I have a hesitation on the car once its warming up but not cold. I also have backfiring on my car. Now I have replaced coilpacks already and replaced maf sensor all good. Now I asked a mechanic today to tell me an idea and he told me thermostat. I looked at him with a confused face. He told me if the car is always cold you will run rich which can cause you car to backfire. Now I dont know if I should believe him or not??? He told me it maybe be stuck open. I search else where and heard that it can run rich but not sure about the hesitation and backfiring. Im not to sure. What do you guys think?

 

surely you can tell if your thermostat is stuck open on your own no?

 

If the car warms up without overheating then the t-stat is fine. Besides regardless of temp the engine should run good. I would start with the coolant temperature sensor.

 

So can coolant temp sensor cause backfiring and hesitation??

 

Yes. A bad ECTS will cause you to be overly rich or lean, causing very poor running, backfiring and hesitation. Do you have any codes or CEL? ECTS is also responsible for triggering your radiator fans. Are they behaving strangely?
There are other things that could be responsible, but withthe colder weather I would start here.

 

Well I did throw codes if I remember it was coilpacks, which i replaced them and still throwing that code. 02 sensor, Maf sensor which I replaced that also.

These are the codes i got:
-p0100
-p1320
-p0505
-p0130
-p0734
-p1105

 

A backfire or misfire is usually ignition related.
Which coils did you replace, were they used or new? Seems only genuine Nissan coils work correctly on our VQ's.

 

They were good working coils from a 00maxima. I have a 00 motor in the car. The coils have spark and they are working. The mechanic was telling me to check the thermostat cuz if the computer is always reading the motor as cold all the time and never get a chance to actually warm up then it will spray more gas. Meaning I can backfire. Now I was thinking maybe it can also be fuel pressure regulator. Im gonna change the temp sensor and cams sensor. Its gonna be free for me. Taking everything out of a 2000 maxima that is working fine. They told me to check the sensor. I have new spark plugs also so I know is not that either.

 

False. If the engine was actually cold, then the extra fuel would make it run better. There would be no backfiring in this case.

If the ECTS sends the wrong signal then the ECM will "see" a cold motor when its actually warm and spray too much fuel. Test your ECTS, or just replace it for $20.00.

 

Misfires yes, backfires no. Backfires are generally caused by a lean condition.

 

I figure it out. It was a broken wire inside the wiring harness. The wire that was broken was the one of the wire going to the back left coil. So there was no signal going over to the coilpack. Ill take picture tomorrow or friday

 

got the same issue when cold, car accelerates fine while cold, but soon as it gets halfway in the middle, it hesitates, I thought I fixed the prob with a new knock sensor, fuel filter, plugs, ect. no cel as of now, I cleaned throttle body, and iac twice. im.stuck.on this.