Jeep with 4.7 stroker, running rough!

mts91xj

mts91xj

Active Member
Joined
May 16, 2012
Location
Fountain, NC (near greenville)
I bought a 91 xj with a 4.7 stroker (homebrew stroker, not a kit) a few months back. 2 weekends ago it started running VERY bad after I 1) did an oil change and 2) got gas from a sketchy gas station outside of town. It was missing very bad and even cut off while idling a few times.

I put in new plugs, wires, rotor and cap this past sunday, and it ran good... until today. Pulled what I called the number 1 spark plug (closest to the firewall) and it looked nasty - burnt looking / starting to get buildup.

Today is monday, 1 day after replacing plugs and jeep is starting to miss again, and has cut off on me no less than 5 times today (only at low rpms - stopped at stopsign / stoplight)

I pulled the # 1 and 6 plug and swapped them, and the jeep ran resonably better, still missed some, but not as bad. - The number 6 plug (closest to radiator) was in better shape than the #1 plug, (the ceramic was still white except for a little black in one area, and no buildup)

The best way i can describe the look of the pulled plugs would be the ones on a plug chart that are called burnt ash buildup.





Any help on what may be the issue? From reading and looking at spark plug charts i'm thinking bad valve seal maybe? The oil in dipstick is also black already from 1 week in the jeep, and has a hint of gas smell to it.

Please help! My first wheeling trip is in two weeks and I want to be running as good as I can when I go.





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ai1158.photobucket.com_albums_p618_Matthew_Strickland_th_video_2012_07_16_21_56_30.jpg
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Pics attached are of 2 of the sparkplugs that I pulled sunday, will post pic of the #1 sparkplug in the morning.
ai1158.photobucket.com_albums_p618_Matthew_Strickland_th_2012_07_16220116.jpg
ai1158.photobucket.com_albums_p618_Matthew_Strickland_th_2012_07_16220107.jpg
ai1158.photobucket.com_albums_p618_Matthew_Strickland_th_2012_07_16220048.jpg


Also attached is video of the jeep idling.***
 
Replies to everyone + an update:

1)
RenegadeT said:
first things first. #1 plug is all the way forward, #6 is on the firewall.
Have you tried checking compression?
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Thanks for letting me know the correct way to identify the plugs! and no, have not checked compression, i have a friend who is a big truck mechanic thats going to help me diagnose more tonight.

2)
tw89yj said:
Does it have an aftermarket cam?
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No aftermarket cam

3)
jeepinmatt said:
Are you still running the same gas?
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Yes, still running the same gas, haven't quite ran it all out yet, have about 1/3 tank of gas left to burn.



Update - have learned that if i keep the rpms above 2k it doesn't miss as bad, also only happens after jeep is warmed up pretty good - i drive 20 miles to work, and it didn't really start happening until about mile 15 or so.
 
Did you happen to use a lighter weight oil at the oil change? Like one of those 0w30 oils that advertises better gas mileage?
 
jeepinmatt said:
Did you happen to use a lighter weight oil at the oil change? Like one of those 0w30 oils that advertises better gas mileage?
Click to expand...

I used Valvoline 10w40 at the oil change, with 1/2 a bottle of sea foam added to it.

I looked back at service records from the previous owner and he had been using 10w30. I get paid this friday, and had been thinking about doing another oil change and going back to the 10w30.
 
10w30 vs 10w40 won't make a difference. I ran 5w30 in my wifes ZJ with a 4.0 and it caused it to smoke and run a little rough at idle.

Check your plug wires, particularly after dark, and see if any are arcing.

But I'd fill it up with good gas and a bottle of fuel system cleaner, change the fuel filter, and run the piss out of it for a couple days.
 
I am assuming it is a xj by the pic. so it is fuel injected. Forget its stroked, diag the same as any engine. Do u have a MIL light on? If the oil has a fuel smell, then yes it is running rich. Dont run it too much if ther is much fuel in the oil... ull wipe out the berrings! Do a comp check on all cyls. Should be within 10% of each other. if one or more are low, add some oil to the cyls and spin it over to lube up the cyls, then do another comp check, be sure all the plugs r out when u do the comp test to get an accurate reading. if oil bring up the readinds then u have a ring problem. if not then maybe valves, head gasket or a cracked head. could even be injector problems. get a good comp reading then we can help more... Good luck!!!
 
If you put regular gas in it I would almost guarantee that's your problem. Most stokers need 93 octane.
 
Ok everyone, thanks for your help, but i think i may have narrowed the issue thats causing it to run bad only at certain times, and it makes very little sense to me....


Yesterday at lunch i started to get a check engine light, so i ran the code. Got code 45. That code from the best i can tell is ' Overdrive solenoid Sensor' So i decided to drive my jeep home from work in 3rd gear instead of Drive/Overdrive. It didn't buck, stutter, or cut off after it got warmed up real good like it has been previously! I thought maybe it was just a coincidence, so i drove around 75 miles last night in 3rd and it never happened again. This morning i decided i'd drive it to work in Drive/Overdrive and it happened just like clockwork, engine / transmission thoroughly warmed up after drive to work - get off highway onto side roads and it started bucking, stuttering, trying to cut off. I let it do this for about 20 seconds, put it in 3rd and it immediately stopped, and ran fine the rest of the way to work.

What would cause the Overdrive Solenoid Sensor to make the jeep run this ragged?
 
the AW4 is electonically controlled, there are 3 solenoids in the tranny, gotta drop the pan to swap them out. You can check the solenoids thru the TCU (mounted under the dash in front of the passenger's knee). Search on NAXJA.org for the "everything you want to know about AW4" thread, there is some good diagnostic info there.
 
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