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HELP! Truck just began cutting out on accel. idle rough

3149 Views 21 Replies 9 Participants Last post by  juggalo_wa
Was fine yesterday. Today it began idling rough and cutting out, misfiring, on acceleration. In park if I ease on the throttle it will rev up fine but if I nail it the engine bogs down and sounds like it backfires a bit. Holding the throttle down it just stumbles and pops. Smells like it is rich but there is no smoke that I can see. I replaced the tp sensor and put in seafoam and heet.

Any ideas?????????
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did it do this after or before the seafoam?
B4, the tp, sf and heet were attempts to fix.
Was this just a sudden problem or did you notice anything before hand?
Nope, was fine when used yesterday. Today I noticed the problem as we started out and it seemed to get worse as we drove. Could it possibly be the MAP sensor?
The check engine light only came on once. It was an 0300 and an 0304, misfire codes. I reset the comp when I changed the TP sensor and the code hasn't come back. STILL won't accelerate without cutting out.
Test the voltage from the TPS sensor on the center pin with a voltmeter. Make sure it's about .75mV

If not, do the TPS mod to that brand new sensor or if you have the old one still, do it to that unless you're sure it was 100% dead.

Here's the steps for testing the voltage:

1) start with the key on, engine off.
2) Stick one node from the voltmeter through the weathershielding of the TPS, ground the other node.

Make sure you have good contact with the center pin.
This is a severe stumble/misfire, not just a lagging throttle. It now has a new tps and map but same problem.
I miss read your initial post and took it as if you were blipping the throttle not letting it have your foot through the floor. ;) My bad!

Still though, not all TPS's will line up with the TB correctly, you still may want to check it just as an off chance possibility.
Thanks for the advice...

Man...I give up. Now has new cap and rotor. It will accelerate if I lightly press the gas pedal but if I go past that point it breaks up and backfires. It damn near sounds like it shuts off but comes back if I let off. Idle is rough. I can rev it up at idle but if I quickly peg it it hesitates/stumbles.

Uggggh...I hate going to the dealer but I think it may be my best bet rather than go to a garage that may get stumped too.

My best bets are on the fuel pump, the fuel regulator or the PCM itself. I am truly frustrated at this one. I guess I can look to see if there is fuel in the vac line going to the regulator.
PS. It needed the cap, rotor and TPS so I am not too bad of a parts changing hack! WTH are ya supposed to do w/o dtc's or a fuel pressure guage?
you had dtc's/codes. p0300 and p0304 . check secondary ignition...........plugs ,wires, cap and rotor. after that you're getting into injectors and or mechanical( compression/ leakdown tests).

most missfires are ignition related. probably time for a tune up. get some plugs and wires on there
Hi ho Hi ho, it's off to the dealer I go. The local garage couldn't figger it out after four hours of looking at it. I dropped it off tonite to have the dealer try.

TPS, MAP, Cam sensor, o2 sensors, cap and rotor. Fuel pressure good. Timing marks on. WTH!
*Having another beer in preparation for the call tomorrow...*
*and a shot of Jose C*
Got the call from the dealer and I sorta welcome the diagnosis. A clogged cat and possible clogged muffler.

Time to seriously start searching the threads for muffler recommendations :D
Tim'sD said:
Got the call from the dealer and I sorta welcome the diagnosis. A clogged cat and possible clogged muffler.

Time to seriously start searching the threads for muffler recommendations :D

Well, I installed the set of plug wires and NGK plugs I bought along with my new muffler. I did the plug wire tsb while I was at it. I started it to make sure I had the firing order correct and guess what? Yep, it runs just fine now. The dealer, local garage and me were all wrong. The horrible misfire was all due to the plug wires. Unreal.

I'm still gonna take this opportunity to replace the muffler and cat but I feel better that it is back to it's old self...okay, maybe better!
As a general rule of thumb, ALWAYS start by replacing plugs, then wires, when dealing with misfires, since they are usually the cheapest to replace and are usually the culprits. It's not too uncommon for several plugs to go at once, it's happened to me on occassion.
I have 04 15oo doing the same thing replaced plugs and wires still doing it 1500 rpm below wont stay running 2000 rpm up runs smooth codes 0300 dont know what to do

Try a new ignition coil. That solved my problem. I bought an Accel aftermarket coil for mine.
04 hemi has 8 coil packs and it says multtiple missfire i hate to buy 8 new coil packs
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