Sorry, I placed this thread under General Discussion category a few days ago and there has been no response, so I am placing it here.

Hi everyone,
I have a 1990 toyota 4R, V6, 3VZ-E engine. With gear in park position, if I press acceleration pedal, it barely makes it to 2000 rpm, and quickly drops to about 1500 RPM, O/D and Cruise light act up too and I get Eng code 42 (vehicle speed sensor), but it runs ok when I drive it on the road. I took it for a drive around the block, pushed it up to 4000 rpm without any rpm fluctuation or drop and the speedometer works fine too. (Can't go farther or faster because the car is not registered with DMV yet and I can't register it because it will fail smog test with an Eng code present.)

NOTE: The car was down for a year due to Fuel dampener leak. Recently I had a mechanic replace the leaking Fuel Damper and since the intake manifold had to come out for this job, I had him replace injectors and PCV too. There don't seam to be any vacuum, water or any other leaks after this repair. Could anything in this area still cause the problem, If not, then what?

I hesitate to jump and replace the vehicle speed sensor for 2 reasons. 1_ when driving, I can accelerate without any problem. It is only when in PARK that rpm drops before reaching 2000, so I am kinda confused. 2_ I already spent $1K for the fuel dampener / injectors replacement and a new battery and want to make sure the sensor is actually the problem before I spend money on it (electronic parts are not returnable).

UPDATE: A few days has passed and no comments. I went ahead and replaced the Vehicle Speed Sensor. I Drove it up to 40mph. I no longer get an engine fault and the O/D does not lit either. But, the rpm issue at Park position remains the same and either at Park or Drive gear, the second I press Brake pedal, Cruise light comes on, stays on solid (no flashing) until I press cruise cancel switch. This will happen again if I press the brake pedal again. (brake switch is sitting tight and break lights are functioning properly). I actually like to disable Cruise Control all together but havn't been able to locate a dedicated fuse for it yet. I hope this additional information would generate some helpful comments.

I would think the cruise control is playing into this based on what you are saying. Let me get my manual out tomorrow and look at the schematics and see what I can find. Need to some digging in there anyhow for my runner. One thing you could try to see if it makes a change is disconnect the cruise control cable from the throttle body. It's the one closer to the firewall. Will post back on here in the morning after I do some reading and let you know what I see in the schematic.

Thanks fwak1234. I disconnected the Cruise Control cable. Still the Cruise indicator lights up if I press brake pedal while in Park and the RPM acting the same if I accelerate while in Park. Right now, 2 things I really need to know:

The next suspect is speedometer cable but while I drive it, rpm is ok and so is speedometer. Neither one fluctuates during drive. Could the speedometer cable still be bad?

To eliminate Cruise from RPM problem I really want to completely disable/disconnect cruise system. In San Jose Bay Area freeway traffic is stop and go, cruise is useless anyway. So, with Cruise Control cable already disconnected, I also disconnected the harness from speed control module which based on its location per manual is the same as (CC ECU) and disconnected the main relay next to it too. The Cruise indicator no longer lights up. The rpm issue is still there.

I'm guessing this is an automatic? Does the problem happen in Neutral or just park? If auto, it may be a tranny issue, something like the converter maybe not disengaging.

The speedo cable has nothing to do with your problem.

Thanks but don't use that dirty word (tranny) please. We already know how much the blue book value for this car is! I already spent $1k. If no Engine light come on, maybe the smog test would go through, I hope. Otherwise, I made $1k gamble. Can't afford no more expensive fixes. I hope an inexpensive solution is found.

Yes the car is Automatic and I checked the status in Neutral and it behaves as in Park. (To refresh: No problem while in Drive!).

Thanks

Well, think about the mechanical difference's between park/neutral and drive. I know where I'd start with my trouble shooting. Could be something simple, even with that nasty word.

I hear no grinding noise nor have gear shifting/slipping (unless drop in rpm is a slip) but I have not done a transmission fluid flush since the engine was rebuilt in 2007. Could a dirty filter here cause this problem and only in certain gear position?