Hesitation/stumbling followed by backfire. need help

[SaleenStang94]

I dont know why but my car has had this problem for a while now and cant figure it out. under light acceleration the car (sometimes, idk why not all the time) will hesitate/stumble for a few sec's then backfire (usally just one small pop). but as soon as the car backfires it will takeoff like it was building pressure then the backfire was its releif. i thought it was my intake leak or bad plugs but nope. the car was dyno tuned and it cont. to do this on the way home..therefore tuning didnt solve the issue. could this be related to a bad tps? i have no problems at full throttle it only backfires/ hesistates under light accel. thanks for ur help!

 

[Midnight_Cobra]

Clean your MAF, mine did the same thing. Mine would go to about 3k then pop, burst in acceleration, then go up to 4.5k then do it again. I cleaned the MAF, because the wires were pitch black, it seriously felt I gain 60hp. It take about 20 minutes to do if you have the right tools.

Your need some security torx bits. The little ninja star things that are sort of like alan wrenches LOL, and they have a hole in them. You will know what I am talking about when you see the screw on the MAF.

 

[Anrev]

Yeah mine did the same thing when cold. Cleaning the MAF worked for me.

 

[SaleenStang94]

thanks for the tip, il try that first but if it doesnt work i guess the tps sensor needs to be replaced.

 

[Midnight_Cobra]

Don't replace it without testing it. With the key in the 'on' position, take the connection off the TPS sensor and put a volt o meter on the actual sensor, not the connection, and at idle it should read .97-.99, and WOT is close to 5 volts.

 

[SaleenStang94]

Don't replace it without testing it. With the key in the 'on' position, take the connection off the TPS sensor and put a volt o meter on the actual sensor, not the connection, and at idle it should read .97-.99, and WOT is close to 5 volts.

i actually just did this about 3 weeks ago b/c i had a bad julting problem and it was at 1.3 so i brought it down to .98 by wallowing out the holes. i did just read that one should replace the tps and never wallow the holes to get the correct reading b.c there are still black spots and other issues. i guess i should replace it and see if it solves the prob. then if not check the maf and o2's.

 

[Midnight_Cobra]

^^^

Good plan.

 

[quickstang_1994]

Don't replace it without testing it. With the key in the 'on' position, take the connection off the TPS sensor and put a volt o meter on the actual sensor, not the connection, and at idle it should read .97-.99, and WOT is close to 5 volts.

i actually just did this about 3 weeks ago b/c i had a bad julting problem and it was at 1.3 so i brought it down to .98 by wallowing out the holes. i did just read that one should replace the tps and never wallow the holes to get the correct reading b.c there are still black spots and other issues. i guess i should replace it and see if it solves the prob. then if not check the maf and o2's.

On 94-95 car the tps sets at start up and pick that voltage to go by. The maf sensor is acting up. I'm shocked your tuner didn't suggest change your maf from c&l (it lies to the computer to compinsate for injector size)My tps is at 1.08 just to give you an idea of what I'm saying. I had your same problem for a year before I got it fixed.

 

[SaleenStang94]

Don't replace it without testing it. With the key in the 'on' position, take the connection off the TPS sensor and put a volt o meter on the actual sensor, not the connection, and at idle it should read .97-.99, and WOT is close to 5 volts.

i actually just did this about 3 weeks ago b/c i had a bad julting problem and it was at 1.3 so i brought it down to .98 by wallowing out the holes. i did just read that one should replace the tps and never wallow the holes to get the correct reading b.c there are still black spots and other issues. i guess i should replace it and see if it solves the prob. then if not check the maf and o2's.

On 94-95 car the tps sets at start up and pick that voltage to go by. The maf sensor is acting up. I'm shocked your tuner didn't suggest change your maf from c&l (it lies to the computer to compinsate for injector size)My tps is at 1.08 just to give you an idea of what I'm saying. I had your same problem for a year before I got it fixed.

what do u suggest i do? clean the MAF sensor? replace the MAF sensor? get a new C&L tube and hope that it is calibrated (made) better?

 

[SaleenStang94]

oh and forgot to add, (not sure if it is related) but when im on the highway goin 60+ i need to push the accelerator pedal pretty far about half way before it begins to accellerate faster.

 

[quickstang_1994]

oh and forgot to add, (not sure if it is related) but when im on the highway goin 60+ i need to push the accelerator pedal pretty far about half way before it begins to accellerate faster.

Get a new maf sensor (not C&L) you can still find pro-m(perfect)

 

[SaleenStang94]

oh and forgot to add, (not sure if it is related) but when im on the highway goin 60+ i need to push the accelerator pedal pretty far about half way before it begins to accellerate faster.

Get a new maf sensor (not C&L) you can still find pro-m(perfect)

i dont get why i would need a new MAF, the C&L one is new. i also heard pro-m's latest ones are crap. also wouldnt cleaning the senor (not the C&L product but the actuall MAF sensor) be the way to go? or do u belive that the $300 C&L MAF system is bad and causing this problem?

 

[quickstang_1994]

i dont get why i would need a new MAF, the C&L one is new. i also heard pro-m's latest ones are crap. also wouldnt cleaning the senor (not the C&L product but the actuall MAF sensor) be the way to go? or do u belive that the $300 C&L MAF system is bad and causing this problem?
[/quote]

you can try and clean it. What size injector do you have? Anything over 24 c&l has a problem with. I put c&l with 30lb injectors it It ran but not good. Your cam is throwing the computer for a wack. So your maf messing up is throwing it further off.

 

[SaleenStang94]

im running 30lb injectors. what i dont get is it doesnt always hesitate/ backfire. and after i got it tuned it ran great but still had this problem. also this never ocurs at WOT. this only happens while cruising. 3 weeks ago i adjusted my tps by wallowing out the holes to achive .98 b/c i was experencing bucking at low rpms. finally on the highway at speeds i need to push the pedal almost half way before i feel some notable acceleration. therefore i would think its some blackspots on my tps. i could be wrong and it is like $120 for a new one.... idk...

 

[quickstang_1994]

these blackspot are from the maf I changed to a prom and it ran like a champ. The sample tubes lie to the computer instead of letting it adopt. Stock sensors in a new tube is still a cheap stock sensor

 

[Trickflow.GT]

check your timing as well...mine had a similar problem...the bolt that holds the distributor down was loose....now it runs 100% better :banana:

 

[SaleenStang94]

nah timing fine and its bolted down. im gonna run a diagnostic then see whats the prob and if nothin shows up il clean the maf then change the tps. i was also told fuel pump... i havent changed mine, im running 30lb injectors with a stock fuel pump with 150k on it.

 

[redmustang95]

mine has the same problems, especialy when cold. It hesitates/stumbles then backfires when taking of on a very chilly day, about 55 degress or less. Cleaned MAF, not much improvement.

 

[SaleenStang94]

mine has the same problems, especialy when cold. It hesitates/stumbles then backfires when taking of on a very chilly day, about 55 degress or less. Cleaned MAF, not much improvement.

right i noticed this too. on very cold days it is worse! what MAF do u have?

 

[redmustang95]

I have stock everything. the only thing i have is bbk cold air intake.