Misfire, backfire, check engine only when I hit a hard bump
#1
Seasoned Member
Thread Starter
Join Date: Jan 2012
Location: Yuma, AZ....yes the 3:10 came here
Posts: 433
Likes: 0
Received 1 Like
on
1 Post
Year: 1998
Model: Cherokee
Engine: 4.0
Misfire, backfire, check engine only when I hit a hard bump
Yesterday I was heading out to go camping when I hit a pothole and my xj misfired (momentary power loss, rpm loss, and slow down) and a check engine light for about 1 second and then it ran normally. Once I hit the dirt road with every hard bump (every 2 minutes), it did the same thing and it backfired a few times too. If I hit a few bumps in a row within a few seconds of each other, it stalled out. Only once though.
The next day on the way home it did the same thing. When I got home I checked the wires on the ignition coil and the spark plug wires (new plugs and wires 4 weeks ago) and can't find any exposed wire. One plug wire was loose but I seated it and test drove it off road and the same problem still happened. The plug wire didn't come loose again.
I plan to check the grounds, but I'm not sure where to check (which ones and where they are located)
I have a cracked aftermarket header (Chinese made) I took off and had welded last week and places back on but it re cracked. I am replacing it tomorrow with Gibson headers. All plugs and hoses are properly connected.
Any suggestions where's else to check or what it can be? The search function doesn't work too well for be on the phone.
The next day on the way home it did the same thing. When I got home I checked the wires on the ignition coil and the spark plug wires (new plugs and wires 4 weeks ago) and can't find any exposed wire. One plug wire was loose but I seated it and test drove it off road and the same problem still happened. The plug wire didn't come loose again.
I plan to check the grounds, but I'm not sure where to check (which ones and where they are located)
I have a cracked aftermarket header (Chinese made) I took off and had welded last week and places back on but it re cracked. I am replacing it tomorrow with Gibson headers. All plugs and hoses are properly connected.
Any suggestions where's else to check or what it can be? The search function doesn't work too well for be on the phone.
#2
Yesterday I was heading out to go camping when I hit a pothole and my xj misfired (momentary power loss, rpm loss, and slow down) and a check engine light for about 1 second and then it ran normally. Once I hit the dirt road with every hard bump (every 2 minutes), it did the same thing and it backfired a few times too. If I hit a few bumps in a row within a few seconds of each other, it stalled out. Only once though.
The next day on the way home it did the same thing. When I got home I checked the wires on the ignition coil and the spark plug wires (new plugs and wires 4 weeks ago) and can't find any exposed wire. One plug wire was loose but I seated it and test drove it off road and the same problem still happened. The plug wire didn't come loose again.
I plan to check the grounds, but I'm not sure where to check (which ones and where they are located)
I have a cracked aftermarket header (Chinese made) I took off and had welded last week and places back on but it re cracked. I am replacing it tomorrow with Gibson headers. All plugs and hoses are properly connected.
Any suggestions where's else to check or what it can be? The search function doesn't work too well for be on the phone.
The next day on the way home it did the same thing. When I got home I checked the wires on the ignition coil and the spark plug wires (new plugs and wires 4 weeks ago) and can't find any exposed wire. One plug wire was loose but I seated it and test drove it off road and the same problem still happened. The plug wire didn't come loose again.
I plan to check the grounds, but I'm not sure where to check (which ones and where they are located)
I have a cracked aftermarket header (Chinese made) I took off and had welded last week and places back on but it re cracked. I am replacing it tomorrow with Gibson headers. All plugs and hoses are properly connected.
Any suggestions where's else to check or what it can be? The search function doesn't work too well for be on the phone.
#3
Seasoned Member
Thread Starter
Join Date: Jan 2012
Location: Yuma, AZ....yes the 3:10 came here
Posts: 433
Likes: 0
Received 1 Like
on
1 Post
Year: 1998
Model: Cherokee
Engine: 4.0
Another weird thing it just did after posting is my fuel gage dropped to E and my light came on and my overhead said 0 to E but it gradually climbed back up to where it originally was. I filled up and sure enough it only took about 15 gallons to fill it. It didn't happen again. Not sure if related or not.
#4
I'll double check that tomorrow when I install the gibson headers but I torqued to spec and re torqued two days later. And I used copper gasket sealer to hold the gasket on both sides. I'll check for any cracks or uneven ware or loose bolts etc...
Another weird thing it just did after posting is my fuel gage dropped to E and my light came on and my overhead said 0 to E but it gradually climbed back up to where it originally was. I filled up and sure enough it only took about 15 gallons to fill it. It didn't happen again. Not sure if related or not.
Another weird thing it just did after posting is my fuel gage dropped to E and my light came on and my overhead said 0 to E but it gradually climbed back up to where it originally was. I filled up and sure enough it only took about 15 gallons to fill it. It didn't happen again. Not sure if related or not.
#5
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,863
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I'll double check that tomorrow when I install the gibson headers but I torqued to spec and re torqued two days later. And I used copper gasket sealer to hold the gasket on both sides. I'll check for any cracks or uneven ware or loose bolts etc...
Another weird thing it just did after posting is my fuel gage dropped to E and my light came on and my overhead said 0 to E but it gradually climbed back up to where it originally was. I filled up and sure enough it only took about 15 gallons to fill it. It didn't happen again. Not sure if related or not.
Another weird thing it just did after posting is my fuel gage dropped to E and my light came on and my overhead said 0 to E but it gradually climbed back up to where it originally was. I filled up and sure enough it only took about 15 gallons to fill it. It didn't happen again. Not sure if related or not.
#7
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,863
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Trending Topics
#8
Seasoned Member
Thread Starter
Join Date: Jan 2012
Location: Yuma, AZ....yes the 3:10 came here
Posts: 433
Likes: 0
Received 1 Like
on
1 Post
Year: 1998
Model: Cherokee
Engine: 4.0
Replaced header with gibsons but haven't been on a rough enough road to test the problem. Checked around the fuel pump and the wires but didn't feel or see anything bad.
#9
Seasoned Member
Thread Starter
Join Date: Jan 2012
Location: Yuma, AZ....yes the 3:10 came here
Posts: 433
Likes: 0
Received 1 Like
on
1 Post
Year: 1998
Model: Cherokee
Engine: 4.0
Ok. Been out a while but I'm back. So I the problem never went away. Any sudden hard bump and the check engine light comes on then off for 1/10 of a second. The RPMs drop. Sometimes it back fires and sometimes the fuel guage drops to E instantly then alowly climbs back to its original level, but a NEW development...sometimes the RPMs shoot up! I'm talking from 900 or 1000 at idle to 2500 or 3000 at idle and then 2000 or 2500 in drive/neutral/reverse. If I hit a hard enough bump it seems to correct it (still with the other symptoms though ). What in the Hell is going on here? Was sure it might be a loose ground connection but the climb in RPMs from a bad ground????
#10
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,863
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Have you addressed the grounds at all? Like finding them, removing them, cleaning and reattaching them? The whole system works pretty much on variable grounds......
#11
Seasoned Member
Thread Starter
Join Date: Jan 2012
Location: Yuma, AZ....yes the 3:10 came here
Posts: 433
Likes: 0
Received 1 Like
on
1 Post
Year: 1998
Model: Cherokee
Engine: 4.0
I haven't even had the time to find out where all the grounds are, how to get to them, what they correspond to, etc...
#12
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,863
Received 1,524 Likes
on
1,236 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Perhaps someone with a FSM will give you the ground locations.
#14
Seasoned Member
Thread Starter
Join Date: Jan 2012
Location: Yuma, AZ....yes the 3:10 came here
Posts: 433
Likes: 0
Received 1 Like
on
1 Post
Year: 1998
Model: Cherokee
Engine: 4.0
I ACCIDENTALLY fixed it! So today I was hit bad with the backfire and check engine. Every little pebble on the pavement was setting it off. Couldn't get over 5mph. So I went to re checking EVERY connection and ground and wire and vacuum and so on. I took off all my plugs and checked the gaps, increased them to about 40-42 instead of 35 to see if there was a difference. Plugged em all back in. Checked all my distributor wires. All good. Found one exposed wire to the tranny but it was the factory cut. Taped it anyways. Yadda yadda.
After feeling defeated again I went to start it up and it was all crank no fire. I cursed the gods and went to checking my plugs again. Jiggling the wires from 1 on to 6. When I got to 5, I jiggled it and my fan came on. Odd. So I made sure it was snug and tried to start it and no fire still. Went to jiggle it again and fan on again. Went to jiggle 6, same thing. When I went to move some connectors that I had already checked out of my way, BOOM fan on...wtf?! So I looked closer and there was a big connector hidden back behind the block a little. It was loose! I snugged it up but felt no bite, no click. Cris crossed some zip ties on it and drove a half mile to a logging road and hit some big ruts and NO BACKFIRE NO CHECK ENGINE! If I'm lucky that was the only culprit!!
Feels a little sluggish but maybe from the increases gap. Still better than it was!
After feeling defeated again I went to start it up and it was all crank no fire. I cursed the gods and went to checking my plugs again. Jiggling the wires from 1 on to 6. When I got to 5, I jiggled it and my fan came on. Odd. So I made sure it was snug and tried to start it and no fire still. Went to jiggle it again and fan on again. Went to jiggle 6, same thing. When I went to move some connectors that I had already checked out of my way, BOOM fan on...wtf?! So I looked closer and there was a big connector hidden back behind the block a little. It was loose! I snugged it up but felt no bite, no click. Cris crossed some zip ties on it and drove a half mile to a logging road and hit some big ruts and NO BACKFIRE NO CHECK ENGINE! If I'm lucky that was the only culprit!!
Feels a little sluggish but maybe from the increases gap. Still better than it was!