# Problem with idle and acceleration



## Asleep (Jan 19, 2003)

1993 s13. ok... thought the engine had an maf problem because the engine wouldnt idle and hesitated and stumbled on acceleration. last night we swapped out the maf with a buddies known good maf and had no change whatsoever. went out to the car this morning and now it wont idle, it backfires thru the intake when you press the gas pedal and unless its floored - it wont accelerate either. even then, it stumbles and pops until it gets there. i pulled the codes from the ecu and got a 12, which is air meter circuit. that could be from when i unplugged the maf while it was running though. i reset it and ran it again all i get is the "all's well" 55 code. my thoughts right now are pointing to the throttle position sensor or an intake leak. was supposed to be at work by 6 this morning so now this is costing me money instead of just being a pain in the ass. i cant hear the fuel pump running either but it may be fully pressurized already too and i dont want to count it out just yet since the engine will rev up readily if its at wot... fuel filter is only a week old too...
time to help the helper.


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## NismoSR (Mar 25, 2005)

AsleepAltima said:


> 1993 s13. ok... thought the engine had an maf problem because the engine wouldnt idle and hesitated and stumbled on acceleration. last night we swapped out the maf with a buddies known good maf and had no change whatsoever. went out to the car this morning and now it wont idle, it backfires thru the intake when you press the gas pedal and unless its floored - it wont accelerate either. even then, it stumbles and pops until it gets there. i pulled the codes from the ecu and got a 12, which is air meter circuit. that could be from when i unplugged the maf while it was running though. i reset it and ran it again all i get is the "all's well" 55 code. my thoughts right now are pointing to the throttle position sensor or an intake leak. was supposed to be at work by 6 this morning so now this is costing me money instead of just being a pain in the ass. i cant hear the fuel pump running either but it may be fully pressurized already too and i dont want to count it out just yet since the engine will rev up readily if its at wot... fuel filter is only a week old too...
> time to help the helper.


Any smoke comin out the back at all ?


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## sunnydet90 (Sep 10, 2004)

AsleepAltima said:


> 1993 s13. ok... thought the engine had an maf problem because the engine wouldnt idle and hesitated and stumbled on acceleration. last night we swapped out the maf with a buddies known good maf and had no change whatsoever. went out to the car this morning and now it wont idle, it backfires thru the intake when you press the gas pedal and unless its floored - it wont accelerate either. even then, it stumbles and pops until it gets there. i pulled the codes from the ecu and got a 12, which is air meter circuit. that could be from when i unplugged the maf while it was running though. i reset it and ran it again all i get is the "all's well" 55 code. my thoughts right now are pointing to the throttle position sensor or an intake leak. was supposed to be at work by 6 this morning so now this is costing me money instead of just being a pain in the ass. i cant hear the fuel pump running either but it may be fully pressurized already too and i dont want to count it out just yet since the engine will rev up readily if its at wot... fuel filter is only a week old too...
> time to help the helper.


 sounds like the timing is extremely off but on enough to run the car. i've only see intake backfire on bad timing with mine and it was shooting flames out of the throttlebody


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## Asleep (Jan 19, 2003)

no flames out the back and timing doesnt seem to be a factor because if i keep the gas pedal around 3/4's to wot, it will run with no pinging or hesitation. wot makes the ecu go into open loop so not all sensors are read at that point. im going to go and get a tps and see what happens.


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## rogoman (Dec 16, 2004)

AsleepAltima said:


> no flames out the back and timing doesnt seem to be a factor because if i keep the gas pedal around 3/4's to wot, it will run with no pinging or hesitation. wot makes the ecu go into open loop so not all sensors are read at that point. im going to go and get a tps and see what happens.


At WOT only the O2 sensor is not read. Check the MAF wiring and harness connector for oxidation on the pins. In particular the shielding which should be grounded; if not grounded, you're going to have all types of problems.


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## Asleep (Jan 19, 2003)

rogoman said:


> At WOT only the O2 sensor is not read. Check the MAF wiring and harness connector for oxidation on the pins. In particular the shielding which should be grounded; if not grounded, you're going to have all types of problems.


i think its further along than that... the pins and connectors are clean... i just changed out the tps because it was reading over 7kohms closed. should have been about 2. new problem now though. although i can get it to shittily idle, it wont rev past 5k and it gives me a hard time doing that. im beginning to think that the chain jumped... gonna pull the valve cover later this week and start checking more in depth.


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