Mark99

I have read a ton of posts on Yotatech and other sites, but have not been able to diagnose what is wrong with my truck.

I have an 85 4Runner that I bought a couple of months ago. I have put about 1000 miles on it. I recently filled up the gas tank after driving on the freeway for 40-50 miles and as I was pulling out of the gas station the truck started running really rough. I drove it about 1 mile and decided that I shouldn't drive it anymore until I knew what was going on. I tried to start it 3 hours later and it wouldn't start. I tried to start it a couple of days later and it started...it still ran rough, but I was able to get it home.

My first diagnosis was that it may be bad fuel. I put some Heet gas additive in there and that didn't make much difference. I changed the fuel filter and it ran like a champ...more power than it has ever had.

After about 70 miles on the freeway it started running rough again. It was nowhere near as rough as when it first had trouble right after I filled up the tank the week before, but I pulled off the freeway and called a mechanic friend. He said it may be corrosion in the tank (the 4Runner has 300K miles). After I let it sit for 20 minutes I jumped back in and it ran like a champ for 5-6 miles, and then started to run rough. It continues to run well for 5-10 miles and then it runs rough until I let it sit for a while.

After I got home I drained the gas tank to see if there was any corrosion or junk in the gas tank. The gas looked good and I didn't see any signs of corrosion (particles or discoloration).

I also changed the fuel filter again to see if it would run well for a while after changing the filter, but this time it ran rough right after changing the filter.

I reset the computer and the engine codes that I am getting for it are:
#3...No signal from the igniter 4 times in succession
#6...No engine revolution sensor (Ne) signal to ECU
HUGE THANKS to 4Crawler for all his help! http://www.4crawler.com/4x4/CheapTri...html#Early22RE

When my 4Runner is running rough, it runs a little smoother at 3-4K rpms, but the tachometer goes all over the place...sometimes the tach surges from 2K to 7K without the engine actually surging. Often when it idles it runs rough enough that the engine dies, but I have no problems starting it again. As long as I give it a little gas, it runs okay.

It seems like the warmer the engine gets, the worse it runs. When the problem showed up initially I had just pulled off the freeway after a 40-50 mile drive. When I pulled out of the gas station it started running REALLY rough. I am assuming that the engine would be the hottest after a long drive and then stopping for a minute. It didn't start for a couple of days after that gas station incident, but after that it hasn't ever had problems starting again. The engine temp may not be related to the problem...just an observation.

So far I have changed the fuel filter, the distributor, the rotor, distributor cap, spark plug wires.

Any suggestions would be appreciated!

Mark99

I had a mechanic friend help me do more diagnosing of the electrical problem. He ended up changing the igniter and the coil...extra parts that he had in his garage. So far it has about 25 miles on it and it hasn't failed yet. I'm keeping my fingers crossed.

Mark99

I have now put about 500 miles on the truck since changing the coil and the igniter. So far it has run like a champ! I hope this can help anyone in the future that is having similar electrical problems.