Hey guys,

So, here's my dilemma for my 91 Volvo 240 non-turbo-we call him "Ed" after his first owner. Engine Light On.
Codes read for MAF and O2 sensor issues:
212 (O2 sensor)
121 (MAF)
224 (coolant temp. sensor)
322 (faulty MAF wiring)

When he started acting up-I hadn't read the codes. We had some intermittent almost stalling at stop lights and stop signs when we tried to accelerate.
So, it had been a couple years since a tune up. Ed got new sparks and a new fuel filter -the fuel filter was a cheapo Carquest-regretting that now.

After the tune up -Ed ran great for a about 24 hours :-) Then, I started to hear a new quirk -His main fuel pump started humming for a short drive. And, he started the stalling again at turns and stoplights. Only now-he almost stalls-no power on acceleration, and we get a surge.

Took out the MAF and cleaned it. Thing is, when we unplug the MAF-we still have the problem. And, we still get the MAF codes. Could it still be the MAF and/or the MAF combined with the other stuff?

I've ordered a new O2 sensor and Bosch fuel filter-this time through IPD. I also ordered a new exhaust system-because it was next on our list anyway. I really don't want to buy a new cat on top of everything else. Trying to find an MAF via a junkyard friend.

Ed has been sidelined for a few weeks now-and we could really use him back in action. He has a rebuilt motor, new ball bearings, new starter, new fuel pump... yadda, yadda... we've put a lot into this car.

Any thoughts, sympathies, encouragement, and suggestions welcome. And, where in the hell is the coolant temp sensor???

Thanks!
Heather

 

Your car has 2 fuel pumps. A feeder pump in the gas tank and the main fuel pump under the car. The main pump gets noisy (and is harmed by working too hard) when the feeder pump goes bad. What's your fuel pressure? The feeder pump could still be running/good - but the hose that connects it to the fuel sending unit could simply be broken (degrades after sitting in gas for x years)

You can use an ammeter on the power wire to the feeder pump or energize it by itself and listen to the tank. Fuel pressure will be lower in hotter temps and with less than 1/2 tank in the car. (if the feeder pump hose is broken it will suck air into the main pump below 3/8 tank, you will have low fuel pressure and the car won't run. )

Coolant temp sensor is located on the intake manifold on the side of the head. Typically the insulation comes off the wire and it shorts out - when the engine moves. Very Rarely do those temp sensors go bad - except when the engine has been overheated.

 

Thanks for the info! The main pump didn't start making noise until after the fuel filter was replaced. Is there a connection? Could a cheap fuel filter cause problems? Or, maybe the intank pump has just been gradually dying? Will check the feeder hose though.

 

I'd say you have a bad MAFS. You can't clean it and you can't test it and it throws all kind of codes like you mention. You may have something going on fuel pumpwise too, but I'd bet on the MAFS. This is a very often repeated scenario with the MAFS. And careful getting a cheap 'new' one, they mostly don't work.

 

Update: And, thanks for the feedback. Yep. I believe it's the MAF. So, I should just spend the $263 for the Bosch on IPD?

Mechanic came out yesterday. Still a strong smell of fuel. Fuel pump working. No vacuum leaks. So, he adjusted timing. Ed ran like a top. Tried to stall just once. I drove it. My daughter drove it. Mechanic drove it. We all drove it together! All good. He messed around with the distributor-it was wobbly and he tightened it up. The motor wasn't moving all over like before-things seemed great.

That evening- we go to get ice cream. Ed decides to NOT accelerate at one of our biggest intersections. Stop signs he takes no problem now. But, major intersections, he's like, "Nope. Not gonna do it. I will take my time." So we inch through each big intersection until we get the surge.

Feeling pretty confident it's the MAF. IPD has two- 1. $156 and aftermarket and not due backordered until Sept. 1. 2. Is the Bosch $263. In stock. So-I guess it will be Bosch.

Next question: It's possible this thing has been bad awhile. Did I do any damage to anything then? How could I tell? Could the ECU be in trouble? How do I check?

Thanks!!
Ed is very grateful.
Heather

 

MAFS are electronic gizmos and as such are prone to intermittent act-ups. It shouldn't damage anything. Many mechanics default to the ECU (always blame the computer when stumped) in the diagnosis and that's usually wrong. You can't check--it runs well or it doesn't. I'd buy the rebuilt Bosch, but even then you are not 100% assured of getting a good MAFS. That's just the way it is, unfortunately. The best way is to swap the MAFS you have with a "known good one" which of course is hard if you don't have one in stock, so many Volvo "enthusiasts" keep one for just such occasions. I went through a similar scenario with a 240 (the guru blamed the ECU) until I swapped every sensor and when I finally got to the MAFS, you knew it immediately. Many of these cars get junked for bad MAFS as it becomes one of those seemingly unsolvable problems with no solution as fewer and fewer mechanics have a clue.

 

Your 240 has an air box thermostat. Below about 45 degrees preheated air is sucked through that silver tube (if still there) running from the exhaust downpipe to the air filter housing. The thermostats go bad and get stuck in hot air mode - then your Air mass meter gets fried from too hot intake air.

So, if you still have a silver tube - make sure you are getting air from the intake in front of the radiator.

 

ECUs rarely go bad in these. The only exception was the "pink label" ECU for the LH 2.4 system which had a weak fuel pump circuit. Your car is a '91 and I think they stopped using the pink label ECU until late '89 or early '90. Yours should be good.

Interesting that your mechanic "adjusted the timing" on it since the timing is entirely controlled by the ICU (ignition computer). While you can rotate the distributor it doesn't affect the timing at all other than make the rotor point to the right conductor when the spark is provided. The crank position sensor is what provides the timing information to the ICU and ECU. Also you said that your mechanic said the fuel pump is running. Did he check both fuel pumps? There is one in the tank and one under the car just behind the rear seat on the drivers side. If the in-tank pump isn't running the main pump tends to be noisier and may not keep up the proper pressure under hard acceleration.

 

Thanks everyone for all the feedback! Installed my fancy new Bosch MAF this week. Ed is feeling better! And!! Wait for it... the engine light is off.

I'm still getting a 322 code though. Could the wire to the MAF be bad? Also, now I'm worried I should check the silver tube mentioned above. Ed did stall a few more times, so I'm not totally out of the woods. But, things are wayyyyy better than they were. Also, when the mechanic checked Ed out last week, before I installed the new MAF-he adjusted the timing with the distributor. Not sure if he coulda messed something up? Also not sure how to switch it back, or what the timing setting needs to be???

Happy Weekend!
Heather

 

OK, you have good news. Yes if you are in a warm/hot climate you should make sure you are getting cold air, instead of hot into your new air mass meter. AND

as others have said the timing IS NOT ADJUSTABLE - If you move /turn the distributor it DOES NOT CHANGE THE TIMING>

The timing is controlled by the ignition control unit. The distributor simply distributes the spark. ( take the cap off - there is nothing inside other than a rotor button) Twisting the distributor would change the timing on much older cars -but NOT YOURS.

You need to make sure the distributor is set correctly - so the rotor button lines up with the poles in the distributor cap. And maybe find a mechanic than understands ignition systems made after ~1985!