4.9L Hesitation..
#16
05-02-2014, 09:36 PM
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Update: Haven't got to the o2 sensor yet. But I'm assuming that it threads in where the two pipes are welded together right before the cat. If so the bolt that threads in is there but no wires or anything!! And an update on the fuel psi.... With the truck running I'm getting a constant 38psi. I find that to be really low? If it's not pumping out enough fuel, it's going to produce these symptoms I've been having and also make the truck run rich because the fuel oil mix will be off? I'm leaning towards replacing that fuel pump? What do you guys think? And to clarify I have a BRAND new fuel filter in there from a week ago so I know it's good.
#17
05-07-2014, 01:50 PM
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Update. New fuel pump and o2 sensor. The fuel psi was low so regardless I thought I'd replace it. Anyways, it seems if I don't stomp on the throttle when accelerating its okay for the most part. But if I give it good gas it hesitates to go it's like it gets tons of air flow but no power from it. Any ideas there??
#19
05-07-2014, 07:14 PM
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05-07-2014, 07:39 PM
#23
05-07-2014, 09:36 PM
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#24
05-07-2014, 10:47 PM
#25
05-08-2014, 12:34 AM
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#26
05-08-2014, 01:25 AM
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It's most likely one of the electrolytic capacitors inside your PCM that control the EGR circuit. If it's leaked out it tends to cause that exact problem. There's several outstanding write-ups on this forum- you could probably search "PCM capacitor leaking" in the search box and find them pretty quickly.
The good news is that if you have a talent for solder and some patience you could fix it for less than $2. The bad news is that it's very meticulous work. You might have luck with a remanufactured PCM. AutoZone sells them from $100-$250 and generally has them in stock or close by, but there's no guarantee that a remanufactured PCM will be any better than the one you have.
The PCM sits in a pocket in the firewall just under the brake master cylinder. It comes out by bending the wheel well cover a little bit.
Good luck! -TK
The good news is that if you have a talent for solder and some patience you could fix it for less than $2. The bad news is that it's very meticulous work. You might have luck with a remanufactured PCM. AutoZone sells them from $100-$250 and generally has them in stock or close by, but there's no guarantee that a remanufactured PCM will be any better than the one you have.
The PCM sits in a pocket in the firewall just under the brake master cylinder. It comes out by bending the wheel well cover a little bit.
Good luck! -TK
#27
05-08-2014, 01:29 AM
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Thanks for the response man. I'll grab one from the auto wrecker tomorrow and try it out it to see if it makes a difference!
#28
05-08-2014, 02:42 AM
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Just pull the PCM and check for blown/leaking/bulging capacitors. I know I have mentioned this quite a few times mostly regarding the 4.9L. It seems to be plagued with this problem, but not forgetting that all PCM's can suffer the same fate. Those capacitors are at most 20+ years old and have been subjected to extreme conditions and have done their job well. Sometime no shadetree mechanic can properly diagnose a problem of the 20+ PCM is failing. FWIW, yours may be completely fine, but your problem and list of replacement parts put it at the top.
#29
05-08-2014, 01:23 PM
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Just pull the PCM and check for blown/leaking/bulging capacitors. I know I have mentioned this quite a few times mostly regarding the 4.9L. It seems to be plagued with this problem, but not forgetting that all PCM's can suffer the same fate. Those capacitors are at most 20+ years old and have been subjected to extreme conditions and have done their job well. Sometime no shadetree mechanic can properly diagnose a problem of the 20+ PCM is failing.
FWIW, yours may be completely fine, but your problem and list of replacement parts put it at the top.
FWIW, yours may be completely fine, but your problem and list of replacement parts put it at the top.
Alright thanks man I'll take it out tonight and have a look at it see if I can find anything that doesn't seem right!
#30
05-08-2014, 03:14 PM
it should have at least helped when you start it up. as for when it hesitates under a load, it sounds like you may have a spark plug in which the porcelain has cracked maybe from overtightening or just worn out