want to shoot myself...

Ok first of this will probally be a long post.

I have been banging my head trying to figure out a problem. since i got this truck a few days ago.

I have a 98 ram 1500 SLT Laramie 4x4 with 318.

After about 30 seconds after start up the idle goes up and down between 400 and 800.

I can rev it to the moon if i want and it is smooth when cold.

It drives good for the first couple minutes also when it was cold. Once it gets warm it starts to pop and kinda like back fire thru the exhaust and i have very little power.......i can put my foot down and it will downshift then take off but still a little rough. Once i let of it is back to popping and back fire. Even at this point i can put it in neutral and rev it just fine ( maybe small popping as it comes back down in rpm's )


Okay now what i have done all ready.

New plugs (stock champion)
New wires (autolite)
New cap and rotor
I routed the wires per the tsb
I cleaned the IAC
Check that the TPS is working correct.
Removed the TB and cleaned totally. New gasket.
New upstream 02 sensor (Denso)
Cat converter was gutted allready.
Cut pipe in front of muffler to eliminate that it is clogged.
Tested fuel pressue ( about 46-47 key on not running. also the same running)
Pulled all 8 plugs(pictures to be added)
I found 1 broken vacuum line and fixed that. I haven't gone thru all the vacuums yet to look for leaks.

Any other ideas.

Runs very smooth untill it starts warming up. (maybe a couple minutes)

After it warms up it starts it's missing sound....if i give it alot of gas it goes sorta smooth.Once i let off at all it starts doing it again.

Again at any point i can put in neutral and rev to the moon if i wanted to.

the other plugs are the same......well 3 and 6 are the same and the rest look alike.

Try replacing the IAC and the TPS cleanning it might not help it...that might help it...

i will go get a iac then.....i tested the tps and it works as it should. Thanks

Any one ideas?

i would replace both to be sure...when you re install it will rev up for a little while to calibrate itself...then it should be ok.

make sure the cap is on tight had a problem just like this with my s10
took me months to figure out that one of the tabs that the screw gose in on the distributer had cracked and was letting the cap move had to replace my whole distributer

egr on this model?

man i didnt think of the EGR!!!! that could also be your issue...

I don't have 1 96 was the last year i think.

It's either a vacuum leak or a blown plenum gasket would be my guess.

Welcome to RF!

First I would think it would be the o2 sensors, as it's after warmup, when the engine enters a closed loop operation. But if you already changed that, then I believe it's 1 of 5 things:

1. Since it's an older model *Vacuum Leak*
2. Throttle Position Sensor (if you tested it and it's working, disreguard this)
3. Idle Speed Control Motor
4. Coolant Temp Sensor
5. Air Charge Temp Sensor (IAT) Mass Air Flow Sensor

I might think EGR valve, but it would most likely hesistate when you hit the throttle, in most cases.

I remember one guy on here, I think, that had this problem or something like it, and it ended up being his coolant temp sensor. Something so simple.

It's a 98, and it prolly has some miles, so it's almost gotta be a sensor or valve thats eventually gone bad. Been looking online, and from what I've seen and experienced here on this forum, that's what I think it is. Hope this helps.

Tru hit the nail on the head, but I'd start with the vacum leak. It wont do it when it is cold because the engine "choke" is on and its feeding it more fuel, when the choke opens up it leans out and already getin too much air causeing your miss, poss backfire and no power.
Coolant sensor is also anthoer good one as it dont come into play untill engine warms up, same with Idle speed, and Air charge Temp sensers.

Well after a week of headaches. i finally stumble across the problem.......it was the timing. i had to turn the dist counterclockwise and now it runs good. So simple. Thank you for all the help.

Timing? wow didn't think the comp would allow you to adjust the timing w/o throwin a code. Have to keep this in mind when I do some more tuning on mine!

Before reading all the way to the bottom I was gonna suggest Timming or maybe a bad coil. I've had coils that work fine till they get hot. Alot of electrical parts will work fine till they get warm or hot. Good find.

Wow... didn't see that one coming. Troubleshooting skills : FAIL! lolz

Timing all the way...does the truck have a vacuum advance? Maybe that's why it's okay when on the gas.
Glad you got it fixed
Ch

Sent from my DROID RAZR