hello....Ive replaced IAC valve...TPSensor ...water temp sending unit and the MAP sensor. cleaned the throttle body thoroughly. throttle body butterfly's are tight and truck still wont run right. idles up to 2500 then down to 1200 at times...other times not as bad.
as the temp comes up it seems to do better. exhaust smells funny also. 115k miles.....plugs.. wires ... rotor button and cap were replaced about 2 years ago. any ideas?

 

Wrong forum?

This is the 97-03 forum....

 

Codes? Look for vacuum leaks.

 

sorry. can it be moved please?

 

i took it to a shop..i didnt get the codes but they say it needs a new PCM I thought id ask on here 1st. seems to me if the PCM is bad...id have other issues like Auto tranny shifting bad....ETC. ???

 

a bad PCM can be a total die in place or as simple as one circuit failure that only causes a repeat code set for the same problem over and over. Last PCM problem I had was a bad evap system circuit, cost me a evap control solenoid lots of circuit testing, new evap cannister and then a new PCM. no problems since.

 

Pull the PCM and look for burnt components.

 

Looks like Rock Auto has the rebuilt ECM for the 91 5.0 for around $85 to $95 plus core charge, depending on type transmission.

 

Considering you never asked a question, it's kinda hard to guess what the actual running issues are. If you cleaned the throttle body while it was still on the engine- there's the problem. You can't clean it on the engine without doing damage to the intake gasket between the upper and lower manifolds. You can't put chemicals of any kind down the intake or expect high idle issues.....if that's the problem. You would have uncontrolled air going into the intake that the PCM can't account for or adjust to. It would be kinda like a busted vacuum line only on a larger scale.

Just as a FWIW, take a look under the hood at the vacuum lines. If they are color coded tiny plastic lines, get them replaced with full size rubber vacuum lines. If one of these tiny lines breaks or leaks, it can cause all kinds of problems from not running right, lack of power, won't start to the air conditioning won't work. One line breaks pretty much lunches the other vacuum operated systems.

If the PCM/ECU goes bad, it normally will smell smoky or burnt. You do not have to have the unit reprogrammed to your engine. It's almost but not quite a one fits all. You will need to old one to compare numbers at the parts house. They are not expensive and a no brainer to install. I think the one I bought at NAPA was around $125.00. Took about 30 minutes to remove the old one and put the new one in. Removing the kick panel was the biggest part of it.

Just so you're aware. You probably have the TFI for an ignition system. TFI means Thin Film Ignition. It is a module on the front of the distributor with wires going in it. This thin film can break but maintain contact when cold. When the engine heats up and blows hot air on the distributor, the film expands and loses contact which shuts the engine down just like turning the key off. So if you ever have the common issue with this engine, now you know how to fix it. It's another no brainer to fix IF you know what's wrong.