My '85 244 runs now, but very badly. After cracking the throttle to rev it up, the idle drops low, almost dies, and hunts up and down like the engine is searching for correct timing. Not enough power to drive it.

I was checking electrical connections under the intake manifold today and pulled the wire off the knock sensor to clean it. Then I noticed that the plastic end of the knock sensor had broken off.



The metal part of the sensor was screwed into the block only finger tight. Maybe the knock sensor was broken internally before I pulled off the wiring harness connection? I hope that is the case if it could be the source of my trouble, because it would be an easy fix after much toil.

What do you think?

Rather unfortunately, the replacements I've found online are very expensive: Sensor from PartsGeek. Sensor from RockAuto.

And now for another ignorant question: Is this style of knock sensor common to any other cars of a certain vintage? If so, maybe it would be cheaper to get a replacement from the local O'Reiley's, I reckon. I called them asking for an aftermarket knock sensor for my Volvo. I was on hold a long time. Then the guys said said they would "have to make inquiries at corporate headquarters" and will call me back. I won't hold my breath on that.

Thanks in advance for advice.

Also good to set the year.

The knock sensor is essentially a microphone attenuated to the valve ping or pre-ignition. The ignition ECU when "hearing" the sound through the knock sensor than changes the ignition timing though timing advance.

Volvo PN 1317296. Bosch may no longer make it. Using Bing and Google may uncover the current OEM brand that you can purchase for far less.

An ebay auction for made in Japan OEM:

https://www.ebay.com/itm/Volvo-Knock-Sensor-Genuine-Volvo-1317296/223070572923

Another auction:
https://www.ebay.com/itm/Volvo-Knock-Sensor-Genuine-Volvo-1317296/223250686275

Tasca has it:
https://www.tascaparts.com/oem-parts/volvo-sensor-1317296

The factory installed style or version you have that fractured at the ABS plastic housing was made by Bosch, I guess.

You do have a host of self service junkyards around you in Snohomish, King, Pierce, Thurston, and other nearby counties. I guess any < LH-2.2 (1988 or older) Volvo has the part.

https://volvoforums.com/forum/volvo-240-740-940-12/need-help-identifying-sensor-83-240-a-64477/

Hope that halps.

--
Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.

Thanks KittysGrayVolvo.

I installed the used knock sensor I bought from Voluparts. I hope it is working ok. The weird idle hunting (unstable rpm) that I had guessed was the timing changing because of a confused ECU has gone away.

It still stalls when I dare to put it in gear and has no power. Can't drive it.

Starts right up though and idles ok, if slightly high. It is very nice to hear it run after a couple months of wondering if that would ever happen again. And the junkyard radio that my friend installed when the trouble began sounds just great.

There was some sudden stalling (as if I turned off the key) from a stable idle...but this seemed to go away when I opened the air bleed screw a few turns. When I twist the throttle open it revs properly with no load on the engine, but snapping back to idle it hesitates- the idle drops and then works its way back up. And if I put it in gear to try and drive -- no power, runs rough, wants to stall.

Following advice given here, my plan tonight is to remove and inspect the hose connecting the air mass meter to the intake manifold. If that is in perfect condition, I will remove the throttle body and clean it (I have a can of TB spray). I will also carefully clean and inspect the idle air control valve and check its associated hose connections. If all of these items and connections are without flaw, I will consult a priest.


“The car has become an article of dress without which we feel uncertain, unclad, and incomplete in the urban compound.”
― Marshall McLuhan

Hi eye5,

Sort of doubted the knock sensor is the cause of all poor tune problems on your 1985 240.

I was at the storage locker Sat-Your-Day this past and I have an unused knock sensor just like what you bought at Voluparts. I guess it is.

I also forgot yours uses the Chrysler MPG ignition as our Uncle Art reminds us. I skipped the 1980s-era 240s, specifically the rotting wire harness years as is your 1985 240. From 1979 240 to 1990 240.

Art and Phil Machine Man can far better help you than I can.

I hope the symptoms you describe do not affect whether you pass CA-state emissions.

With key out of ignition, have you tried starting the engine with the AMM / MAF connected and disconnected?

You will have a silver accordion hose between the exhaust manifold heat shield and the bottom of the air filter box. Inside the air filter box, in front and upstream of the air filter, is a thermostat that moves a flap valve back and forth maintaining a temperature of air inducted into the engine for emissions control. The thermostat failed in all of them, eventually, to hot only all the time. During a hot summer or two, the all hot all the time air will ruin an AMM / MAF. You AMM may be weak or failing. In CA-state, the emissions control like that are visually inspected. As you reside in a moderate SoCally environment, you do not need the preheat feature. Some will replace the thermostat. Other will force ambient air all the time and plug the preheat inlet, yet the silver accordion hose remains in place. The thermostat is Wahler 70411. There is a Volvo OEM version that may last more than a year or two.



I'll suggest the FAQ for information on tune:

https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm

Though so far as I know, 700 and 900 series did not use the Chrysler MPG ignition.

If you perform emissions inspection, and you have high HC, there exist some article here to disconnect the vacuum line to the Chrysler MPG ignition control unit hanging on the washer fluid reservoir basket. Plug the vacuum port on the ignition control module and the vacuum line.

Do you know whether the engine control wire harness has been replaced?

Hope that halps yoo-hoop-hoo.

Questions?

Happy Mundane.

MacDuffed.
--
Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.

Hi,

Yes, I think you need to sit down with the priest, since you have your Bentley bible.
If anyone can decipher a book, that hundreds of years old and get any worth out of it, a Bentley should be a snap!
Both the Bentley and the Bible both have their errors even though they are supposedly “good books” will still have their flaws!
Both came into being as what they are, while being written and interpreted by several men learning how to write up something that changes with evolution!
Absolutely very Tricky to get right without proofreading and collaboration during the dark ages!

Had to be tough stuff to do with out bottles of “White-Out” or the spell checking by candlelight on scrolls ... let alone the use of quills and ink!
I can remember those Sheaffer fountain pens being a mess!
Especially, if You slung the tip at someone! (:)
Penmanship turned into marksmanship!
No ball point pens were around until about junior high school for me!

Also Remember this. it’s been proven that “molds” grew in the cheaper (rye?) bread flour that the nobles didn’t eat but the monks did! All of that was in a neighborhood near Transylvania!
Just how far is Transylvania from those Swedish Vikings, with pointed noses, that Walt Disney likes so much?
http://nordicmuseum.org/events/nordic-stories-dec18

Ok serious stuff now!
Since the engine seems to be better with the new knock sensor the ECU must be working with a RPM signal. This is very important for the ECU it to talk to the IAC.
You need a good throttle switch to be adjusted to be “right on Position to the throttle plate.

You want the plate shut but not jamming in the bore only tightly shut.
There is stop screw but is only there to keep the spring pressure on the pulley from jamming it down too tight.
There is a specification, in the Bentley, but like the Bible, it’s wrong or is a vague in statement for most readers.
After touching up to the stop lever, turn it only about the width of the screw slot that’s in the head to 1/8 of a turn and lock it down with the jam nut!
Do not let hold it open at all because all of your idle air has to go through the IAC so it bypasses the throttle plate!

Since you are cleaning the throttle body, now is the time to get those two things set right.
Using an Ohmmeter on the switch while watching for a changing state across two terminals tests the switch and your hearing.
I don’t remember which way it goes, closed to open or open to closed.

Get this done as the plate cracks open from being totally shut! I mean you just barely noticed it wiggle open as the switch clicks or the readings change when you “think” you saw it open!

The ECU cannot see when you open the throttle. Yet, it needs a heads up that it’s happening like right now! The airflow changes there super fast and is very turbulent of which works the FPR for more fuel.
Otherwise, it has to wait for the AMM to send a signal.
In most cases, that is not enough information for the ECU to know you are wanting power and not the idle mode program any longer. This Is one of a few reasons for hesitation or stumbles.
A bad accordion tube behind the AMM is another.
Use a bright light down the center and wiggle it for cracks, splits or pin holes. The ends must fit smoothly and tightly under the clamps.

The IAC. Is the next culprit to rule out.
Notice when starting that it must raise the idle up, all by itself, well above the normal 750 idle speed and then move it immediately down to 750 and hold it there.
If not, it’s bad or not working from being stuck or sticking from wear or smut from vapors.
You will want to refrain from using that black knob to bypass any air except when setting basic idle speed when using the blue wiring to lock out the IAC.
The knob is there to just keep it limping under the lowest speed the IAC has while restricted.
The IAC, when released, has to be just above the completely closed throttle plate speed.
When the transmission or A/C is engaged, it must be able to add more air or have the range to open for the loading and still hold the 750 rpm!

On the 1986 it uses a “three” pin connection. It uses 12 volts to oscillate by reversing polarity between two pins. The unit does not have an internal reversing spring like the later cars using only two pins.
I use a nine volt battery to simulate a cranking systems voltage. Using straight 12 volts slams the vane as hard since when it might be sticking.
Using 12 volts is ok during cleaning but not for my final test for lots of wear.
Worn out is when the brushes on the inside stick in the far ends of a tapered groove created in the armature from back and forth wear.
The most wear of the armature is in the middle of the rotation and less at the ends.
The brush is still wider as it continues to wear downward.
The Sticking at the ends slowly occurs and is unpredictable. Sticking and arcing gets worse despite cleaning the vane or wishful hoping it was the cure!

It is time to replace it because as far as I know, the brushes and armatures are not readily available or rebuilds would be on the market.

Good luck on getting the last of those green, pointed nosed, gremlins out of the way.

Phil

Thanks for the wealth of advice KittysGreyVolvo.

The accordion hose was in good shape, unfortunately. The throttle body idle switch seems to be adjusted correctly.

I cleaned the throttle body carefully and made sure that all hose ends associated with it were cleaned and sealed with Permatex as a temporary measure. But I need to replace the hoses. They are hard and ill fitting. Where do you guys prefer to buy replacements?

To my surprise, I discovered the kick down cable is broken off. No action there until I replace this cable. Too bad it could not cause my problem.

The silver hose from the airbox is not connected to the manifold on this car. Some PO had the open end flappin' down in the breeze down by the exhaust header on the passenger side.

My AMM still might be bad though. And they are relatively cheap...Likewise the Idle Air Control Valve. This item ranges from about $35 to $250. Strange.

Maybe I should replace them.

Hi eye5,

Are you the same person as I-5 Librarian? I-5 Librarian is in or near Seattle.

The silver accordion style hose connect at the air filter box at one end if disconnected from the exhaust manifold preheater, you say.

You are in California? I dunno why I guess you are in California.

It is inside the air filter box the issue lay with the preheater thermostat. Yet poor running tune may be caused by an AMM / MAF that was exposed to excess preheated air. Yet a guess in my instance. The flap valve in the air filter box fails to hot air all the time. Cold air inlet is totally blocked. One or two summers will ruin an AMM / MAF. They are not cheap yet new aftermarket may be and seems to work as other posts here indicate.

You can find many articles, one or two in the current index, as to how to test the AMM / MAF.

I find vacuum, both regular vacuum and vapor line, as the junkyard. You can also get new. You have to search. I find useful vacuum line bits off of newer junkyard cars and such.

With 1985 240 you do not have any sort of OBD. You have to diagnose and use tools including a digital electric multimeter.

1985 is in the middle of the years of the deteriorating wire harness where the wire harness sheathing and the wire insulation deteriorate. A close look at the harness may suggest a rotting harness or not.

The kick-down cable is entirely missing or disconnected from the throttle doo-hickey?

Art helps you here:
https://www.brickboard.com/RWD/volvo/1658879/220/240/260/280/1985_244_start_fuel_injectors.html
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Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.

Kitty, I don't know if you noticed up in the thread; the OP already found a used part, solving the thread's question. He posted under a different name. But your suggestion brings up another thought I had, given the high cost of the original part. It may have been a Bosch sensor originally, but I doubt it, since it was provided as part of Chrysler's ignition system.

Faced with a high price, I might be tempted to terminate that Volvo/Chrysler coaxial cable with a Bosch connector, and install a Bosch microphone in the same spot.

I'd do it myself, if I still owned a car with V/C or "computerized" ignition and needed a knock sensor for a reasonable price. Problem with doing this, and with using an unknown junkyard part, is there's no procedure to reliably know it is working correctly. The only test given by Volvo is that where you tap the block with a hammer while observing a timing light. Unless you'd done it before with a known good sensor, you'd not know how sensitive the replacement was in comparison.
--
Art Benstein near Baltimore

Eat, drink, and be thoughtful.

Check that the large accordion duct from the Air Mass Meter to the throttle body has no leaks or splits. They can be hard to see down in the folds. Mine was split giving the symptoms you've got. Replacement gave a 100% fix. Check also the hoses going to/from the idle air valve below/behind the throttle body. If that duct is OK, check that the timing belt pulleys are all indexed properly - ie: that the belt hasn't jumped a tooth. With No. 1 piston at top center, the distributor rotor should be pointing at the No.1 spark plug terminal, and the camshaft pulley mark should line up with the notch in the cam cover.

Also look for vacuum leaks around the intake manifold.

Failing any issues with the above, you may be looking at a fuel pressure problem. Using the search box above and also the 700/900 FAQ's will reveal a lot of good trouble shooting info.

As others have said, a failed knock sensor is very unlikely to be associated with the symptoms you see. But you should replace it, especially when they are as cheap as this one: https://www.fcpeuro.com/products/volvo-knock-sensor-0261231046
--
Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), and XC60. Also '77 MGB and four old motorcycles. Long gone: 1981 244, 1994 940 and 1998 S90.

Thanks Volvodad, I'll try your suggestions.

How about checking the timing and set it if necessary.

You could check it after a few days to see if it changes.

You could also fill up with Sunoco 260 to see if higher octane helps.

James, I check and the timing is right on. All the marks line up.

James, I will double check the timing as suggested.

Could there be an idle air bypass valve problem?

James, I will double check the timing as suggested.

Could there be an idle air bypass valve problem?

Used part
http://www.voluparts.com/

I got an Ignition switch from them--the one the key turns--No Longer Made -- New $110.
Used from these guys $40


Very odd that your sensor came apart.

However the Knock Sensor only changes the timing IF it Senses a KNOCK. (a Ping). It would not cause the engine to do what you describe. It does a Minor dynamic adjustment to the ignition timing.
If the Sensor is not working your engine could PING under load---like accelerating up a steep hill.
The test for one that does not eliminate PINGing is to rap the block near the sensor --knock it--and see if the engine reacts.

http://www.voluparts.com/

I got the knock sensor from Voluparts today. $36 is better that paying $100. Pricey little devils.

I keep flogging these guys here.
Once Upon A 240 Volvo Time
there were quite a few "recyclers"
Now since these Beasts are 43yrs old (starting with 1975 --B20 engined), the Keepers of the Flame are now few and far between. Because No New Volvo Owners( $35K-60K) wud event pop the hood on their rides.

fyi --- Volvo Fun Facts - Seattle and environs was once rival to the WashDC and environs (Md and Va suburbs) for the most per capita Volvos in the continental US. Was neck and neck for a while.

Survivors: unfortunately...we used salt on the roads. You in the Pac NW, not so much.

http://www.voluparts.com/

These guys shud have an Add on BB --- Gratis. The last, when they are gone...

Deal with RockAuto/AutoParts are US/Volvo/What's a 240 Chump/Volvo Hybrids Only.

Yep, lots of Swedes and Norwegians in this town, but the 240's are getting few and far between. Seattle has had a Nordic Heritage Museum for a long time, long before the name acquired vaguely disquieting associations. They currently have a Viking artifact exhibit that I would like to see: LINK

I figured there must be a fairly large diaspora there, as a while back a friend - also a beer aficionado - offered me a microbrew from (I think) the Seattle area called "Ya Sure, Ya Betcha". No, really.

It was quite tasty.
--
Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), and XC60. Also '77 MGB and four old motorcycles. Long gone: 1981 244, 1994 940 and 1998 S90.

Thanks CB. I'm getting a replacement from voluparts.com for $36 shipped.

Thanks CB. I'm getting a replacement from voluparts.com for $36 shipped.

So a bad knock sensor would not retard the timing significantly?

I did reset the timing, but it runs very badly at 12 degrees BTDC. It wants a lot of advance, and even then wont idle properly or make power.

Thanks for the knowledge and link CB. Too bad a new knock sensor isn't the key to my problem, but I need to get a replacement anyway. I just asked Voluparts for a quote.

I'm going to try reinstalling the distributor according to Bentley. Maybe that will help.

Have a good week everybody.