RPM issue at idel or neutural only

[hadia]

Hi everyone,

1990 Toyota 4R, V6, SR5, 3VZ-E engine, 187K+

I had a gas leak from fuel dampener at the end of fuel line. This part is not easily accessible. In order to get to it the intake manifold had to come out. I had a mobile mechanic to do the work. Since the intake manifold had to be removed for the dampener, it was a good time to replace the injectors and PCV too. He did a good job. There is no fluid or air leak after the fix. None the less, I have a small problem since.

When I start the car and the gear is in idle or neutral, the rpm acts up when I press the gas pedal. It has a hard time reaching 2000 rpm and then has a sudden drop to 1200 rpm. every time I press the gas pedal same thing happens, I can not maintain it at 2000 rpm or higher . The car does not stall and here is no engine fault either.

I don't have this problem when the car is in drive. RPM is maintained for whatever value I want to hold it at when I drive.

I would not worry about it if I did not have to go for smog test. I am worried this will cause the smog test to fail.

To eliminate things, I completely have disconnected the Cruise Control but problem is still there. Though I don't feel any leaks or hear any hissing sound, I still replaced all the vacuum hoses but did not help. The intake valve was cleaned, the air filter is clean, all hoses are in good shape and clamped tightly.

Since there is no problem when I drive, what are the components that are not a suspect, so not to waste time on?

What are the components that are only active or involved when gas pedal is pressed in idle or neutral (and not in drive)?

I appreciate any help or suggestion.
Hadi

 

[Ahlem]

I would check your Throttle Position Sensor and your transmission kick down cable if its an Automatic. You might double check to be sure the rubber intake boot is properly clamped in place. Finally I'd check the timing.

 

[hadia]

Thank you Ahlem. I have actually purchased a new Throttle sensor but hesitate to change it yet because I think if it was the sensor, I expect it would generate an engine fault ( one of its function) but there is none.

Yes, the 4runner is automatic. Could you please expand on transmission kick down cable. Are you referring to the cable that is connected all the way to Throttle body?

 

[Ahlem]

Typically anything you took off when doing a repair should be double checked if you have a problem afterward. If you removed the throttle cable and transmission kick down cable and put them back on too loose or too tight, you might get this result. Did you check your timing? If the TPS was loose when you disassembled the intake, you might have bumped it. I had the same thing happen last year when I did a similar repair and that solved my problem.

 

[hadia]

Hi Ahlem,
Good news. I know that the mechanic had to remove the Throttle sensor when removing manifold intake. I had already suspected that and I called the mechanic but he said if it was the sensor, it would generate an engine fault. He just did not want to come back and take a look at it. When you suggested it might still be the cause, I used a mirror and saw that the mounting is not centered. I loosened the mounting screws, wiggled it a bit to seat properly and tightened the screws back. Problem fixed!

Thank you very much for your help.

 

[flyinhawaiian01]

Ummm, if you loosened the throttle position sensor and adjusted it to the center, chances are you threw the tps off. Now, you may be the luckiest guy in the world and actually nailed it by moving the tps to the exact spot, but those of us who have set the tps in the past will know that this is near impossible to do just by looking at it!

I'd suggest checking to see if you are able to pull codes from the ecu, if you don't get the flashing check engine light, its definitely off, but even if it gives you a quick flashing light, it could still be off.

The ONLY way to make sure its adjusted properly is to just do the procedure to set the tps correctly.

 

[hadia]

Now you are confusing me!

"....if you don't get the flashing check engine light, its definitely off, but even if it gives you a quick flashing light, it could still be off......"

I thought it would be other way around. you get an engine light if something is not working right!

This is not the first time the tps has been removed. Two years ago (another Thread here), for troubleshooting another problem I removed it and put it back with no negative after effects. As long as the contacts are matching in the right place when you mount it, it should do its job correctly unless there is more to it that I don't know. (and that is possible!)

Well, now if I press the gas pedal while in Park or neutral, there is no rpm drop and I have no engine light of any kind. I drove it for a short distance and there was no issues in Drive either.

I will check to see if there is any codes and I also will get a one day permit from DMV to drive it a bit more to verify everything. (The Truck is registered as Non-Operational at this time)