Misfires and stalls even after replacing parts

Greetings and thanks for having a forum for Jeeps. I became a Jeep owner in 2011 by buying a 2007 Jeep Grand Cherokee Rocky Mountain Edition. It seemed to be a certified used car, but was sold as is. Every component had a blue mark. This Jeep seems incredibly well built. Driving in New Orleans, with extreme potholes seemingly everywhere, the off-road suspension and higher street clearance comes in handy. It also floods after rains a lot here, so the extra height is handy.

About 3 years ago, the low reverse solenoid went on permanent vacation. I was also getting a P0300. Took to Jeep dealer and a week later they confirmed code P0750. Estimated $3,500 to repair along with a new valve body. They went on to say it would take 3 weeks to get the part. Dealer did not see the P0300. I did not want to part with my Jeep for so long, so I found a new Mopar solenoid and it arrived in 3 days from New York. I also ordered a rebuilt valve body which arrived in 4 days. It was not too difficult to remove and replace. That was 3 years ago. Since then, I get misfires on the second trip. Jeep starts fine in the morning. I can drive to a store, go shopping, but the Jeep will misfire on and off all the way home. It will also misfire after 20 minutes +/- when I am at a stop light. The engine stalls, but usually starts right back up. I get DTC for all injectors P0201 thru P0208 and P0300. Been to many repair shops. ! convinced me to replace the computer because they could not find any other reason. Sid it might be hairline cracks. After replacing computer, I still have the same issue. I replaced the IM gaskets, put new seal at the EGR tube to the TB. Replaced the PVC hose to the back side of the IM. (It was cracked) New Mopar Crankshaft position sensor, TPS, and new Ox sensor B2S1 because it had oil on it from valve cover leak. Now has 175,000 miles. New copper spark plugs. I tried unplugging the horn fuse to see if the coil spring circuit was acting up. Not that.

My trusty mechanic used a scan tool and turned each injector on and off, but still get P0201-208. Replaced ASD relay and MAP sensor and Coolant temp sensor. All Mopar.

Any suggestions on what to try? I replaced all if the injector connectors, but no fix problem.

 

I am about to try a new Jeep dealer. I replaced the battery last night. Drove about 20 miles and the issue has not come back-- yet. It feels like it wants to stop and think, then proceeds. Jeep stalled at a red light, but started right back up.

The "new" jeep dealer offers rental cars, so that's a plus. It often takes them several days after you drop off the Jeep to have a look.

 

p020x codes are often a WIRING issue. simply put the PCM is NOT seeing the expected voltage on the injector driver circuit.

All eight having the same problem, p201 thru p0208. All inj going bad at same time, unlikely.
The ASD supply circuit to injector.
the connector on the injector.
the wire from inj to PCM.

tell us is jeep STOCK, no added (aftermarket) remote starter, a tuner, programmer?

 

Thanks for the reply. You are terrific to help.

It was factory original everything when I started to have this "stump the mechanic" problem. I replaced all injectors with Standard Motor injectors about 2 1/2 years ago.. I keep the Chrysler injectors in a baggie. My next step is to clean the old ones and re-install them. I put new injector connectors on because they were coming loose and the red tab came out and did not want to return. I am thinking that my crimping skills are lacking. I used heat shrink and a good tug.

One mechanic replaced the fuel pump about 1 year ago. Another replaced the computer, because they found nothing else. The problem persisted, on and off. About 2 years ago, a Jeep dealer found no problems. It comes and goes. I replaced the TPS, MAP, and IAC, with new Mopar parts.

The Jeep always starts and runs seemingly perfect for at least 15 minutes. The engine will go into open loop when the problem happens. I read P0300, active and pending often.

The puzzle is why does it always start in the morning and runs. The check engine light will go dark, I think that I finally solved the mystery. Then, the jeep starts to run rough and sometimes dies. Check Engine light comes on. The jeep usually starts right back up, but runs poorly. Often, the jeep will run normally.

I am going to go over every inch of injector wiring. I am also considering that the engine heat is causing the injector connectors to loosen, from expansion??? That fits with the car starting in the morning. I orders new one that have locking tabs.

Thanks again. No new tuner, starter or anything. I really like this Jeep and thought they built a fine vehicle.

 

the p0300 is a multi cylinder misfire, with several injectors not spraying (P020x) it is safe to say the injectors are causung the misfires.
A simple circuit for the injectors, 2 wires, one wire gets 12v from the ASD relay on a common circuit, the other inj wire called driver, a different wire/circuit for each inj goes to the PCM.
The code is when the PCM does not see 12v on the driver wire.

Changing the injector connectors- is a good idea, they are known to be a cause of this code.

Using a scanner I would look in freeze frame MAYBE a clue - Also check PENDING thats to easy to ignore.
The inj harness- inspecct feel it looking for a break, pinch point, rub thru.
You could ohm the injectors but all 8 bad seams unlikely. Yes installing original as I worry about aftermarket parts.

change the inj connectors.
inspect harness.
ohm or replace inj.
SCANNER- do you have a good scanner - live data, etc?

 

Change fuse 28 in PDC - check it is tight corossion free.
check the splices I marked and the connector C104 marked also

good luck.

 

Thank you kindly for the advice.
I put the Chrysler injectors back in, after cleaning and ohm testing, and heard a click with 9v battery applied. and used new connectors, which were attached with but splices. I noticed debris in the gas when I emptied the fuel rail. Hopefully that came from the outside of an injector and was not in the gas. I blew compressed air to clean the area before I removed the fuel rail. How can debris make it passed the fuel filter?

Car started and ran fine for 10 minutes. Today, the engine started and seemed to purr. Drove about 5 minutes and stopped the car. About 10 minutes later, the engine started but started to rumble and stumble. Proceeded a few blocks homeward but the engine stalled a few times, but would start right backup. CEL started flashing. Made it home. Scanner says P0300. System was in closed loop. Fuel trim bounced around mostly +/- from 0.00 to 2 to 4 but an occasional + 10, then back to fluctuating from 0 to +/- a few%.
Seems that the P020x codes are gone for now.
I just now saw your post. I am going to check fuse 28. If the splices that you are mentioning are the power feeds to the injectors, they get battery voltage with koeo. I am off to find C104.
Thanks again.

 

Start the violin music. A longer test drive and things seem more like they used to be than they are now. Doesn't make sense. The scan shows all p020x codes are stored and pending. P0300 is stored and pending. It's back to square 1. Live data showed stft b1 and b2 around +20% . The trims would go to 0 then bounce around. O2 readings went to bouncing around, seemingly normally, between 0.1 and 0.9 then would go to 0.000 to 0.015. Both of them. Started running on open loop-drive, but ran all the way back to where I started. I am glad that I have AAA, but did not need it yet. Time for an automobile electrician/
I might have to retire my ohmmeter. The other part of this puzzle is that the Jeep will start tomorrow and run fine for 10 minutes or so. Someone suggested that I soldier the new fuel injector connectors. I used but splices with heat shrink, but the one that I did yesterday, came loose today. I gave all a good tug before I sealed the connection with heat. I could hear each injector click loudly using an automobile stethoscope.

Another observation is that I saw debris in the fuel when I removed the fuel rail. How it got past the filter is perplexing. Maybe the fuel line is decomposing? I might test the injectors that I removed and see if they are open or clogged?

I removed the fuses associated with the injectors and they all looked good, with no corrosion. I may have sensory deprivation???

It's dealer time, again.

 

TPS test results. Pi 1 , ground, 0.000 v ko and .001 koeo (specs 0.015-0.025) so that maybe out of spec?
Signal wire 0.0 ko, then 0.54 koeo , so that is within spec and the voltage runs smooth to wot , which was 3.61 v and smooth back to idle. no jumps
Supply 0.000 ko, then 4.98 koeo.
Then with the key in my hand, I get 4.98 v on the signal and 0.54v on signal wire. There must be 2 capacitors in the circuit?

 

WHY are you checking the TPS?

Let me pull up a diagram and get back to you. GTG busy day.

Attached is a TPS pin out, be sure we are talking about same wire.

 

Thanks for the images and useful information. I tested the TPS because when I test drove yesterday, the short term fuel trims B1 & B2 went to +30%. The computer then commanded open loop-drive and I made it home. All O2 sensors were reporting voltage, jumping up and down and were hot. All looked normal on Live Data, then +30%. Car speed was around 25mph.
Today, the only code pending was P0300. No injector codes!!! All fuel trims, live data, looked normal. Bouncing around + and -., and sometimes 0% I drove about 10 blocks and all went well. Then the next drive, the Jeep stalled once, but started right back up. On the way home, the CEL went off. I was very happy. About 3 hours later, took another drive and the CEL light came back on. P0300 pending. I could feel some stumbling or missing, then it seems to straighten out and drive normally. Fuel trims seemed normal. I did notice the command EGR seems to stay at 7.1%, even when started and idling. When accelerating , the EGR would sometimes jump to 40% or such. The EVAP would come on. I would then get command EGR errors, but then they would read 0.0% So far all driving has been in the city and under 35 mps. I am thinking I might risk highway speed tonight and see. Thanks again for your assistance.

 

The TPS showed 4.98 volts koeo wire 1, supply, 0.54 volts at the signal wire #2 and 0.01 volt at #3 or sensor ground. The ground seems below specs? My volt meter only has 2 decimal places.

 

Might want to inspect all your ground wires for corrosion or decay. There are usually more than one. The pics are some samples and the nEverStart wires make a simple inexpensive fix available in 4-6 gauge wire.

 

Thank you kindly for the photos. I checked all grounds visible from the top of the engine and all looks good. Will have a look under. I ran a new ground from the engine block to the computer housing last year. So far, I found an amazing lack of corrosion. Just put in new battery and had a good look at the battery cables and found no corrosion. No green, no white, just copper colored.

After replacing all injector connector wires, the P020x codes are gone, knock on wood.

It's back to solving P0300. That code comes and goes.

 

fingers crossed on the inj (p020x) codes.

As for p0300 - I would suspect some additional codes - the p0301 type, with no other codes might be a good time to review the fuel system - pressure ck etc. Spec - 58 psi +/- 2 psi

But I am suspecting other codes.

 

Thanks. I will have a look at fuel pressure today. No other codes so far. Just P0300 --pending.

 

I see that P0300 is pending - a cliff hanger keep us posted.

 

While trying to find out why the persistent misfires, I kept in mind that the engine would always start in the morning and run fine. The misfires would only start after the engine got hot. After determining that the fuel delivery seemed to function properly, and there were no noticeable vacuum leaks, the problem had to be on the electrical side. The ignition seemed ok. While looking at the wiring from the relays toward the PCM, I noticed that the ASD relay was really hot, and so was the neighboring A/C relay. I could withdraw the relay easily as though the connection was loose. My first thought was that the heat expanded the metal. While looking closely at the relay, I noticed that the installed relay had 4 blades. The A/c relay had 5. I then looked online for an ASD relay and they all had 5 blades. The correct version has 87A in addition to 30, 85, 86 and 87. Plus some have diodes and some have resistors. Long story short, I replaced the ASD relay with the apparently correct one and the misfires have, so far, gone away. Curiously, the slot into which the 87A blade inserts, is blank. Also, I tugged on the wires that went on the drivers side of the engine. The wire shielding had melted from engine heat. I separated the bundle, but could not find any problems. All wires were coated and no bare metal could be seen.

I hope that this solves the problem. I have only made 3 trips over 3 days, but no stalling and no misfires. Still keeping my fingers crossed.

Thanks for all of your assistance.

 

Good luck

 

Well, surprise. Misfires returned. Jeep always started right up in the morning, and and ran great, but after about 20 minutes, it would run rough, go into open loop and misfire all the way home. Or after a short trip to the store, the Jeep would start up and die or run rough. When I got home, I opened the hood and could hear the ASD relay clicking away. And it was hot to the touch. Much hotter than the other relays, except the neighboring HVAC relay was really hot too. I measured about 165 Degrees F. I ohm tested the brown/white strip wire between the relay and PCM and found no issue there. Next I noticed that the relay came out fairly easily. The other relays seemed like they were glued in place and very hard to pull out. The HVAC relay also would come out easier than the others. They seemed snug, but not tight. The female side of the connection was where the problem was. (go figure) Seems that the loose connection might be causing the problem. After disconnecting the battery ground, and removing the ASD relay, I probed the female part with a small screwdriver and when I pushed, the connector retracted fully into the fuse box cavity. Apparently, a plastic tab holds the wire connector in place. To fix this problem, I took this power junction box apart. It has 4 tabs that hold the box to the car and another 4 tabs that release the underside. I used a small screwdriver and twisted it a bit to close the gap so the connection would be tight. I noticed that the control wire (brown with a white stripe) was stuck to a power wire, which I reasoned was caused by the wire getting hot and partially melting the sheathing. I then installed the relay and used the screwdriver from the underside to push the wire and connector onto the spade part of the relay. I then pushed all the other connectors upward to make sure that I got tight connections. I then did the same procedure to the HVAC relay and then reassembled the fuse box. The car started and ran for about 20 minutes and then started the misfire routine, but the relay stopped clicking and was no hotter than the other relays which were active. I then installed a re manufactured PCM and the car now runs like new. No check engine light, no misfires. So, it seems that the loose connection heated the relay control wire and damaged a circuit in the PCM.

When I initially looked at the ASD connection, there was no corrosion. I never thought about pushing down on the individual relay inserts in the fuse box. Seems that when the relay was removed, the terminal connector wire got pulled up, so it looked normal and the female side was not recessed into the cavity. Then, when the relay was installed, the prong pushed the female part down resulting in a poor connection. Because the other terminals were reasonably tight, the relay seemed to be connecting correctly.

If you are having P0300 issues, and can not find an obvious problem, try the ASD relay inserts and make sure that the connection is real tight. If the relay is clicking, or getting real hot, solving the connection might be the answer.

If the problem returns, I will sadly post. Its only been two days, but no stalling, no misfires and no check engine light.

PS. The company selling the reman. PCM's put an insert in the box which stated that PCMs don't normally go bad on their own. If it breaks, you should find and fix the problem that caused the PCM failure, or you will be buying another PCM. They offered solenoid failures as a common cause. I can add voltage drops to the list, if it was not already there. Poor connections can cause voltage drops and the resulting increase in current can cause a wire to fry and cause a PCM circuit failure.