Misfires & No Check Engine Light - JeepForum.com
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post #1 of 16 Old 02-19-2015, 07:01 PM Thread Starter
2OO8LAREDO
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Misfires & No Check Engine Light

I have a 08 Grand Cherokee 3.7L that continues to misfire. Has anyone else had this issue?

- Only misfires when attempting to start car within 20ish minutes of turning off the vehicle after a long drive.
- Violent shake and the engine won't quite turn over.
- Letting the car sit for 20ish minutes after a misfire allows the car to start up again normally.
- Break pedal locks up after misfire and won't release for approx 20 minutes.
- No electric issues.
- No check engine light.
- No codes were available from a simple engine code pull.
- Occasional rough idle at stop lights.
- Car is kept well with full synthetic oil changes always on time.

HELP!

Thanks!!

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post #2 of 16 Old 02-19-2015, 07:43 PM
Tango.
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fuel too low in octain will cause that.

Life is hard-John Wayne
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post #3 of 16 Old 02-19-2015, 07:53 PM
JRLT
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You have 85 octane gas like they do in Wyoming?

2010 3.7L, 4XGuard Matrix, Fastman TB, TB Ground Mod, Injen CAI, 255/60/18 Nitto Terra Grapplers, Bilstein Shocks & Struts, Cruiser Alloy Wheels - Switchblade, Stillen Brakes, Cargo Light Strip Mod, Electric Ashtray Mod, Jet-powered, Monkey Navigated...
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post #4 of 16 Old 02-19-2015, 07:53 PM Thread Starter
2OO8LAREDO
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thanks tango, ive heard that before, but these misfires have happened maybe once a month for 5 months now, ruling out bad fuel
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post #5 of 16 Old 02-19-2015, 08:05 PM
Tango.
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could also be carbon build up in the cylinder. usually this is from a lot of short trips. there are several easy ways to clean it out.

Life is hard-John Wayne
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post #6 of 16 Old 02-19-2015, 08:40 PM Thread Starter
2OO8LAREDO
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we do have 85 octane gas here and thats all i use to fill up... better gas seems like such an easy fix here i dont think i could be that lucky...
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post #7 of 16 Old 02-19-2015, 08:47 PM Thread Starter
2OO8LAREDO
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im worried about a cracked head gasket but think it could be something like spark plugs or fuel filter?
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post #8 of 16 Old 02-20-2015, 08:27 AM
msully725
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Quote:
Originally Posted by 2OO8LAREDO View Post
we do have 85 octane gas here and thats all i use to fill up... better gas seems like such an easy fix here i dont think i could be that lucky...
A litle while ago we filled up both our WKs (3.7 and a 5.7) at a gas station that recently changed hands. Shortly after both Jeeps had acceleration problems, and the 5.7 had baddd idle problems after warmed up, would try to stall at red lights.

If just one of the Jeeps did this, bad gas wouldn't have been on my list to check out. But because both of them had issues, and that gas station was the only common tie, we ran through the suspect gas then topped off from another gas station. All issues went away. Bad gas happens I guess.

If you're running 85, that means if you get slightly bad 85, it's pushing it. Try a fresh tank of 87 from another station and see what happens. FWIW, bad head gaskets usually show in the exhaust.. lots of white smoke.
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post #9 of 16 Old 02-20-2015, 09:32 AM
tom19511
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How long have the plugs been in? They should be changed every 30 thousand miles.

Tom

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post #10 of 16 Old 04-13-2015, 01:04 PM
yem514
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Any update on this? I am also having issues that seems similar...
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post #11 of 16 Old 04-13-2015, 01:17 PM
Cainley
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The combination of the break lock up, idle, miss fire and stalling all have one thing in common. They require vacuum to operate. In the passenger side behind the head light is a canister. The Hose is subject to both heat, moisture and other. Check for cracks and replace.
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post #12 of 16 Old 11-16-2015, 05:59 PM Thread Starter
2OO8LAREDO
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::UPDATE:::

I've noticed something new this go around that could be significant to someone reading. I don't know **** about cars. When the death shake starts to occur, if I immediately give some gas the car pulls out of the shake and starts, albeit a bit rough. Thoughts??

I had this problem for quite some time. Seemed to be getting worse. Then I thought I found a fix. Now it has reoccurred and I'm at a loss. As all have described this is occurring when 'running errands'. Seems to consistently happen when I start/stop the engine three times, with the car sitting off for less than 30 minutes between the second and third drives. I do this type of driving for work a couple times a week.

I upgraded fuels to mid grade, threw a fuel system cleaner in, and went almost a month without having the problem again! Thought things were completely solved... Few weeks went by and the misfire-death-shake started happening again. Still using mid level fuel. Pretty pissed off.
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post #13 of 16 Old 11-17-2015, 09:24 AM
Cainley
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Did you check the vacuum line? You have to remove it to confirm it is not cracked. Are you still experiencing the same issues including the Breaks locking up? Please post what your currently experiancing if no longer the same.
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post #14 of 16 Old 03-31-2020, 08:55 AM
lameandboard
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Sounds like an injector
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post #15 of 16 Old 03-31-2020, 09:49 AM
jtec
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maybe put a professional scanner and look at live data.

The jeep is STOCK - no mods, add on's, proms, chips, tuners?

The brake pedal being HARD is interesting - the pedal being hard suggests no vac assist, could inspect check valve to master.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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2008 grand cherokee , misfire , misfires , shaking

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