Topic: Bad hesitation when cold

[sharpxmen]

Still havent figured out this issue. Now it seems like the dreaded bucking is coming back. I get a rpm drop between 2200 and 2800 RPM again. Its just a 5k drop but you can feel it. Like I am running out of gas (which I know the feeling cuz I did that last week too). And if I throttle through the bad spot and I just get lucky timing i get a backfire in what sounds like the intake manifold. My gut keeps pointing me toward the TPS but its new and never changed anything from the old one. But it DOES have to be in a certain throttle position and/or RPM range for it to happen. Mind boggling. 

just for a test, try to unplug the o2 sensor and drive it like that to see if it changes anything - you'll get a CEL but will go away once you plug it back.

[tommy69z]

I will try O2, there has to be a common fix to this problem....mine will spit and sputter at cruising speed, will feel like it drops power, floor it and it picks up and goes??

[sharpxmen]

I will try O2, there has to be a common fix to this problem....mine will spit and sputter at cruising speed, will feel like it drops power, floor it and it picks up and goes??

sounds like tps or map if it's not the o2, but that's just based on the couple of things you mentioned. there could be more than 1 cause for the same [sort of] effect so it's not sure that both of you have the same problem

[tommy69z]

I need to see if my gm scan tool(auto xray) will let me scan it while driving....I'm not going to just buy parts to see what is wrong

[sharpxmen]

I need to see if my gm scan tool(auto xray) will let me scan it while driving....I'm not going to just buy parts to see what is wrong

you don't have to buy parts (i didn't suggest that) there are methods to test the sensors. It helps if you post the year of your Jeep, but if you're MPFI you can download the FSM and look for the testing procedures on sensors. Also if you have a CEL then the answer could be there. If you're OBD2 then yes, you can monitor your PCM while driving so that would work as far as diagnostic better.

[tommy69z]

you don't have to buy parts (i didn't suggest that) there are methods to test the sensors. It helps if you post the year of your Jeep, but if you're MPFI you can download the FSM and look for the testing procedures on sensors. Also if you have a CEL then the answer could be there. If you're OBD2 then yes, you can monitor your PCM while driving so that would work as far as diagnostic better.

97 tj-4cyl

[cz777]

please look at the ''air/coolent temp sensors'' and ''O2 sensor '' all of them will fight each other at times  !i have used gm coolent temp sensor for some apps they work out better ..... sometime read the specs on the sensor  ''temp vs. ohms'' find the most accurate range helps running etc 

[Steve-0]

Pulled the O2 and the bucking stopped. I really had to try to find the bad spot. But now, I have been driving it for a few days without the O2 sensor and the bucking is back. Does this still mean the sensor is bad or do i now need to look at the temp sensor?

[Steve-0]

No more bucking and hesitation. Hopefully my gas mileage will get better too. It was obviously a faulty O2 sensor that was the main problem. Still feel a little stumbling around 2200 RPM though. No codes, so who knows. But much happier now.

[tommy69z]

No more bucking and hesitation. Hopefully my gas mileage will get better too. It was obviously a faulty O2 sensor that was the main problem. Still feel a little stumbling around 2200 RPM though. No codes, so who knows. But much happier now.

Is this with a new O2 sensor?

[Sidscan]

Make sure you reset the computer.  I'll bet it learned some bad habits from the bad O2 sensor. 

[Steve-0]

Yes, its with the new sensor. How do I reset the computer? Pull the battery cable for 10 sec? Or can I use the OBD1 scanner to reset it?

[sharpxmen]

Yes, its with the new sensor. How do I reset the computer? Pull the battery cable for 10 sec? Or can I use the OBD1 scanner to reset it?

pull the ground wire off the battery and touch it to the positive - leave it off for 5 min.