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goboleko 11-06-2013 06:47 PM

2000 Grand Cherokee - running rough after new cooil - next step?
Hello Everybody,

I got a "deal" on a 2000 Grand Cherokee at the local auction. It's got 200k miles on the straight 6. It's in decent shape overall, but I'll be replacing the radiator once I sort out the rough running and idling. I replaced the air filter, plugs and plug boots immediately after purchase

When started from cold, it runs good for the first mile or so, but it starts missing out and running rough pretty quickly. According to the guy at the local OReilley's, it's got several codes for misfires, coil failure and an injector circuit error.. I just installed a new coil, but the condition persists. My next step would probably be a new ECU.. I've never dealt with fuel injection systems, but that would be my other suspicion - fuel / air delivery. I've not replaced the fuel filter. I'd like to avoid taking it to a pro, but what's the point if I end up just replacing a bunch of part that I don't need to.

I was initially kinda frustrated after realizing the thing has some issues, but I'm more excited to get it running right. It seems like a good vehicle once running right.

Any advice would be greatly appreciated.

goboleko 11-06-2013 06:57 PM

One other thing..
I haven't re-checked the codes since installing the new coil pack.

chris87xj 11-06-2013 09:41 PM

Welcome to Jeepforum fellow Hoosier.
I moved this thread to the Grand Cherokee forum section where your fellow WJ drivers can best assist. Good luck with the jeep.

goboleko 11-07-2013 12:20 PM

At the advice of a friend, I'm going to do a top end clean with a chemical to see if carbon might be an issue. Sounds better than a ECU or injector issue.

Dealer24028 11-07-2013 01:10 PM

What are the specific P codes?

Dealer24028 11-07-2013 01:17 PM

I've seen similar issues before that were caused by the engine harness rubbing through. First thing I'd check would be the harness. Look on the backside of the engine near the firewall. Ive seen the harness rub through on the back of the valve cover stud as well as on the cylinder head itself. The wires that run through that harness are for the injectors and coils. It may also have rubbed through on the injector rail.

Also check if the harness seems stressed around these areas. Sometimes the wires can fray, but not break through the colored insulator.

goboleko 11-07-2013 04:51 PM

These were the codes prior to replacing the coil rail..
p0302 - cyl 2 misfire
p0301 - cyl 1 misfire
p0352 - ignition coil 2 primary circuit malfunction
p 0305 - cyl 5 misfire
p0201 - fuel injector 1 control circuit malfunction
p0300 multiple cyl. misfire detected.

I pumped some Subaru top engine cleaner through the brake vac line and it seemed to make a difference. It's better, but still not right.. idling and running rough. I'm thinking ECU or possibly a bad injector or injectors, but that's my best guess, not based on training or Jeep experience. There's definitely something up with the air/ fuel/ ignition equation. I'm working on a budget, so I'm hoping to avoid just randomly replacing parts.. which is pretty much where I'm at. I'll post updated codes when I check with Oreilley tomorrow.
I have not replaced the fuel filter yet... off the top of my head, that would be the only thing still effecting air or fuel flow.

fletchFL 11-07-2013 06:35 PM

Might I suggest clearing the codes you have, if you haven't done so, and drive it until the light comes back on? Probably won't take long, and see what you're left with(since you have already replaced a couple things). This will help you narrow down which cylinders you are still having an issue at. You can rent things like a noid light set to check each injector pigtail individually. That would help you rule out an injector, ECM, or wiring. 'Wiggle-testing' the harness in any visibly damaged spots Dealer24028 mentioned, while it's running, may help find the problem.

Dealer24028 11-08-2013 05:33 AM

In my opinion P0352 no doubt is causing p0302, and p0201 is probably casusing p0301. those two misfires are most likely causing the p0300. The cylinder 5 misfire is puzzling.

Again, I recommend checking the harness - It's free.

If the harness looks okay, let us know because I have a few other suggestions, but the harness MUST be verified okay.

goboleko 11-08-2013 09:34 AM

Inspected the wiring, and everything on the firewall seems in order. Most of the circuitry is contained in a plastic flexi shield and seems pliable with no visible issues. Connection to the coil appears solid. The leads to the fuel injectors are a different story. There's no visible fraying, but the wires are stiff and brittle. They crunch when you try to move them. I'm pretty limited in fuel injection experience, so I'm not certain what role that circuitry plays in the system or how best to replace it.

fletchFL 11-08-2013 04:42 PM

I'm curious, are those codes the same that were there before the coil pack replacement and tune up? Or had they been cleared after the repair, and returned already? The reason I ask is that, the #2 misfire and the accompanying coil circuit failure could now be a non-issue. Obviously, you'd still have an injector circuit fault. You can rent a noid light set for free, just leave a deposit-if you gotta buy one, you can get a cheapie one for about $20 I think-and check to see if you have a signal to that connector. If you have an intermittent or non-existent signal-the light should blink steadily-you can move on to checking continuity in the wiring harness and verifying the ECM is sending the signal. If you have a good pulse at that injector, the injector is bad. This is free, easier to do, and rules out simpler stuff before you start chasing shorts and broken wires in harnesses, which is time consuming, and not something alot of experienced techs look forward to. And it does beat throwing an injector at it.

As far as the #5 misfire, that MAY be gone, too. But if it returns, pull the spark plug, check the gap and how it appears to be burning.

goboleko 11-08-2013 04:59 PM

those were the codes after the tune up but before the coil pack. I have not run codes since the pack install, but I will in the next 24 hours and post the latest. Trying to drive it a little and see if there's any further change following the top end clean.

goboleko 11-09-2013 11:43 AM

Just checked codes. Down to 2 after the coil swap and top end cleaning. P0301 and P0201. That's encouraging. The guys at OReilly did not have a noid light to lend or sell, but suggested using my multimeter to check the circuit. Going to do a quick internet search for info on using my meter for the test. Any thoughts on the next step would be greatly appreciated.

fletchFL 11-09-2013 07:50 PM

Best I can say is that first, you will want to check between the two terminals in the connector for the signal. If none, you'll need to check them both between ground and then power. BUT, if done wrong this next step can definitely hurt the ECM.

Depending on how some multimeters work, you may not get a definitive answer by using any rate, if you do, an old school analog meter with a needle & gauge would probably be more helpful, since the display on a digital may not give you anything useful. And you gotta remember that touching the probes together while they are touching the terminals is no bueno...very bad for the ECM. I would check Advance Auto Parts, if you have one nearby, coincidentally, that's where I got my noid lights...not a tool truck. I'd also have a power probe ready-makes it easier to find out if the power or ground wire is the problem, IF there is one-but that's one of those things that you probably don't have access to.

Hell, if you had some kind of small 12v DC lightbulb, that might have a couple wires soldered to it, you could use that to test for pulse. Let's say an old blinker or tail light bulb, still in the socket with wires, cut out of a harness. Again, it will flicker steadily, but it will not be very bright
I forgot to mention it-and I don't know if I have to, so I will anyway,-but the engine should be running. Could be obvious to you, but just gonna throw it out there, lol.

goboleko 11-11-2013 06:36 PM

Good news .. strange news. I pulled the injectors and manually cleaned them. I could not get the first injector to flow, but inspected with a magnifier and found a piece of debris in the intake side. removed that, and could get some flow.. I reassembled the system and took it for a test drive, expecting little change. It ran fine. It was smooth and quiet. I took it to have the codes reset and it immediately gave me a code when restarted. Drove it for awhile and got the coded rechecked. It's down to 1 code - p0201 - injector circuit open. It does seem to be using more gas than I'd expect, but is running smooth. I haven't run a pulse test of any kind yet, but will go that route if it's not obvious it needs a new injector from what I've described.

I'm thinking bad injector at this point - stuck open maybe?

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