Hello all,

I have an '85 SR5 4x4 with the 22rec EFI engine. I recently developed a strange stalling issue. The truck will stall out when coming to a stop, but only under electrical load. Sometimes it will even seem to cut out, but I will let the clutch out a little and get on the gas....and the thing will fire back up on it's own.

It will only happen with the headlights on, or with the blower fan on high. I have also noticed when at idle, the volt gauge on the insturment cluster will drop quite a bit when I turn on either the lights, the blower, or both. I do not recall the needle on the gauge dropping quite as far (or even at all) before the issue began.

I put my multimeter on the battery, and at idle, the alternator seems to be charging the battery as it should. I get a reading of about 14.5 volts. If I turn the headlights and blower fan on, it drops to about 12.4.

I've checked all the grounds, checked for vaccum leaks, checked TPS values at closed and WOT. Seems to run fine going down the road, so don't think it's a fuel pump or filter issue. If I start it with foot on the brake, I can feel the vaccum assist kick in, so don't think it's an internal leak in the brake booster.

With the more than 2 volt drop when running power accessories, and the fact that it only happens when I'm running power accessories and put my foot on the brake (pulling more power for brake lights + RPM drop when decelerating), I'm thinking it's a bad voltage regulator in the alternator?

Any other yota heads out there run into a problem like this? Pain in the ass to get the alt out of these trucks, so just looking for a little advise before I drain the cooling system and pull the thing apart to have it bench tested. Possibly something else I'm overlooking.

At this point still fine driving during the day without heat on....lol.

Any help would be greatly appreciated.

Thanks.

 

This should probably go in the electrical section, but if you head on over there you will find the exact same problem being discussed...

Check your main headlight harness plug, and re-check grounds. I would suggest just replacing/upgrading all ground wires anyways. I extended a bunch of mine and ran them to the same spot. The block is a good place to tie in, but if you use it, make sure it has a FAT 2ga or so ground to the frame and at least a 6ga to the body. Your block can actually turn into a battery and start doing some nifty (catastrophic) electrochemical reactions if it isn't grounded right either.

 

Thanks for the reply Mr Random,

I double checked all grounds. I replced the batt ground cable, and the ground from where the bat cable connets to the underside of the upper intake to the frame when I was doing my original checks. They didn't have any resistance, but just looked a little old and crusty, so replaced them with some premade fat 2ga cables from local auto parts store.

The throttle body is clean.

All vac passages in the upper intake are clean.

Disconnected and plugged brake booster hose just to double check for an internal vac leak. Still had same symptom.

Bypassed EGR and EGR vac modlator. Still had same symptom.

Have noticed that when I step on the brake at idle, blower motor drops in speed big time. Also, had the door open when I was playing around with it one day, and noticed that the interior light dims big time when I step on the brake while the truck is at idle.

Volt gauge on dash is steady where it should be sometimes, and drops low or fluctuates at other times.

Sticking with my original theory of bad alt, or voltage reg.

Seems as soon as the alt gets hot, it just can't keep up at low RPMs.
Even with the smallest electrical load.

Ordered a DENSO 110amp. Going to stuff that thing in there, and see what happens. Current alt is a just a cheap one from Autozone. Last alt was several years old, and developed a gnarly bearing sqeal, so put the Autozone alt in last Sept. Noticed minimal volt gauge flucations after I first installed the thing that I had never noticed before, but everything ran fine, bearing squeal was gone, so just went with it.

Have found that these trucks hate aftermarket parts, so think cheap alt is most likely the problem.

New DENSO alt will arrive next week. Will post results