Can an over rich mixture make 3FE run too cool?

[ARSmay]

Well this post is basically a hodgepodge of questions but it all stems from the fact that my motor is running too cool and rich.
Lousy MPG, black sooty tailpipe, and stinky exhaust. The temp gauge sits right at the bottom (COLD) and barely moves up from there. It does move slightly after shut down when the motor heats up so I do not think it is the sending unit, also you can place your hand directly on top of the radiator and it's not too hot to the touch to leave your hand there. Lukewarm air from the heater as well. The heater hoses on the firewall to the heater core are warm but not real hot to the touch after ample time to warm up and both heater fans blowing.
I replaced the thermostat with an OEM unit, as well as the gasket and rubber ring on top. I've purged all air from the system.

After searching and reading up a bit, I see some folks talking about the fact that a lean mix will cause a motor to run hot- Well I'm wondering if the opposite is true. I have replaced a blown fuel pulsation dampener on this rig, and it IS running really rich. I'm thinking fuel pressure regulator replacement time? I have a spare in a box that came from SOR and supposedly tests good...
If that doesnt raise temps then I'll try back flushing the heater core and let you all know what happens.

Anyone else have any ideas?

I'm aware of the usual consensus regarding no heat problems, and burping the system, replacing the thermotat, etc. I've done all that short of backflushing the core. I just wondered if running really rich could contribute to the problem.

Sorry for the long post and thanks for letting me think out loud. I'll update as I get it ironed out.

 

[RockDoc]

The ultimate control on how hot your system gets is going to be the thermostat. Did you happen to check it (in a pot of water heating to boiling) before you installed the new one? Running rich or not, I think your thermostat is the culprit here. Have you flushed the system?

For the rich condition, is the computer throwing any codes? Oxygen sensors? In addition to the fuel pressure regulator, check the VSV that feeds a vacuum signal to the FPR (on the driver's fender, rear of the 3). If the FPR is seeing atmospheric pressure when it should see vacuum, this can lead to a rich condition.

 

[ad20k]

As a last resort, perhaps adjusting the AFM?

http://www.steelnthings.com/wagontech/fi/mafadjustment.html

 

[Wile E Coyote]

I know you don't wanna hear this, but, I'd put my money on the T-stat, LONG before rich running causing your problems.
Actually, your truck is likely rich, but probably as a result of the computer not seeing a warm motor.

You probably know this, but for clarity, remember the upper rubber O-ring can get installed wrong, and it's just like there's no T-stat at all.

 

[ARSmay]

Hmm, as far as the upper rubber O-Ring goes- I do not see how it could be installed any other way than how I put it in...But I'll try taking the thermostat out to see if that is the culprit. Thanks for the advice, and I'll kepp you posted.

 

[Mace]

yes, a very rich motor will run cooler than one running at peak performance (heat is absorbed by the excess liquid fuel)

 

[FJ40-GARAGE]

Thanks for the advice, and I'll kepp you posted.

A friend of mine has similar problems with his 3F-E.

It fires up perfect, needs more gas than usual and does barely start up again once it has normal running temperatur.

They have virtually checked *everything* but still no change.

 

[cruiser88]

yep folks are correct....3fe needs heat to utilize complete combustion......do not forget the rubber ring that sits on top of your stat

 

[Moby]

Agree with what others have posted above. However if nothing else pans out consider testing your o2 sensors. It is possible for an O2 sensor to be contaminated/killed such that it causes you to run rich but is not so far out of range that the ECU throws an error code. I never noticed my truck running cold when this happened though. Anyway the FSM has the test proceedure.

 

[Texx]

You really need to pull codes. However, the fact that your truck is running cold is probably not the cause of it running rich, unless there's a problem in the cold start injector circuit. That could certainly cause it.

 

[CruisinFJ60]

yes, a very rich motor will run cooler than one running at peak performance (heat is absorbed by the excess liquid fuel)

yup!

i used to tune my old 68 beetle to run rich during summer months (texas) for when i got stuck in trafic. other than a small puff of black smoke from time to time she seemed to run better when sitting in trafic on a 100+ day.

 

[cruiser88]

yup!

i used to tune my old 68 beetle to run rich during summer months (texas) for when i got stuck in trafic. other than a small puff of black smoke from time to time she seemed to run better when sitting in trafic on a 100+ day.

Did you not see the summer winter selection on the breather?

 

[CruisinFJ60]

Did you not see the summer winter selection on the breather?

I ran a 2 barrell Progressive Weber. It would do 115mph wound out on the freeway with the 1600cc engine i had. (never shoulda sold it...:whoops:)