Throttle body causing bad RPM control?

[briwayjones]

First what does the rubber line that attaches to the throttlebody do? Second I installed a BBK 66MM throttlebody and a 75MM aftermarket MAF. After I installed them the RPM control is off. I have a manual transmission so all of this is very noticeable. While driving it won't let the RPMs go under 1500-1800RPM. Stock it would go down to 1000RPM. And when I stop it will hover at 1500-1800RPM for a good 10 seconds sometimes before it drops to idle speed. When stock it would hover at 1200RPM for a second or so at the most then drop to idle. I thought maybe the MAF sensors needing cleaning (didn't look like it though when I installed it) but I couldn't find my cleaner. So instead I stuck the stock MAF sensor on there. That helped a little but basically still does the same thing. So I'm wondering if the throttle body can be causing this?

 

[jimcom]

I don't want to sound stupid, because I am not sure about the differences in how the manual revs versus an auto, so this is just a shot in the dark.
But, how many miles have you driven since you put these on?
and...
Did you disconnect the battery, and let the comp. reset?

Perhaps it is just relearning everything?
It may still be working on the info it has from the old air/fuel mixture and trying to adjust rpm's to match this new mixture?
I dunno. I can't express what I am trying to say for some reason.

Basically, I think the batt. needs to be disconnected (if you didn't do that upon install), and you need to drive it probably 500+ miles before it will learn everything the right way.
Even if you did disconnect the batt. it still takes awhile to relearn everything. If you didn't, it will eventually relearn, it'll just take longer.

I am probably just telling you stuff you already know, sorry I can't be of more help.

And I have no idea what the rubber line is for.

 

[briwayjones]

Yeah I disconnected the battery. I put the old sensor back in hoping it would run the same as it did before the install. But I guess because of the differences in the MAF it didn't like the old sensor in it because after a little bit I'm now getting a CEL. And the old sensor is running the same way so it's got me thinking it's the TB somehow. So I need to throw the sensor that goes to the TB back in today. I drove about 65 miles after I first installed it and probably about 120 since I changed out the sensor yesterday.

 

[jimcom]

Geez, this is weird.
Maybe send Jefe a PM and see if he experienced anything like this when he first had this stuff. He may be able to lead you in the right direction.
At least now with the CEL though, you can pull the code and see exactly what the problem is. Thats a good thing. Make sure to let us know what the code is, I'm betting a dirty O2 sensor, I think every CEL is a bad O2 sensor, lol, but it'll probably be something else entirely.

 

[briwayjones]

It's the MAF sensor that's causing the CEL so it's probably a bad MAF sensor CEL or something if there is such a thing.

 

[BrooklynBay]

I had to give this a little thought, but I figured it out. It is probably the tps. If it is misaligned, it will cause a fast idle, and a CEL. I once had that on a 3.8 GM that I was repairing. It is also a good idea to check for any air leakage. That could also cause a high idle.

 

[briwayjones]

The thing is this didn't happen until I changed the MAF and throttle body. And when I'm stopped it will go back down to a normal idle, it just takes a while. While your moving though it won't go below 1500RPM.

Wait I forget where the TPS is. Is it on the throttle body? The sensor thing I had to take off to install the new TB? If that's the case then maybe it is misaligned.

 

[BrooklynBay]

The tps is on the side of the throttle body.

 

[briwayjones]

Hmmm.....

 

[karl_burns]

I have the same issue, but mine only occurs when it's less than 35 degrees outside. I've never had a consistent idle on my truck ever since installing the BBK 65mm throttle body. I disconnected the battery everytime I work on the truck, and when I clean the MAF. I moved up to the 75mm Granatelli MAF a while back, and this still idles out of control. I did the TPS mod to get it to .96 volts. Maybe it came loose? I dunno.
1998 Explorer Sport 5 speed......
Karl

 

[karl_burns]

No CEL though.....
Karl

 

[briwayjones]

I'm 99.9999999% sure that the CEL was just because I installed the stock MAF sensor on the 75MM MAF. I put the sensor that goes to the 75MM back on it but haven't driven it yet.

Did adjusting the TPS have any effect on it? How long ago did you install the TB and have been having the idle problem?

On your throttle body is the nipple where the rubber hose connects a lot smaller than the stock one? How did you connect it? On my BBK TB it came with a piece of rubber that hose that fits on it's nipple. I just took the that hose and stuck it inside of the rubber hose that's supposed to connect to the TB.

 

[MONMIX]

Hey man, I have a full function scan tool. Datastream and all. Lemmie know if you need me to hook up to your ex. I dont have much going on tomorrow.

 

[briwayjones]

What's a full function scan tool with Datastream do? I pulled codes from my scanguage. The ones I could find are errors with the MAF with fits with putting a sensor on there it doesn't like.

I might have to take you up on that offer just so I can have some place to wash my X without freezing.

 

[Jefe]

The hose to the bottom of the TB is the gas tank vapor recovery (or whatever the offical term is). You may or may not eventually get a code without that connected. If it isn't connected that hole needs to be plugged.

As for the idle, thats simple. There is an idle screw on the TB. With the engine warm, disconnect the connector to the IAC (idle air control) so that the only air suppy is through the TB. Now adjust the idle set screw until the engine idles around 500 rpm. Now reconnect the IAC and all should be good.

Putting the stock MAF sensor into the 75mm tube is definitly going to throw a code, as the MAF sensor is not calibrated correctly.

 

[karl_burns]

I asked around, and the consensus was the issue is the TPS. Makes sense, because the engine doesn't understand when the accelerator is no longer depressed. A replacement is $10 from AutoZone, so that's the next part.
And I'll have to drill it out to get the .96 volts position.
Karl

 

[karl_burns]

Found some on-line discussions which seemed to support the idea of a bad TPS. It's off to AutoZone I go! $18.99 part.....
Karl

http://www.240sx.org/faq/articles/throttle_position_sensor_adjustm.htm

http://www.ukcar.com/features/tech/Engine/injection/injection.htm

http://groups.google.com/group/rec....98c?sa=X&oi=groupsr&start=0&num=3&safe=active

 

[jimcom]

was this problem ever resolved bri?

 

[briwayjones]

Oh yeah I finally did last week. I had to adjust the idle control on the new TB, it was set too high. Then I did the TPS mod where you set it too .96 volts. After that it's been great. The only thing is the throttle response doesn't seem as good as it first was after I installed the new MAF and TB.