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  #1  
Old March 17th, 2020, 11:14
Neuner Neuner is offline
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4.0 Stalls on Highway, Appears Heat Related

4.0 OBDII out of a '98 ZJ with a '98 XJ PCM in a CJ7 so didn't know where to post...

Swapped in 5 years ago and has been running great. 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.

With cooler morning commute and lunch errands it runs great, lots of power.

Cruising along about 70mph and 80+ degrees out, it will all of a sudden just quit. Immediately afterwards, if I get it started;
- engine temperature normal
- idles low and rough, barely running
- no change in rpms if I increase the throttle / open butterfly
- has a deafening air rushing noise at the IAC port
- has no OBDII codes thrown
- feathering the clutch in gear will kill it so no power

After it cools down a little after about 10 minutes, it runs good and strong all the way home with no issues.

I replaced the MAP, TPS and IAC and it still left me stranded on the highway IN THE EXACT SAME SPOT from work the 2nd time.

Scanned PCM and no Codes either time. I cannot figure out what would cause this except maybe a PCM going bad?

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

https://www.youtube.com/watch?v=du5be8qtjgA
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  #2  
Old March 17th, 2020, 11:16
Neuner Neuner is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

The weird sound you hear in the video is only the air at the IAC, not the engine, belt or fan.
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  #3  
Old March 17th, 2020, 15:13
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Tim_MN Tim_MN is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

The Crankshaft Position Sensor is the first thing to suspect for unexplained and/or heat related stalling. Test the CPS.

The low idle, barely running, suggests low battery voltage rebooting the PCM. Load test the alternator. Load Test the battery. Remove, inspect, clean, and snug all the starting and charging connections and wires.

The throttle response symptoms suggests a faulty Throttle Position Sensor. A faulty TPS may have low idle and rough running as symptoms.

Are you installing genuine Jeep sensors ? Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Cheap parts are cheap for a reason.
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Quote:
Originally Posted by bimmerjeeper

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Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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  #4  
Old March 18th, 2020, 00:28
Ralph77 Ralph77 is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

I am also thinking CPS.
Kinda sounds like thermal failure.
I went through the same thing on my '00 XJ with a 4.0.
No CELs or pending CELs.
No no bus crap or anything else that seems to be a more common symptom for it.
Just stall when it reached operating temperature. Like you turned off the key.
Thing about testing if it is thermal failure is that testing it when cold it will give you a good reading.
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  #5  
Old March 18th, 2020, 05:57
Neuner Neuner is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

Thanks for the reply and suggestions. I'm tired of the 'lifetime warranty' parts. Got some work to do.

I have a Mopar IAC on it's way.

Since I was able to use the battery 7-8 times to try and start afterwards with no drop in starting power, I assume it and the alternator are good? I do have a newer battery I believe will fit.

Does a place like O'Reilly's test the alternator or where do I need to take it?

I'm using a Hesco CPS conversion kit for the front damper. They say it's a Mopar part. It gets a good amount of air in it's position which is why it's hard seeing it as heat related but I'll get a new one anyways. New part is Mopar as well. I'd post images but don't think I'm able to yet.
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Old March 18th, 2020, 05:59
Neuner Neuner is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

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  #7  
Old March 18th, 2020, 06:53
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Re: 4.0 Stalls on Highway, Appears Heat Related

I would also confirm with an oscilloscope or DRB-III Scan Tool that the CPS synchronization is correct.

No assuming. Have the alternator and battery Load Tested inside a test machine. Handheld testers are inaccurate wand will often pass weak alternators and batteries.
.
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Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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  #8  
Old March 18th, 2020, 07:58
Neuner Neuner is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

Ok, will do. Where do you get you get an alternator load tested like that?
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  #9  
Old March 19th, 2020, 03:45
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Re: 4.0 Stalls on Highway, Appears Heat Related

One of local auto parts stores has an alternator and starter test bench. I prefer to go to the local shop that specializes in alternator/starter rebuilding and electrical trouble shooting. They use German and Japanese parts to rebuild my alternators, no Chinese crap parts for me thank you.
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Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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  #10  
Old March 21st, 2020, 19:57
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Runnin'OnEmpty Runnin'OnEmpty is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

You might try checking the sensor connector.
Unplug it, clean with electrical cleaner, then
apply dielectric grease to the connection.

Sometimes it's the simple stuff that give the
biggest headaches...
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  #11  
Old March 23rd, 2020, 05:41
Neuner Neuner is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

When I did the swap, I couldn't find a matching Hesco connector so I had to hardwire it in. Probably the best connection on the whole Jeep by the time I was done with it. I think I've found the female connector part and hope to splice it in instead so will be some time before I install the newer CPS.

Installed Mopar IAC and idle is back to normal.

Conducted a Load Test on the alternator for a good amount of time, cold and hot. Engine off and Battery 12.05v, Idle cold and hot 13.84-13.86v consistent, under Load 13.94-13.97v consistent. AC Meter to check Diodes and was a 0.00 for 10 sec and then stayed consistently at 0.08v. Looks like all is well.
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  #12  
Old March 26th, 2020, 07:08
Neuner Neuner is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

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.

https://youtu.be/xts_RyBgDek
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  #13  
Old March 26th, 2020, 07:16
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Tim_MN Tim_MN is offline
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Re: 4.0 Stalls on Highway, Appears Heat Related

The coil can have partial failure that could be heat related, or not. Testing is simple.
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Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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