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mjshealy 10-25-2010 07:02 AM

UNSOLVABLE PROBLEM Please help! Spitting, misfiring, etc.
Hey all, i have a 2001 Dogde Ram 4wd 5.2. I've had a problem going on for months now that has left my truck undrivable, i'm relying on my POS oldsmobile now. Basically, when i start the truck, anywhere from 1 to 30 minutes into idle, it will kick down to 300 rpm's, spit, sputter, misfire... and that lasts anywhere from 1 to 20 minutes. THEN, it kicks up to 1,200 RPM and works back down to normal idle, and idles fine, but this cycle continues about every 20 - 30 minutes. If you get in the truck, you can either gently push in the gas to where it won't do anything, or you can floor it and its fine. If you put the gas pedal anywhere between all the way down and all the way up, it spits, sputters, misfires & wont do anything. Again, sometimes it'll sputter and then go fine for 60 seconds, but it comes back to running like crap. I get NO check engine light when any of this is happening.

What i HAVE done/replaced: Replaced TPS sensor 3 times now, unrelated o2 sensor replaced, replaced all plugs & wires, replaced ignition coil, performed a fuel pressure test: 44 PSI at normal idle, NO fluctuation when engine kicks down and sputters. (so 44 psi when acting up too). Cleaned Throttle body, cleaned IAC valve, replaced PCV valve, and a couple others i cant think of right now.

EDIT: When it kicks down, the IAC valve starts to open up to try and compensate for some kind of fuel change obviously, but pressure is normal.

chithead 10-25-2010 07:11 AM

Check with 98sst on the ForumZ here... I believe he experienced a similar issue and got it sorted out. Can't remember what the problem was off the top of my head though...

UltraFlame 10-25-2010 07:12 AM

Sounds like the Throttle Position Sensor, but you say you have replaced it several times. Even though there are no CEL lights on I would have it scanned for error codes and have a diagnostic done. A tuner like a Diablo has a diagnostic scan capability and you could set a couple other parameters. But don't take what I said to heart and go buy a bunch more stuff - let the more experienced people chime in and try their hand at your situation.

jason3506 10-25-2010 07:58 PM

maybe you should check the vaccume lines. dont they help controll the idleing?

RamTech 10-25-2010 08:23 PM

What about the plenum pan gasket? A view of the OBDII data stream would be very helpful in diagnosing the problem. I notice you didn't mention the MAP sensor.

coonhound130 10-25-2010 09:02 PM

Mine was acting similar and my crank position sensor was loose ...

98sst 10-26-2010 12:09 AM

I wish I had a solid answer man, mine did just that. I disconnected the neg battery cable, found out that cures it, then did that for some time. Now it runs beautifully. In that time period I've replaced a recalled K&N intake tube, removed a jet chip, added superchips, run 92 octane, use synthetic oil, Cleaned my IACV.

I honestly have no clue what went on. No codes got thrown, but man did it run shitty. Nobody really believed me at the shops because it would disappear on the drive there! I'll do my best to look into it further man, I know how ya feel.

mjshealy 10-26-2010 06:52 AM

Thanks 98, i appreciate your response. I'm firm with believing there are no DTC's, so it's not a sensor issue. There's always been people telling me "that's not true, the light doesn't have to be on for a computer controlled sensor to be bad" But, in my 9 years of working on vehicles i've never found one with a bad sensor that didnt flash a code. I'm not going to replace the MAP. That would be acting different and steady if it was. Coonhound (lol) i will be checking the crank sensor tonight for tightness and do an electrical test. And no ramtech, the plenum gasket is ok. I've leak searched intake mani and the TB for leaks, none found. No vacuum leaks that i can find either. Im so lost i don't even know what to do. It's been connected to my brother's girl's uncle's Commercial OBD-2 scanner and he said there isn't anything he can find either. Thank you guys for your input, but PLEASE keep it coming, i really need this truck. thanks.

coonhound130 10-26-2010 07:01 AM

My light never came on or did it store a code . So it is true , I was like you before and thought it would show a code also , but it didn't .....

whi3500mag 10-26-2010 07:52 AM

mine is doing the same thing i changed the map sensor and it did help some but i truely think i have a blown plenum gasket that is behind the hole thing and if i were a betting man i would say you do to

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