hubbazoot

When I'm cruising around 40~50mph, my jeep occasionally jolts. This isn't a constant jolt, it just happens once, seemingly randomly. I have a 5-spd manual 1987 cherokee and no idea what's going on.

BlueXJ

Do you think it is a random misfire or is it a backfire or a power loss?

hubbazoot

I'm thinking misfire, I haven't heard any bangs or anything like that so I don't think it's a backfire. I just seem to get one sudden random jolt. I don't think it's a power loss, vent keeps blowing through it without hesitation and there isn't even a twitch in volts or anything like that.

BlueXJ

Have you done an ignition tune up lately. Could be a random sparkplug wire that is crossing over to another wire or a bad wire, or even a cracked cap. I have also seen a carbon track inside a cap cause a crossfire to an adjacent plug contact point. So I would consider a cap, rotor and wires to see if that eliminates your "jolt".

hubbazoot

i don't know how to do an ignition tune-up, but I wouldn't be surprised if that is the issue. This vehicle is 20 yrs old and all of the plastic and rubber is pretty brittle.

BlueXJ

It is a simple exchange of parts but when you do the wires do just one at a time so as to not get them mixed up.

hubbazoot

Alright, did a bit of googling and it looks like there's a kit for this I buy. I'll poke a look into this next weekend. Thanks for your help. I'll post as soon as I find out if this is the case.

BlueXJ

Most any parts store will have what you need. It can be bought seperately. Dont let them sell you something real special. Just basic wires with the ends already in place and a distributor cap and a rotor button. If you have a radio you will want the radio suppression wires so you won't have to listen to the static background on your radio.

hubbazoot

Alright, I'm replacing my hayes clutch tomorrow but I'll see about doing an ignition tune-up next weekend.

BlueXJ

Good deal.

hubbazoot

What are the radio supression wires so I know what to look for? Are they just a thicker wire?

BlueXJ

Sorry to be so slow in answering. They have a sheild built in that does not increase the size but is usually about like a covering within the rubber shell of the wire like a sleeve but it is integrated within the wire. It may be like a faraday cage (Google that) and keeps the magnetic pulses going through the wires from being picked up by the radio.

JayM

When you are replacing your clutch, replace the crank position sensor as well.
It is a royal pain to get to unless the tranny is out, take advantage of having room to get to this sensor.

At night open the hood and disable your under hood lamp.
Start the jeep, if you have really bad wires, you will see the wires arching together, Mine was arching from the wires into the head, got that studder (jolt) just liek you described. Just go to autozone, or whatever you local parts house is and get new plugs, cap rotor and wires. That is the extent of you ingnition tune up. Be carful of the gap on the plugs, make a big difference. Just get a gap guage and make sure you are gapped correctly. The gap is listed on an under hood sticker, and in your manual.

hubbazoot

Thanks, I'll check for arcing tonight. My '87 actually doesn't have an under-hood light, but I'll make sure I'm somewhere nice and dark (buhaha)

hubbazoot

Did the tune-up, runs like a charmer now. I noticed my jeep also starts a little better and it feels like I got a few more horsepower out of it. I'll write up a guide with pics.