intermittent hesitation and check light on

[Valdanilov]

This is the new to me 1987 4wd 5-speed TV, that I bought with a blown head gasket. Originally a CA van with lots of heat damage under the hood. Brittle wiring, cracked exhaust manifold and downpipe. I just finished the HG replacement and associated repairs to exhaust components, wires and hoses. Took it for a test drive.
It starts and runs well, but every now and then the check engine light will come on for a short while, accompanied by power loss and hesitation. After the light goes off, the engine runs normal again. This repeats itself randomly, regardless of engine temperature.
Before I go down the long check list, I thought I would check here to see if there's a known primary suspect for this kind of behaviour.
Thanks!

[timsrv]

What code(s) are stored in the ECU?

[Valdanilov]

What code(s) are stored in the ECU?

#11 only

[timsrv]

If you don't know the history of the TPS, get a new one and replace it. On an 87 code 11 is almost always a faulty TPS. There might be something else going on, but the symptoms you describe are consistent with a TPS issue. Tim

[Valdanilov]

Well, I swapped out the throttle body with TPS from a known good van, and that didn't make any difference. Swapped out an ignitor too, same thing.

I'm going to try the coil, plugs and wires next. If that doesn't help, will move on to fuel system pressure, fuel filter, and fuel tank. In that order. Does it sound like a good plan?

[Valdanilov]

It was a bad ECU.
I remember reading about someone repairing bad ECUs. If this person reads this, please contact me. I'd like to get mine fixed. Or, will buy one outright. Tx,

Val

[timsrv]

Very interesting. May I ask how you were able to prove that was the fault? I've still not seen a bad Toyota van ECU (ever) but like anything I'm sure they can fail. I've read a few threads over on TVP within the last few months where others have claimed the same failure. Perhaps 25 years is the life expectancy of one of these? Thanks for sharing your findings. Perhaps it's a good idea for the rest of us to keep a spare ECU laying around. Tim

[Valdanilov]

Hey Tim,

I was able to recreate the problem by tapping on the B-pillar post where the ECU was located. I then removed the ECU and opened it up to look for any obvious damage (non found). Upon reconnecting the ECU, the engine ran almost perfect, so I knew I was getting close. Took the car for a test drive, and the check engine light just barely flickered a few times, but overall the improvement was huge.
So, disconnecting/reconnecting the ECU actually did something.
I then replaced the ECU with a known good one, and the problem went away completely!

Val

[timsrv]

Awesome! Do you still need another one or are you good now? There's a Toyota part number on the old ECU, if you still need another one, having that number might help somebody else identify if they have the correct one. Tim

[Valdanilov]

Yes, I need an ECU!
The numbers on it are: 89661-28060 and 175600-0211 12V.
Thanks,

Val

[coronan]

The problem could be in the connector.

In the VW world we solve alot of connector problems by adding spark plug boot grease.
It can help bridge any shorts and help keep water out.