Car backfiring and hesitant at the top end

[stevesLX]

For a week now my car has been backfiring thru the exhaust and the intake anytime you put it under a load whether its a light load or heavy load once you reach 4000 RPM's and higher. It only seems to do this from 3rd gear on up. Every once in a while it will do it in 2nd but very seldom. The other day when I went to drive it home after work, it started backfiring real bad from 2 nd gear on up no matter what kinda load I put on it. You can rev it up all you want sitting still and it wont do nothing. You actually have to put it under a load. So within the last day I have replace the cap and rotor, fuel filter, control module, plug wires, checked my plug gap, adjustable fuel pressure regulator, I put my factory coil back in. All this and no changes at all. I tried to pull codes and nothing relating to what its doing. I also sprayed carb cleaner all around my manifold and the idle didn't change so I dont think its leaking there. I also disconnected my O2 harness and drove the car and that didn't fix it either. Earlier tonight I cam to almost a complete stop, I was rolling in 2nd gear about 20-25 MPH I had the clutch into the floor I was coming up on a red light and the light turned green and I let the clutch out and went to give it alot of gas and the car did nothing and then within a second it reved and Boom loud backfire and a big cloud of black smoke out the exhaust. The car runs alright if you gradually bring it up to speed but anything more that that and it starts banging out. I need help guys I dont know what else to do. I also performed a cylinder balance test and it was fine.

 

[bill302]

have you checked for vacuum leaks?

 

[stevesLX]

Yes I have and nothing

 

[bill302]

what codes did you get, have you cleaned your maf sensor?

 

[stevesLX]

Yes I cleaned my MAF and the only code I got was a 12 idle speed control. I went ahead and dropped the fuel tank just now and the strainer was a little dirty but nothing that looked super bad to me. I put a spare computer in also and drove it and it still acted up. The backfire is relly muffled when it happens and the car just bucks almost like its running out of gas.

 

[bagnonu91]

the same exact this is happening with my 88LX. The hesitation, crappy idle, and loud shotgun backfiring, have u figured out what it was? please if you did i need to know this is driving me crazy. I replaced all the same stuff you did and im still having the problems.

 

[n2o-89fox]

Mine did this but it was a couple of things that made it happen. One was my computer was shot the other one was the bap sensor. I had a couple of codes for emissions but had that taken of in the tune. I actually caught it on the dyno going threw its sudders and to my surprise it wasnt leaning out like everyone suggested but was running rich at idle would show 12.5 way to rich. My tuner said it was trying to go into limp mode (stupid mode). With the new computer and bap sensor it was back to normal.

 

[Fast63]

You didn't mention that you checked the timing, so did you do that? Maybe your distributor is loose and worked it's way to really retarded timing. Easy thing to check.

 

[ttop88]

I know the OP didnt bring this back from the dead but It sounds like you have a dead spot in your TPS. I would also put a new pickup in the dizzy. It is a cheap part that will have you pulling your hair out when it gets weak.