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  #1  
Old 10-15-2015, 02:04 AM
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Frikking 3.7

I know this has been beat to death, but after three days I still haven't found the answer.
Wife and I bought a 05 jeep grand Cherokee Laredo with a 3.7 for our son. Jeep is loaded and is nice and when we first bought I thought all I soils do is an one lift and tires.But I have been driving this past week and have found a few issues that are troublesome. 1. Very low idle. Dropping from 500-400 and back in idle or sitting at stop lights. When it does this it sounds like everything is labored. No accessories are on. I changed plugs as I pulled one and saw that gap had burnt to in excess of 0.80. They were all this bad. No change though. Went with champion double platinums 0.42 gap.
Pulled coils and all of them made engine miss when pulled. I am not showing any check engine lights.
Changed IAC,TPS and PCV. nothing made a difference. Had alternator checked ....was OK. Seafoamed and while it huffed some smoke it made little diff also. I have checked for vax leaks visually and by listening as I thought I may have heard some hing on drivers side, buy it may be power steering pump internals and or alternator bearings that I'm hearing. I am at a loss. I'm supposed to take back to a shop on Friday, but this mechanic is the same that told.me it was ideling fine, no issues because there was not a check engine light on.
2. The heater\ac is making noise in every speed weather in heat or ac. The mech told me it would go away if I run it for a while. It's like a ticking coming from glove box area.
3. Seems like the rear end is making noise while on interstate while under acceleration going away when I let off or coast?
And lastly the steering wheel started clicking when I turn wheel. Feels like its coming from indicator? Just started..
I'm kind of ocd and while I could probably turn up the what seems like a very loud stereo and dismiss the issues ......I can't..its driving me nuts not being able to fix the idle.
I've never had anything idle this low. Any one that has had these issues please chime in, as we would be greatfull

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  #2  
Old 10-15-2015, 06:05 AM
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Re: Frikking 3.7

Welcome to the garage.
Since the plugs where worn that far, most probably all preventive maintenance was more or less neglected. Did you change the air filter as well?
When i´m not wrong, also the 3.7 runs best on standard copper core plugs. For some reason those fancy plugs don´t work well.
You did change the IAC stepper motor, but did you clean the throttle body as well (especially the IAC air canal)? Does it idle low when just started as well, or only after heating up?
Noise from the glove box area could be coming from the blend door actuator. Is heating and cooling working ok?
For the rear end noise, i would start checking the U-joints from the aft prop shaft for play. Also check the fluid level from the aft diff and take a small sample of the fluid and check for glinsters (metal flakes). Maybe a good idea to change all the fluids, since the maintenance seems to be neglected (Diff fluids, T-case fluid, transmission fluid/filter, brake fluid and coolant).
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Old 10-15-2015, 01:52 PM
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Re: Frikking 3.7

Thanks for the welcome Frango100.
I took your advise and after work i stopped by oreileys and picked up some different plugs. NGK came out and they said that they had oem type to replace the x2 champ platinum, theu are copper core champions. I replaced all six after checking gaps and then pulled the intake and thoroughly. re-installed the intake made sure i had all vac line back and fired it up with fingers and toes crossed. The rmps went to 700 and i was smiling, but i heard a rattling noise and went to investigate....ended up being the new pcv that i had put in a couple days ago? i went back to town and returned it for another thinking that it was faulty. In all of my years i have never heard one rattle like that and i was able to hear it inside while driving....anyway while i was looking for the rattle the jeep got to temp and the rpm dropped back down to 500....grrr.
I will say however from your advise the jeep is running better past idle...
Wouldn't have any experience with this symptom with the pcv? i put the new one in and it does the same thing... I checked the diff fluid and it is low enough i cant feel on my finger so this weekend ill do a full fluid change...as per your advise.I started thinking about what you said about the plugs and i think your right....mechanical neglect.
But i sure would like to get a handle on the rough low idle...
Thanks for the welcome and advise.\
Evan
Sherman il
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Old 10-15-2015, 08:08 PM
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Re: Frikking 3.7

Have you replaced the fuel filter? On my '02 4.7 WJ it was outside tank above it by diff., don't know if yours is in tank or not.
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Old 10-15-2015, 10:07 PM
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Re: Frikking 3.7

when i asked about the fuel filter this morning they said it was non serviceable and that it was by order only? thought i might go by the stealership in the morning
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Old 10-15-2015, 10:12 PM
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Re: Frikking 3.7

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Originally Posted by coaldigger View Post
when i asked about the fuel filter this morning they said it was non serviceable and that it was by order only? thought i might go by the stealership in the morning
so its an in the gas tank unit....
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Old 10-15-2015, 10:38 PM
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Talking Re: Frikking 3.7

my thoughts exactly. ive only had the jeep a week and a 1/2 and have been chasing this down ever since...finally talked dealer into looking at it tomarrow, but like i said the mechanic that is going to look at it is the same one that told me the sound commimg from heater would fix itself, lol. Any thought on weather i might suggest the fuel filter and possible vacuum leak? i was thinking that maybe the pcv was going crazy because of a vac leak? this thing (pcv) sound like a baby on straight sugar with a rattle....
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Old 10-16-2015, 06:27 AM
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Re: Frikking 3.7

You could let the fuel pressure checked at the rail, but i wonder if this would be a problem with the filter.
That the PCV is making such a noise, could only come from a pulsating crankcase air pressure. Don´t know the 3.7, but there probably are some breather hoses connected to each cylinder head and than going to the inlet. I would check those for obstruction. If ok, maybe a good idea to do a compression/leakdown test and see if there is no problem with leaking piston rings.
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Old 10-16-2015, 10:01 AM
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Re: Frikking 3.7

I agree the fuel filter may not be it but since you are dealing with idle issues and you have attended to spark then fuel delivery is an obvious spot to drill into.

How about removing the pcv valve and replacing with a straight barb tube? If problem is gone then you know the source. Short term engines will "usually" run better than with it but it will snot out blowby in many places if you keep it out. I always pulled mine when I dragged my '70 Challenger and put it back in for the trip home.

Did you have oil/gunk around the old valve or vent hose connections? This would mean the old valve was stuck closed or a worn piston ring as Frango100 suggested.

Does this vehicle have tow? Was it used anlot to tow? If the rear end noise is traced to the differential then it may have worn gears since you only hear it under load. Be sure to eyeball the old oil for shavings. It will have some. A small amount looking like very fine dust is normal but a large amount and visible shavings are not.
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Old 10-19-2015, 03:07 PM
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Re: Frikking 3.7

The pcv does show signs of oil.. Took it back to dealer and like i thought when they called and said it was done....." idles fine" They did say i could take it to a different shop and if they find something, they will take care of it. Im thinking about a compression test. Im glad you said something about the oil on the pcv, i was wondering about it.
Thanks
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Old 10-19-2015, 03:10 PM
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Re: Frikking 3.7

i do also notice a slight backfire sound comming from exhaust maybe when starting after engine warm
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Old 10-19-2015, 05:31 PM
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Re: Frikking 3.7

Quote:
Originally Posted by coaldigger View Post
The pcv does show signs of oil.. Took it back to dealer and like i thought when they called and said it was done....." idles fine" They did say i could take it to a different shop and if they find something, they will take care of it. Im thinking about a compression test. Im glad you said something about the oil on the pcv, i was wondering about it.
Thanks
Its absolutely normal to see oil inside the PCV valve. The air is coming from the crank case vent and this air contains oil. For this reason, many put a catch can in this line, to catch the oil which is in the air and not to burn it of in the engine, causing carbon buildup on valves and combustion camber.
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