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Toyota Pickup - Computer Problem

1994 6Cyl. Manual, Toyota Pickup. I had the engine replaced with a 4-runner engine. Since then I have had to replace the computer twice. They ran for a while but after a week or two the computer quit when driving at high speed on the highway.

Was the engine the same model year as the pick-up? Did you swap over all the sensors? When I did a couple of swaps like this, I’ve always swapped over the sensors from the original engine to the replacement one. The sensors may look similar and hook up the same, but I’ve always noticed that they seem to make subtle changes from year to year and the senors may not be the same. Swapping out all the sensors prevents problems like that.

The engine was from an 1988 4-runner

Engine swaps became very difficult beginning in 1981 when computerized controls became standard. Computers, sensors and wiring harnesses are specific to ONLY ONE MAKE AND MODEL…Emissions control systems (and testing) make no provision for engine swapping. If you can make it work, it’s just a matter of luck.

For openers, you must use the computer from the correct model 4-runner, and, using both the 4-runners wiring diagram, and the P/U wiring diagram, re-wire the truck to match the 4-runners inputs. Most people discover that the published wiring diagrams are not 100% accurate making success VERY elusive…

Specific to only one make and model? Only if you’re lucky! Specific to only one make, model, engine, transmission, and emissions package (CA vs. 49 state) combination. Even then things might change mid-year.

I would suggest you try to find a model-specific enthusiast board-- that’s where you’ll find the nitty-gritty knowledge about exactly what changed what years that you’ll need to figure this out.

I’m not a mechanic myself and don’t know what to do now. I’ve, at present, got around $2000.00 invested in a second hand 1988 4 Runner,a fuel filter, fuel line to the tank. fuel sending unit, and the fuel pump. The initial reason for the swap was a leaky head gasket. It was suggested to me by the mechanic doing the work that it would be easier to swap the engine than do the head gasket, considering that the heads might be warped and the cost of the complete gasket set($250.00). The mechanic supposedly swapped "everything over from the original engine(don’t know about the sensors). My question to you now is: what would you do now? Do you think the Toyota dealer could straighten out the problem? I feel that I’m between a rock and a hard place being that I already have so much invested. Thanks for your help and advice in this matter.

If you are not subject to emissions testing, a GOOD mechanic might be able to “de-smog” your truck and get it to run reliably…

The mechanic who advised you to do this might be willing to buy your truck for $2000 and let you off the hook…You are indeed between a rock and a hard place…Had you posed this question BEFORE work was started, we could have helped you a lot more…