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Engine Misfire

1466 Views 15 Replies 6 Participants Last post by  pudge_slugfest
I was wondering what is going on, it seems as i was city driving and idling around the thing ran like a piece of crap and when i would floor it it would bog and then go good, seems like if i kept my RPMS up at 1000 while idling i would punch the gas and it would go good, it only seemed sluggish while waiting there for a bit, then i got a code P0300 which means random multiple misfires, could this be a bad TPS ??
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Could be plugs, wires, cap and rotor. Replace all those and see if it helps. Probably wouldn't hurt to replace them anways. Goodluck!
Not a TPS, won't cause misfire code. With dodges it is usually plug wires, BUT---if that does not fix the prob, plugs, cap and rotor as Loud Dodge suggests. Then think about coil, plenum gasket, crank and cam position sensors and PCM. BTW seems Rams like wires from the dealer better than aftermarket. HTH and good luck.
dont have one lol
Before you replace the wires, you can also use some flex conduit (convolute) and insulate every other plug wire. This will prevent the induction (cross firing) that is throwing the multiple misfire code.
If the wires, cap, rotor, etc have over 80,000 on them might replace them anyway.
What do the plugs look like?

edit: you will need about 9-10 feet of convolute.
plugs have a little bit of brown on the bottom, and then get whiter as it goes up the plug
I dont know the milage of you engine, so we'll assume you still have adequate compression.
Invest $15 - change the plugs and wrap every other plug wire in convolute. The will eliminate the possibility of cross firing (induction).
If you replace the plugs and still get the misfire, then move on to cap & rotor, then wires.
I had the same problem and the solution was in the IAC (idle air controller) runs between 50 and 60 bucks. what it does is make a controled vacume leak and allows for the fast idle, which is why you don't have a prob when yuo keep the idle around 1000. IF you have a low idle around 400-600 and it seems to miss, also do you have your engine light on, if so your codes will say both the IAC and a missfire, at least mine did... hope this helps.
I had the same problem and the solution was in the IAC (idle air controller) runs between 50 and 60 bucks. what it does is make a controled vacume leak and allows for the fast idle, which is why you don't have a prob when yuo keep the idle around 1000. IF you have a low idle around 400-600 and it seems to miss, also do you have your engine light on, if so your codes will say both the IAC and a missfire, at least mine did... hope this helps.
I ran my IAC disconnected for almost a year, I highly doubt the IAC allowing too little air into the throttle body via the plunger assembly it actuates would cause a misfire.
Usually IAC failures result in low idle or stalling at idle, in addition to throwing a code for the IAC itself.
it is not that it allows too lottle it is that it allows too much, it is some what like a choke, on a carburator, but yes chizzle yu are right, that is why i asked if he had the engine light on...
the IAC is usually effected more in colder climates or on cold mornings, once mine warmed up it ran better, not great but better...
the IAC is usually effected more in colder climates or on cold mornings, once mine warmed up it ran better, not great but better...
that's usually the case since the IAC's function is to maintain idle RPM during cold starts or when the A/C compressor cycles.
you can disconnect the IAC and idle it manually via the set screw that's capped off, that's why I did when I got the 52mm installed.
why was it necessary to essentially by pass the IAC in the with the bigger TB
why was it necessary to essentially by pass the IAC in the with the bigger TB
it wasn't neccessary, i just wanted it to idle lower. It idled at 750 after I installed the 52mm, that caused it to creep against the brake when in gear.
To disconnect it I got the engine to operating temp with A/C off (to ensure the IAC was fully closed) and unplugged it.
After I idled it down to 550 it would only move when the gas was applied, but it still idled high enough to run the alternator and keep the oil pressure around 45-50 psi.
once it got cold I cleaned and reconnected it. For whatever reason, once it's warm it idles at 550 now...perhaps the PCM was still recalibrating for the larger TB when i was having the idle problem originally.

edit: I did have the eternal CEL while it was unplugged. Since reconnecting it no light.
my truck has 190,000km and the only code i get is " System to lean ( Bank 1)" which means there is a vaccuum leak somewhere. and just the other day i was taking a sensor off, i Think it was the TPS because it rotated with the throttle body like the inside of it did, when i went to put it back on the damn side broke off so it dont work
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