Hi Guys,

My '89 765T (B230FT)is not doing well, my wife's a little peeved - you know the story.

I repaired a intercooler hose leak and restored the performance this weekend. We were driving and all of a sudden, the car almost stalled and began to "buck". We were close to home and made it to the garage, where it's sitting now.

It will start, with difficulty and the idle surges between 500 and 1500rpm. I've checked all hoses, tried unplugging the AMM with no change and gone over the hoses very thoroughly. There is a fairly large gauge wire running from the coil and tapping into a wiring harness along the drivers side, from the PO. I'm wondering if there was a problem with the ECU and something was bypassed(?)

I'm thinking ECU, Idle control motor, fuel pressure regulator as the next to test. Maybe some sensors that may cause these symptoms? Anyone have procedures to verify that these are working? I'd rather not "shotgun" and buy a bunch of parts that I don't need. The other option is to take it to my local Volvo guy (he's excellent), but I'd like to at least have a shot at it.

Any other feedback, experiences and tips are greatly appreciated.

Stormie - '89 765T (247,000 miles) + '88 240DL (448,000 miles)

Try the hooter valve (or better known as the turbo bypass valve . .

Hope it works, because that is what my Saab Turbo did. It also would die on de-accelleration

I would read the 700/900 FAQ if you haven't already done so. There's a lot of good information in there and it's well worth your time to read all the material that applies to your car.

If I were in your shoes, I'd probably do the following items in this order:

1. Verify all vacuum hoses are in good condition and have hose clamps where appropriate (since the turbo creates pressure). Stiff ends or cracks merit replacement. Also remove and inspect your Turbo hoses and look for soft spots where tiny splits may occur (and open up depending on vacuum/pressure).

2. Test your Fuel Pressure Regulator. If this hasn't been changed in the last 100,000 miles, you would be well advised to replace it now. The factory Bosch units are available from FCP Groton for only $35 and it's cheap insurance against being stranded by the side of the road. A basic test of putting 25"HG of vacuum on it for 2 minutes at the vacuum port should just about guarantee that the current one is still in decent shape. If it starts to leak down or you detect fuel in the vacuum line (when you removed the vacuum line initially), these would indicate a failure. Sometimes the pressure regulator might leak when it has pump pressure behind it so a vacuum test (stand alone) does not always find the problem.

3. Clean your Idle Air Control Valve and all the various tubes and ductwork that lead into it. If your IAC Valve gets oil inside it (through the positive crankcase ventilation system), you can have a variety of symptoms. Unstable idle, no fast idle, high idle, low idle, surging idle, hard starting, etc. I clean my IAC Valve once a year for good measure as part of my annual-comprehensive tune up. More info available in a recent post I wrote:
http://www.brickboard.com/RWD/index.htm?id=777199

4. Inspect the AMM, is the Platinum wire intact or broken? Try swapping your current AMM with a good working spare. (-using the spare 007 AMM that you hopefully keep in your trunk, right next to your spare Main Relay, spare Fuel Pressure Regulator, and spare Radio Suppression Relay since these are the 4 weakest points on your car that can leave you stranded and calling a tow truck, and all of them can be swapped in a couple minutes or less. Used parts in known working condition are just fine as backups, and buying $50 worth of used parts now can save you hundreds later.)

5. Buy a copy of the 240 Haynes manual (yes, I said 240) to complement your 740 Haynes manual. Complete chapter 1 in the 240 book which covers a complete tune up and use the 740 book as needed when differences exist. Note: The 740 Haynes book does not have a tune-up chapter, -which it desperately needs. These cars are similar enough that most of the information in chapter 1 of the 240 book will apply to your 740. Also, read through the service schedule in your Volvo owners manual (may be a separate pamphlet) to see what Volvo recommends your car should have done to keep it in good running order.

6. ECU issues: You'll need to tell us what ECU you have. Remove the kick panel on the right side of the car and tell us the Bosch part number on the ECU tag. This is by the passenger’s right foot for a Left-Hand-Drive vehicle. There were a few ECUs that had known problems, and there are several people on this board who can help (and/or speculate) once we know what you have. If you have extra wires in the engine bay or at the ECU, try to trace their path. What device do they go to, and what pin of the ECU are they spliced into.

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 234K

Fitz, You are THE MAN!

Thanks for the great info. I removed the IAC last night and cleaned it with carb cleaner. The color of the stuff coming out was very dark, so I repeated the process until the carb cleaner coming out was clear. I'm letting it dry out and will reinstall tonight. Is it necessary / possible to bend the tabs near the top outward and take it apart to check the inside?? I hear a clicking sound when I turn it upside down (I hope that's a good thing).

I pulled the vacuum side hose from the FPR and smelled no gas, which I assume means that the FPR is OK.

I will know more tonight and will post accordingly. Thanks again......

Thank you, I'm glad to help.

Since I wrote my initial reply, a longer thread about Idle Air Control Valves has come up. Feel free to check out the following thread:
http://www.brickboard.com/RWD/index.htm?id=778266&show_all=1

If you're considering pulling the IAC Valve apart to clean the electrical motor, -I would advise against it. I've dismantled two of them and it's much more difficult than it looks. Putting it back together can be difficult and I've had less than acceptable results. Re-inserting the motor core/windings without damaging the commutator or the brushes can be challenging.

I'm glad to hear that the situation is progressing and I hope your vehicle is back on the road soon. If the problem still remains after cleaning the IAC Valve, I'd remove your turbo hoses and check for a very small split (or a spot where the hose is soft enough that you can push your finger through it). -also look for a loose vacuum hose or one that's missing a clamp.

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 236K

Found a similar post, maybe it will help you out.

Idle Air Control Valve 700 1991
posted by jchiodi on Mon Mar 29 14:23 PST 2004
Author Info: [PROFILE] [EVERY POST] [THREADS]
the car doesnt want to idle! But the symptons on mine were very rough idle. The car seemed to want to surge and then drop from about 1500 to 500rpm.

The way I found out it was the IAC was when it was having problems, I tapped on it with an open ended wrench, (19MM I think). And it ran okay for a short period of time.
these can be cleaned and there is a definite test procedure, Ohming it out, checking voltage, etc, but I don't have my manual handy.

good luck,

jc
--
1985 740gle na, 1990 740gle 16 valve