Engine/Transmission (1998.5 - 2002) Truck running rich??

[Nick H]

My truck seems to be ruining rich when idling. It is so strong if you stand by the tail pipe your eyes water. I checked my friends truck and it does not do this, any ideas. Thanks

 

[Rebel Ram]

I'm not sure but Diesel engines dont run rich. More fuel means more go. If anything I would suggest that your timing is retarded (late) somehow and not burning all the fuel. 98. 5, That is a 24v, Yes? So that's a tough one to easily figure out. Could be mechanical or electronic. Smarter folks chime in.

 

[Fishin Guide]

I don't think I am smarter, that's for sure. I would look at the simple things. If you have a fuel rich idle, what can cause this?



First guess would be air filter dirty. Although, you would most likely notice more smoke all the time and lack of acceration in order to be that dirty. Is there any play in the turbo or any leaks? Could be that it's "sticky" at idle? Doubt it, but a guess.



I would think the first thing I would look at is the injectors. If it's stock, you may have an issue with a dirty injector or two. maybe the pop off pressures are screwed up? They can be checked at most diesel shops for a few bucks. You do have to pull them though.



I would start by dumping a double does of fuel system cleaner. Power Service, Sanadyne, Deere, Roteela, DFA, whatever. I think that would be the best place to start.



Also, sometimes just by hooking alot of weight and going for a 200mile mountain climbing, gear clashing, foot to the floorboard trip does wonders for cleaning carbon out of the motor.



That's the simple stuff I can think of. There's always that pesky lift pump, VP44, ECM, PCM, ect, ect.



Clean all your battery connections and check all your grounds. That'll make any further diagnosing easier.



Dave

 

[Nick H]

Thanks I will start with the simple stuff first. I just replaced the lift pump, pressure is 15psi at idle.

 

[joemyers]

If it's a 24 valve, try cleaning the IAT sensor.

 

[PSchwering]

Diesels don't have to run any certain air-fuel ratio. The only time the run "Rich" is when rolling black smoke, so Running rich is not always bad

I would check the injectors, & maybe timing.

 

[ToolManTimTaylor]

Extended idle periods will also do that too. Cooler cylinder temps at idle are not sufficent enough to completely burn all the fuel charge in the cylinder. That is why idleing to warm up is a no no or extended idle too. Varnishes can build up on exhaust valves , and in some bad cases cylinder washdown can happen (Alltho none seen or posted about yet anyhow) But being diesel is a form of Kero and Kero is a cleaning agent ... .



That is why it is best to idle with a load up against the engine (Exhaust brake for instance) that puts a load on the engine to bring temps up.

 

[ToolManTimTaylor]

In Fact Here is the TSB on Extended Idle.

 

[Nick H]

Thanks everyone. I took the truck on a 60 mile hard pull and it seems to be running better.