Sexy stroker turned into Bucking Bronco...

[gradon]

I had an Accel coil go bad on me last year and when it acted up it wouldn't let me rev past 3K, it would buck, and then if I turned it off and tried to restart, I'd get nothing. Then 20 min later it would start right up and be fine. It'd be nice if faulty sensors/equipment would just die instead of all the intermittent bs.

[Mgardiner1]

New Video Included

http://www.youtube.com/watch?v=9vbOcX0jYpU

This is at its worst people, this is with a luke warm engine, in neutral, in my garage.

As you can see, when it breaks over 2800 RPM she is READY TO GO!!

I modified the Crank position sensor after this run, i milled it to get it about .040 closer to the flywheel. However, this has not cured the problem, or even made it any better. I'm really thinking its the ECU.... BTW, the warmer it gets, the less it happens.........

[Flash]

I wouldn't rule out the ign brain box , coil or a shorted tach..............Do you have a spare ign brain box or coil that you Could try?

Flash

[Mgardiner1]

Whats an ignition brain box? I'd call that the ECM, ECU, or PCM (AKA powertrain control module)

If the tach was shorted, i can't see engine temp effecting it. If the coil was shorted, IN THEORY, it just wouldn't work while shorted. The computer still does not supply any other fault codes then ones i've previously mentioned. Unfortunatly i don't know anybody around here with that model year jeep to test a different ECU. I hesitate to spend $100 on a Ebay ECU for an automatic jeep, just to test it.

[Flash]

Whats an ignition brain box? I'd call that the ECM, ECU, or PCM (AKA powertrain control module)

If the tach was shorted, i can't see engine temp effecting it. If the coil was shorted, IN THEORY, it just wouldn't work while shorted. The computer still does not supply any other fault codes then ones i've previously mentioned. Unfortunatly i don't know anybody around here with that model year jeep to test a different ECU. I hesitate to spend $100 on a Ebay ECU for an automatic jeep, just to test it.

The one on the fender.............What year is it?


Flash.

[Mgardiner1]

91 with manual transmission. From what i understand, a 91 thru 95 ECU should work. The local junk yards here charge a premium (literaly 10% less then what a new part would cost), and ebay seems to be in short supply of "deals". The majority of the ECU's on ebay are for auto transmission anyway.

[Boilermaker]

Are you looking for a '91 ECU from a manual transmission XJ?...pm me i may still have one from my '91 MJ part out laying around.

[Mgardiner1]

PM sent

[Boilermaker]

PM returned....

[heartlandoffroad]

have you checked or swapped out the coolant temp sensor sounds to me like it could be the culprit I had a real similar problem occur on a comp. buggy I was working on awhile back.

[Mgardiner1]

Being one of the only sensors i had not changed at this point, i thought for sure it was no good. However, after running the engine up to normal operating temp and then testing the sensor, it tested at about 800 ohms, which at 190ish degree's is exactly what it should test.

[Mgardiner1]

Thank you very much to Boilermaker, i received another ECU today. However, the problem is still exactly the same.... Furious, i drove down to the autoparts store and picked up a coil...... and its exactly the same.... Disconnected the tach lead, even added an ADDITIONAL ground from the block to the battery, exactly the same....

FOR SALE 87 YJ with serious damn issues......

I'm really getting sick of this

[dwg86]

I was talking with a friend that owns an auto shop. He says to check the crank position sensor. He's pretty sharp, and said that jeeps are know for the cps to go bad.

[Mgardiner1]

I agree 110%.... My sensor only has a few hundred miles on it, and i modified it to make it closer to the flywheel to make the signal stronger. The few times i have experienced a problem with a faulty CPS, the engine usually will not start. However, that is the next sensor on my list that will be changed

[dwg86]

This is from alldatapro.com, on how to test the crank position sensor ...
Disconnect the engine speed sensor electrical connector from the wiring harness. Check the resistance of the sensor by placing an ohmmeter across terminals A and B (marked on sensor connector). With the engine at normal operating temperature, the ohmmeter should read 200 ±75 ohms. Replace sensor if ohmmeter readings are not within specifications.

That's for a 91 jeep wrangler

Hope this helps