stumbles/miss when cold and sometimes warm

[DDSTANG94]

on a cold morning my car hesitates and stumbles around 2-3 thousand rpms, has new plugs, wires , cap rotor, fuel filter, pvc filter......what can cus a stumble to be more presinte when the motor is cold. it deos it a lilttle when warm but is worse when its cold...??

 

[HISSIN50]

Dave, have you pulled codes?

Even if none are present, something like an ECT that is out of calibration can cause an issue like yours.

 

[DDSTANG94]

Dave, have you pulled codes?

Even if none are present, something like an ECT that is out of calibration can cause an issue like yours.

i have not pulled codes, overall the car runs pritty poor when cold, when it warms up it runs ok, but the stumble is still present...

 

[juiced_94gt]

o2 sensors, ECT, Air intake temp sensor...usually a faulty coolanrt sensor will cause it, mine does the same thing and im about to change the sensors since my problem seems to be more pronounced because of the built motor.

 

[mo_dingo]

I would start with cleaning the MAF & IAT sensors. Then you can check out the ECT readings at various temperatures (do a search here for testing parameters). Disconnect the battery before cleaning; once your done and reconnect, if the sensors were really dirty, the comp needs to reset the kamrf's & this will take care of that. (carb or elec. contact cleaner w/ q-tips are fine)

Does the car stumble during part throttle cruise, part throttle acceleration, decel, WOT, etc?

After 120 seconds, even though the engine is cold, the engine goes into CL and runs mostly off of the O2's, except WOT. So if after 120 seconds, the car runs normally, I would concentrate on the MAF/ECT/IAT/TPS sensors.

Let us know how it goes!
Scott

 

[DDSTANG94]

I would start with cleaning the MAF & IAT sensors. Then you can check out the ECT readings at various temperatures (do a search here for testing parameters). Disconnect the battery before cleaning; once your done and reconnect, if the sensors were really dirty, the comp needs to reset the kamrf's & this will take care of that. (carb or elec. contact cleaner w/ q-tips are fine)

Does the car stumble during part throttle cruise, part throttle acceleration, decel, WOT, etc?

After 120 seconds, even though the engine is cold, the engine goes into CL and runs mostly off of the O2's, except WOT. So if after 120 seconds, the car runs normally, I would concentrate on the MAF/ECT/IAT/TPS sensors.

Let us know how it goes!
Scott

thanks for the reply, i no the maf is clean, but i will try the IAT, it stumbles on part throttle, also i noticed if i drive the car then park it then get in it shortly after when it is still pritty warm it seems to stumble more...

 

[DDSTANG94]

pulled codes...got nothing..

 

[desertcox05]

how old is the plugs and wires? sounds like a tune up is in order

 

[HISSIN50]

You got nothing on codes or you got system passes?

Again, I'd check the ECT calibration.

 

[DDSTANG94]

You got nothing on codes or you got system passes?

Again, I'd check the ECT calibration.

I got code 111 system passes.....

how do u check the ECT calibration, and if i was bad wouldnt of it threw a code?

 

[HISSIN50]

I got code 111 system passes.....

how do u check the ECT calibration, and if i was bad wouldnt of it threw a code?

The ECT can be within absolute spec but out of calibration. For example if the ECT tells the EEC you're at 200*F but your engine is actually at 100*, that can lead to issues. The 200* reading is still within absolute spec so no code is generated.

Put your DMM on the signal wire for the ECT and write down the reading. Do this at the temp where the engine acts up. Be sure to note what the actual coolant temps are (via an aftermarket gauge) so we can compare your actual temps and the ECT reading.

 

[DDSTANG94]

The ECT can be within absolute spec but out of calibration. For example if the ECT tells the EEC you're at 200*F but your engine is actually at 100*, that can lead to issues. The 200* reading is still within absolute spec so no code is generated.

Put your DMM on the signal wire for the ECT and write down the reading. Do this at the temp where the engine acts up. Be sure to note what the actual coolant temps are (via an aftermarket gauge) so we can compare your actual temps and the ECT reading.

i forgot to add the miss/stumble is rpm deppentant, about 2300 rpms. it does it warm and cold, just worse when cold....

thanks i think ill swap it out and see what it does, there cheap anyway...

 

[HISSIN50]

i forgot to add the miss/stumble is rpm deppentant, about 2300 rpms. it does it warm and cold, just worse when cold....

thanks i think ill swap it out and see what it does, there cheap anyway...

If it's RPM dependant, it's most likely not an ECT issue.

Check your TPS signal - when you get near that range, you might find an open in the wiper (the voltage reading will drop for a little duration and then pick back up).

Though your wires are new, I would mist them with water while in the dark (be careful of moving and hot engine components) to be sure you dont have a leaky wire.

 

[revhead347]

Does your tachometer skip up and down with the engine? If so, I say distributer.

Kurt

 

[DDSTANG94]

Does your tachometer skip up and down with the engine? If so, I say distributer.

Kurt

no