'90 740 Idle Problem

NewToOldVolvo · Post by **NewToOldVolvo** » 21 Mar 2011, 19:07

My 1990 Volvo 740 has stopped idling consistently. Typically, when it is first started, it won't idle at all...just dies. I have to play the two foot gas/brake game for about the first 20 minutes I drive, then it resumes normal idle operation. The local shop diagnosed it as needing the Idle Air Control Motor replaced with an estimate of about $420, which includes cleaning the throttle body.

It seems to me the IAC motor is not completely dead? Is there a simple way to clean it to see if that corrects the problem?

The car has 190,000 miles on it. I am no mechanic, but can do most mechanical tasks with some good advice.

Thanks for your help.

SkyVolvo · Post by **SkyVolvo** » 22 Mar 2011, 00:22

If it's the IAC - and that sounds likely - then you can definitely do this yourself and save several hundred bucks. If you dig around under the intake you'll find the IAC. It looks like this, but not so shiny: http://www.fcpeuro.com/products/volvo-i ... 0280140516

My first thought is that yours sounds like it's not completely dead yet, since it resumes normal operation after awhile. You can disconnect the two hoses and the electrical connector from your IAC and then clean it out thoroughly with some carb cleaner - just spray a bunch of it in there until it seems...I don't know, clean. Some people get a bunch of gunk out of theirs.

Cleaning the throttle body is probably also a good idea, but you'll want to get actual throttle body cleaner for that, and you'll need to have a replacement gasket on hand, like so: http://www.fcpeuro.com/products/volvo-f ... 40-1271488
This gasket can also be purchased from a nearby dealer, if you choose.

For cleaning the throttle body, here is one of many great walkthroughs:
https://www.matthewsvolvosite.com/forums ... =2&t=27092

If cleaning your IAC doesn't work and you determine that you do need a new one...ebay it. There are plenty of perfectly good ones available for cheap.

All of this is very do-able. Follow instructions, make sure you reconnect hoses the right way - nothing to it.

SkyVolvo · Post by **SkyVolvo** » 22 Mar 2011, 00:40

Oh yeah - if you want to check out the functionality of the IAC yourself, here are some excellent instructions from SwiftJustice - make sure you follow the thread to the second page. Requires some poking and prodding with a multimeter...I plan to do it myself in the next week.

http://volvoforums.com/forum/volvo-240- ... oms-24535/

NewToOldVolvo · Post by **NewToOldVolvo** » 22 Mar 2011, 09:35

SkyVolvo...thanks so much for the great advice and feedback. I now have a project for Saturday morning!

I am also faced with paying about $400 to replace the OverDrive solenoid. I read some posts on here about doing a bypass within the solenoid so that the fluid flows all the time, thereby alleviating the need for the electric function of the solenoid. Do you recommend that I start a new post on this or do you have some feedback on this as well? This is a great site and I'm very pleased that I got such great feedback on my first post! Thanks so much!

SkyVolvo · Post by **SkyVolvo** » 22 Mar 2011, 13:10

Never a bad idea to start a new thread, but it's funny you ask about the overdrive solenoid, because I just did THAT as well about two months ago. I definitely recommend the bypass. Here's a link to a little more info: https://www.matthewsvolvosite.com/forums ... =2&t=35573

You can find all kinds of info on this if you want. I originally thought about doing a write-up for it, but it didn't really seem to need one. It's a real pain to find a sensible angle to reach those bolts on the overdrive solenoid, but once you get it, it's a piece of cake. Of course, that's the story with about everything on a car, I'm discovering. I don't know how much you meddle with your cars, so forgive me if this is obvious, redundant, or both, but do NOT get under a car supported only by a jack - it needs either a good set of ramps or jack stands and blocked wheels. You can find easy instructions on building a set of wooden ramps out of 2x10s, if you want.

I did the bypass; I have my fourth gear back. Simple, cheap, painless. Once you do both of these repairs, you'll also have the satisfaction of having saved some $700-$800 (not that I would've recommended replacing the solenoid at full cost - many people just drive without 4th gear).

By the way, make sure you post back with your results on the IAC. It helps future lurkers find their answers quicker.

NewToOldVolvo · Post by **NewToOldVolvo** » 22 Mar 2011, 13:38

SkyVolvo,

I feel like I've just found a gold mine on this site! Thanks so much for the great information. I will definitely post the follow-up information. I will attack the IAC this weekend and then plan on the od bypass on an upcoming weekend!

I really appreciate your help!

NewToOldVolvo · Post by **NewToOldVolvo** » 23 Mar 2011, 07:40

Update:
Last night I took the IAC motor off and thoroughly cleaned it with a carburetor/throttle body cleaner that the local Auto Zone fella recommended. During the process, I also tried to clean the intake hose that runs from the air filter box to to the air intake at the throttle body. There is a small "return" hose that runs from the top of the engine and connects into the air intake hose that was actually disconnected from the plastic "port" at the top of the engine. It was nasty and full of gunk and oil. This prompted me to try to clean it and the air intake hose as best I could with the carb cleaner and some gasoline? I also cleaned the exposed part of the throttle body that I could get to without removing it at this time. When I reinstalled everything, I tried to reconnect the rubber hose to the plastic port at the top of the engine, but it doesn't fit tightly at all. I'm assuming this is an emissions hose?

Anyway, the idle has worked well this morning, with one exception at a stop sign (it died completely). This could indicate that I just need to go ahead and buy a new/used IAC motor? Now the bad news...I must have stirred up a hornets nest of gunk or something because the engine is trying to stall/stutter during acceleration...typically from takeoff up through about 2500 rpm. It runs fine at higher rpm's.

Would a SeaFoam assault or a complete cleaning of the throttle body be the best next step? Any feedback would be greatly appreciated.

Thanks!

SkyVolvo · Post by **SkyVolvo** » 25 Mar 2011, 01:59

Hmm. I'm not much of a diagnostician when it comes to things I haven't yet encountered myself - truth be told, I've only been working on my cars for about a year now. I'm with you, though - this site is a gold mine, and I would be sadder and a poorer man without it. This and a handful of other sites have turned me into quite the auto enthusiast.

One of the sites that was most helpful to me in diagnosing running problems was this one:
http://www.vcoa.org/700-900-faq/EngineP ... ptoms.html

Before I cleaned my own TB, my car started doing this horrible rolling idle and trying to die as I came to a stop. It was made worse by the fact that I also had a bad radio suppression relay at the same time, which meant that the car would become very finicky about starting, and I wasn't sure what was what. Cleaning my TB fixed the rolling idle, the dying at stops, and the need to keep on the gas to keep the car from dying. From what I know, the IAC shouldn't be affecting your car during acceleration, as it should only be functioning when the throttle is fully closed.

I should have said this at the start, but go ahead and check your car's OBD box for any trouble codes. Instructions and explanations are pinned at the top of this forum. If you get codes, that can really help narrow down the issues; if you get 1-1-1, that can still help (because, for example, a fouled throttle body doesn't set a code).

Oh, and you mention that the hose doesn't fit tightly. Some of these vacuum hoses are only held on by a bit of friction, and shouldn't be clamped in place because if pressure builds up, it's better for the hose to pop off than to blow a seal. But does it seem like the hose might be letting air in? If you have a vacuum leak, it could definitely cause running issues. With the car running, spray a bit of that TB cleaner near the hose and listen for a change in idle. If the idle responds to the spray, you've got a vacuum leak. (I've never found one this way, but it seems to be the simplest and most common recommendation for finding one.) In fact, checking for vacuum leaks in any place they might exist would be a good idea.

This may or may not have any effect on your issue, but while you're working on all of this, you might order a flame trap kit for your car like this one from IPD http://www.ipdusa.com/version.asp?strPa ... V_ID=10657. Mine wasn't blocked up like some people's are, but the little hose pretty much crumbled in my hands when I went to change it. This can affect the idle, but really it's just a good idea to make sure it's clear, especially since most people never service theirs. Since the parts are dirt cheap, I'd go ahead and toss one in on my next order.

Anyway, check your codes and take a look at that diagnostics page to see if your symptoms line up with anything. I'll keep helping if I can, but Bill of Durham is the man to listen to here in the RWD forum. Anything he says should take priority over anything I say.