This is my first time, so be gentle. My 1989 F250 with EFI runs great, but when pulling a 6,000 pound trailer uphill (which I often do) it lacks power and gets poor gas mileage. However when I increase the initial advance from the recommended 10 degrees to about 18 degrees operation is much improved, and there is only occasional pinging. It doesn't seem like this should be necessary. Could there be something wrong with my ignition module or one of the sensors? This is a CA smogged machine, and maybe that is the problem. I have had it since it was new and don't think it was always this way. It has about 90K miles.

 

do you have a mech fuel pump? if so pull off the pump and check for slack in your timing chain. Just stick your finger in the hole and try to wiggle the chian inboaard to outboard. If you feel noticed rotate the engine the other way and se what you feel. Could be due for one if you haven't changed it yet. Also look at the last power thread. They mention the cat as a possiblility.

 

Thanks for the tip, airharley. I don't have a mech fuel pump, so I'm not sure how to easily check the timing chain, but it seems to me that the slack in the chain would be the same when setting the initial timing as it is when towing the trailer uphill. I have recently replaced the cat, as I was having the same problems as the other post you referred to.

 

I would check the vacuum advance 18 initial would be way to much total if the advance is working properly.

 

I don't have a vacuum advance or a centrifugal advance. I have an electronic ignition module bolted onto the side of the distributor which communicates to the same computer that runs the EFI. The computer then sends info back to the ignition module thru the "spout". That procedure is supposed to take the engine speed, etc. into consideration and determine the proper advance for all conditions. I'm thinking maybe the ignition module is not well, but I don't know how to test it.

 

You need to have the codes pulled from your engine management system. You have sensors in your exhaust which control the fuel mixture and advance. I'm not up on your engine, but if we keep this at the top there are plenty of people who are and someone can help you.

 

I don't think the module has any control in the timing I believe it just follows the computer commands for timing adjustment
You may be able to check timing chain slop by removing the dist, cap and see how far you can turn the crankshaft back and forth before the dist. shaft turns (if the chain is real bad)

 

bluene,

I doubt that your timing chain is stretched yet. I have 128000 on my truck with the original timing chain, but it could be. If you disconnect the the spout and use a timing light, does the timing mark move? If it does, then yes, the chain has slop in it.

My thoughts would be the catalytic converter. It may be getting clogged and reducing the exhaust flow.

It could also be an O2 sensor.

Click HERE and it will tell you how to pull the codes. I would check for codes first.

My truck is also CA equipped and as soon as I get the time, I am taking the pump, lines, etc off when I do a custom exhaust.

 

georgedavila, thanks for the tip
jbalestri, I'm not sure what the codes are or how to pull them. Do I need special equipment? I went to the Chilton site you posted and found a place to enter codes, but I couldn't locate any help on finding them. Please advise. Thanks.

 

Bluene,

Ok, go back to the site. Enter your vehicle information. Click on "Driveability and Emissions Controls". Then click on "Trouble Codes EEC-IV". Then click on "Reading Codes". It'll tell you how to do it.

There is also a thread on here about it from Steve83, but I don't have that bookmarked.

Let me know if you found it. You can also take it to a place like AutoZone(parts house) and many of them will pull the codes for free.

 

jbalestri et al,
OK, I finally got the code-pulling routine. Both the KOEO and KOER tests come up as 11, which apparently means OK.
I set the timing at idle to the specified 10* with the spout disconnected, but when I connect the spout it changes to 25*. What does that mean? It advances even more at higher RPM, which sounds right to me.
I replaced the cat 30K miles ago. Could it be bad already? I have never replaced the timing chain.

Thanks for all your advice.

 

If the timing marks didn't fluctuate when you were setting the timing, the chain is fine.

As far as the cat goes, that's hard to say. Its definetely a restriction, but beyond that I don't know.

Also, it could be the O2, even though it didn't throw a code. Have you replaced the O2 recently? As in the last few years? If not, I would do that. The O2 sensor can malfunction and not throw a code.

What kind of plugs are you running? Are all your plug wires good?

 

The timing marks are steady. I have never replaced the O2. Plugs are regular Champion with about 4,000 on them. I keep the wires clean but have never replaced them. Maybe I'll change the O2 and have the cat checked. Is there a way to check it myself? Is there anything special about changing the O2, or is it pretty straightforward?

 

Spray a mist of water on the plug wires (dark garage) with the engine running and you can see any visable leakage. If you've had the truck for awhile, I'd suggest changing the plug wires.

 

The reason I asked about the wires, is exactly what George is getting at. They probably need to be replaced. I have heard that these 460's (late 80's early 90's) are hard on plug wires. I don't know why or anything, but they are. I had a miss right after I bought my truck, about two weeks after I bought it. It had new wires and plugs. Somehow, in the two weeks I had it (600 miles) it destroyed 2 wires. They looked good, no cracks, as they were new. I ohmed them out, and they came out good. So I replaced the plugs, didn't change the miss. Talked to my father-in-law, he has owned a lot of 460's and he said to replace the wires. So I did, even though they checked out good, and it got rid of the miss. Even though you are not missing, it might be causing the poor economy. Actually, the only way I really knew I had a miss was my radio antenna developed this weird sine wave looking vibration. I knew it wasn't there when I bought it and it would really only do it on load. It isn't there anymore. It doesn't make sense to me, but that is what happened.

So, I would do plug wires and check the cap and rotor. Then check the O2, then the cat. I bet the wires help your problem.