New Guy with a question!

Adams95 said:

Ahh thank you bob, that makes much more sense, it's also the best explanation i've read of what the fan clutch does exactly. What kind of resistance should I expect when spinning the fan while cold? 1 full rotation or so?

Also the reason I was thinking about replacing the O2s was just because they are the stock sensors and have 215,000 miles on them. What do you think bob? Thanks for all your help throughout this thread as well

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Not sure about fan resistance - and wife has the truck right now. I'll try to remember to give it a spin in the AM and see then let you know.

I generally would not replace O2 sensor's without some indication the they are bad. However, if you stilll have poor performance/lousy gas mileage after doing other stuff, they may help.

Did you ever check out the Engine Coolant Temp sensor that the ECU uses?? If the computer thinks that engine is cold, it will dump in more gas, thus contribting to lousy mileage. There are separate sending units for the ECU and the guage - the one with two wires goes to the ECU. One of the wires should be light green/red.

Good luck!!

I'll test the ECT tonight when I get home from work, my question is, is it possible for an ECT to fail and still pass KOEO/KOER?

So tonight I found some more information out. My plan was to change the ECT since I knew it was either fan clutch or ECT, also the ECT was 10 bucks so i figured why not.
Well to get to the ECT, I decided to pull the throttle body and see if it needed some cleaning as well. Warning: Pictures are graphic





I guess thats what happens if you run the engine before closed loop for 150,000 miles or so. I had enough intake cleaner to fix up the TB a little bit.



However I definitely noticed that there was no gasket between the TB and the manifold whatsoever. There was what appeared to be a shot O-ring, do I need a gasket as well? Should I try to clean the intake?

Also it doesn't appear the ECT fixed the temperature problem, I kind of had a feeling it wouldn't after what you told me Bob. So it looks like the only answer is the fan clutch.
What do you guys think I should do about that intense carbon buildup?

Unless things have changed since I did mechanic work, the proper test of a viscous fan clutch is: when cold the fan will be stiff, so it would only spin maybe a quarter turn. When warmed up and engine shut off, the fan should spin more freely, so it would spin maybe a turn and a half or so. When the engine gets up over normal temp the fluid in the clutch gets stiffer causing the fan to spin faster thus cooling more. Years ago, when you first started the engine the fan would roar until the fluid warmed slightly, then the fan would slow down until the engine got to the temp where the fluid got stiff enough for the fan to pull more air. On my old 77 GMC with small block, that temp would be about 220 or a little better. Hope this helps.

Sorry to hear the ECT didn't fix your cooling issue. You did say you replaced thermostat - right? Maybe you got a bum one - it happens. I went and spun my fan cold and only got about quarter to half a turn also. I would do test post above suggests before I changed out fan. Good luck and keep us advised.

So, over my past 2 days off, I took off the TB, thoroughly cleaned the TB, replaced both gaskets (o-ring and base gasket), and also changed the oil. The truck seems to be running pretty strong, however...Now when I run the KOER test it's coming back with a '411' code (can't control the low speed idle).

I'm thinking i did something to clog up/screw up the TPS. Ever since I originally cleaned the TB the idle has been a little sporadic, the idle bounces between 900-1200.

Should I try taking off the TPS and cleaning it? Or is that a bad idea?

So this story finally has an ending...2 nights ago I wanted to fix the trans leak, so i dropped the pan and replaced the gasket...However what i found when i dropped the pan started to worry me. The fluid looked a bit like a strawberry milkshake...
I cleaned out the pan, put in the new gasket, and tried to be optimistic. The truck had been sitting for 2 weeks waiting for the fuel pump to be repaired and the weather in vegas had been really wet and rainy. I put the new ATF fluid in, ran around the block a few times checking the level. Finally when I was just about done, I decided to look in the coolant overflow to see how my recent radiator flush was looking...What i saw put me a little bit into panic mode...All I could see was brand new ATF in the overflow.

It was at this point I realized the radiator was definitely shot. So I planned to swap the radiator, flush the tranny, flush the coolant system, drop the trans pan again, change the t-stat for good measure, and get it all done yesterday.

So it took a little while but I was able to do all of this yesterday, when I changed the t-stat I verified I was swapping it with the same part # and tested the 2 month old t-stat (which seeemed to work fine) but I figured its $5 I'll continue to do it anyways.

The end result was the culmination of a lot of research, a lot of luck, and a thing of beauty!! The truck now runs at the proper temperature (see pic):


Also the transmission feels like its brand new, it shifts so smooth you have to try to pay attention to the rpms to know when its shifting. Before this the transmission would shift not extremely hard, but very firm, almost like the truck had a Shift-Kit. I can only guess but after talking to the previous owner he thinks it's been like this for 3-4 months. I'm not sure if its just luck that kept the trans from blowing, but I also found out from the previous owner the trans has a little less than 100k miles on the trans rebuild.

I also had my buddy, the P.O., drive the truck around the block last night to see what he thought, perhaps I was just crazy? But he agreed and said he hasn't felt the truck run this well in about 5-6 years at the very least...it's been a ton of work but very worth it. Only thing really left to change is the shocks!

Lesson:
If ECT, Fan Clutch, and T-stat all appear to be working fine but your coolant temps are right, don't forget the obvious and look for ATF in the coolant

Thanks everyone

how did you fix the sporadic idle? My explorer is doing the same thing, although it seems to run pretty constant at about 1200 RPM. I have just replaced the IAC because my old one was causing my car to idle so low that it would choke out