Fox body going into limp mode?

[Bonestk87]

I have a 90 Gt, 302/ 5 spd..

Stock long block with these mods:
E cam
Roller rockers
Rpm intake
70mm throttle body
24 lb injectors
C&L mass air
BBK cold air
BBK longtubes
BBK O/R H-pipe
Spintech's dumped
Msd 6AL
MSD pro billet efi dist.
Blaster Tfi coil
Ford Racing Wires

Here's the deal. It will run fine sometimes for a 30mins or sometimes for 2 mins then it acts like the ecm is yanking the hell out of the timing. I can kill the car and start it back up and the issue is gone until it does it again. It will spit and sputter and sometimes small hiccup back through the throttle body when you try to rev it up. It also acts like its dumping a shit ton of fuel in it when it's messing up. When it goes into what I'm calling "limp mode" the entire sound of the car changes. It's like the timing goes retard 30 degrees

The only codes pulling up are Emissions thats it.

I have swapped out dist with a good stock one (timing set at 12 degrees), replaced the coil and by-passed the MSD box, replaced the ect sensor with a new one from Ford, swapped out the mass air with a good one, replaced the ecm with 2 good ones and still no luck. Fuel pressure is set at 34 lbs and I have moved it up to 38 and had it back down to 32 with no changes. I have monitored the fuel pressure while the car goes nuts and nothing changes. Hell I even swapped out the plugs with a new set of stock Motorcraft and another new set of Ford racing wires with no luck.

I have had the break out box on this and couldn't really find anything out of spec.

Good grounds all over the place!


I'm truly stumped on this one.

ANY IDEAS?????

Thanks,
Jeremy

[Slow Five-O]

Did you recently clean out the air filter? Sometimes if it's not dry and you put it back together it can mess up the MAF.

[projectPONY]

O2 sensors. Willing to put $ on it.


sent from an htc EVO, the iCrap killer.

[89gt306]

Yeah man plz post when you figure out your issue, I have the exact same problem with similar mods. Tia

[Bonestk87]

Air filter is good.

Bought 2 new O2's today. I will get them in tonight and let yall know.

I will keep ya posted.

Thanks,
Jeremy

[89gt306]

U get a chance to throw them O2's at your car yet?

[Bonestk87]

Not yet. Maybe in the morning.

[Diabolic]

so you say you checked the fp, but what is the fp under load when it's acting up? Could be a weak pump, or a pump that's getting hot. Could be an ECT sensor that is out of range as well.

[Bonestk87]

Fuel Pressure does not drop off under a load. I put a brand new ect sensor from ford on it and checked the wires with the break out box. I'm going out to put the O2's in it now.

Thank y'all!

[Diabolic]

Does it feel weak under wot? If yes then the oxygen sensors won't fix it. If it's only under part throttle then you are on to something with the oxygen sensors. Should throw a KOER code for lean in the bank.

[scootro]

yea i'm curious, too

[Bonestk87]

When it goes into "limp mode" it runs like shit through out the entire rpm range. Popping, missing etc. It really does sound like I just grabbed the Distributor and retarded the shit out of the timing. I do not try to push the motor when it does this. I have tried to rev the engine up to see if it will clear up and it does not. Engine gets that low tone like the timing is 30atdc. It has that barely running sound and idle gets low. It just won't run worth a shit. I just replaced the O2's and put around 10 miles on it and IT has not screwed up yet. That is the longest its gone in sometime without screwing up. I'm called for work so it will be a few days before I can really drive it for a while and see if that really solved the problem. So far projectPONY has nailed it. Thank ya!

[SEB]

When it goes into "limp mode" it runs like shit through out the entire rpm range. Popping, missing etc. It really does sound like I just grabbed the Distributor and retarded the shit out of the timing. I do not try to push the motor when it does this. I have tried to rev the engine up to see if it will clear up and it does not. Engine gets that low tone like the timing is 30atdc. It has that barely running sound and idle gets low. It just won't run worth a shit. I just replaced the O2's and put around 10 miles on it and IT has not screwed up yet. That is the longest its gone in sometime without screwing up. I'm called for work so it will be a few days before I can really drive it for a while and see if that really solved the problem. So far projectPONY has nailed it. Thank ya!

Good to hear you got it back up with good 02 Sensors

[projectPONY]

. :beer:??


sent from an htc EVO, the iCrap killer.

[89gt306]

Congrats man I ran the codes on mine and this is what I got
Koer test:21, 92, 33
Koeo test:67, 85
Memory:29, 33, 41, 91..