Good Tech help please. - Toyota Nation Forum : Toyota Car and Truck Forums

johnr · 10-23-2005, 02:47 PM

Hi guys, Im back again for some ideas. I've had the same problems for some time now however, with alot of your help nothing has yet pin pointed the problem and I'm running out of $$$ trying to fix by replacement to find the parts replaced is not the problem. I'm sure some of you have been there as well.

This is what happening...Start up the 91 NA when cold, and the battery light is on until the engine warms up in (min or so). During driving and accellerating around 3000-4000 RPM (in any gear) the engine bucks like its out of timing and the battery light, brake light and at times "engine check light" will flicker the same instant of the bucking. The bucking is very bad like driving a very cold engine. I think I have almost replaced everything electrical including fuel filter.

This is the kicker...a while back...I had the Alt rebuilt due to battery charging problems and I think they replaced the regulator or diodes?? At first there didn't "seem" to be a problem. Of course when you have something fixed your mind wants to look somewhere else.

For you smart good Techs...Could it be possible that when the Alt was repaired they fixed it "wrong" and at high RPMs (like when cold or accellerating it's overcharging)?? If this is possible...will the overcharging tell the ECU to cut off the high RPMs like a rev limiter making the engine buck and the above stated light blink? I think I'm getting closer to the problem here. I have already got a new distrubuter,igniter,coil,plugs,wires and timed it to a tee. Any ideas or driveway tests I could do??

Ironmike4x4 · 10-23-2005, 03:53 PM

Is there anyway you can take it to a mechanic with a good scan tool? If so ask them to take a test drive with you and repeat the conditions. Tell them to put the san tool on a "freeze mode" where the scan tool will take a snapshot of the CEL and show you the parameters of what is happening on the engine. Kinda sounds to me like the injectors may be having some sort of pulse problems because of the ECM reading something it doesnt like.

johnr · 10-23-2005, 05:03 PM

Quote:

Originally Posted by Ironmike4x4

Is there anyway you can take it to a mechanic with a good scan tool? If so ask them to take a test drive with you and repeat the conditions. Tell them to put the san tool on a "freeze mode" where the scan tool will take a snapshot of the CEL and show you the parameters of what is happening on the engine. Kinda sounds to me like the injectors may be having some sort of pulse problems because of the ECM reading something it doesnt like.

Thanks, I'll first read up on the injector circ.
Going to a mech looks like something I'll have to do. I tried talking to Toyota

and they said they would do a dianostic test for 80.00 bucks. I told them I've done that but no codes show up? (like you said I should try to freeze test) I also asked them for a shop test ECU and I couldn't believe they said they don't have one for troubleshooting. They only fix by replacement which could mean (flippen hours or days) of trying swapping different parts until it worked. Just a note..One senior mech there told me he will never "ever" work on those bloody things (not good news)

Anyways thanks alot dude...If ya think of anything else......, please drop a line for sure.
Jim

MitchB · 10-23-2005, 06:04 PM

Put a digital voltmeter on the battery terminals and have a friend rev to 3000 RPM and hold it. You should NOT go over 14 volts or so at the terminals. It does seem like you might have a bad voltage regulator, which is inside the alternator.

It is possible that a high voltage will make the ECU go a bit nuts.

BTW, I don't believe that you can get too much useful info on your car with a scan tool. Only OBDII cars have that ability (injector info and such).

fredk · 10-23-2005, 06:52 PM

check the charging rate and check all the grounds

Ironmike4x4 · 10-23-2005, 08:00 PM

Quote:

Originally Posted by MitchB

BTW, I don't believe that you can get too much useful info on your car with a scan tool. Only OBDII cars have that ability (injector info and such).

Yes you are right. I am glad you caugt me on this. I keep thinking of computer components for GM, but you couldn't do the freeze/frame fail records unless it was an '96 and up vehicle. My apologies on the wrong info there johnr

johnr · 10-23-2005, 09:06 PM

Thanks guys...beleive it or not...after about six months on this problem, I think I have found it.

I decided to do a "complete" under the engine "look see" and notice that just above the ALT is a bracket...(of some sort). A bolt was missing and it was hanging down. As I took a closer look (got my F-in glasses) I also notice that this plate/bracket had some wires going to it. These wires (two) were held on by a push pin clip that was half off. Of course after putting everything together.......well the rest is good news. Must be of course some kind of ground? Couldn't find anything on it in the books.

Overall, I really would like to thank all you guys for the good help. We can only learn by our problems. Jim