BlueRidgeMark

There are a bunch of videos on the Tube. Much easier than walking through it here. Testing is the right idea.

Biggerhammer

Well I crawled underneath this thing and checked the one o2 sensor I could find…

It shows that it’s bad, multimeter showed open loop on the two black wires of the heater circuit when it should have shown some kind of reading to be still working.

4.3L XJ

OK, it is not getting hot then. Did you have a check engine light?

Biggerhammer

It would only give a check engine light once it would drop idle and begin to die. I would hit the gas and bring the idle up over 1000 rpm then let off the gas and the idle would fluctuate and then it would drop below 500 rpm and then die.

It only gave a check engine light one time for the o2 sensor heat circuit. After it was cleared, it would only show one for a bad coil. Shut it off and it would run just as before, high idle then drop off and then die.

4.3L XJ

OK, but I still think you should address the O2 sensors. What engine do you have?

4.3L XJ

And do you have the CA style cats and exhaust, two cats visible under the manifold or just a single pipe under the manifold if you have a 4.o

Biggerhammer

Definitely going to change the o2 sensor. I have 4.7HO. It has three cats…

4.3L XJ

Sounds like you have it in hand then. You should have two upstream and two down stream

Biggerhammer

Changed the one I could get to and that checked bad (open). Here’s a vid of what it still doing…

Biggerhammer

I got brave and took it for a SHORT ride… I barley made it back…

At first it ran down the driveway (100yards) then started up the road. After about thirty seconds it started missing and running rough (check engine light came on) so I turned around and headed back. It barley made it up the driveway it was missing so bad. I shut it off, Er well it died and I turned the key off… I grabbed my code reader and it says that four coils were malfunctioning and the bank 1o2 sensor had a bad heater circuit.

I cleared the code and started it back up, it ran on all 8 but still did the little stumble and die routine…

I guess I’ll have to get the other two O2 sensors and give them a shot…

dave1123

The reason I suspected the capacitors was 4 coils (probably one bank) misfired when it got hot. The 02 heater circuit only heats the sensors to bring them into closed loop mode sooner. The tips of the sensors don't start sending a signal until they reach 600*F. Those signals are in millivolts and hard to read without an oscilloscope or scan tool.

Biggerhammer

I’ll look into the capacitors when I get a chance. I tiki a few days off for the 4th of July to visit family out of town.

Biggerhammer

I’m done fussing with this thing and it’s been posted for sale on FB Marketplace.

I want to thank everyone for the help and guidance.

Biggerhammer

I walked away from it for a few days…

I made a last ditch run to pull a part a grabbed those capacitors. After installing them it will start up and go to 950/1000 rpms then drop to 450/500 for about fifteen seconds. Then it will surge back to 950/1000 for a few seconds then drop to 450/500. It will do this several time’s before dropping to nothing and stalling out. Now I can keep it running with my foot on the gas to about 800/1000 rpm and it will let my rev it but, once I let off, it will surge a few times then die…

I would say, it’s an improvement but not awesome…

Biggerhammer

Ok, I’ve ran the code reader on it and it keeps giving me the following codes, p0354 (coil D), p0355 (coil E), p0357 (coil G) and, p0358 (coil H). After searching on the web I determined that it is the following coils, #4, #5, #7 and, #8 are misfiring. Not at start up but after a few minutes. I can shut it off and restart it, it will run fine for a few minutes then back to this cycle.

So far I have replaced all the coils, plugs, IAC valve and both resisters that are inline with the coil harness and at least one O2 sensor. To now avail, it runs the same no matter what!


A friend suggested maybe the computer was trashed but…