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ok here is goes i have a 91 pu 4cyl with MPI and it was given to me, the thing started and runs but when i get to about 1/2 throttle it starts to die out untill the RPM's get back down to under 2000 and it pick back up untill 3500 and dies back down again. it does this driving down the road and in nutral. in nutral in i slowly pess the gas it makes it to 3500 and dies down to 2000 and climes back up. when it dies it sounds like its starving for fuel. here is what i have done so far. i have changed the plugs, wires, cap and roter, tested the fuel regulator i get 10 psi higher readings then the manual said i should have (32psi and idle and 42psi with no vacum and i had 45 at idle and 55 with no vacume). tested the ignition coil, tested the TPS also checked the timing . i am at my wits end, i cant figure it out. ooh ya and at idle it puuurrrrs like a kitten. what else can i do?? thanks.
 

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well it should shrow a code if bad...but if it's cheap stuck a new one in ther anyway...can't hurt.

do the big 3

at 1/2 tank to 1/4 can of b12 in gas run till about emty fill up and stick new fuel filter on ther. then do a seafoam treatment threw the brake booster right before a oil change. i don't think thats your prob but maybe a cloged fuelfilter and if so do the big 3
 

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i will give it a try but i am starting to think maby the cat is clogged? im going to try to remove it and see how it runs free.
 

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Let us know on the cat.
My cat is stock i believe and its got 175,000 on it. I'm thinking of replacing it since the rest of the exhaust needs replaced anyway.
Curious if yours is plugged, how many miles are on your truck etc..

I just tuned up my truck with weekend. A new Bosch O2 sensor was only $22 at Orileys. Mine looked super old, and it came out like it was super old. LOL Nothing some map gas heat couldn't handle though. :)
 

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oh, and do the seafoam and B12 stuff Smikster mentioned. I did that to mine and it ran noticably better afterwards. Thanks for the tip Smikster!! :)
 

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sounds like same problem i am having not sure if 91 is same engine as mine z24? But maybe ignition control module? Does it feel like a rev limiter? And oh eah what the heck is seafoam and B12?
 

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sounds like same problem i am having not sure if 91 is same engine as mine z24? But maybe ignition control module? Does it feel like a rev limiter? And oh eah what the heck is seafoam and B12?

They are cleaners(injectors, engine.. etc..) can be bought at walmart and your local parts stores.
 

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is there a wisel (omg how you spell that word lol i'm tired) when it does the rpm cut? one guy on here had the same prob and it was his computer i think.
 
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