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Peter Bagley
Peter Bagley, Toyota mastertech
Category: Jeep
Satisfied Customers: 777
Experience:  master tech at Toyota dealer
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Have something very strange going on. got a 1999 jeep grand

Customer Question

have something very strange going on. got a 1999 jeep grand Cherokee with 4.0 vehicle has a misfire and will stall after warm up. only codes are p0306, and p0505. we changed coil and car wont even run& back fires put old coil back on and doesn't do anything like new one. what do you think never seen this before. tried 2 different coils same thing. again original coil only will misfire until warm, then will stall
Submitted: 10 months ago.
Category: Jeep
Expert:  Dan replied 10 months ago.

Hello, my name is ***** ***** I'm here to help get your problem solved.

Expert:  Dan replied 10 months ago.

Have spark plugs been replaced? Have you checked for spark strength on cylinder 5?

Customer: replied 10 months ago.
we did check for compression it was good plugs have been changed, why when we put new coil in that vehicle will not even run like plug wires are crossed yea I know no wires but that's how it acts, fuel pump, plugs, and iac have been changed
Expert:  Dan replied 10 months ago.

Put old coil back in and check to see if cylinder 5 has good spark, you can remove coil and connect as park plug tester directly to coil. If spark is good check to see if cylinder 5 injector has good pulse. Let me know, thanks.

Customer: replied 10 months ago.
we have checked all that except for spark why are we looking at #5 when misfire code is for #6
Expert:  Dan replied 10 months ago.

Sorry, I meant to say cylinder 5. Let me know if spark is good, thanks.

Customer: replied 10 months ago.
once again why would I be looking at #5
Expert:  Dan replied 10 months ago.

#6 is what I meant, the P0505 keeps making me think cylinder 5.

Customer: replied 10 months ago.
still don't explain why we put new coil set in and it wont even run back fires stalls wont stay running at all. I will check spark at #6
Expert:  Dan replied 10 months ago.

New coil could be problem, let me know how test goes. Thanks.

Customer: replied 10 months ago.
tried 2 different coils. we have strong spark at all plugs,
Customer: replied 10 months ago.
we ohms inj they checked good did compression tests all good
Customer: replied 10 months ago.
we have replaced crank sensor also
Expert:  Peter Bagley replied 10 months ago.

Hello and welcome to just answer. I value your input to my questions so I may help you better.So I see you have tried coils ,done compression testand have good fuel pressure at the rails? Now try this, swap the injectors from the cylinder that shows misfire with a good one and see if that misfire code moves?

Customer: replied 10 months ago.
We have checked ohms and noid light a shorted in under pressure could be possible. We will check and let you know
Customer: replied 10 months ago.
Won't be back on until tomorrow 8am Mt time
Customer: replied 10 months ago.
moving injector would tell us the misfire, but why the stalling, and why when we put new coil in it runs worse then with old coil, vehicle wont even start back fires like not firing in time. seems to me that we have a ecm issue.
Expert:  Peter Bagley replied 10 months ago.

Lets do the injector swap and see what happens first You may have injector problems ,and then we can take it from there.one thing at a time .Our manufacturer told us when diagnosing " KEEP IT SIMPLE STUPID " In other words go one step at a time..Question were the new spark plugs original OME plugs?

Customer: replied 10 months ago.
plugs are new,
Expert:  Peter Bagley replied 10 months ago.

I understand that but are they OME original plugs that same make that was in it new?

Customer: replied 10 months ago.
even if they are not oem. no chance it can be plugs, I don't know if you are reading question but your responses to me don't make much sense