My daughter's '88 240 suddenly won't stay running. It will start then die, if I don't pump the accelerator pedal. If I give it gas, the RPM will rise appropriately, but if I hold the pedal in position, the RPM will then drop and the engine will stall. As long as I keep pumping the pedal, the engine will respond, but it just won't stay running no matter where the pedal position is if I don't constantly pump it.

Any thoughts as to what the problem is? I'm thinking it's not the fuel pump, as the engine does respond to the accelerator petal. I did a visual inspection on the vacuum hoses, they look fine. Plugs, wires distributor cap were all replaced within the last year. Could it be the O2 sensor?

Thanks in advance...

 

its definitely not the o2 sensor, that would at worse make the car not pass a smog test, and might knock your fuel mileage down a few MPG, but otherwise the engine would run fine.

those are weird symptoms, not sure I've heard of that sort of thing before on one of these cars. things I'd check, in no particular order...

*) mechanical throttle linkage
*) air pipe between throttle and MAF
*) idle postition switch, make sure it closes at idle and opens off idle
*) rubber tubes to idle air controller under the intake manifold
*) clean idle air controller and throttle body
*) MAF (best tested by swapping with another known good 240/740 LH 2.2 1985-88)
*) ignition timing (with timing light), does it advance properly when revved?
*) verify fuel pressure (requires fuel pressure gauge with volvo specific T adapter)

 

thanks Pierce, I'll take a closer look. This may be beyond my pay grade...

 

I disconnect the MAF and it runs! At least I was able to move it off the street in to my garage. It idles and holds steady rpm, it just hesitates on throttle tip-in. This is counter intuitive, can someone explain how this is possible?

I'm guessing I need to go to the pickapart to find another MAF, but is it possible that one problem is cancelling out another problem??

-John

 

make sure the last 3 digits of the bosch PN on the MAF match yours. I believe you have a 0 280 212 007. so thats a '-007'. newer LH 2.4 cars are -016. ancient LH 2.0 are -002 and neither of those would work.

your BEST bet would be a genuine Bosch rebuilt one,
https://www.fcpeuro.com/products/vol...-760-780-940-1
but they are expensive.

 

oh. with the MAF unplugged, the ECU goes 'oh crap' and falls back to an emergency open loop program, where it guesses how much gas, on the rich side, based purely on RPM. yeah, it starts and idles OK, but has lousy throttle response, barely driveable in fact, just enough to get you home.

 

thanks Pierce, that makes sense. I'll clean it tomorrow to see if that helps. Thanks for the tip on sourcing a rebuilt one.

- john

 

It's fixed! I was lucky, the local pickapart had an a fresh '88 wagon. I swapped the MAF and it runs perfectly!

I checked the resistance across terminals 2 & 3 per the shop manual. Resistance was the same on the old and new units, so I guess there was something else in there that was bad.

Thanks again Pierce - saved my poor daughter a bundle!!