boggs with more than 1/2 throttle

The wife's DD is a 94 4.0, AW4, and started having problems yesterday. She got gas yesterday morning and then about 20 miles later starting having bogging, hestitation, and internal backfiring. She was able to make it home and I drove it and got the same symptoms. She did not tell me she got gas, so I immediately checked the cps and 02 wires to make sure they had not got against the exhaust manifold (cps is about 1 yr old and the 02 is about 3 months old) and they were both fine. I thought the next logical thing would be the tps and the local parts store had one for about $25. I replaced the tps and ran a can of seafoam through the tb. After the smoke cleared, I drove it again and the bogging was not as bad and the backfire was significantly less, but still there. She then told me she got gas and I assumed there was some water in the tank. I put a can of seafoam in the tank (only about 1/4 tank) and the problem decreased, but it still boggs. I then put about 1/2 tank of premium in it and the problem is still there. It is fine if you don't push the throttle more than half down, but when the pedal is fully depressed it idles up like it is going to downshift but then hesitates and loses power and doesn't downshift. All I have to do is let the pedal up and depress it about half and the engine calms and the idle is stable.

What do I do now? The fuel filter was changed at the same time as the pump. Do I need to change the filter? Is the MAP sensor bad?

I'm not sure if it matters, but I think the gas cap is not holding pressure.

Thanks

Check your fuel pressure. I bet your pump is going out.

mcnamaag said:

Check your fuel pressure. I bet your pump is going out.

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The pump and filter were replaced at the same time about 1 year ago, and I don't think the pump is bad, however I would definately replace the filter before jumping to the conclusion the pump is bad.

When you turn the key on do you hear the pump running. BTW if you purchesed you fuel pump from the Zone they dont last long. Good luck.
atriot:

mcnamaag said:

When you turn the key on do you hear the pump running. BTW if you purchesed you fuel pump from the Zone they dont last long. Good luck.
atriot:

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I did get it at AutoZone, and the wife just got home and I went a listened to it. I can hear it when the key is turned on, but it is slightly louder and doesn't stay on as long as the pump on my 89. Does it matter how long it pumps when the key is turned on if it is already warm? I think my pump is still under waranty.....time to check.

Jess said:

I did get it at AutoZone, and the wife just got home and I went a listened to it. I can hear it when the key is turned on, but it is slightly louder and doesn't stay on as long as the pump on my 89. Does it matter how long it pumps when the key is turned on if it is already warm? I think my pump is still under waranty.....time to check.

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I was incorrect, I got it at Advance, but it was still in waranty. I changed the pump and sock just now and the sock was completely covered in gunk. It now seems to be fixed.
Thanks for all your help.

I only thought it was fixed!!!!

After about a 20 mile drive, while in 3rd gear, when I went to accelerate hard, it went to about 3800 rpms and lost all power and surged up and down within 1000 rpms. Shortly thereafter, I let it cool for about 45 minutes and returned home and I was unable to replicate the symptoms....so it seems to only do it when it is very hot outside (it was 91*) and at or slightly above 210*.

I am planning on changing the filter tomorrow, incase any gunk made it through the sock and pump. Is there anything else I should try?

Aniyunwiya said:

Sounds like a classic symptom of a clogged fuel filter. Check your air filter while you are at it. Been in any red dirt lately? Good luck man!

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No dirt! Wife's rig is stock suspension. I have the fenders cut out with 31's, but with any flex the tires would eat the fenders. It stays on the road until I find her something else for a DD and she lets me build it.

Air filter is mostly clean. It has the normal amount of oil in it, but it has been through no mud or thick dust..........hopefully the fuel filter will fix it!

If the sock was covered in junk chances are the filters clogged also. Any time you change a pump you should change the filter BTW.

Ither fuel filter or clogged CAT.

old_man said:

Ither fuel filter or clogged CAT.

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new cat back less than 3 months ago. I'm about to change the filter.

update?

mcnamaag said:

update?

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Sorry, I had to go to work.

I changed the filter today (gas inside filter looked like chocolate milk) and it seems to be good now. I did not have time to get it to full operating temp and push it hard, but during warm-up on back-roads it showed no negative symptoms. I will update again tomorrow after more driving and give more results.

Thanks for all the help!

Glad it seems to be working for ya. I think you mentioned that your fuel cap does not seal. Get that fixed right away; as it will help prevent more dirt and other contaminants from being drawn into the fuel system. Most folks don't realize how much dirt is sucked in just driving the interstates.