So here's latest on my last post entitled: "Probably wasting your time"-(and thanks to all who replied.)

OK>> Latest> Replaced (at a Volvo repair shop) knock sensor, and ignition control module; replaced (again) idle air control valve, (first new one was defective) Re-adjusted throttle plate. Replaced ignition ECU (used)

Results= Emptied another $442.31 out of my pocket. Same symptons still exist, maybe a little "lighter" (not counting my pockets).

Next step-try another ignition ECU (no charge)--then if necessary (so to speak)remove transmission to inspect something that goes over and around the flywheel (flex plate?) that you can see completely only by removing the trans and could affect timing. Forseen $$$?-- if that ring around the flywheel has to be replaced, $650, parts and labor. If no parts needed, labor still about $400 to R&R trans.

My "final decision", if it comes to it: 2 pounds C4-------

From your previous post, you have a fast idle. As if the throttle is stuck open.

Disconnect the AMM (key out of ignition) and see if you can obtain the fast idle. If you can't then it may be the AMM. If you can, then remove the hose at the throttle and see if it is still open. (The AMM being disconnected won't come into play.)

If the throttle is closed then plugging the hose to the Idle Air Control valve should stall the engine. If it doesn't you may have a vacuum leak. Eg. brake booster, heater air controls.
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1980 245 Canadian B21A with SU carb but electronic ignition and M46 trans in Brampton, Ont.

Done do did that also but thanks. Never know when something that wasn't thought of might come up.

Few days ago I bought a premade 'For Sale' sign at O'Reileys, (really!) not that im actually going to sell the brick (hmmm---?) but thought I'd at least threaten it--

( I think 'it' knows I really wouldn't use C4---)

In the words of Dr. Frankenstein--'IT'S ALIIIVE--------'

There was a guy on here a couple of years ago who kept going to a shop he was sure was treating him fairly and honestly, and he believed that a new water pump every year (the most outrageous of the thefts that I clearly recall) was necessary.
He was at first completely disbelieving those here who told him differently.
Eventually though he did get the idea.

I have never seen an ICU go bad. Nor a knock sensor. Now it can happen, Anything Can happen, but... it seems to me that the mech is simply firing the parts cannon, and you pay the cost.
Re: trans removal, There is a flexplate attached to the crank. On the edge of that is a set of spaced notches, which are read by the CPS, the Crank Position Sensor. To check it, you check to see if there is any timing registering, with a timing light. And see if it changes. The notches don't wear out.
I personally find the idea that something might be intermittently wrong with the flexplate, and that sometimes affects the idle, to be totally bizarre. But hey.

It does appear that as you seem to know little, but pass back and forth bits of info from the mechanic and from the board, there's a lot of room for things being lost in translation.

Has anyone pressure or smoke tested the intake? Do you lose any coolant? Is the oil clean?

I agree 95%, but my 5% doubt is not at all pertinent to a mechanic who would dismiss the VSS signal's role in idle control. A tech who really knew how EZK ignition worked would not do that, but might suspect a bent tone ring was giving marginal crank position input to the EZK. It could happen, but we on the other end of the internet cannot deal with much more than sheer likelihoods. The guy in the shop can put a scope on it and become much more certain than we can.

The tone ring is but sheetmetal, formed and spot welded. Easily damaged by dropped bolts, and perhaps ill-thought-out methods of crank immobilization. This often-posted photo of mine shows the variation in amplitude in one revolution of the tone ring -- the signal the EZK has to use to locate the 58 holes in it. And this tone ring looks good to the eye.

Philip, take this post to your mechanic and ask her to explain to you how she has determined you need the transmission removed to investigate this. Ask her if she has examined the tone ring through the CPS hole or the starter opening. Ask her what the runout is in electrical terms. That's a lot of money on a guess.





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Art Benstein near Baltimore

Mistakes are the portals of discovery. -James Joyce

my mechanic--'she'-- "her'? a bit unusal to see somone refer to an automobile mechanic as female, but, they are there. Thanks for your input Art. (AND EVERYONE ELSE!)

Great pics Art, I hadn't seen those before.
Yes the mech can do that, and maybe find something without taking out the trans. If there was something, it'd be repeatable I'd think, and not random nor giving widely varying results at different times... eh I dunno. I recall John S and his damaged tone ring, and that gave a repeating consistent problem.
The VSS I have no idea of, that's not an issue on 7/9 cars, that I know of.

You got me to thinking about the 7/9 cars. I know the code is the same and VSS performs the same function in the 940 with Bosch (LH2.4) but I don't recall anyone ever having a Regina idle problem like that.

So, I got to playing with VADIS, switching between Regina and LH2.4 on a "94 940" and sure enough, the DTC is there, with all the same troubleshooting information except the reference to idle symptoms in the case of Regina.

I'm still unclear why Bosch does it. I might speculate, but I'd rather not, just to keep the confusion level down in this thread. The symptom in every case has been high idle at stoplights and such which reverts to normal on shutdown and restart. It doesn't happen in the driveway, because the ECU must wait for load to occur.

It has plagued those of us who come to the board and want to know what their broken speedometer, removed cluster, or busted differential sensor wire has to do with idling. The 311 gives it away. Here's what Volvo says about both the Bendix and Bosch fuel controllers, so I assume it was specified to the supplier:

"If the engine speed (RPM) is above 2100 rpm, the load signal is in the part-load range and the control module does not receive a signal from the speedometer for 8 seconds a diagnostic trouble code (DTC) is stored."
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Art Benstein near Baltimore

Always keep your words soft and sweet, just in case you have to eat them.