'94 Previa LE S/C unusual acceleration problem

[pdgizwiz]

I don't have an SC, but I have the '94 supplemental manual. It shows a distributor with holes instead of slots as you describe.
The SC has a crank position sensor that the NA engines don't. I expect that the computer handles ignition timing using that signal.
Heck, most cars these days don't have distributors at all. Timing lights have become as old-fashioned as point files.

[jmrodz0]

I don't have an SC, but I have the '94 supplemental manual. It shows a distributor with holes instead of slots as you describe.
The SC has a crank position sensor that the NA engines don't. I expect that the computer handles ignition timing using that signal.
Heck, most cars these days don't have distributors at all. Timing lights have become as old-fashioned as point files.

I've ordered the Factory Repair manual...and fully expect the procedure to set the timing will include the sacrifice of a live chicken.

[timsrv]

I don't have an SC, but I have the '94 supplemental manual. It shows a distributor with holes instead of slots as you describe.
The SC has a crank position sensor that the NA engines don't. I expect that the computer handles ignition timing using that signal.
Heck, most cars these days don't have distributors at all. Timing lights have become as old-fashioned as point files.

Makes sense. Why would you run off a phone modem when you have wifi? When you think about it, given the level of technology, it's almost surprising that they still had distributors at all in 94. Of course my brain is still oriented to 1985.........gosh, I'm getting old

[jmrodz0]

I've ordered the Factory Repair manual...and fully expect the procedure to set the timing will include the sacrifice of a live chicken.

I'm finally back in MA with my Official Previa Repair Manual!

The manual asserts that the timing can be adjusted by loosening the distributor and turning. Unfortunately, the distributor on this van doesn't have that option. I guess it could be that this has a nonstandard type distributor without the slots, but the van drove pretty well from SC to MA albeit with the same shudder/lack of power at 2500RPM. Upon my return, I gave the engine compartment(s) a visual check and everything seemed to be in place (ie PCV, vacuum hoses, no leaks, and of course no ck eng lights). So, I'm back to square one with this issue.

I'm fairly confident of all the repairs made to date, and the van runs very well under most conditions. The big variable in all this is the supercharger which is not documented in the repair manual. I have ordered the Supplemental Repair Manual which covers the 2TZFZE engine....I hope.

Understanding the cause of this problem has become a quixotic quest! I did get a referral to a Toyota specialist in Quincy MA, but they were too busy on other projects, so if anyone knows of a Toyota specialist in MA please pass it along.

[timsrv]

The supercharged units have a crank position sensor. With that, the ECU adjusts timing. No need for you to do anything.

[timsrv]

BTW, I would have offered this information earlier, but just recently discovered this while working on another Toyota from this era. There was absolutely nothing in the service manual to suggest this was the case. I figured it out when I found holes on the distributor mounts (instead of slots). That got me looking around and sure enough, there was a crank position sensor. Tim

[jmrodz0]

Last week I located the Air Control Valve that is mounted on the radiator. This valve somehow regulates the air flow/pressure to the supercharger. The Supplemental Repair Manual has some information about the operation but not much. Anyway, after locating the valve, I disconnected the attached vacuum hoses and the electrical connection and started the van. It ran like crap and eventually stalled. I reinstalled the ACV and it returned to normal operation however I got a P0800 and a P0401 code. I did not clear the codes and took the van for a few errands and when I got back I checked the codes again. This time the 401 code was still there, but the 800 code was gone and a P0006 code showed up.

There is no explanation of either the P0800 or P0006 codes in the Repair Manual, but the P0401 is an ERG insufficient flow problem. This morning, I drove 50 miles and again checked the codes. The only code that showed up was the 401 EGR insufficient flow. The more significant epiphany was that I was able to rev the engine over 2500 RPM without any problems!

This was a revelation and a frustration since I hadn't done anything [of significance] that would change the behavior. I had tested the EGR months ago with a vacuum gauge and it seemed to be operating properly, that is, the engine stalled when I put vacuum to it. I had cleaned the EGR and the pipe also.

This can't be a self correcting problem, so I'll revisit the EGR system. The manual claims it may be the VSV or the Camshaft Position Sensor and since the van is running great otherwise, I'm discounting a fundamental problem with valve timing, compression, MAF sensor, and ECM.

[jmrodz0]

The supercharged units have a crank position sensor. With that, the ECU adjusts timing. No need for you to do anything.

Tim,

I found the problem...and feel very stupid.

The issue was with the connector on the crankshaft position sensor! It appeared to be connected, but popped right off when I wiggled it. After cleaning it out with some electric spray and seating it properly, the van is now running perfectly through the entire rpm range.

Thanks for all the help!

Jim

[timsrv]

Thanks, but admittedly I got there by fumbling around (I learned something too). pdgizwiz actually had the timing/sensor thing nailed early on. That's awesome you got it figured out. On the one I was working on (a NA 95 Corolla) a crank position sensor was the last thing I expected to find. I swapped distributors, igniters, and the ECU (ECU is a real PITA on the Corolla) before fumbling my way to the crank position sensor. What gave it away was pdgizwiz's comments about the lack of slots in the distributor.

I was using a factory service manual, but it was a 94 (shouldn't have mattered I thought). Absolutely nothing in there about a CPS. No big deal now that it's over. Stuff like this just makes us better mechanics. Tim

[tbkilb01]

I don't have an SC, but I have the '94 supplemental manual. It shows a distributor with holes instead of slots as you describe.
The SC has a crank position sensor that the NA engines don't. I expect that the computer handles ignition timing using that signal.
Heck, most cars these days don't have distributors at all. Timing lights have become as old-fashioned as point files.

I had forgotten about those points.. I was steady filing on them back then, under the distro cap!