Stalling only in Park... 96 5.2L - JeepForum.com
 
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post #1 of 12 Old 04-03-2020, 06:47 PM Thread Starter
johnsland8
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Stalling only in Park... 96 5.2L

I just finished installing a transmission (used) and swapping in a 242 transfer case. After I finished, the Jeep fired up like normal. Ran for quite a while in the driveway while I checked fluids, picked stuff up, etc. Took it for a few mile drive, everything seemed OK. Came home, pulled in the driveway, put it in Park, it died. Tried to restart, would eventually restart but very roughly and would not stay running. Put it in Neutral. Fired right up. Ran fine. Went through all the gears, no problem. Put it in Park, dies. Rough restart and won't stay running. Only does it in Park.


Anyone got any ideas? This seems like the opposite of most of the posts I can find on stalling issues.


Thank you.

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post #2 of 12 Old 04-04-2020, 09:30 AM
MaintMech
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I would bet it's the neutral safety switch.

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post #3 of 12 Old 04-04-2020, 10:19 AM
jtec
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will it start in GEAR? try R.
maybe confirm gear shift and TV cable adjustment..

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 12 Old 04-04-2020, 11:25 AM Thread Starter
johnsland8
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Quote:
Originally Posted by jtec View Post
will it start in GEAR? try R.
maybe confirm gear shift and TV cable adjustment..

No, it will not start in gear. Will only start in Neutral or Park. Really only runs in N or any Gear, just dies in Park.
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post #5 of 12 Old 04-05-2020, 06:05 AM
V8GCZJ
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Any codes? Did you check if any wires got pinched in between the trans/engine? Crank sensor bent? Vac lines all in good shape?
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post #6 of 12 Old 04-05-2020, 06:55 AM
jtec
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agree with above - check for codes - never know till you look.

It starts in P or N only,
idles OK in N and gear but acts up in P.

Try starting in N shift to P and shake shifter lets see if the NSS is 'off' a little a confused signal .

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #7 of 12 Old 04-06-2020, 03:32 PM Thread Starter
johnsland8
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Went out today. It fired right up and ran great for about 10 minutes in Park and then just died. No idle down, no indication, just like someone flipped a switch, it died. It would re-fire pretty easily and run for about 30 seconds or so and die. It will run fine in Neutral or any Gear, it only seems to act up in Park.

I put the code reader on it and it returned NO codes. I did get a yellow light that indicates there's a "potential" problem or something didn't complete it's test, but that's all I get from that.

Is there anything I can see from the live data screen as it's running that might be an indicator?

The vacuum lines appear to be OK. I can't see any pinched wires or anything but most of it's not visible. Also can't see the crankshaft sensor so not sure how to tell if it's bent unless I can reach in there and feel it?

Would a bad Neutral Safety Switch throw a code? Any way to test it?

Any other ideas?
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post #8 of 12 Old 04-06-2020, 06:28 PM Thread Starter
johnsland8
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Quote:
Originally Posted by johnsland8 View Post
Went out today. It fired right up and ran great for about 10 minutes in Park and then just died. No idle down, no indication, just like someone flipped a switch, it died. It would re-fire pretty easily and run for about 30 seconds or so and die. It will run fine in Neutral or any Gear, it only seems to act up in Park.

I put the code reader on it and it returned NO codes. I did get a yellow light that indicates there's a "potential" problem or something didn't complete it's test, but that's all I get from that.

Is there anything I can see from the live data screen as it's running that might be an indicator?

The vacuum lines appear to be OK. I can't see any pinched wires or anything but most of it's not visible. Also can't see the crankshaft sensor so not sure how to tell if it's bent unless I can reach in there and feel it?

Would a bad Neutral Safety Switch throw a code? Any way to test it?

Any other ideas?

Just to further update this, I just got back from a test drive. It runs great all the time. I pulled over a couple of times and sat on the side of the road for a minute or two, in gear, with my foot on the brake. Shifted into reverse and sat there for a few. It never hesitated or anything. Got back from my test drive, sat in the driveway for a minute in drive. Shifted into Neutral and sat for a minute. All was great. Shifted into Park. Boom, dies instantly. Double checked, it will not start or do anything in any gear. Only turns over in Park or Neutral, like it should.



I'm not sure if it's temp related or just coincidence, but it seems to start and run fine in Park for about 10 minutes the first time I've started it the last two days. Then it's just like a switch flips and power just disappears and dies. After that, it will not run right in Park. I can get it to start roughly in Park and keep it running if I keep the RPM's up, around 1500+, but if I let off the gas, it will die instantly.


Also, threw the code reader back on after the test drive and got a green light. No codes, no errors, nothing.



Thanks!
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post #9 of 12 Old 04-07-2020, 04:32 AM
V8GCZJ
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Quote:
I can get it to start roughly in Park and keep it running if I keep the RPM's up, around 1500+, but if I let off the gas, it will die instantly.

That would be the iac not acting quick enough to keep it at an idle. Might try cleaning out the throttle body and iac ports. Might want to pull out the crank sensor just to see if it got bent in the trans swap.
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post #10 of 12 Old 04-07-2020, 11:37 AM
Timo_90xj
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I'm wondering if this could be an NSS or IAC issue at all, or something completely different.

NSS is on the ground circuit; engine starter motor relay gets the +12V to the relay coil from the ignition switch "Start" position, negative is the control side and is normally open. When the gear shifter is in "N" or "P", it allows ground to pass through the NSS switch and into the starter relay coil.
Ground path is the same for park and neutral, so if it would die in park I'm pretty damn sure it should die in neutral as well.
PCM does get an NSS sense from the same center post (BK/WT wire) as the starter relay coil ground, so that PCM can sense when transmission is in park or neutral and adjusts fuel/ ignition/ idle based on that. Then again, it is the exact same sense signal from the center terminal of the NSS no matter if transmission is in park or neutral.
There is an insulator attached to the rooster comb that is related to the NSS switch in that a failed insulator can cause problems. On the other hand, I don't really know if it could behave in a way where with the transmission and engine warmed up it'd cause the engine to stall in park but not in neutral.

Idle baseline on the magnum engines is factory- adjusted with the set screw on the throttle body, IAC increases airflow when needed. Since the engine runs in neutral and any gear while sitting still and foot on the brake, IAC must be working properly.
There's no harm done checking the IAC and cleaning throttle body, but I don't believe that's the issue due to reasons mentioned above.


This is just a very wild guess, but if NSS and IAC checks out OK, all I could think is that it's the transmission itself causing the issue somehow once things have warmed up. Possible valve body/ electrical issues where for reason or another torque converter lock-up tries to engage - or something like that?

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post #11 of 12 Old 04-07-2020, 04:46 PM Thread Starter
johnsland8
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Quote:
Originally Posted by V8GCZJ View Post
That would be the iac not acting quick enough to keep it at an idle. Might try cleaning out the throttle body and iac ports. Might want to pull out the crank sensor just to see if it got bent in the trans swap.

Cleaned the throttle body and IAC port. Replaced the IAC valve with a new one. No change. Still acting the same way. I can actually keep it running in Park as low as 1000 RPM but will not idle or run below that.


I will check the crank sensor but not sure how that would only affect it in Park since I thought it was reporting the position of the crank at all times?


I also tried "resetting" the PCM just to be sure it wasn't "confused" but that didn't make any difference either. Not sure that's actually a thing but it was a reported fix in other cars so thought I would give it a try.


It's just so odd to me how good it runs all the time... except in Park, and only after it's warmed up. It ran for 20+ minutes in Park on first start up today before it died.



Next?
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post #12 of 12 Old 04-07-2020, 04:56 PM Thread Starter
johnsland8
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Quote:
Originally Posted by Timo_90xj View Post
This is just a very wild guess, but if NSS and IAC checks out OK, all I could think is that it's the transmission itself causing the issue somehow once things have warmed up. Possible valve body/ electrical issues where for reason or another torque converter lock-up tries to engage - or something like that?

Thank you for the reply and observations. Sounds like you were reading my mind. LOL.


This actually makes some sense since the transmission is the only thing that's changed since this problem developed. I just don't really understand all the communication and valve functions that could be going on to test/check it. I feel like I could chase this forever and never figure it out...


Something electrical also makes some sense since there are so many wires and connections that were in the way removing and re-installing the transmission. I easily could have knocked something loose or nicked a wire or something strange that I'm not sure how to detect? Unfortunately, it's nothing the computer recognizes since it shows no codes or faults.
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