Topic: misfire or something else

[bpet72]

My jeep runs fine for the first 10-15 minutes then starts to jerk foward a couple of times but I usually could ease of the gas or power through it. The tach spikes when this occurs but I never get a check engine light. I'm thinking about replacing all the plugs, wires, cap and rotor. I just don't know if its a misfire or should I be looking at somthing else. Any feedback would be helpful, thanks.

[VA_YJ]

Use a code reader to check for diagnostic trouble codes.  Some auto parts stores will read your stored codes at no charge.

[sharpxmen]

what year of jeep?

based on that check the FAQ on how to read the trouble codes (if you have a CEL)

[bpet72]

its a 97 tj. If the check engine light doesn't come on it still might show codes? On another forum some people were suggesting it might be my o2 sensor. thanks for all feedback.

[sharpxmen]

its a 97 tj. If the check engine light doesn't come on it still might show codes? On another forum some people were suggesting it might be my o2 sensor. thanks for all feedback.

could be the O2, hard to tell for sure though - could be other things too but again if you start replacing might end up running the bill (could be tps, cps or even fuel related).

it would show whatever codes were stored since last reset, but if you're not getting a CEL won't be (or might not be) relevant to your current problem.

i'm thinking that it could also be some electrical problem, some connector getting short disconnects or something.

[JFortner5]

If it hasn't been done in a while it would be a good idea to do a tune up on it. You can check the o2 sensor by unplugging it and going for a drive. You want to unplug the upstream sensor (before the cat). If the issue goes away then more than likely you will need a new o2 sensor.

[bpet72]

I'm going to do a tune-up on my next day off, if its not raining. I will try disconnecting the upstream o2 sensor to see if that could be the problem. When I'm doing the tune up should I replace the ignition coil as well?

[sharpxmen]

I'm going to do a tune-up on my next day off, if its not raining. I will try disconnecting the upstream o2 sensor to see if that could be the problem. When I'm doing the tune up should I replace the ignition coil as well?

just so you know there's no tune-up you do on your Jeep other than replacing the dist cap, rotor, wires and spark plugs. The _only_ thing they can do is to put a scanner on it and monitor the parameters and measure the fuel pressure to the injectors rail - that could help identifying the problem, but again there is nothing to tune on that engine (the PCM takes care of all that).

just mentioned it so you don't throw money away. Now, if you go in for a diagnostic it's a different matter.

[bpet72]

thanks. I keep saying tune up but I mean changing the plugs, wires and cap.

[sharpxmen]

thanks. I keep saying tune up but I mean changing the plugs, wires and cap.

you're taking it to the shop for that? if i were you i would just do it myself and then go in for a diagnostic, your money would be better spent.

[Dylan]

I'm going to do a tune-up on my next day off, if its not raining. I will try disconnecting the upstream o2 sensor to see if that could be the problem. When I'm doing the tune up should I replace the ignition coil as well?

You could replace the coil, but I doubt that it is causing your problem.  Since it's running fine initially then starts having problems after it has warmed a bit, I'd lean toward there being a problem when it's swapping from open loop to closed loop, most likely a faulty O2 sensor.

[bpet72]

Thanks Dylan for the advise. Which o2 sensor are most people using? I heard bosch isn't that good. How about ngk?

[sharpxmen]

Thanks Dylan for the advise. Which o2 sensor are most people using? I heard bosch isn't that good. How about ngk?

bosch has the best quality parts money can buy, they have patents on most fuel injections related systems. make sure it is the bosch brand though.

[Dylan]

I've always had good luck with Bosch but don't have personal experience regarding Bosch O2 sensors for my Jeep; I still run OEM in mine.