940 1994: Throttle Body Service

[writer100]

My efforts to improve the durability and drivability of this 16 year old car continue. Today I cleaned the throttle body. As you all know, modern cars route blowby exhaust gases back into the intake in order to burn them. This causes coking in the throttle body which must be periodically cleaned. This is an easy service requiring few tools and is suitable for a beginner.

I don't even remember when this had last been done on this car -- several years ago, that's for sure. The car had ran well, but cold start idle was rough, and it seemed to run quite rich, emitting a lot of fumes, reminiscent of my mother's old 1969 Mercury station wagon, back in the happy days before catalytic converters.

There she is

First you'll need to go to the Volvo dealer and pick up a paper throttle body gasket. They charged me $7.56 for this. Can you believe it?

stuff I used

Be sure to use throttle body cleaner, not carburetor cleaner. The brand I used was CRC. Here's what you do:

1. Disconnect the negative terminal to the battery. (You will be working close to the back of the alternator.)
2. Squeeze the bailing clip on the throttle position sensor lead and disconnect it.
3. Pull off the two vacuum lines from their brass fittings.
4. Use a small flat screwdriver to unclip the lower throttle linkage from the throttle body. Basically, you snap open the clip, and then gently pull the fitting off the ball joint.

Throttle linkage disconnected from ball joint

5. Now remove the accordion air intake hose, using a large flat screwdriver to loosen the retaining clip.
6. Finally, remove the three attaching nuts. Careful not to drop them!
7. Remove the throttle body. The paper gasket should come right off. If it doesn't, gently remove with a plastic scraper to ensure that the mounting surface is clean and smooth.

Does this look clean to you?

8. Use the throttle body cleaner and a toothbrush to clean the entire throat of the throttle body. Clean especially the vacuum fittings (one of mine was clogged, so I had to wrench off one of the brass fittings to clean properly). Cleaning the throttle body was easy, if tedious and quite messy. I used safety glasses as the cleaner shoots out rather violently in all directions. Try to keep the cleaner off of the black plastic throttle body position sensor.

all clean

9. When clean, refit with the new gasket. (The gasket goes on dry.) Tighten the nuts moderately; no need to over torque. Reattach everything else. I lubricated the ball joint of the throttle linkage, as well as the throttle cables.

I had intended to use my analyzer to test idle rpm before and after. But I think my analyzer is on the fritz, because I couldn't get a good reading. However, the engine did idle smoother when cold, did not seem to run as overrich as before, and from the tachometer, idles at a lower speed than before. So I'm happy with it.

One more thing done -- many more to go!

Alex

[billofdurham]

Thank you for a very clear write-up and the pictures make it even clearer.

It will be going into the Repair Database.

Bill.

[TWR1980]

What is the smaller vacuum hose for. I want to clean my TB but I cant remove the smaller hose because it is deteriorating...if i pull too hard it will surely rip/disintegrate? It doesn't look like a standard vacuum hose or I would just rip it off and replace it.

Update: Whatever that hose was for, it crumbled a bit but i was able to ease it off, and get it back on. Throttle body was very dirty and it was easy to remove and put back on. Nice write-up."

Now if I can just find my vacuum tree...

[rgk]

What might happen if you get throttle body cleaner on the plastic sensor? I actually sprayed quite a bit of cleaner on it. Is there any way to test the sensor?

[Brain in a body]

My Volv was running terribly on the road a few days ago. So I called my Dad for some advice on where to start. He suggested I start here, so I did and followed this guide.
Now Shes running beautifly! I am very suprized that such a minor and simple job as this is could have such a major effect on performance.

Thanks to all the good folk in this community for access to such information!

[voodoorobaz]

Awesome write up. Thank you.

[cbfunky]

I know it's an older post, but I also wanted to say thanks! Very clear and understandable - super easy to follow.

I'm curious though: I spent the majority of my time on this on trying to get the top right nut off - I couldn't fit any of my tool in between the nut and the sensor. I ended up unscrewing the sensor so that I got an extra 3mm and with a bit of brute force it eventually came off. Was there an easier way of doing that?

I also second the safety glasses, I totally got some cleaner in my eye. Didn't hurt, but somehow that worried me more than if it had. Let's see if I'm blind tomorrow :/