Your truck will have two temp sensors, one for the gauge, (one wire) and one for the PCM. (two wire) In order to know what temp the PCM thinks the truck is running at, need to plug in with a scanner that can read live data.

 

Paul - Assuming you have no check engine lights now and all your cylinders firing as they should, it sounds like possibly a lean condition from a vacuum leak or the ignition timing too far advanced. Either one of those could deliver high NOX readings. Check for any faulty vacuum lines or even a bad power brake booster, and inspect to make sure the distributor initial timing is set to spec.

 

[QUOTE=zonker;3398462 it sounds like possibly a lean condition from a vacuum leak .[/QUOTE]


No personal experience with this motor, but, thinking out loud here, I would look down the throttle body bores and see it there is oil in the intake. If so, then the bottom plate on the intake is leaking, and this could be your vacuum leak. From what I understand, this plate gasket failure is a common problem on these trucks.

 

Truck was never getting over 160 degrees. Checked thermostat, and there wasn't one. I read somewhere that until the engine reaches temp it will run lean. Did a lot of things yesterday.
new 195 degree thermostat
flushed cooling system
New CPV and hose
fresh coolant
new plugs
Added sea foam to gas tank, crankcase, and sucked in vacuum line.
still need to run the tank dry
and change the oil.

Last monitor (O2 sensor heater) is now reset.
Once the gas in gone and I refill it, I'll try getting it smogged again.

I'm hopeful but not optimistic.

What are your guesses, pass or not???

 

More likely to at proper temp.

RwP

 

I get one free retest so I'm hoping.

 

Did you look in the throttle bores to see if there is any oil in the bottom?

 

No I didn't, I'm really hoping that's not the issue. Would rather gamble on the smog test. If it turns out to be the intake that's going to take some time and I only have a few days left before my free smog check expires.

 

The timing is adjustable on my older '89 3.9, I know the magnums are a little different, but do they use a crankshaft sensor to determine TDC or do you still have to base time them so the computer knows where TDC is.

 

I dont know the answer to that question. To be honest I followed the spark plug wires to the back of the engine until they disappeared from easy sight. I didn't see an obvious distributor cap and just assumed the timing was not adjustable. Add to that the factory sticker on the hood that states no adjustment is necessary (it doesn't say adjustment of what). I'm hoping someone else here answers that question, but if not I'll follow those plug wires to whatever they are connected to using flashlights, mirrors, cell phone cameras step stools or whatever else is necessary. But honestly, I'm getting a little tired of chasing this down and I just want to believe it's already resolved. Do I sound friggen frustrated, lol