Backfiring

[Wolfie]

OK I have spent way too long on Google and trying to figure out what's wrong. I thought I fixed it and I guess I didnt.

It back fires from the exhaust. Jeep shakes. At 1500 it won't. Every other rpm it does.

I've been having so many problems with my jeep lately that its starting to bum me out bad. I just want my jeep back.

It has new spark plugs. Wires and cap are newer. I've never messed with any of those.

It threw a code for a mass air flow or something along those lines. I don't remember its been a year since I checked it.

I do not want to take it to a shop. I am pretty close to just buying a running 4.0 and saying screw the one I have now.

I don't want to buy a new xj. But stuff hasn't been going right and I'm pretty much at my breaking point here.

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[4.3LXJ]

That code is a good indication of where to start. IIRC, the mass air flow sensor going bad will cause an occasional backfire

[Wolfie]

That code is a good indication of where to start. IIRC, the mass air flow sensor going bad will cause an occasional backfire

But it wouldn't cause constant back fire?

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[4.3LXJ]

I suppose it depends on how bad it is and how intermittent the screw up is. But I do remember a few instances where replacing it cured the problem

[Wolfie]

I suppose it depends on how bad it is and how intermittent the screw up is. But I do remember a few instances where replacing it cured the problem

Well crap. Those things aren't cheap. Oh well if its needed...

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[4.3LXJ]

Sensors do have to be replaced once in awhile

[Wolfie]

Sensors do have to be replaced once in awhile

Besides mass air flow. Any other sensors that might need replacing? MAP? TBS? Anything else I should do? Or should I suck it up and take it to a shop to get looked at?

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[Wolfie]

Back fire at idle really bugs me. Coolants not in the oil. So again I don't think its the head gasket. This is gonna bug me all drill.

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[4.3LXJ]

Besides mass air flow. Any other sensors that might need replacing? MAP? TBS? Anything else I should do? Or should I suck it up and take it to a shop to get looked at?

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The only one that comes to mind is if the camshaft position sensor is messing up in the distributor. But I think the MAP sensor will get it

[Wolfie]

The only one that comes to mind is if the camshaft position sensor is messing up in the distributor. But I think the MAP sensor will get it

Well I'll order a new one. If the camshaft position sensor was messed up wouldn't it not start/run? Or that the crankshaft sensor that does that?

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[4.3LXJ]

Either one can stop the engine if not working. But is possible to have an erratic spark because of the camshaft position sensor. But don't get one unless you know it for sure is bad.

[Wolfie]

Either one can stop the engine if not working. But is possible to have an erratic spark because of the camshaft position sensor. But don't get one unless you know it for sure is bad.

If a map doesn't fix it then I'll take it to a shop and have them look at it

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[4.3LXJ]

Sounds like a plan

[Rocco83]

Sounds a lot like what my Jeep was doing. Cam sensor in mine was bad.

[Wolfie]

Sounds a lot like what my Jeep was doing. Cam sensor in mine was bad.

Well as I said. If the MAP sensor doesn't fix it. Or the O2 sensor then I'm gonna take it to a shop and see what's up. If its the cam sensor... well its the cam sensor then

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[Wolfie]

Changing the map sensor didn't help. Also something I didn't notice before because I was rushing. Its idling at a higher rpm then it did before. It used to idle around 750. Now its a little over a grand.

And the exhaust smells kind of rich. Its got hesitation. The idle is very rough.

Until certain rpms it kind of reminds me of a machine gun. Constant tat tat tat kind of noise.

I'm stumped?

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[4.3LXJ]

Does it do this when cold or at operating temp?

[Wolfie]

Does it do this when cold or at operating temp?

Cold yes. Running temp no. I restarted the Cherokee a few times (temps were still up) and ran fine.

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[4.3LXJ]

It will run rich when cold. Kind of like having a choke on a carburetor.

[Wolfie]

It will run rich when cold. Kind of like having a choke on a carburetor.

So what's my problem? What do I need to replace and or fix?

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[4.3LXJ]

For running rich at cold temps, nothing. It is supposed to do that. I still think you are running lean though, or you might have carbon buildup in the combustion chamber. Some SeaFoam will fix that. If you pull a few plugs what do they look like/

[Wolfie]

For running rich at cold temps, nothing. It is supposed to do that. I still think you are running lean though, or you might have carbon buildup in the combustion chamber. Some SeaFoam will fix that. If you pull a few plugs what do they look like/

They have a bit of carbon on them. They are brand new too. In case that helps.

What would I have to fix if its running lean?

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[4.3LXJ]

If lean, check fuel pressure while running and you may need to replace the O2 sensor. I know you changed it a few months back, but it is still no guarantee that it is good now. They do wear out and they are not all perfect by any means

[Wolfie]

If lean, check fuel pressure while running and you may need to replace the O2 sensor. I know you changed it a few months back, but it is still no guarantee that it is good now. They do wear out and they are not all perfect by any means

Change the plugs or the o2 sensor?

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[4.3LXJ]

O2sensor. Check those plugs after running at operating temp for a few minutes. Should clean up

[Wolfie]

O2sensor. Check those plugs after running at operating temp for a few minutes. Should clean up

I'll seafoam it while I'm at it too. I haven't touched the o2 sense I bough it. So I bet its in need of a change.

Glad things are finally getting better with my jeep.

Any other things I should look at?

Thanks for the help by the way

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[4.3LXJ]

Outside of making sure the fluids are up, coolant possibly. Most people neglect changing it, even me at times

[4.3LXJ]

One more thing, change the O2 sensor after Seafoaming. It can sometimes not be good for the sensor

[Wolfie]

Outside of making sure the fluids are up, coolant possibly. Most people neglect changing it, even me at times

I just recently changed the coolant. I haven't done a flush though. Might be a good idea. Wouldn't it?

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[Wolfie]

One more thing, change the O2 sensor after Seafoaming. It can sometimes not be good for the sensor

Seafoam it then change the o2?

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[4.3LXJ]

Never hurts.

[Wolfie]

I already pm'ed 4.3LXJ. But I have a new problem.

Jeep made it to drill and back which is a 400 mile trip. No real issues. Now the backfire happens all the time. Not only when cold.

Put injector cleaner in the tank. Going to be putting a new air filter in. Also checked spark plugs, and wires and what not and they all seem fine.

TPS or coolant temp sensor? I already have plans on replacing the coolant temp sensor. Should I get a TPS also?

I'm at a lose here.

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