[newjeepster]

It's been about a week since I posted my last question. I only received one response. I guess my problem has everyone stumped including me. Since my last posting, I have replaced the following on my 89 Jeep Wrangler (Weber carburated):

1. Ignition Module (mine failed the test so I replaced it). The other ignition module wasn't even a year old.
2. Ignition Switch (I installed a switch from Standard)
3. The entire Distributor with a new rebuilt one
4. Coil
5. Fuel Pump (mine is mechanical)

A gentleman at Autozone has been helping me try and solve this problem. He has talked with many mechanics who each have their own theory as to what the problem is. Yesterday, it was suggested that it was my mechanical fuel pump. From what I understand either these work or they don't. I didn't think that was my problem and I was correct. My problem about a week ago was intermittent now it is a daily occurrence. The car only does this weird thing once it is warmed up to operating temperature, the tachometer needle goes from zero RPM then immediately back on. What is weird is that I can drive around town and it will not do it, but if I take it out on the highway and get it up to 50 mph the ignition cuts-out, the tach goes to zero RPM immediately and back on. In the last week this problem has gone from intermittent to NOW it dies when the tach does its thing. Once it dies, I now have to let it sit for a few minutes and then I can restart it and limp home. My engine is newly rebuilt maybe has 10,000 miles on it. I have also noticed that it seems to do this tach thing when I turn the headlights on (this may be a coincedence but I thought I would mention it anyway). Last night, I duplicated the tach problem without leaving my driveway. I warmed the car up to operating temperature turned the headlights on. We noticed that when the tach needle does its thing and the engine dies, when I turn the key into the off position the engine does an 1/8 revolution. Weird. My car does not have a Crankshaft Position Sensor. I looked and could not find one and my transmission guy confirmed it. I was also told that it could be my computer but very unlikely. The one response I did have the person suggested that I do a Nutter Bypass. 1. Since I don't know what I am dealing with here and from what I have read, no one is certain that it will work on an 89 YJ Jeep Wrangler, I am not inclined to start cutting wires and mess it up more.

I sure would be grateful to anyone who has an idea of what my problem could be. I love this site and have searched extensively to try and find my problem. When I do find out what the problem is I will be sure to post it so that it could help the next person. This is driving me nutts!

[smok3y]

im stumped man, youve done everything i would have, except on thing, my friend with a 94 fuel injected YJ had a similar problem but it was the TPS and the O2 sensor, good luck with yours

[lostboy]

Originally Posted by newjeepster

It's been about a week since I posted my last question. I only received one response. I guess my problem has everyone stumped including me. Since my last posting, I have replaced the following on my 89 Jeep Wrangler (Weber carburated):

1. Ignition Module (mine failed the test so I replaced it). The other ignition module wasn't even a year old.
2. Ignition Switch (I installed a switch from Standard)
3. The entire Distributor with a new rebuilt one
4. Coil
5. Fuel Pump (mine is mechanical)

A gentleman at Autozone has been helping me try and solve this problem. He has talked with many mechanics who each have their own theory as to what the problem is. Yesterday, it was suggested that it was my mechanical fuel pump. From what I understand either these work or they don't. I didn't think that was my problem and I was correct. My problem about a week ago was intermittent now it is a daily occurrence. The car only does this weird thing once it is warmed up to operating temperature, the tachometer needle goes from zero RPM then immediately back on. What is weird is that I can drive around town and it will not do it, but if I take it out on the highway and get it up to 50 mph the ignition cuts-out, the tach goes to zero RPM immediately and back on. In the last week this problem has gone from intermittent to NOW it dies when the tach does its thing. Once it dies, I now have to let it sit for a few minutes and then I can restart it and limp home. My engine is newly rebuilt maybe has 10,000 miles on it. I have also noticed that it seems to do this tach thing when I turn the headlights on (this may be a coincedence but I thought I would mention it anyway). Last night, I duplicated the tach problem without leaving my driveway. I warmed the car up to operating temperature turned the headlights on. We noticed that when the tach needle does its thing and the engine dies, when I turn the key into the off position the engine does an 1/8 revolution. Weird. My car does not have a Crankshaft Position Sensor. I looked and could not find one and my transmission guy confirmed it. I was also told that it could be my computer but very unlikely. The one response I did have the person suggested that I do a Nutter Bypass. 1. Since I don't know what I am dealing with here and from what I have read, no one is certain that it will work on an 89 YJ Jeep Wrangler, I am not inclined to start cutting wires and mess it up more.

I sure would be grateful to anyone who has an idea of what my problem could be. I love this site and have searched extensively to try and find my problem. When I do find out what the problem is I will be sure to post it so that it could help the next person. This is driving me nutts!

You say the computer is not the likely problem ,but when I had the exact same problem, I replaced the ignition module and it solved the problem. You've already done this ,so that's probably ok. The module I replaced was on the drivers side under the overflow bottle. Is this what you replaced? I've heard it also called ignition computer.
FYI, mine was so bad the jeep would buck and shudder and it actually stretched the timing chain. That was fun to replace.
HTH

[newjeepster]

Originally Posted by lostboy

You say the computer is not the likely problem ,but when I had the exact same problem, I replaced the ignition module and it solved the problem. You've already done this ,so that's probably ok. The module I replaced was on the drivers side under the overflow bottle. Is this what you replaced? I've heard it also called ignition computer.
FYI, mine was so bad the jeep would buck and shudder and it actually stretched the timing chain. That was fun to replace.
HTH

Thanks for your reply Smok3y. I am going to need all the luck I can get.

Thanks for your reply Lostboy. Yes, the ignition module that I replaced was underneath the overflow tank. When I replaced the coil and still continued to have the same problem, I went so far as to pull the ignition module again and have it retested. It passed the test. I am thinking that this is maybe some sort of electrical connection that is getting hot? The 95$ question is what. Once the car is warmed up and I turn on the headlights I can duplicate the problem; the tach going nutts and the car dying. I am thinking that when I turn the headlights on there is an additional draw on the juice and perhaps there is some connection lead that is getting hot and opening up? When I have had the car on the highway and the tach has done its thing I have tried to give it gas and the car spitters and sputters and has even backfired. I even thinking it could be a relay but I don't which one. As I am looking in the engine bay, there are two relays to the left of the battery. Any idea what those go to? I have looked in the Haynes Manual and can't seem to find what they are.

Thanks.

[JKNIPE2000]

well your definately loosing your fire somehow....bad spark, loading up w/ fuel, im just shooting in the dark here. is it missing at all, or backfireing when it shuts off and back on going down the road? have you checked for vacuum leaks around the carb that could cause it to fall on its face? If your not familiar how to check w/ vacuum leaks just ask ill explain the easiest way.

Jimmy

[Qcwrangler]

I don't think your problem is your ignition module, because I never had an intermittent problem with this one, is work or isn't!!!
The black wire at the ignition module send a pulse to your coil and if this wire is shot or ... it must be your problem !!

But it's an intermittent problem so... !!!

Maybe bad gnd wire, Maybe computer ( do Nutter ), Maybe bad choke ajustment!!!

You should try your old ignition module!!!

Sorry man!!

[CanukYJ]

Here's what I think...
The spark plugs need juice to fire the engine, then engine when in cold cycle (choke on or off) will run differently then when warmed up. If once warmed up the computer changes the way its running it will alter the electrical path. When the headlights are turned ON and it's warmed up and the engine looses spark (which is what is happening) they must be sharing a common component. Read- trace the wires all the way from the headlights right back to the switch and see if they are sharing a 12v\grnd with the computer, Ig mod, coil, distributer, etc etc. For the headlights to be causing this loss of spark they have to come into one of those components once it is warmed up. Might be worth checking the wiring from the headlights back, gotta start somwhere. Btw- a friend of mine had a pathfinder with a similar problem, he had someone 'fix' his electrical and as his Tach would climb on accel hit parking brake light would slowly light up brighter and brighter until he his about 3000rpm and the brake light would be SO bright it would blind you and the engine would then cut off, what was going on? A short was grounding through the brake light LED and eventually it would drain SO much juice the spark plugs could not fire and the engine would stall. Sorry for the long post..

[NaeKid]

After reading all that .. I would start at the battery and clean both connections - one by one, then coat with die-electric grease and re-make the connection.

Then I would replace all the ground straps .. between the frame/body/block.

After that, I would verify that the connections to the starter, to the main wiring harness and the solinoids that control all the electrical in the Jeep (near the battery).

[newjeepster]

Originally Posted by NaeKid

After reading all that .. I would start at the battery and clean both connections - one by one, then coat with die-electric grease and re-make the connection.

Then I would replace all the ground straps .. between the frame/body/block.

After that, I would verify that the connections to the starter, to the main wiring harness and the solinoids that control all the electrical in the Jeep (near the battery).

Thanks to Jimmy, Qcwrangler, CanukYJ and NaeKid for your responses. Your suggestions give me several more things to check.

Jimmy, I would like to take you up on your offer to explain the easiest way to check for vacuum leaks. Thanks.

Does anyone have an actual wiring diagram for my 89 Jeep Wrangler The wiring diagrams in the Haynes Manual are in general terms encompassing years 1987 through 1995. Thanks.

[JKNIPE2000]

Originally Posted by newjeepster

Thanks to Jimmy, Qcwrangler, CanukYJ and NaeKid for your responses. Your suggestions give me several more things to check.

Jimmy, I would like to take you up on your offer to explain the easiest way to check for vacuum leaks. Thanks.

Does anyone have an actual wiring diagram for my 89 Jeep Wrangler The wiring diagrams in the Haynes Manual are in general terms encompassing years 1987 through 1995. Thanks.

No problem...its very simple, you used a portable propane torch. Just start your engine, turn on the knob to allow propane to leak from the torch nozzle, but be sure you DO NOT ignite it...could be bad on the carb...gas and all being in there :P make sure your breather assembly is mounted and tight when doing this.. just run the torch around the joints on the carb, and where the carb mounts to the intake on the engine. If you do have a vacuum leak, the propane will be sucked in and mixed with the gasoline/air mixture, causing a slight increase in idle speed. Then if you do notice a leak, its just a matter of checking that the bolts are tight. if they arent, tighten them and check for a vac leak again. if they are tight then you probably need to replace whichever seal it may be that is leaking. Hope thats clear...im typing fast so the boss dont catch me :P

Jimmy

[newjeepster]

Originally Posted by JKNIPE2000

No problem...its very simple, you used a portable propane torch. Just start your engine, turn on the knob to allow propane to leak from the torch nozzle, but be sure you DO NOT ignite it...could be bad on the carb...gas and all being in there :P make sure your breather assembly is mounted and tight when doing this.. just run the torch around the joints on the carb, and where the carb mounts to the intake on the engine. If you do have a vacuum leak, the propane will be sucked in and mixed with the gasoline/air mixture, causing a slight increase in idle speed. Then if you do notice a leak, its just a matter of checking that the bolts are tight. if they arent, tighten them and check for a vac leak again. if they are tight then you probably need to replace whichever seal it may be that is leaking. Hope thats clear...im typing fast so the boss dont catch me :P

Jimmy

Thanks Jimmy. I'll try that.

[greatime]

One other possibility after you check all battery connections (the most likely cause), is the fuel pump relay. Less than $10. I thought it would either work or not work, but mine had an intermittant problem which led me to pull the gas tank out and replace the fuel pump, when it was only a relay in the fuse box, which sometimes worked, and then wouldn't work. Just a thought....

[Jimmylh]

I had a new 89 Mazda 323 one time that would do crazy stuff like that. It turned out to be the crimp where the postive battery connector was attached to the cable harness. They re-crimped it and the problems went away. That's just an example of how wire connections can cause all sorts of intermintent electrical problems like that. I like the suggestion of checking your main grounding points. Did you replace your coil wire on your distributor cap?