Jeep died while driving - Looking for some input -
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post #1 of 4 Old 09-20-2017, 10:48 AM Thread Starter
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1994 YJ Wrangler 
Join Date: May 2007
Location: Dillon
Posts: 398
Jeep died while driving - Looking for some input

Went to run a quick errand and was cruising down the hill and realized the jeep had stalled out. It was at idle because I was cruising downhill for a few miles. I tried to restart while cruising and it didn't start. Let the clutch out in gear and that got it started but I had to manipulate the throttle a ton and it sounded like a damn machine gun but not loud, just the way it was firing for lack of a better term. No power, then it would kind of seem ok, then really rapid stuttering?, then no power, etc. Pulled over shut it off for a minute then restarted and drove home. It sputtered on me a few times but was fixed by giving it more gas.

That being said, I recently replaced the Oxygen Sensor, the TPS, and the Temp Sensor because I had had stuttering issues and those codes came up. Seemed to fix it until this morning.

Codes I am getting are:
DTC 14 MAP - Map sensor input above max acceptable voltage
DTC 13 MAP - No difference recognized between map reading at idle and stored bar pressure reading.
DTC 44 - Ambient/battery temp sensor input voltage out of acceptable range - used to get it all the time

Should I just do the obvious and go get a new MAP sensor or are there other things I should check first?

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post #2 of 4 Old 09-20-2017, 02:40 PM
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MAP sensor is a relatively expensive part, and while it might make the jeep run crappy, it shouldn't make it shut down. Save this for last after the following suggestions.

First, clear your codes before going any further by disconnecting the battery negative cable for 30 seconds. Trouble with the Jeep can sometimes trigger a ton of unrelated codes. But getting random code dumps is VERY common if you have a bad main ground connection. See number 2 below.

I would suspect a few things first:
1.) Bad fuel pressure, pump, fuel filter, or regulator. I put this first because you can test for it with a fuel pressure gauge. You can borrow a fuel pressure gauge for free from autozone if you leave a deposit. If you haven't changed your fuel filter in the last couple years, get a new one while you're at autozone borrowing the pressure gauge. It is $7 and this fuel system is especially susceptible to pressure variations. You need to be at 30 psi at idle, and 40 psi at idle with the vacuum hose disconnected from the fuel pressure regulator.
2.) dirty ground or battery cables. I put this second, because replacing all of the main battery cables and cleaning all main ground connections is routine maintenance after 20 years or so. Replacement cables for engine block to battery negative, firewall to battery negative, starter to battery hot, PDC to battery hot are very cheap and worth replacing with 4 gauge or better if they are old. Clean each connection with a wire brush, seal with dielectric grease after reconnecting the new cables.
3.) bad ignition coil. This is very very possible (maybe even likely). but the above things are free.
3.) bad CPS (this is least likely since you were able to bump start it again).
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post #3 of 4 Old 09-21-2017, 06:52 PM Thread Starter
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1994 YJ Wrangler 
Join Date: May 2007
Location: Dillon
Posts: 398
Thanks Mike. I had checked the fuel pressure about a month ago when I replaced the oxygen, TPS, and temp sensors. But did it again just to be sure.

35-36 at idle with the vacuum connected
42 at idle with the vacuum disconnected

I also checked the vacuum as well just because I had time. It's low, 12 at idle, but very steady. The motor does have 233K hard miles on it.

Cleaned up a few grounds, battery terminals are good and clean.

I did go ahead throw a new MAP sensor in because I know its never been replaced and it's going to be winter here any freaking day now.

Drove it around for a while and all seems good but a lot of the problems I've had in the last year are impossible to replicate or anticipate so, fingers crossed
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post #4 of 4 Old 09-22-2017, 10:28 AM
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1989 YJ Wrangler 
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The low vacuum and high idle fuel pressure are related. Both due to vacuum leak. The fuel pressure will go between 30 psi and 40 psi in inverse proportion to your vacuum pressure. i.e. at 0 hhmg vacuum pressure to the gauge, you will be at 40 psi fuel pressure, and at 20 hhmg vacuum you should be at 30 psi fuel pressure.

Its possible that when you swapped the MAP sensor that you found the leak accidently. Could have been on the tube, connection, or the MAP itself.

For peace of mind, idle the vehilce and spray carb cleaner around the engine bay. Listen for a change in engine RPM. This will help you find the leak. Take extra car to spray around the intake manifold bolts. 
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