99 dakota rt. Stock except m1 intake manifold, ported throttle body. Headers and exhaust.
It's a friend's truck that I built as a flipper but he bought.
Apparently it recently started "backfiring" when he went wide open from a roll to pass, but I never was notified. Last week, it started misfiring and giving a flashing check engine light. This is when I was first notified.
Scanner brings up p0300, p0301, and a downstream 02 code for sluggish response.
Test drive shows normal performance, if a little down on power from what I remember, up until about 3/4 throttle. Then, engine breaks up, doesn't rev, flashing check engine light. This is at about 3500 rpm or so from what I've seen, but doesn't seem rpm related.
Watching live data on my inexpensive scanner while event occurs, tps signal drops out and the timing drops about 25 degrees.
Tps with key on engine off shows good response, maxing at 75% of open.
I'm stumped. It seems timing related, but theres no mechanical or vacuum advance to hang up.
Ideas?
I was thinking weak fuel pump, but that would not explain the TPS behavior.
It's dodge... and a cheap one at that. Plugs wires cap rotor. TPS sensor is butter simple to replace too. O2's in them are barely functional when new. These are literal parts cannons.
Plugs, wires, cap and rotorvall have under 10k on them. Tps is unknown milage
So, at WOT the TPS only shows 75%?
In reply to iansane :
Key on, engine off. Yes. Running, with misfire event, scanner shows -- for a value
Can you get actual resistance or voltage measurements from a sweep of the tps?
Sounds very similar to 2nd gen rx7s when the tps fails. Since they don't have an obd port to get codes, you needed to "manually verify" the sensor values with a DMM.
I'd throw a tps at it and see what happens. (If cheap).
Ooh, I just read something about this. Does it have cruise control? Is the airbag light on?
There was something about the clockspring failing in such a way that voltage from the airbag system was blowing down the cruise control wiring to the engine computer, which was taking out the TPS signal. The fix is a new clockspring.
Has cruise. No airbag lights on though. Has a brake light on in the dash for no reason I've ever found.....
In reply to Pete. (l33t FS) :
Mopar continually impresses me with their ecclectic failures modes.
In reply to iansane :
No wonder Daimler bought them.
iansane said:
In reply to Pete. (l33t FS) :
Mopar continually impresses me with their ecclectic failures modes.
I still love the power steering switches in vehicles of this era (usually 4.7/3.7 trucks) that would kill oxygen sensors.
The switch would leak, and weathertight connectors work in both directions, so the power steering fluid would be pumped under pressure through the wire to the engine computer, where it would go through all the other wires to the oxygen sensors, which would get poisoned by fluid.
It's always kind of a mind bender when you unplug a PCM and a bunch of oil leaks out 
Dusterbd13-michael said:
Plugs, wires, cap and rotorvall have under 10k on them. Tps is unknown milage
With what tho? The junkass champions that I hate are the best plug for them.
Pete. (l33t FS) said:
iansane said:
In reply to Pete. (l33t FS) :
Mopar continually impresses me with their ecclectic failures modes.
I still love the power steering switches in vehicles of this era (usually 4.7/3.7 trucks) that would kill oxygen sensors.
The switch would leak, and weathertight connectors work in both directions, so the power steering fluid would be pumped under pressure through the wire to the engine computer, where it would go through all the other wires to the oxygen sensors, which would get poisoned by fluid.
It's always kind of a mind bender when you unplug a PCM and a bunch of oil leaks out
Automatic corrosion protection! I've seen DEF fluid and coolant do the same thing. Gross.
