1989 740GL throttle body

Yes - under the throttle body is the small cylindrical Idle Air Control Valve. That also gets its share of glop. Between the throttle body and the IACV you can expect to go through a pint or so of carburetor cleaner spray... no kidding!

The throttle body is best cleaned by removing it so you can "shoot" through it, but it can be cleaned on the car. Pay special attention to the small passage on the lower part of the TB that connects each side of the throttle area to the knurled idle adjustment screw at the bottom. I prefer to count the number of turns and 1/4 turns the screw is open, then remove the screw for cleaning the passages. Squirt lots of cleaner through there, then reinstall the screw as far open as it was. BTW, the idle speed is actually set by the ECU, so the screw merely adjusts the range of the IACV operation.

Be careful with the hoses on the IACV. If they have hardened they can be brittle.

Mike

Thanks Michael. I'm betting the hoses will need to be replaced. Is the retro-fit for the flame trap the way to go?

The flame trap can be cleaned, but most people prefer to replace or remove the screen altogether.

Mike

I think it's worth it, the kit was only ~$25 last time I bought one and it makes servicing the all-important flame trap so much easier. I have no idea why Volvo chose to hide such a critical but otherwise simple to deal with part so well.

Thanks James, have a nice Easter. You too Mike-

Well, I spent the beter part of Saturday cleaning the throttle body and IACV. Also replaced the flame trap. On the first try, the car ran rough for 5 seconds, peaking at 1000 RPM, and died. Tried to restart, but it wouldn't catch. Pulled the plugs, they were gassy. Dried and replaced. Car did the same thing. I'll continue to research the newsgroup to see what else I should look at. Thanks again for your help-

John

How's the wiring harness? '89 may be updated or it may have the crumbling engine wiring.

I was hoping the wiring harness wasn't the issue, guess that's the next step. And so close to 200,000 miles...Only scrap yard with a Volvo in my area does the pulling for you. $150 still a good price? Thanks again for the reply.

I dunno, the harness is only $15 around here, but you have to pull it yourself. Might check and see what Dave Barton has, he sells good harnesses but they're in the $150-$250 range IIRC.

You'll want to check your harness first though, the one you have might be fine, '89 is the transition year.

Since you have no other suspect, run a test to rule out a failing fuel pressure regulator.

I can't thank you guys enough for all the help!! Now on to the 200k medallion. Thanks again-