped smooth out my idle but i still get the random stall. Do you guys have any idea what this could be? Also my speedometer stopped working about 6 months before the swap and still doesnt work. I know what i need there to fix it but im just throwing that out there as a reason my car maybe stalling.

Thx

Jay

BraMas

If it where me I would by Hand held tuner and get some one to e-mail you a canned tune. Tell them what you have and what you have done and they will get allot closer than you are now. Your fuel trims are for the NPI GT not a 4V so you are leaving some power on the table also
I got mine from these guys and they worked with me until it was right.
http://www.morepowertuning.com/
Some people are going to jump on and say Canned tunes are junk but for a almost stock car they are just fine

JC316

What type of MAF did you use?

WhiteFoxGT

Please excuse my ignorance (been drinking) but I want to say you need the "decay rate" adjusted.

Has something to do with the pcm hanging the RPMs during shifts and pushing the clutch in to ease smooth shifting. Possibly this could be causing the stall

v8power4life1

i forgot to talk about two other topics. One 2 of my 4 O2 sensors r either bad or not reading right for the codes i scanned. I put bbk long tube headers on my motor and needed to extend the wires to the O2's. Sec thing is really weird, when the car stalls, and i start it back up, it pulls like a mother Fer. When i say this i mean like 30 to 50 hp more and it revs a lot faster as well. I used a sniper tuner to bump timing and stuff like that but i think i need to changed a lot to get it closer to running right. I used the stock maf from my gt and the one from the lincoln and both did the stall thing. Right now i have the stock lincoln maf cause it was with that motor.

JC316

Use your GT MAF since the computer is tuned for it. I think I know what your problem is though, the early Mark VIII engine use 24lbs fuel injectors as compared to the 19lbs injectors that the GT is tuned for. Didn't affect me since the later Mark's used 19lbs injectors just like the GT. Also, get those O2 sensors fixed.

masterofthepuppets99

could also be your idle settings in the computer. my my 2v used to stall on deceleration at moderately slow speeds like you describe. i bought a tuner and bumped up my idle to 800 rpms and solved my problem

ct_white_stang

And you did no tuning, even for the long tubes?

v8power4life1

i did tune it for long tubes and off road h pipe. I bumped timing a little and adjusted for 24lb injectors. I have been trying to do process of elimination. Today im going to try and retune it and adjust fuel and idle and see if it helps.

ct_white_stang

What tuner do you have? I would assume you have a wideband too?