pearlheartgtr

2000 XJ Sport Cali Emissions

Changed:
Coil (tried 2)
Plugs (From NGK to Autolite Copper. NGKs had about 20K on them)
Crank Position Sensor

Chrysler Combustion Chamber Cleaner as per the TSB for this issue. I used 3 cans on 3 seperate occasions

Codes:
P0300
and whichever cylinders it misfires on. It changes.

This started last summer and had been intermittent. First, I thought it was heat soak. I drove for 45 minutes and stopped somewhere, in and out. The truck coughed and wouldn't start. I gave it a few minutes and it started right up. It coughed and bucked a little until it cleared itself out. It would do that here and there and sometimes threw a #3 misfire. I put the Mopar sleeve over injector 3. Then it started misfiring (flashing CEL) and bucking when I went up a particular incline on the way home and it was running at 210°. It usually cleared up after I let off the gas when I got to the top. One day, it kept bucking here and there all the way home. The last time I took it out, everything ran great until I was on the way home, and I had to pull over on the highway to let it cool down for a bit.

Here's what I have been able to find. It runs fine when it is operating below 210°. I can put as much load on it as I want and nothing happens. But, when it reaches 210°, and it goes over 3100 RPM, the CEL starts flashing. If I keep pushing it, it will get rough. I can recreate this in the driveway, over and over again, just letting it sit and get hot. 210° is the highest it goes sitting and heavy traffic.

I checked the fuel pressure on the rail and it is 49 psi running and stays when I rev it to 3100 and the CEL flashes.

This is getting frustrating and I don't know which direction to go next. I have an old Snap-On red brick I haven't gotten around to using yet. Is there anything I can check with that, that I other wise wouldn't be able to do with a regular scanner?

My father wants to do a compression test. He has a feeling that there's a vacuum problem somewhere. If I remember what he was saying correctly, that it heats something up and it doesn't close all the way, creating a lean condition.

cruiser54

Did the combustion cleaner treatment help at all?
Do you ever get a P0303 since you insulated that injector?

pearlheartgtr

I want to say the cleaner helped a little by smoothing it out a bit, but the problem is still there. It can still be recreated exactly the same way. I still get a P0303, but it's not alone. There's always 4 or 5 other cylinders involved.

Saudade

I don't have the Snap-on scanner but does your other one have live data? Does it also record? Mine has a graphing function as well as export. (Sadly can't use it on my Renix but works great on my other cars).

It would be very useful to observe the live stream and record as you pass through the transition from "runs OK" to "wants to die".

pearlheartgtr

I have the MT2500 brick and I believe it can record live data, just don't know much about it. I have to dig it out and mess with it. My other scanner, an XTOOL Anyscan A30BT, doesn't do too much with this car. My newer cars, it does just about anything an expensive shop scanner can. It's just the old Jeeps the scanners have issue with because it was something about Chrysler not releasing the software and stuff for them to anyone but Snap-On, if I remember correctly. I've never been able to get live data or IM readiness out of any basic scanner with the Jeep.

pearlheartgtr

Update:
Getting misfires at all temperatures, now. I get one or two at idle, but they pick up when I raise the RPMs. It's on all cylinders. Depending on the cycle, the bulk would be on 2 random cylinders. The CEL flashes, then runs a little rough.
I changed the upstream O2 sensors
Fuel pressure test -- 48psi
Compression test.
--1 and 2 -- 143psi
--3-6 -- 153-155psi

Smoke test. This was interesting. Last time I did a smoke test for an evap leak a couple of years ago, it poured out of the filler neck (bad cap). This time, I took the cap off and nothing came out. I tried both lines off the purge solenoid. Everything is buttoned up tight up front with no leaks, but it seems to not be making it to the tank. I had an on again, off again evap leak on this truck that would come and go with the cold and warm weather. I timed my annual inspections around it. For a few months before the misfires started happening, the tank would pressurize here and there when I took the gas cap off and would also give me problems when filling up. The mystery evap leak has disappeared since the misfires started.

Could this be an issue with the evap canister?

I'm at my wit's end on this one.

pearlheartgtr

Update:
New Evap Canister
New TPS (reinstalled original)
New MAP (reinstalled original)
New Cam Positon Sensor
Viper Coil Mod (got tired of futzing with the coil rail)
Sea Foamed the hell out of it (throttle body spray and in tank)
Fuel pressure Test: 49-50 PSI running, key on engine off, revving, and while misfiring
Checked wires: They are all still in the loom and attached to the places they're supposed to be attached to with the clips. Nothing's rubbing.
Checked wire connectors and sprayed with cleaner for the hell of it
Checked and cleaned all of the grounds
All injectors turn on and off while prompted by the Snap-On red brick scanner (they are 784's I bought from someone here a few years ago)
All solenoids turn on and off when prompted by the Brick
Purge solenoid holds and releases vacuum (tested with vacuum pump)

What I noticed in the scanner's live data is that the Leak Detection pump SL is always Blocked and SW Closed. I don't know what I'm really looking at there, but is that significant? There are also no codes for the pump or solenoid.

When I rev it to over 2500, the fuel trims go rich and misfires on all cylinders until I let off and it returns to idle.

I did notice that when I cleared the codes via the scanner, the misfires will happen almost immediately on the next restart when I rev it up. But, if I reset by pulling the negative terminal for a couple of minutes, it runs fine and it pretty much takes several miles of hard driving for the misfires to start up again. Basically, if the truck is sitting and idling in the driveway with me revving it, it won't misfire, but after driving for 5-10 miles, they come back.

Because of the drive cycle misfires I just mentioned, I'm almost wondering if this is a PCM problem. I already popped the connectors off and checked them. They were shiny and clean. Nothing changes if I wiggle them.

pearlheartgtr

So, here's an update. I took it to a shop where the guy said he would give the truck an hour of diagnostic time. With his scanners and such, he found that the timing was off, so he adjusted it. When I started the truck up with my Brick plugged in, it showed a misfire on two cylinders. I restarted the truck and they were gone. Drove it home (about 2 miles) and no misfires. Revved it up in the driveway, a surefire way to set off the misfires, no misfires. I think it may be fixed. I have to drive it around more to be sure.

I'll update the saga if anything changes.

I forgot to mention, a few weeks ago, I did get a brand new PCM from NAPA. Plugged it in and nothing changed. I returned it and put my PCM back in.

cruiser54

Keep us updated plz.

Saudade

How did he "adjust the timing"?

bluejeep2001

That was going to be my question...timing is only computer controlled, rotating distributor or cam synchronizer does nothing for timing

pearlheartgtr

I didn't know anyone was actually reading this thread.

All I know is that he had it hooked up to his scanner/computer and said the adjustment in the oil pump drive was a little off. He really didn't go into too much detail. Grumpy old guy.

Either way, whatever he did improved things. I took it on a ride to the nearest Walmart (40 minutes, one way) and no misfires. However, it did have a few misfires after I had parked and left it running a few minutes and revved it up. Although, not as many misfires as usual. Normally, it would rack up the misfires on every cylinder until the scanner reset the count (around 30) and now it's 1 or 2 on a couple random cylinders. I did some shopping and went home. No misfires. I got home and did the same thing, I sat with it running for a few minutes, while the temperature rose to about 210°, revved, and got a few misfires.

As it sits, I'm thinking some heat soak is happening. Right now, it's in the 30's (Upstate NY). Over the summer, when all hell was breaking looses, it was 90-100°. The night I took the truck to the shop, I drove it a few miles before going there and it was misfiring all over the place (it was 20-30° out). I wanted to see if it was heat soak before I spent the money on a shop, being that it was cold out and I hadn't driven it in the cold after this issue started.

I'm kinda thinking of doing an experiment with opening the hood and putting a fan on it to see if I can replicate it.

pearlheartgtr

I believe it is fixed! It's been around 4 months without symptoms. The fix was a new TPS (again). I had tried one from Amazon and nothing changed. I got another one for the hell of it and everything is good.

Before I went for the TPS, I put a new fuel pump and new injectors in. It seemed to be fixed for a day after each fix, but went straight back to misfiring.

If it starts showing symptoms again, I'll get a Mopar TPS. I just can't afford it right now and I already owe my father a lot of money over this whole debacle.

I'm going to be making a new thread about a mystery front end squeak.