Missing and Backfiring

[Dana G.]

I have a 1997 Jeep wrangler, 4 cyl. I was driving down the road and it started missing and backfiring really bad!! The backfiring was so loud it sounded like a shotgun goin off! I had to pull over it was missing so bad. Anyway, my check engine light came on! Please help!

[fredjacksonsan]

A sudden problem like that may be a sensor gone bad. I'd have the shop check the crank position sensor and if there is one, the camshaft position sensor.

Were there anything else odd that you noticed prior to this sudden problem?

[Dana G.]

Nothing else really, just the missing and cutting out, and backfiring! And the check engine light, i had a guy test it, and he said oxygen sensor??? Does this sound right, he also checked the coil wire and he said fire was shooting from the end of it! He also said the computer read cylinders 1 and 4 had something wrong with it! But i dont know cause, do u think the oxygen sensor could be giving them problems????

[fredjacksonsan]

I haven't heard of the O2 (oxygen) sensor causing those types of problems, but it could be contributing. How long has it been since you had a tune up?

Were there any symptoms prior to the episode on the highway?

[Dana G.]

Probably about a year ago i put new plugs and wires on it! could be the plugs fawling out?? it had a little miss to it about for about 2 or 3 months before all this happened!

[fredjacksonsan]

It sounds like the problem might have been getting worse as time went on? The plugs might be falling out if they weren't tight enough but that's not often the case. Wouldn't hurt to do another tune up and check all that out.

[Dana G.]

i tested the plugs and the #4 plug seemed like it didnt have as much spark to it as the others, so im goin to try a new plug! Could my coil wire have anything to do with this?

[fredjacksonsan]

Mmm, it might, but if one plug seemed weak, (and especially if the plugs haven't been changed for the last 30K miles) I'd consider changing them all out.

[Dana G.]

thats probably what i'll end up having to do! im goin to pull the # 3 plug out and try it on the # 4 cylinder and see if it fires any better, then i'll know if it is the plug or the wire!

[fredjacksonsan]

I'd check the cap also, if it's cracked it could cause the problem, especially if it's damp outside.

[Dana G.]

Well, i think i figured out the problem! The # 4 wire was losing fire put a new one on it and it seems to be running fine. no missing or anything, (yet)! But my check engine light came on again, could this be because the oxygen sensor?

[fredjacksonsan]

Cool! Glad it was just the wire.

Check engine light could be the O2 sensor; have you noticed your gas mileage going down lately?

[Dana G.]

Actually i have, i use to get about 13 or 14 mpg, cause i have 31 inch tires on it, now im only getting about 8 or 9 mpg. Do u know how many oxygen sensors there r on a 97??

[fredjacksonsan]

I'm not sure but I think there's only 1. Single exhaust; the O2 sensor will be just before or just after the catalytic converter (both if you have 2 sensors).

As a temporary fix, you can unplug the O2 sensor until you get the new one. Just make sure the wires are held up and away from anything that could damage them.