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Discussion Starter #1
94 HB 4x4 KC V6, running smooth for ten years... now a rougher idle (poof poof poofing at the exhaust pipe, where it used to just purr) sounds like its missing?

replaced spark plug wires and PCV, gave it some seafoam love (dirty injectors?), cleaned MAF... tried fuel injector cleaner-- no change.. now I can't accelerate at all in 5th gear, have to downshift (even though its always been a pooch anyway)... so it takes longer to accelerate and i cant climb those hills like it used to
gas mileage is the same tho

what else should i try? it used to just purr at idle.. now it needs help!
should i try replacing the fuel filter?

tried checking error codes -- once i got 11 22 33 44 55, which almost looked like an error itself

any help is appreciated thanks!
 

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Discussion Starter #3
BTW this truck has 170000 miles

going to check these things this weekend

spark plugs (even tho they were replaced 15K mi ago)
try using carb cleaner on vacuum hoses to identify leaks
recheck codes
replace fuel filter

anything else to look at or try?
thanks for your response!!
 

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Discussion Starter #4
this weekend I did some things
1. couldn't find a vacuum leak (tried the carb cleaner spray method)
2. replaced cap & rotor (it was the original)
3. replaced fuel filter

no improvement at all, yet.
will pull codes later
 

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erase all your codes first. Wait till the CEL comes back on, and then pull those codes. I've hear that if you drive around long enough with a bad part, it will throw everything else off balance and make the computer think other parts have gone bad, too.
 

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Discussion Starter #7
update 10/18
well I checked all the plugs -- all of them are grey/white (good!)

pulled error codes again, this time 55 - no malfunction

I should mention that the speedometer cable broke 7000 miles ago and I never fixed it (it was a $200+ job, and I can just use GPS instead),
but does the electronic injection system need to get a reading from the speedometer in order to mix fuel/air correctly?
Is this somehow screwing it up? I don't see how it can, since it ran 6K miles fine without it...
just a thought
 

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the computer could care less what speed you are going...all it cares about is RPM's. Try checking your ECT (engine coolant temp) sensor Measure the ohms across it...should be very little resistance and check the voltage going in should be 5 volts reference signal and 0.5 volts coming out going to computer. Also your IAC (idle air control) valve plunger may be stuck.
 

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Discussion Starter #9
the computer could care less what speed you are going...all it cares about is RPM's. Try checking your ECT (engine coolant temp) sensor Measure the ohms across it...should be very little resistance and check the voltage going in should be 5 volts reference signal and 0.5 volts coming out going to computer. Also your IAC (idle air control) valve plunger may be stuck.
well, it froze last night, and I started it up this am and she purrs like a kitten again!
All of the lost power is restored, can accelerate in 5th gear at 75mph again and the exhaust note is smooth... no more puffing, I'm a happy guy!

my guess is the IAC area, and I appreciate that tip! If it happens again, I'll check that next

How do you fix a stuck IAC valve plunger?

thanks !!
 

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remove the IAC valve and you can try cleaning it with a solvent or PB Blaster but they arent that expensive so i would recommend just replacing it
 

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remove the IAC valve and you can try cleaning it with a solvent or PB Blaster but they arent that expensive so i would recommend just replacing it
I thought it has to be cleaned out with throttle body cleaner to get all the gunk out. I've had good luck with that stuff in the past. Didn't know PB Blaster would do the trick too.
 
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