[EricE]

My '94 is throwing a CEL 25. It is also running hot. I recently modded my Temp gage and haven't had it in long enough to get a baseline. I was towing a 5K lb load of wood with it yesterday when the CEL came on the first time. During this time I was watching the temp gage climb and stay above normal most of the time. It even got as high as a couple of needle widths from the bottom of the red. I got it home and checked out the codes. It was codes 12,21,24,25,and 31. I cleared the codes and let the truck cool. I checked all the obvious electrical connections and checked the operation of the VAF. I checked the coolant levels too. I read some relevent threads on here and replaced my K&N air cleaner with a stock one I had on hand. Link to thread:
Code 25 26 Rich Lean Air Fuel

On my next wood run the CEL stayed off for 30mins or so but the truck was still running above normal temperature towing an empty 1.5K lb trailer at freeway speeds (ambient temp ~70F). As I said I don't have experience with this temp gage but I am thinking that even towing like that the truck should not be running hot. I checked the CEL code and this time only code 25 came back. I am thinking that running hot is indicative of an engine running lean and code 25 talks about a lean condition.

I am really leaning towards the injectors as the problem. The injectors are original equipment and have 164K miles on them. This truck is a DD and my normal commute is 17Miles each way city driving.

Anything else people think I should/could check before I drop $200 on refurbished injectors?

[IdahoDoug]

What's with the "40k on engine" in your sig? Did it get a new radiator at that time also? How about a new fan clutch? What color is your fan clutch?

DougM

[lagwagon]

Call C-Dan for some O2 sensors. Check the radiator and thermostat if you were at higher speeds, fan clutch if it was getting hot at lower speeds.

[EricE]

I did get a new radiator when the engine was replaced 40K ago. I put in a crate engine from ATK. It has a stock fan clutch and I know I need to do that at some point. The truck is one week back from getting a new HG done. The O2 sensors have only like 5-10K on them. That is why I am leaning towards injectors. It is just about the only thing that has not been replaced. Thermostat might be an issue but that will not clear a code 25. I think the overheating is a symptom, not the cause of the code 25.

[lagwagon]

I have cleaned the injectors with wonderful results. Did you use Toyota O2s? That is very important. If you blew a HG and any coolant got into the exhaust it could hurt the O2s. Also did the radiator get flushed after the HG?

[IdahoDoug]

So what's with the HG being done??

DougM

[KliersLC]

I'd do the fan clutch first. I have had a 25 on my rig, but IIRC it wasn't due to overheating, rather an interruption in electrical current. Maybe you guys over on the coast just have thicker air--semlin seems to be having the same problems with running hot.....

[EricE]

Originally Posted by IdahoDoug

So what's with the HG being done??

DougM

Its a DD. I am probably capable of doing a HG replacement but I don't have the time. I would need to take a week off of work to do that big of a job.

[EricE]

Originally Posted by lagwagon

I have cleaned the injectors with wonderful results. Did you use Toyota O2s? That is very important. If you blew a HG and any coolant got into the exhaust it could hurt the O2s. Also did the radiator get flushed after the HG?

I would have thought that if the issue was with the O2s then I would see a 21 and/or 28 come back rather than a 25. I didn't use OEM O2s this time around because my last set of OEM O2s only lasted 2 years. I figured, heck, if I am going to replace them every two years then Id rather pay $150 a set rather than $300.

The radiator was not flushed with the HG replacement. But I still want to cure the lean condition first. running lean = running hot so I want to cure the lean problem first. There are few things you can do to an engine worse then running it lean...like dropping metal bits into the combustion chamber, Pouring bleach in the oil, etc. hehe

[BHMCruiser]

Originally Posted by EricE

Its a DD. I am probably capable of doing a HG replacement but I don't have the time. I would need to take a week off of work to do that big of a job.

I think he meant "why was the hg done?"

[EricE]

Originally Posted by BHMCruiser

I think he meant "why was the hg done?"

It was blown out around #6. It was not installed correctly when the long block was put together. There was maybe a 1/4 inch of gasket material outside the sealing surface.

[EricE]

Well, last night I tried a few things. On the suggestions here I decided to see if I couldn’t eliminate O2 sensors as the problem. I pulled the existing ones (I am REALLY good at this now) and put in my old stock ones. That didn’t help as it threw a code 21 right away. I was hoping they might work for a few drives and I could see if I got the code 25 again. Anyway, then I cleaned the aftermarket ones I had in there (Walker brand) and put them back in. The rear one (corresponding to the blown cylinder #6) was really dirty. It could easily have been clogged…possibly causing a code 25. I then cleared the code.
No code showed on the way to work today but it is a two trip logic test so I won’t know anything till I can drive it again in a few days when I get back from out of town business. I’ll update with the outcome once I know.

[Beowulf]

The 2-trip logic can be accomplished by driving it for ~5 min up to ~60mph; stop, turn the ignition off; restart the engine; and driving it for ~5 min up to ~60 mph. You can do this in about 15 minutes on your way home from work.

Sounds like people should avoid this ATK place for rebuilt engines...

-B-

[EricE]

Originally Posted by Beowulf

The 2-trip logic can be accomplished by driving it for ~5 min up to ~60mph; stop, turn the ignition off; restart the engine; and driving it for ~5 min up to ~60 mph. You can do this in about 15 minutes on your way home from work.

Sounds like people should avoid this ATK place for rebuilt engines...

-B-

Well, one data point isn't a trend but mine didn't work out too well.

[IdahoDoug]

Yes, I was wondering WHY the HG on the rebuilt engine was redone after it was installed?? Was it just because you noted 1/4 inch hanging out, or because the engine overheated?

Frankly, I'd be checking the basics. Like basic engine timing correct on this engine (valve/crank timing)? Then ignition timing correct? Since you also have aftermarket O2 sensors in the mix you've got quite a complex set of variables going on here and should start with the basics.

DougM

[EricE]

Originally Posted by IdahoDoug

Yes, I was wondering WHY the HG on the rebuilt engine was redone after it was installed?? Was it just because you noted 1/4 inch hanging out, or because the engine overheated?

Frankly, I'd be checking the basics. Like basic engine timing correct on this engine (valve/crank timing)? Then ignition timing correct? Since you also have aftermarket O2 sensors in the mix you've got quite a complex set of variables going on here and should start with the basics.

DougM

Yes, HG blown out on #6. Overheated several times due to it. Caused a water pump to fail, general mayham, cats and dogs living together. You get the idea.

[EricE]

Update:
Cleaning the O2 sensors seems to have resolved the code 25 and most of the overheating issue. After cleaning the sensors the CEL 25 has not come back. I also had it cruising out on the freeway at 60+ with overdrive off and didn’t have any overheating problems…the needle stayed stuck just below half. Before, if RPMs went above 2K or so I would see the needle climb.

I think I’ll replace the thermostat as it is cheap and I occasionally still see the needle move above half but its not a big deal. It usually dips back down after a short while.

[EricE]

I think I solved my slightly overheat problem. I replaced the thermostat and now the needle doesn’t go above center. I think my old thermostat was working but not opening all the way. I’ll be towing with the rig tomorrow so I’ll give it a good workout.

Just posting up my solutions in case someone with similar problems comes upon this thread looking for answers.