89 with a 3.0. Was running but very hard to start. Check engine light was on and had a couple codes( knock sensor, and couple others. The strange thing is once it started it would run just fine. But if you let it sit it would be hard to start. The really strange issue started today, my heater wasn’t blowing very warm air. So I pulled the hoses and flushed the heater core. This cleared the problem with the heat, the truck started right up (idled a little high) it the check engine light went out. But when I would give it and pedal it would fall on its face and die. Then it seem to start die, start die etc. ow I cannot even get it to start. Prior to this the fuel pump, fuel pressure reg, filter have all been changed.
It also will just quick engaging the starter but I am guessing a relay is warm and not letting it complete the circuit until it cools down. I’m not really up on the computer trouble shooting but could manage with a little help. Any ideas. Like I said it was running just before flushing the heater core.

 

Hi did you ever figure out what the problem was? My Toyota is doing the same exact thing it was right after I power washed the engine said knock sensor all this other codes so I replaced the sensor. It’s got new everything on it. I’m still getting that only thing I can come up with is wiring or relays, so I was wondering if you might have some insight

 

it ended up being the sensor in the heater bypass. I pulled it out and checked the Ohms of resistance and it had a zer reading. Found a used one that tested good and installed. Truck fired right up and check engine light went out. Never had another issue.