SD to MAF conversion

[ncontt]

well I sold a guy a computer to do a speed density to MAF swap on his 88 Tbird (already has the HO swap), at any rate, This thing is about to drive me crazy and I want it out of my yard/driveway!

He got the IST http://www.mass-air.com/Products.htm mass air conversion and we followed directions to the TEE, Now car will not start and STAY running, it will turn over and "start", then just shut off. Double/triple/quadruple checked wiring and no dice yet...IST's "tech" support while answering quite quickly was no help..

Fuel pressure is LOW (imo) at around 24lbs as measured on the rail with a gauge.

You can get it to stay "running" (and I use that term loosely) by feathering the throttle but there is no decent idle and it certainly won't run on it's own.

The computer came out of my fairmont (a9p) and is known to be good...

and ideas or things to check that maybe I haven't thought of would be GREATLY appreciated!!!! I'd be willing to give a "reward" for proper tech support too.....:chug:

[coupe]

Had a local guy with a similar issue (his first MAF conversion). I do remember it was something with the wiring... a pin was either mis-labelled on the instructions, or in the wiring schematic... can't remember for sure.

Also, that fuel pressure is awefully low. It's not helping your issue. Fuel pump?

[QWKSNKE]

what wiring harness is in the t-bird? OEM or Mustang?

[ncontt]

Ya I agree, FP should be in the high 30's if I'm not mistaken? :shrug: AFAIK it is the OEM wiring...I got volunteered to help this guy out on this thing and now it has me about ready to roll it on down to my burn pile!!! I was thinking it was something wiring related too...but I'll be damned if I can figure it out...there is so much crap that is cobbled together it's not even funny. And this guy isn't that mechanical, so 1/2 the stuff I don't know what he's done to it or a previous owner has done.....FML....

Any and all suggestions are MORE THAN WELCOMED! :chug:

[ncontt]

At first I may have thought that it was the injector wiring harness (batch fire/bank fire or whatever it is) or the wrong firing order (as the instructions ASSume the HO firing order) but a quick check AFFIRMED that is in fact the HO firing order....

[EHardy1971]

May be a wrong pinout like Coupe said. Lemme find the instructions where I did mine and see what it says.

[ncontt]

he got another FPR for it and I'm going to get that one once I get my head above water here after Easter....One of the pins or the instructions has to be mislabled or something because I have checked, checked, checked and rechecked at least 5-6 times to make sure I followed the directions....so IDK :shrug:

[ncontt]

well it idles now....while the upper intake was off to replace the FPR, I see an empty plug with nothing plugged into it....search around and Lo and behold...it's for the O2 sensors...WTF?!?!, plug that in, checked the plugs and he's got some crappy autolite platinums (just never had good luck with platinums) that we swapped out, put another cap/rotor on it and replaced the meter with another meter I had laying around, also swapped his O2's with some I had laying around AND put two new terminal ends on the battery cables and now it's backfiring out the exhaust...

Out the exhaust means rich right? Backfiring through intake is lean?

Also, fuel pressure is still around 25#s at idle with vac. ATTACHED, with vac line OFF it goes up to about 38#'s, does this sound OK? I have had my fill of this thing and just want it out of my sight...LOL

[coupe]

Still a bit low on FP, but its not the problem. Really sounds like a faulty MAF is the problem...that will really jack up the timing, which makes it backfire.

[ncontt]

funny you should mention the MAF, we took out the one I had originally put in there and put another "stock" one (this one had the screen in it), it "sounded" better as soon as we started it, but still backfires out the exhaust.

This car is so cobbled together! It has some kind of longtubes on it, and the 02's are down close by the collectors towards the bottom. I also forgot to mention he put a new fuel filter on it too, he "claims" it has a newish fuel pump on it (put a new one in but it's been some time ago, car runs off and on for a couple of months at a time then he decides to do something to it and it's down for a time...off and on..LOL)

Just about at my wit's end with this raggedy ass car...haha (prayers kindly accepted, divine intervention would be great!)

[/vent]

[QWKSNKE]

Have you double checked for crossed up plug wires?

[ncontt]

yes, double checked plug wires, installed new plugs, cap/rotor. I may swap injector harnesses and see if that helps (suggestion from another buddy)

[waypastcrazy]

Is this an all stock and untouched engine mechanically?
Was it running absolutely fine before the MA swap?
I would get a vac reading and a cylinder pressure test just to see what shape the engine is in.LoL jmo

[waypastcrazy]

Just sayn make sure its healthy because leaky gasket between cylinders
Tight valves
Bent pushrods
Vac leak etc can cause some of your symptoms.

[ncontt]

Is this an all stock and untouched engine mechanically?
Was it running absolutely fine before the MA swap?
I would get a vac reading and a cylinder pressure test just to see what shape the engine is in.LoL jmo

yes basically stock (think it may have a cam in it...:shrug:) It was running but not well (certainly the O2's not being hooked up did not help) But I will try the vac and cylinder pressure test too...

[ncontt]

pretty sure there are not any vac leaks but not 100% sure on that one...