Chasing a slightly lumpy idle...still

[Laird Scooby]

Glad you've got it sorted Phil! I know i've mentioned this bit before but removing fuse #1 to reset the ECU memory might just improve matters further, if you can't be bothered it will almost certainly re-learn things by itself in a few days.

Sane scenario as i had with mine - instant improvement in idle quality/responsiveness etc. I suspect what was happening was that after the car previously started, it detected the engine speed and airflow were at idle settings but it wasn't getting the throttle closed signal from the TPS so it wound the IACV in so it wasn't controlling the idle speed. Because of that, it now automatically winds the IACV in (dropping the revs to 400rpm) but then gets the TPS "Throttle Closed" signal so winds it out again to 700rpm and keeps the idle speed at that setting.

It should learn to forget to do the first bit soon, quicker if you pull fuse #1 maybe.

[TonyS9]

Excellent news! I'm sure that is satisfying.

The idle drop is often associated with dirty throttle body, but could also be the IAVC, but they work surprisingly well even when a bit sloppy. I did find one of mine was a bit loose and had hysteresis. The other one actually higher mileage seems fine. Both had other issue, and its very tempting to blame the 'idle' valve for idle problems, its rarely the cause.

I think the mechanism is dirt requiring a different IACV position and the ECU doesn't learn the new position, just has a hard coded starting position. So takes longer and longer to react as the dirty builds up in the TB.

Incidentally Saabs and Alphas use the same part so look for the Bosch PN, price is about £70-£90.

Not sure what mgt + drive you are running, but if manual + O2 sensor system you should find an MPG improvement with the shut off working better and lean idle/ closed mode used more often.

[AllHailKingVolvo]

Good plan, I shall whip out the #1 fuse before I set off for work tonight, I have a nice 3hr round trip to make so a good chance to give it a good run and see how things are. It all makes sense symptoms wise now...as a nice aside, my passenger’s side washer nozzle randomly started functioning again today too! I need to take them off and do the white vinegar trick at some point, but I’m glad to have stereo squirting rather than mono for now!

[AllHailKingVolvo]

Originally Posted by TonyS9

Excellent news! I'm sure that is satisfying.

The idle drop is often associated with dirty throttle body, but could also be the IAVC, but they work surprisingly well even when a bit sloppy. I did find one of mine was a bit loose and had hysteresis. The other one actually higher mileage seems fine. Both had other issue, and its very tempting to blame the 'idle' valve for idle problems, its rarely the cause.

I think the mechanism is dirt requiring a different IACV position and the ECU doesn't learn the new position, just has a hard coded starting position. So takes longer and longer to react as the dirty builds up in the TB.

Incidentally Saabs and Alphas use the same part so look for the Bosch PN, price is about £70-£90.

Not sure what mgt + drive you are running, but if manual + O2 sensor system you should find an MPG improvement with the shut off working better and lean idle/ closed mode used more often.

Yep it’s a manual with the Lambda Sond system, an MPG improvement would be a very nice bonus! The TB is all freshly cleaned, I initially did it a few weeks ago but gave it another clean today. It was still very spick and span so just gave it a cursory blast of carb cleaner and made sure all the hose stubs and inlets were clear. I changed all the 4mm vacuum pipes today too as the existing ones were a little ratty so wanted to make sure all the airways were 100%.

Thanks for the tip about the other brands who share the IACV, I’ll seek one out!

[Laird Scooby]

Originally Posted by AllHailKingVolvo

Good plan, I shall whip out the #1 fuse before I set off for work tonight, I have a nice 3hr round trip to make so a good chance to give it a good run and see how things are. It all makes sense symptoms wise now...as a nice aside, my passenger’s side washer nozzle randomly started functioning again today too! I need to take them off and do the white vinegar trick at some point, but I’m glad to have stereo squirting rather than mono for now!

Looking forward to the report on that one Phil!

A nice upgrade for the washer jets is a pair of these :

http://www.partsforvolvosonline.com/...oducts_id=3644

Got a pair on my 760 and they're a lot better than the originals! Got some photos and/or a video somewhere, if i can find one or t'other i'll add it to the thread.

[AllHailKingVolvo]

Those look the business!! Were they a straightforward swap with the 760 nozzles or did you have to do any mods?

[Laird Scooby]

No mods at all Phil, straight swap. When i bought mine, they were listed as an upgrade for the 850 which uses the same nozzles as ours. Logic dictated if they were an upgrade for something else that used the same nozzles, they would be an upgrade for mine and they were.

Simple to fit, pull the rubber hose off the base of the existing nozzles then i used the 11mm end of a 10x11mm box spanner (for the length) but a deep 11m socket would probably work as well. Just slide it up so the flats on the inside of the socket compress the two tangs that retain the nozzle and out the old one pops!

Grab it and take it away, i like to clean and polish the bit of bonnet the washer jets normally hide then just push the new nozzle in, connect the rubber hose and enjoy!

There are cheaper versions available on fleabay, mainly from China but i know these work and work well.

By the way, when you first fit them, you'll find they're addictive so carry some extra screenwash!

[Rversteeg]

You said somewhere that the butterfly is shut at rest. Maybe I do not understand correctly, but the butterfly should actually never be fully closed. At rest (idling) it should be slightly "leaking", just enough to have the engine tick over at about 500 rpm. The IACV should take care of the rest.
The butterfly should first be adjusted to 500 rpm with one of the IACV hoses blocked.
If the throttle body gets dirty the basic speed will drop. The IACV can compensate for this, but the control of the idle speed will be more sluggish.

[AllHailKingVolvo]

Thanks Rversteeg, I’ll check and readjust if need be. It sits at about 750rpm at present but could maybe come up by 100rpm.

The last couple of days have seen more progress on the car, I replaced the over-axle section of the exhaust which was holed and blowing, replaced the knock sensor which has made it a little smoother under power, found a small crack where the breather pipe meets the intake bellows and have cleaned up and sealed that with automotive silicon sealant, and also decided to have a look at the radio suppression/injector relay.

That and the fuel pump relay were both running hot and had several dry joints, so i reflowed the solder on both and all are functioning exactly as they should now and carrying much less heat.

I noticed that the red supply lead to the RS relay is quite hard in places (especially where that part of the loom contacts the inside wheel well) and I’m wondering if it would benefit from the two hardened sections being cut out and replaced with fresh wire. I bought some wire from ECP but forgot to get any tubular crimp connectors...thought I had some but they were female Lucar connectors from when I changed the coil!

In summary, I’m getting there...I have twelve hours of driving to do in the next three days, so hopefully I’ll be “getting there” in that sense too!

[Laird Scooby]

Originally Posted by AllHailKingVolvo

I noticed that the red supply lead to the RS relay is quite hard in places (especially where that part of the loom contacts the inside wheel well) and I’m wondering if it would benefit from the two hardened sections being cut out and replaced with fresh wire.

If you can minimise the joints in the cable Phil, so much the better. In other words, instead of removing a hard, brittle section only, remove from where it starts to turn brittle and replace all the way to the relay socket.

You should be able to release the existing feed wire from the relay socket by using a long, thin screwdriver (terminal driver for example) and the using what are often known as "W-crimps" with the tab on to replace that terminal on the new length of wire.

If you're any good with a soldering iron (it sounds like you are if you've reflowed the joints within those relays) and have some heatshrink sleeving, you could join the new piece in by cutting then splicing the new bit in, soldering the joint for good measure then insulating with heatshrink.

Besides being more reliable than a simple crimped connection, it is physically stronger and much less likely to break at some point in the future.

Good work on finding those hot relays as well! I'll try and find the procedure for setting the idle speed from scratch for you in the Haynes manual, i think you've missed the idle air bleed screw and perhaps got the base idle slightly out on the throttle butterfly - a "quick fix" would be to unscrew the idle air bleed screw a little to bring the hot idle speed up slightly when first started from cold - would be trial and error though unless you follow the complete method.

The idle air bleed screw is a large knurled headed screw with an Allen key insert/hole, probably only needs 1/4 turn anti-clockwise.

I'll try and find the method later for you.