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Amedee
Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 25245
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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I have 1997 jeep Laredo 4.0 4wd, has been running fine then

Customer Question

I have 1997 jeep Laredo 4.0 4wd, has been running fine then yesterday after driving at turnpike speeds turned off on local road it suddenly started mis-firing at low speed and stop,putting it in neutral stopped the rough idle and engine seems fine only in drive above 15 mph does it start to misfire , what do you think could be the issue?
Submitted: 1 year ago.
Category: Jeep
Expert:  Amedee replied 1 year ago.

Hello and welcome! My name is ***** ***** I can assist you with your question. Is the check engine light on? Are there any codes in the computer? Does it stall out at times when ilding or driving?

Customer: replied 1 year ago.
no check engine light on, it does not stall but close to it at stop in drive, runs fine in park or neutral, the misfiring starts above 15MPH
Expert:  Amedee replied 1 year ago.

Thank you for that information. The most common causes of a rough running condition on this engine are bad tune up parts, bad/weak fuel pump or even a bad camshaft position sensor or crankshaft position sensor.

Expert:  Amedee replied 1 year ago.

You are going to want to check for air or vacuum leaks under the hood as well

Expert:  Amedee replied 1 year ago.

The TPs (which is the throttle position sensor), oxygen sensors and MAP sensor can all affect how the engine runs.. but these are less likley to cause this issue you are having.

Expert:  Amedee replied 1 year ago.

When was the last time the engine was tuned up?

Expert:  Amedee replied 1 year ago.

IF it has been a while, you might want to start there.

Customer: replied 1 year ago.
this seemed like a vacuum leak, it was tuned about 5 months ago, is there a particular vacuum line I should check?
Expert:  Amedee replied 1 year ago.

Dont forget about checking fuel pressure and the cam and crank sensor. YES, check near the intake manifold and gasket, and the throttle body and gasket.

Expert:  Amedee replied 1 year ago.

Be sure to check all vacuum hoses and vacuum lines as well. They all get engine vacuum from the intake manifold.

Expert:  Amedee replied 1 year ago.

So if one of them are leaking vacuum, it can and will cause this sort if issue. It might just be that simple.

Expert:  Amedee replied 1 year ago.

I hope this helps! Please don't forget to honor your good faith deposit by rating my answer as "excellent service" so I get credit for the time and knowledge that I have shared with you in a timely manner.

Best Regards

Amedee

Customer: replied 1 year ago.
if there was an code for this vacuum issue what do you think that would be? I was changing the radio out a few days ago and took off the battery cable which reset the PCM and I only drove it 29 miles afterwards so it most likely would not display any data, is that correct?
Expert:  Amedee replied 1 year ago.

Thats correct. It would take the computer a while to trigger a code related to this issue. Are you asking me what code it would flag if there was a vacuum leak? It would be a P0171 lean code.

Expert:  Amedee replied 1 year ago.

That is from the computer when it sees the oxygen sensor too lean for too long.

Customer: replied 1 year ago.
do I run it in park or does it need to drive to complete the reest to get a code? since you suggest so many possibilities that might narrow down the problem
Expert:  Amedee replied 1 year ago.

The vehicle needs to be driven.

Customer: replied 1 year ago.
about how many miles?
Expert:  Amedee replied 1 year ago.

That all depends on the issue, the severity of the issue and other factors. My experience has been that the computer will pick up on this problem and flag a code after 2 or 3 days of driving.. maybe sooner.

Customer: replied 1 year ago.
okay I will try that then get back to you for more help by phone,do you answer questions that way, I know there is an extra cost
Expert:  Amedee replied 1 year ago.

YES, I would prefer to speak on the phone rather than chat on line.

Expert:  Amedee replied 1 year ago.

You can request a phone call right now if you would like.

Expert:  Amedee replied 1 year ago.

I can talk now

Customer: replied 1 year ago.
fine I will do so once the unit resets and I get a code or codes for you
Expert:  Amedee replied 1 year ago.

Ok sounds good! I do ask that you rate my service now for answering your questions.

Expert:  Amedee replied 1 year ago.

We can do the phone call thing later after you get the codes.

Expert:  Amedee replied 1 year ago.

You should see the rating system towards the bottom of the page

Expert:  Amedee replied 1 year ago.

Hello!

It's Amedee from just answer. I am just checking in to see how things turned out and if you need further assistance? Please let me know.

Amedee