Engine hesitation and sudden jerk

K

KY_Jeep

Member
Looking for some help with a new issue that came up last night. ( I tried searching the forum but found nothing related)

2010 JKU Sport 3.8 AUTO, 117,XXX miles, 35s ,4.88s and running a Traildash.

So driving last night all of a sudden I fell like the engine cuts off or has a misfire. This happened several times before I really started trying things. No check engine light as of yet either. Also gets a hesitation under load or no load but only till about 2500RPM then clears up. Its intermittent at best and cannot point to anything causing it. I do all my own maintenance, It does have a new PCV valve. I have not put new plugs/wires yet as it has been running good. ( Only had a few months and put 4000 miles on it) Just replaced EGR valve the other day to take care of a P0404 code I was getting. It was raining/snowing last night when all this started. Engine idles smooth and no other issues that I can find at this time.

Ideas on what to check?
 
KY_Jeep said:
Looking for some help with a new issue that came up last night. ( I tried searching the forum but found nothing related)

2010 JKU Sport 3.8 AUTO, 117,XXX miles, 35s ,4.88s and running a Traildash.

So driving last night all of a sudden I fell like the engine cuts off or has a misfire. This happened several times before I really started trying things. No check engine light as of yet either. Also gets a hesitation under load or no load but only till about 2500RPM then clears up. Its intermittent at best and cannot point to anything causing it. I do all my own maintenance, It does have a new PCV valve. I have not put new plugs/wires yet as it has been running good. ( Only had a few months and put 4000 miles on it) Just replaced EGR valve the other day to take care of a P0404 code I was getting. It was raining/snowing last night when all this started. Engine idles smooth and no other issues that I can find at this time.

Ideas on what to check?
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Any chance you got bad gas? Also check that battery terminals are tight.
 
WJCO said:
Any chance you got bad gas? Also check that battery terminals are tight.
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Checked battery cables and both are tight. Don't suspect gas as I get fuel there all the time for 3 vehicles and equipment. (not saying it isn't a possibility still tho)
 
Kind of a stretch but I would make sure your air and fuel systems are operating properly. Check the fuel pump relay and your butterfly valve to make sure fuel and air are coming in. Also check air filter. Maybe some mysterious clog killed air flow or something 🤔

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Little update: Drove tonight across town. About 5 mile total round trip. No issues noticed at all. Still no check engine light. Roads are dry tonight too. Wondering if water was somehow spraying into the fender on to the plug wires??? Never been an issue before in the rain but who knows???
 
KY_Jeep said:
Little update: Drove tonight across town. About 5 mile total round trip. No issues noticed at all. Still no check engine light. Roads are dry tonight too. Wondering if water was somehow spraying into the fender on to the plug wires??? Never been an issue before in the rain but who knows???
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I would at least check your relays and fuel and air system. You don't want that to crap out on you when you least expect it. Hopefully it was just some fluke though

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it's recommended to disconnect the battery for about 15-20 minutes so the system relearns for the new parts.

if you didn't disconnect the battery, it takes a few engine start cycles to relearn for the new parts.

I'd still check all the grounds and also do plugs and wires if it's been awhile since they were last replaced.

I've always been of them mindset if the EGR was fouled then check the plugs.
 
I had something similar happen with my 2007 3.8l. The problem was an original OEM spark plug that went bad that was causing misfires. As I remember there wasn't a code thrown until the frequency of misfires hit a certain threshold.
 
jeeeep said:
it's recommended to disconnect the battery for about 15-20 minutes so the system relearns for the new parts.

if you didn't disconnect the battery, it takes a few engine start cycles to relearn for the new parts.

I'd still check all the grounds and also do plugs and wires if it's been awhile since they were last replaced.

I've always been of them mindset if the EGR was fouled then check the plugs.
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Yep. What Jeep said.

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Thanks for all the ideas and info. Will be putting a set of plugs/wires on soon. So far its been doing ok. Just bought my wife a 2015 JKU today so now to go through it and get it all serviced up.
 
I had mine do something similar sometime ago. No dash lights but the OBD2 reader showed a cyl 3 misfire code. From the surface everything looked fine but a closer examination showed the cable's wire was broken and causing sporadic issues.

However, it wasn't related to being raining or wet. So, that could be just a coincidence.

Check cables and plugs. Change all of just one is bad. Never knows.



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