My 89 Volvo 240 (244) DL wagon runs extremely rough on low idle. The engine shakes like it has a broken motor mount. When I rev up the throttle the engine runs smooth. I get a check engine light on the dash and the diagnostic unit flashes the code 2-2-1 in module 2 position.

How do I know if the problem is the Air Mass Meter? When I unplug the AMM unit, the engine revs up and the rough idle goes away. I also checked for leaks on all the vent tubes and didn’t find any. Could this also be a timing issue?

Thank you for your help and feedback!

 

with the AMM unplugged, the fuel injection runs 'open loop', a failsafe mode designed to get you home in an emergency. since it has no idea how much air the engine is sucking in, it has to guess how much fuel to use. and since too little fuel (aka too lean) will burn holes in pistons, it errs on the side of rich.

2-2-1 is described as "Fuel trim (lambda control) too lean at part load", with possible causes "Lean; air leak; low fuel pressure; bad AMM" ...

so, yes, you COULD have a bad AMM, and in fact since it runs smoother with the AMM unplugged, that raises the possibility of this. however, you also could have air leaks anywhere in the path between the AMM and the intake manifold.

replacement AMMs are hit and miss these days. Ideally you want to find a genuine Bosch rebuilt one, but there's a lot of real crap on the market, including Bosch AMM's "rebuilt" by 3rd parties who just clean them up and repackage them without adequate testing.

I would try and find another LH 2.4 car that runs fine (that would be any 1989-1993 240, and most 1989-1995 740/940 except regina FI cars, and 1989 turbos) and temporarily swap your AMM with theirs. if their car now has the problem and yours doesn't, then you KNOW your AMM is bad.

good AMM: https://www.fcpeuro.com/products/vol...-760-780-940-1

note what that says about the airbox thermostat. under your air filter, there's a hose that comes from the heat riser on the intake manifold, and in the airbox there's a 'flap' that is supposed to open when its really cold out. these flaps fail and stick open, then the hot air cooks the AMM causing premature failure. rather than replace the stupid thermostat spring thing, I tend to wire them closed with bailing wire.

 

eXACTLY! My car had a similar problem, so I did the Airbox Flap delete (there is a thread here that explains hot to do it ) cleaned the AMM with AMM cleaner, changed some vacum hoses, changed the Flame trap box underneath the intake and the car still had some hick-ups, then ultimately I changed the o2 senser, bam! car ran like new. I had the same code as you. So I'd start by changing the 02. Then you can do the rest later. good luck.

 

Thanks for the detailed insight. My hose from the exhaust to the intake box rusted out about a year ago. I will check the flap and secure it i place. Thanks again

 

Thanks for the O2 feedback. I will work on it this weekend. Where is the sensor located? Underneath before the C converter?

 

the 'thermostat' is like a wire spring in the hinge of this flap. its a bimetal thing that mechanically opens it when very cold, and closes it otherwise, just outside the airbox.

 

wait, sorry, I see, yuou meant the O2 sensor. phew.

its just in front of the catalytic converter. on a 240, the wires for it come up the firewall on the right side, and are attached via two connectors near the windshield wiper motor, one is a single pin round connector (for the O2 sensor signal), the other is a 2-pin square connector (for the O2 sensor heater circuit).

 

Yep ^, what Pierce said, this guy knows volvos inside out man!

 

Thanks Pierce & Woc2,
I took apart my intake hose. Cleaned the AMM with brake cleaner, the throttle body with carb cleaner, and wired my air cleaner housing flap open. I put it all back together and have the same rough low idle. When I spray starting fluid up near the intake manifold of cylinder 1, the engine revs up. Is this a sign the intake manifold gasket needs replacing? I also hear a hissing sound. Appreciate the feedback.

 

ahhhh, eeeek. brake cleaner will likely DESTROY the AMM. Brake cleaner, especially the original formula stuff, should ONLY be used on plain metal things, not anything with plastics in them. its NOT for use on your brake pads, or calibers for instance, its JUST for degreasing the rotors.

i've never found any cleaner to actually do any good on an MAF, and many will do harm. the ONLY thing I would use is the CRC brand MAF/AMM cleaner sold specifically for this purpose, and I would always hold the AMM so the circuit board is on the top side, so the spray won't run down the wires into the circuitry. only if there's significant buildup on the little hot wire assembly deep inside the MAF would I even attempt to clean it.

I'd locate the source of that hissing sound. it might be innocuous or it might be a major vacuum leak, hard to say.

yes, if you spray starter fluid outside the manifold and things speed up, that IS a good sign there's a leak, so maybe you DO need a new intake manifold gasket, I dunno.

 

I had the same problem with my '90 240- air box thermostat flap stuck open. Cleaned MAF with above mentioned CRC spray cleaner for electronic gizmos, bought 2 used MAFS at junk yard for $25 (installed one) covered the air box thermostat hatch with a finely calibrated travel coffee mug lid and some JB Weld. Check engine light went off and engine stopped randomly dying! Ran like a top afterwards!

 

Similar issue with my 1991 Belgian made 740 B230F 2.4LH purchased about 2 months ago. Idled low and speedo didn't work at time of purchase, but no codes were showing up other than 311 and Check Engine light wasn't on so I did the basics:

Cleaned throttle body, air intake hoses, pulled the AMM (it's visibly dirty, but like Mr Peirce I hesitate to clean these things), pulled and cleaned idle control, replaced spark plugs, wires and distro cap. Replaced some rubber hoses here and there, and the idle went right up to where it should be. I've been doing a lot of work to the interior too, and I really like this car. It's my 4th Volvo from this era and my first 740.

Earlier in the week the idle went back to low. But last night - FINALLY - the Check engine light came on. The car, very briefly, seemed to lose power. It didn't die, i just had to press harder on the gas pedal and it caught back up.

Checked codes this morning, got the following from port 2 (port 6 showed 1-1-1, phew):
311 - "signal missing from speedo" (duh, but I had no idea this could cause a bad idle, Volvo lists that as a symtom)
121 - the dreaded "bad signal to/from AMM"

So I think I have several things going on here, all manifesting with the rough idle (funny how at 300-400rpm these little bricks shake like chihuahuas).

Before dropping $300 on an AMM I'm going to:
Replace the fuel pressure regulator (it appears to be factory...ugh)
Spray the intake area to check for leaks, address as necessary
Clean the flame trap
Check the oil separator (there was black liquid in my intake hose when I cleaned it, but not much. still, this could be one of the culprits)
Visual check of o-rings on Injectors and other hoses
Do the "listen test" for the Throttle Position switch - might be a waste of time, but no stone unturned...
Clean the AMM with the specific cleaner designed for it

Even though I am getting the AMM code, I think something else is actually wrong. So I'm giving the intake a "full physical" and tune up.

The box thermostat flap will be added to my list too. Thanks for all the good info in this thread.

 

I don't think speedo signal code will set CEL. I drove around with no instrument cluster for a while in my 2.4 240 and I had moments of high idle mostly. Probably some low idle too.

I would fix your speedo ^^^ and then start from there.

My MAF just died on my 240 the other week. It ran lean, had inconsistent idle, and finally threw some 'mixture' codes at me. Junkyard bosch MAF fixed it.

Just like so many threads the OP disappears! Disappointing.

 

I know right? Whats the point in asking for help if you're going to vanish?


I would inspect the speedometer output cable behind the speedometer, if its loose your car may have a wonky idle and not always start. It'll throw codes here and there too.

For a few months I was having similar issues with my '90 240, simply re-tightening the speedometer output fixed it.

I'd try it before ordering a MAF or anything, its free and takes about 10-20 mins tops.

 

Mostly it goes like this:


OP:I have a problem. It is blah blah blah.

Responses: You should try xxxxxxxx.

Then the OP ignores the suggestions, rambles on about other things they tried, and then stops posting! Ha. Frustrating, but predictable.

 

Revolv - you are correct, speedo won't set CEL. I *think* that weeks of bad idle pushed the problem around until the AMM threw a signal because it wasn't getting the feedback it needed to push the correct air through. The car wasn't breathing well, so I'm surprised that it took as long as it did.

As for a junkyard AMM, I was just at a pick-n-pull Saturday and all 4 of the compatible volvo's engines were picked clean. Found some functioning window switches though, which solved another problem. 90's Volvo's aren't exactly rare in North Texas, but they are far from common.

To both you and 92Sedan, thanks for the tip on the speedo. I will start there. Completely blew my mind when the code chart listed "rough idle" as a symptom of a bad speedo signal, but it makes sense after a little thought.

One other weird thing - might be unique to the Belgian models because I haven't seen it before - there are no screws anywhere on the instrument cluster bezel. It has 2 tiny slits, one on each sidewall of the bezel. Apparently there is a clip on the other side of the slit that you have to depress just right to get it to "let go" so you can pull the bezel. I've tried twice and failed, the second time following instructions from a youtube video that just didn't seem to work. I'll be working on it tomorrow night. My weapon of choice to get at those clips: a paperclip. Hi-tech, right?

As for the OP, I'd really like to know how/if he fixed his problem, and if not...is his car for sale?

 

that slit thing is how all 740/940 instrument bezels come off. long thin screwdriver is weapon of choice, as you need a fair bit of force to depress the clip so the bezel comes forward.

 

So i decided to see what i could get done tonight cause I had a few minutes free. Fixed the issue in 20 minutes.

Pierce you are correct about the removal - there is a ton of bad info on the interwebs that had me looking at it all wrong. Appreciate the tip.

I've been treating this bezel with kid gloves thinking its 24 year old plastic. Not even close. It's solid metal, and very well made. It popped out fast once I realized what I was up against and could put some elbow grease into it.

Pulled the cluster, pulled the speedo wire, blew on it like a lit birthday candle, put it back in and drove the car for a few minutes. Idle is exactly where it should be, CLE didn't come on, the codes cleared (I know this could be temporary but I did not clear them manually), and the speedo worked. Most importantly, she was breathing correctly for the first time in a few weeks.

I'm still going to clean the flametrap and check the oil separator tomorrow. Want to stay ahead on the maintenance game. She appears to have sat for a while before I got her.

Thanks again to all of you for stopping me from the wild goose chase. If you're ever in the Dallas area let me buy you a beer.

Next up- hydraulic arms on the trunk, miscellaneous interior trim replacement, and getting a good stereo system into it.

 

740/940 door speakers, get these 2 sets of adapters, PVC Speaker Adapters - CNC Machined - In Stock or Custom Made and get 4 quality 5.25" coax speakers.

take the door panels off, and mount the adapter plates *behind* the panels, mount standard coax 5.25" speakers in the adapters, use some silicone aquarium sealant on both the adapter ring and the back of the rim of the speaker to keep it from buzzing. I also applied sealant to all the screws that hold the pocket trim to the back of the panel and put the screws in wet, to keep it from buzzing when I crank it up.

install the in-dash deck of your choice in the dash using the appropriate wiring harness. a deck with 50W 'music power' x 4 will easily drive 4 5.25" speakers to plenty of volume. my 1992 740 had dash speakers and rear door speakers, and a stereo with a seperate amplifier under the far left end of the dashboard. I removed this amp, and got a harness from Metra or something that plugs into the amp connector, and the factory deck connector, and has all the wires to connect to a jap stereo harness. I got wierd and put two way component speakers, with the tweeters mounted in the gutted dash speaker place, and teh woofers in the doors, I should have just stuck with 2-way in the doors, and disconnected the dash speakers.

boom, new toons.

 

oh, there's a trick to the 700/900 door panels. the speaker grills slide forward about an inch and come off, unscrew the lock ****, pry straight out the red light bezel on the safety doorjam light (its a clip!), remove the plastic 1/4 lock in the door latch handle pocket, then pry out the bezel from around the window switches (the switches lift up some but don't come completely off, then the bezel comes out), then there's 3(?) clips in the bottom of the door, align these clips so the flat side is directly on the bottom, and slip a small screwdriver around the center of said flats and pop them straight down. its really pretty simple, but its probably a good idea to have some spare clips and pins on hand the first time you do it as you'll likely break one or two til you figure it out. once those bottom clips are out, you swing the bottom of the panel away from the door, then lift it up and unhook it from the edge of the window sill and lift it away, there's a couple wires behind it you have to unplug before you can take the panel completely clear of the car.

if you have a tan interior, the plastic is extra brittle. grey and other dark colors are much better.