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I have a 99 Grand Cherokee, And have had many problems with…

Customer Question
HI Chris I have a 99...
HI Chris
I have a 99 Grand Cherokee, And have had many problems with it - mostly electrical & had the starter replaced few months ago. Don’t know why but the Jeep starts and has been running very loud and high, meaning it Idles very high, like 3000 RPM and doesn’t ever settle or come down , this didn’t happen prior to Starter being changed.
Back to current problem.
, but last Wednesday , I was driving and noticed that the Temperature was low and the Oil Pressure was High on the gauges on Dash. (It was 28-30 Degrees here in Dallas. First real cold front of the year) and it just quit while I was driving. literally in the middle of the street. Tried starting , it would crank , but not actually start . After trying this for 5 minutes, called AAA for tow. whilst waiting , I checked the fluids, etc.. The oil was Full , although very Dark , and I saw some room in the Coolant Reservoir , so I added 1/2 Gallon or Coolant and 1/2 Quart of Oil. Tried starting it again, and same results. Waited 5 minutes, and
Baby started right up , like nothing was wrong.
Was able to drive about 10 miles towards home, and She broke 1/4 mile from the house. My luck, anyhow had it towed to Mechanic, and he is having trouble, The absolute Nicest most honest mechanic I've ever met , but Is not a specialist and was hoping you might be able to help?
He said 2 error codes were showing - p300 and p1291 -
Do you have any instructions or clues as to how he might proceed??
Thanks for your help
Newman
Stuck in Dallas
Submitted: 4 years ago.Category: Jeep
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Answered in 14 minutes by:
12/4/2013
Jeep Mechanic: Chris, Shop Foreman replied 4 years ago
Chris
Chris, Shop Foreman
Category: Jeep
Satisfied Customers: 14,872
Experience: Jeep Certified Master Tech
Verified

Hello, my name is***** you for allowing me to assist you! Hmm, Newman P0300 is a multiple cylinder misfire, but code P1291 is not a valid Jeep code. Could it have been P1391??

Chris

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Customer reply replied 4 years ago

Just got off phone with Mechanic. He said there were 3 error codes

300 , 303 , & 1291 & that there is no current to the ignition coil at all.

When I searched online for 1291 for chrsyler this came back as results:












P1291



No Temp Rise Seen From Intake Heaters



Energizing Heated Air Intake does not change intake air temperature sensor an acceptable amount.



Jeep Mechanic: Chris, Shop Foreman replied 4 years ago
that P1291 code is only for diesel engines, that is why I asked if that was the correct code. Now a code P1391 is for a crankshaft position sensor and that would explain the stalling and would also prevent the ignition coil from being energized. The P0300 codes are misfire codes like I mentioned. I think maybe the mechanic's code reader is reading the code wrong. I think your problem is with the crankshaft position sensor and you may want him to consider replacing it. Now your other problem with the high idle may be a Throttle Position Sensor (TPS) and that may need to be replaced to cure that problem. The only other thing that would cause the high idle is a vacuum leak or a stuck IAC (Idle Air Control ) motor on the throttle body, so mention that to him also.
Chris
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Customer reply replied 4 years ago

Okay-

Thanks for your help , just got off phone mechanic. and he is going to purchase that tomorrow morning and try that . hopefully that does it , Can i check in with you tomorrow afternoon and let you know how it goes , Obviously , if it works , I ll be one a happy customer.

Does that sit well with you ?

Jeep Mechanic: Chris, Shop Foreman replied 4 years ago
You are welcome, and of course you can check back with me tomorrow! I will look for your reply and will continue to help you until the Jeep is fixed. Have a good evening, and I will see you tomorrow.
Chris
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Customer reply replied 4 years ago

You were right , it wasnt p1291 ,

It was p1294 , i was just informed by mechanic. & that is idle not being reached , at least i was consistent , lol.

so the complete error codes list was p300, 302, 303 , 1294

And he informed me tat he went & bought a crank shaft sensor .

Any recommendations ?

Jeep Mechanic: Chris, Shop Foreman replied 4 years ago

Ok, that makes more sense. That code coupled with the high idle problem, tells me tat this is going to be either the IAC (Idle Control Motor) or a large vacuum leak like I mentioned earlier. It has to be one of these things. So tell the mechanic to look for any disconnected vacuum lines at the intake manifold, brake booster, etc. If none are found, then replace the IAC motor on the throttle body. Also have him check and make sure the plate in the throttle body is closed all the way at idle. I am 98% sure that one of these things will fix the problem.

Chris

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