Topic: I am stumped; please help!

[jfrabat]

well, i had this issue with a vehicle way back when i started driving. I replaced the coil with a better one combined with a spark booster and after a little while i started to have an issue, turns out the spark was closing on the outside of the coil rather than thru the wire>distributor>plug and was misfiring, rev it up past a certain point it would come to life (probably when the spark booster was less efficient). I removed the booster and all was good - makes me think of your coil problems, i can't remember if you have a stock one or the 48kV one.

EDIT: could be MAP and x3 on crank sensor - might as well replace them since you put all the other new stuff in it. I think it's spark related but who knows.
Does it backfire out the intake at all (or whatever you call that)? if yes that's possibly too lean, so in that case could be MAP or an injector.
Does it do this at idle (like running in 3 cyl?)

As far as coils, I have tried everything from Screaming Demon, to Mopar, to the cheap stuff.  As for the backfire, it is caused by the unburnt fuel reaching the exhaust manifold, I think, as when it does this, I get a code for a rich mix...  I am replacing the sensors I already got (MAP, CPS, Oil Pressure, and Intake Air Temp)  plus the cam position sensor (I ordered one online, but I am also looking locally; dont mind carrying a spare!).

[Jeffy]

Have you tried swapping out the engine harness?

[jfrabat]

Have you tried swapping out the engine harness?

You mean all the cables in the rig?  No; but I think Id rather sell he rig than get into that....

[sharpxmen]

You mean all the cables in the rig?  No; but I think Id rather sell he rig than get into that....

is not that hard but you can probably get away without doing it, you could rather measure the wires from the sensors to the PCM if it comes to that

[dwtaylorpdx]

Have you pulled the ECU connector and checked for corrosion? Some of the yj's had issue with that...

Dave

[jfrabat]

Have you pulled the ECU connector and checked for corrosion? Some of the yj's had issue with that...

Dave

That would be simpler; but how to correct it if it is the problem?  I mean, it's not like I can put a steel brush in there...

[Jeffy]

You mean all the cables in the rig?  No; but I think Id rather sell he rig than get into that....

There really isn't that many wires in the engine harness.  It would be plug & play.  I'd probably check the bus to the ECM.

[sharpxmen]

i doubt there's corrosion at the PCM, its a sealed connector, but if there is you can use some electrical contact cleaner spray and should do the trick (dont use a brush or needle or anything of that sort).

[dwtaylorpdx]

That would be simpler; but how to correct it if it is the problem?  I mean, it's not like I can put a steel brush in there...

It comes out with a couple bolts easy peasy..  Lift the washer jug out first...

I used some electrical cleaner (Sparingly) q-tips and then used electrical grease on the pins.

A toothbrush worked pretty good for just scrubbing it up..

I did a U-Boat maneuver a few years ago.. Luckily got clear through and made it to dry land... :)

Dave

[jfrabat]

I did a U-Boat maneuver a few years ago.. Luckily got clear through and made it to dry land... :)

Dave

I've done a couple of those, and even though I have swapped out the ECU's, I never really looked at the plug itself....  I'll check it out just in case...

[jfrabat]

OK, guys, I am REALLY STUMPED now!  As it is mentioned earlier on, the Jeep has a fault where it is running fine, and all of the sudden there is no power whatsoever (as if you unplugged the coil), then it starts up again.  If you give it fuel, it will detonate (my thinking is that the injectors ARE in fact pumping fuel, but since there is no spark, the fuel goes out of the exhaust, and detonates when it comes into contact with it).

Since I was not sure if it was ignition, fuel, or computer, I replaced the following parts:

From the fuel side:
Fuel sending unit (includes pump)
Fuel Filter
Fuel injectors
Fuel Pressure Regulator

Ignition:
Rotor
Cap
Wires
Coil
Plugs

Computer:
ECU (I had another one as a backup)
TPS (was faulty anyway)
IAC (had some idle issues)
CPS
Cam Position Sensor
IAT
MAP
Oil Pressure Sensor (was also acting up)

I also checked the plug on the ECU, and there is no corrosion whatsoever.  There is also no cat on my Jeep, so it's not the cat.  Air filter was recently cleaned out (along with the whole TB) and oiled (Fram AirHog).  I am really stumped as to what it can be, and I need help tracing this down.  Other than swaping out the engine harness (which, if I were to do, I would start considering an engine swap instead, but I would have to evaluate costs), what else should I be checking for?

Felipe

[neale_rs]

Maybe a faulty ignition switch (down on the column) or faulty relays.

[jfrabat]

Maybe a faulty ignition switch (down on the column) or faulty relays.

You know what, I have NOT checked relays...  Thanks for pointing that out!

[sharpxmen]

is your rpm on your tacho still up when this happens? it is important to know.

[jfrabat]

is your rpm on your tacho still up when this happens? it is important to know.

It happens under load, but it is not tied to RPM.  I have had it happen when off the line, or when driving (always below 4K RPM, but the point in the RPM range varies).