idle loops
 

I have a 1997 dodge Ram 5.2L that has been acting crazy ever since I did a tune up. Many moons ago I was an ASE tech for GM, but lately you wouldn't believe if you knew how much this truck is kicking my butt. I replaced the rotor, cap, spark plugs and wires, but the darn thing acts like it has a vacuum. It originally has a P1391 code in the PCM, but I replaced the Crank sensor and cam sensor. The code is gone, but this truck is not happy at idle. I can make it continually run with the idle screw tighten down, but it has to idle at 1200RPM. I also replaced the TPS and IAC with no avail. I've unplugged the O2s to watch a difference in idle speed...but nothing. I also isolated all of the vacuum lines to see if something is cracked or leaking. I sprayed down the intake surfaces looking for a difference in idle speed, but still nothing. I disconnected the battery and did the hard reset on the computer. I also found that the spark wires must be ran in a unique fashion according to a bulletin I found on the internet. My next guess is distributor or intake gasket, but what say you?

Check out the plenum thread stickied at the top of this forum. Its likely a contributor, but, unless it is REALLY bad, I doubt it is the whole problem.

These trucks REALLY don't care for aftermarket sensors in critical locations..... (crank sensor being right up there on the list.) Also, what plugs did you put in it? The rare-earth fellers don't do you any favors either.

Did you clean the port in the throttle body under the IAC? What brand sensors are you using? Our trucks prefer Mopar sensors. I've also used Standard Motor Products (red box) from Rock Auto with good results. Not the BWD junk. If you replaced the PCV valve you might have a vacuum leak. Some cheap PCV valves flow too much air, making them an undetectable leak. Yes, your plenum gasket could be leaking if it hasn't been replaced.

I haven't tried cleaning the IAC portion, but I did spray it out with carb cleaner. Also, I am using Duralast parts from Autozone, but I didn't see Mopar manufacturer parts on Rock auto. Are they named something different?

Gotta get 'em from the dealer, or, one of chryslers online outlets.

Its running rich. Do all the plugs look like that? Or just a couple?

How old is your 02 sensor?

Not necessarily a bad thing. If the PCM isn't whining about it, leave it. It is sensor 1 that has the most control over mixture.