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starts and runs but dies when driving

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let me start by saying renix systems are confusing as hell .


but after tracing down my vacuum leaks. and basically redoing my fuel system. i finally got her running right again .


and on my test drive she died . and wouldnt start back up till it had cooled a bit . but now shes doin the same thing over and over again .


and now its not gettin out of the apartments .

i think its a sensor . i know the flywheel has a bad spot. which is leading me to believe the cps is causing it to die ... but idk and i really don't want to replace the flywheel since i will be doing either a 302 or 350 swap in 8 months or less (alot less if i can't figure this out)



also when it dies out . it will crank, fire up and die. NOT just crank forever

and for about a 20 seconds or so before it dies it will try to stall out under anythrottle at all . and then it just stalls out on its own.


ive replaced the

injectors (used with only 120k but still good looking)

map sensor

egr solenoid

fuel pump (now on its own switch)

tune up consisting of rotor cap wires and plugs

and ive put seafoam in tank


it only dies when driving . it will idle for what seems like forever (ive waited 30 minutes) i don't know what else to do


any help is appreciated

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Sounds exactly like my xj when the CPS went. It almost felt like it was running out of gas then wouldn't start for 30 mins. After waiting for it to cool down it would run again til it got hot. A new CPS solved the problem, but your flywheel may be the problem. Go to the junk yard and pick up a couple used CPS sensors and try em instead of spending 80 buck for a new one.

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Definently check the Crank Sensor and also the Ballast resistor.


also check your TPS voltage. :wrench:

is there a way to check the tps? besides just for power i mean


and where would the balast resistor be . its not bolted to the inner fender.

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do you still have the catalatic converter on your mj if so it may be getting cloged and choaking the engin under throttle. my 1999 grand am did this aswell as my 94 xj took yhe cats out of both after dumping considerable cash in them. just make sure that you are not in a state where the cat is reqired.

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i know the flywheel has a bad spot


You just answered your own question. If your flywheel is bad then the CPS will not read correctly.

its only bad on a single tooth of the fly wheel. the cps looks as though it reads off the hollowd part


plus that would not explain how it idles just fine and dies when driving

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I just did a tranny swap and it looked to me like the CPS reads off another wheel right behind to the fly wheel. Have you tried the O2 sensor? It could be telling the computer that it isn't burning right and that would inturn screw with the air/fuel mixture? think.gif

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I know you replaced the fuel pump, but did you replace the "sock" filter at the time?

The fact that after it sits for a while, then runs is a sort of clue, after it runs for a while does the pump get noisier? Pump is having to work harder.

Had a mini van did this, new sock and pump quiet after, current MJ same.


You did change the gas filter, right?


Good luck, seems to be lots of this going around right now! :shake:

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