4.0 Stall Issues - JeepForum.com
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post #1 of 20 Old 03-14-2020, 06:35 PM Thread Starter
Neuner-9R
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4.0 Stall Issues

Been enjoying the 4.0 from a ZJ that I swapped in about 5 years ago. Twice recently it has shut down on me on the highway on my return from work but only when it was about 80+ degrees out. Thought I'd start here as CJ owners are always much more knowledgeable about any engine regardless of type than others.

Cooler temp morning commute and lunch errands were fine.

Immediately afterwards, if I get it started, it idles low and rough with a very loud air rushing noise around the IAC. Twisting the throttle / opening butterflies doesn't do anything.

After it cools down, it runs fine.

I replaced the MAP, TPS and IAC and it still left me stranded on the highway IN THE EXACT SAME SPOT from work.

This second time I grabbed video. Doesn't do it justice as the air rushing sound is almost deafening. It's louder than the engine and highway noise.

Scanned PCM and no Codes either time. I can not figure out what would cause this.




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post #2 of 20 Old 03-15-2020, 01:11 PM
dirtdudeaz
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With the info you provided, coolant temp sensor comes to mind or EGT probe. The other thing is vacuum leaks, not for the sound reason (I am certain that's your IAC wide open), but from old cracked/dry hoses that may have let loose finally.

Have you worked on anything lately or messed around in the engine bay before this started up?


Can you plug into the OBD with a full scan tool/data logger that can display all the engine parameters while it's running? Knowing what your sensors are telling the ECM ill be your best bet.
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post #3 of 20 Old 03-15-2020, 02:09 PM Thread Starter
Neuner-9R
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I did do a full scan and even while running normal afterwards and nothing shows up. I wasn't able to scan while it was acting up because I was on the highway and anxious to stop blocking traffic.

Since I don't have power brakes, A/C, etc, I don't have rubber hoses except for power steering and coolant. All ports are capped off and I replaced all of them about 2 years ago. Thanks for the suggestion, I did check them all and no leaks. I did have one of them split on me in the past but it didn't make the engine run funny like this.

It's been cooler out and I can't get it to act up again.

I had the same thought, what was the last thing I did - After all of these years, I finally found a lid for the engine fuse box. I've had issues in the past with the ASD relay and it's fuse wondering if being exposed caused them to fail. It could be now that the lid is trapping heat and causing one of the relays or fuses to act up?

There are only 3 relays and 4 fuses that I need with my basic swap so I'm replacing all of them.

Since there are no codes, can it be the PCM going bad now when it gets warm?
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post #4 of 20 Old 03-15-2020, 11:42 PM
pedal2themetai
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Hi unhook the belt that should stop most of the noise so you can listen for whats is leaking air.You can run without the belt for a short time. it sounds very noisy like water pump or idler pulley making noise..
good luck
tim
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post #5 of 20 Old 03-15-2020, 11:51 PM
pedal2themetai
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Hay at 13 sec. into the video it shows a small broken part on the fender ?? whats that off of?
good luck
tim
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post #6 of 20 Old 03-16-2020, 06:35 AM Thread Starter
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Neuner-9r

Quote:
Originally Posted by dirtdudeaz View Post
(I am certain that's your IAC wide open),
IAC is suppose to be fully closed when not idling, correct?

First time this happened, I pulled the intake hose off and yes, IAC was wide open and it was the area generating the whooshing sound.

I've replaced the IAC and not until now is it throwing a P0505 code. Idle is now at 1200 instead of 790. Reset PCM several times with and without IAC connected and it finally brought the idle down to normal but is still throwing that code. Wondering if I've gotten a bad batch of IACs recently?
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post #7 of 20 Old 03-16-2020, 07:18 AM
pedal2themetai
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another OH clutch fans can make a ton of noise when going bad. just my .o2
good luck
tim
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post #8 of 20 Old 03-16-2020, 08:09 AM
dirtdudeaz
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Quote:
Originally Posted by Neuner-9R View Post
IAC is suppose to be fully closed when not idling, correct?

First time this happened, I pulled the intake hose off and yes, IAC was wide open and it was the area generating the whooshing sound.

I've replaced the IAC and not until now is it throwing a P0505 code. Idle is now at 1200 instead of 790. Reset PCM several times with and without IAC connected and it finally brought the idle down to normal but is still throwing that code. Wondering if I've gotten a bad batch of IACs recently?
Yes, IAC I think is typically open when your TPS shows the computer your butterfly is closed.

Just a thought, have you checked voltages at your TPS at the different openings?

Another thought is the wires themselves. I heard of a situation where the harness/connector had a bad joint, and when someone would wiggle the wires or harness, the IAC would act up or engine would run rough. It wouldn't hurt to check the connections and wires.

One thing to check; have your battery load tested. A faulty battery could have enough power to start everything, but not provide enough to make the ECM happy.

Last thought; do you think it could be fuel related such as vapor lock? What type of fuel rail do you have? Do you have a return system? Is there a pressure regulator external somewhere, or the fuel rail with one on the end?

It does sound like you could have gotten a bad IAC out of the box (I have heard of this happening frequently as well unfortunately).

I found this info; I think it's the right diagram.
Attached Thumbnails
Visio-Drawing1 IAC STEPPER MOTORS.jpg  
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post #9 of 20 Old 03-17-2020, 01:43 PM Thread Starter
Neuner-9R
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I think you're correct in a bad IAC. Drove again and idle was up to 1200. Cleared PCM and idle dropped down to 600 and barely running. Removed, rechecked, installed and cleared and back up to 1200 rpm. I've since ordered a Mopar version.

Good idea about the battery as I forgot about it. It did stay strong trying to start the engine about 10 times so had kindof put it out of my thought although I do need to get it load tested.

Meanwhile, I've disconnected the PCM to check it out. I'm cleaning the plugs and pins although it appears clean. Also trying to hunt down another PCM from salvage just to try out and see if it acts the same. for $60, not a bad test and at least hopefully eliminates it from the equation.
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post #10 of 20 Old 03-19-2020, 11:05 AM Thread Starter
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PCM pricing I've received has been costly so I'm going to hold off for the time being.

I have a Mopar IAC on the way but with Covid19, it's taking a while.

Consensus of other input I've received appears to be a bad CPS unit even though the one I installed was a Mopar unit from Hesco. I've ordered another from them but shipping is delayed.

Once I have all of the replacement parts, I'm going to load test the alternator & battery and be done with it.

I hate that I'm not able to commute to work in this great weather and light traffic!
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post #11 of 20 Old 03-20-2020, 10:14 AM
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Hopefully it's one of those things; keep following up once you find out! The main thing to think about is you aren't getting a code, so the computer thinks everything is working correctly.

CPS is a good idea too especially if you are using a HESCO one; I have heard of those going bad as well. I was thinking the engine operation is typically more erratic, or you get a complete no-start, when they go bad though.

What intrigues me is your narrative about the Jeep dying in the same exact spot each time. So that kind of got me thinking about what changes as a vehicle drives down the road... temperature. So I was thinking something is heating up that doesn't want to be or the computer isn't in sync with the temp change (IAC, coolant temp sensor).
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post #12 of 20 Old 03-20-2020, 01:51 PM
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Both the crank sensor and cam sensor are possibilities, but you usually get a code. Not unusual for the vehicle to start and run fine, for 15-30 minutes, then stall and require cool off before restart.

Where is your fuel pump located?

1983 CJ7, 5.3, NV3550, D300 4:1, Fr D44 Detroit, Rr D44 OX, 4.56, 35" Falken A/T3W on beadlocks
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post #13 of 20 Old 03-26-2020, 08:03 AM Thread Starter
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To summarize, replaced CPS, IAC, TPS and MAP with Mopar parts. I've load tested the battery and altenator and they're great. Still stalled the same on my way home from work in the same spot.

It is heat related for sure.

I've let it idle and driven around for a long time when it's cooler outside with no issues but as soon as its above 80 degrees out, it stalls/acts up. I think it's been the same distance from work because it stalls just as I'm done cruising down the highway at 60+mph and I have to start going slow, 20-30mph, because of lights/traffic. Lot's of wind flow vs very little. The engine temperature when it acted up was 188* which is a little cooler than the high of 197* it gets during the middle of summer. Driving around on cooler days, it stays around 176*

SO...what could be heat related? I keep going back to the PCM but I'm wondering if this might be the coil? I thought a coil either worked or didn't, no inbetween? Would it cause this?

Safe area so I took additional video. I filmed the exhaust so you could hear how it is randomly firing / low idle since the air sound under the hood drowns it out. Sound is from air rushing through the IAC port. This time, increasing the throttle kills the engine which it didn't do before. Strong smell of fuel at the exhaust.

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post #14 of 20 Old 03-26-2020, 08:39 AM
schardein
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What fuel pump are you using, and where is it mounted?

When you say CPS replaced, you mean the crank sensor, correct? You haven't replaced the cam sensor?

Have you ever checked your fuel pressure at the fuel rail, either when it is running correctly or when running rough?

1983 CJ7, 5.3, NV3550, D300 4:1, Fr D44 Detroit, Rr D44 OX, 4.56, 35" Falken A/T3W on beadlocks
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post #15 of 20 Old 03-26-2020, 08:53 AM
dirtdudeaz
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I had asked about fuel as well a couple posts ago too. If it smells like fuel and is rough, and is sucking a ton of air, it leads me to think you're way too rich and then just dumping a ton of fuel at any throttle opening.
  • I am curious to know if you have a regulator, fuel pressure gauge, and a return or return-less system.
  • What's your O2 sensor readings like during all this? Have you looked at replacing that too? If you can't get a good reading with your scan tool, it may be worth checking into.
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