HELP....codes 172 / 136 flex fuel control

miljeep66

Registered User
:mad: I have a 1993 Cougar XR7, 3.8L,Auto, completely stock, car had blown engine when i got it, I swaped in another 3.8L and it has ran fine for the last 6 months, now it falls on its face within 2-3 seconds of acceleration after stop, I have changed fuel filter, fuel pressure is 29-30 at idle, 39-40 with regulator vac disconnected, under acceleration fuel pressure never drops below 25 lbs, a friend thinks my cats are clogged, I have been diagnosing these codes useing mitchell on demand5, i know the oil and fuel are not contaminated, the only codes that i can pull are 172 and 136, it passes 111, car runs at 17-19 degrees spark adv. and retards to 11-13 degrees when it falls on face, HELP, Im allmost outta the cougar bussiness:mad: :confused: :mad:
 
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ok birds, i checked the fuse, its good, went back over all the vac connections and they all seem ok, and all the engine to frame grounds are good...........:confused: .....now what???
 
I would check to make sure the air filter is not clogged, and check the ground that comes off of the ground cable at the battery and mounts to the radiator support.
 
Is it possible that the first engine that blew took out the o2 (lambda) sensors? I know with a blown HG that it often takes out the O2's and the Cats.
 
The original motor didnt have blown head gaskets, it came apart in the bottom, i have no codes for 02 sensors, and their seems to be good flow thru the exhaust system, Birds, I checked all the grounds, batt to core support, frame to engine, etc etc, and I went back over the vac system and can find no air leaks, and i checked the air filter and air box for restrictions, and found none, this car is driving me nuts, I have never had one stump me as bad as this one has, it wouldnt bother me so much, but its mine, I own it, my Hemi Dodge costs to much to drive right now.....HelPPPPPPPPPPP:mad:
 
Do you have another MAF to swap out? Or try driving it without it hooked up (the MAF). It will run like crap to begin with, may even need to be power braked, but it should clear up.
 
I think at full throttle, your fuel pressure should be somewhere over 50psi. If it's dropping to the 20's under acceleration, it sounds like the problem might be fuel delivery (bad pump, bad electrical connection to the pump, bad regulator, etc.)
 
The fuel pressure under acceleration does seem a bit low. I would try driving the car with fuel pressure gauge attached to the car and see what it does. It should stay fairly steady, if it is very erratic I would suspect fuel pump or filter. I have never seen a fuel problem throw both of those codes, but I suppose it is possible.
 
If he's getting lean codes, it's going to be pump, filter, regulator, injector (or harness), or O2 sensors. I can't think of any other reasons for the car to lean out.
 
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