69 1/2 Six PAck Bee

I am going to make this a really condensed post to save bandwidth and reading time. I need some of you with 3VZE-powered vehicles to confirm or deny the following condition I am about to describe. When I turn the key to start my 1990 SR5 pickup it turns over and when I am releasing the key to "run" the engine stumbles and recovers much like an ignition cut with a power shifter would act if you are familiar with those.

Suffice it to say I have checked each and every thing imaginable with alot of time invested troubleshooting to eliminate from the more obvious to the lesser "suspect" components in the chain . Everything I have checked from switches to sensors to the ECU pinouts themselves with the correct procedures and with the help of the FSM are just where they should be. I used alot of jumper wires to bypass entire circuits and it is still the same. Even swapped ECU's....same, same. It is really nothing more than an annoyance but an annoyance none the less. I even clipped some wires releated to the "start" circuit into the ECU with obvoius results but not eluded me to the trouble I am experiencing. It is really noticeable when starting a cold engine as it almost stumbles then recovers. Warm, and you never notice it.

Try this with your engine and tell me if it does it too:


Start your engine then ease the key back to the "run" position. Did it stumble? Another thing to try is while it is already running ease into the "start" position once again and when the starter engages does your engine briefly cut out as well? Maybe this is yet another wonderful innovation that the guru's at Toyota packed into their ECU by hardcoding.

I have never had an engine that cuts out like this when coming out of the starting sequence. The newer vehicles completely inhibit starter re-engagement. That is a no brainer. This is a 1990 and **should** act like their earlier siblings. Am I full of it?

It is just starting to eat at my conscious.

Thanx,
Bud

zachb55

I'd say my '90 runner does that about 1/3 - 1/4 of the time starting up, the inconsistency is what bothers me, and its been around freezing here every day for a month already... stumbles from a stop when i put down the pedal even a little hard, in almost exactly the same way. wish there was an easy fix... i was guessing my timing belt probably could use a replacing... keep us updated on any solutions!

aviator

I've noticed it once in a while when it is cold out or I hav'ent started the truck for a few days... no big deal for me... it might be something to do with the cold engine "idle up" vacuum pot or something like that... it's like the engine is getting to rich a mix for a second or two...