1988 240DL - Won't run with MAF connected

Krampus · Post by **Krampus** » 27 Dec 2012, 16:54

I finally have time to work on my long idle '88 240DL! I replaced the goofed up crankshaft seal and timing belt (and cleaned the flametrap) and it now starts without leaking oil. However, as soon as I connect the MAF, the engine stalls. Now the catch is that while the original MAF had gone bad, this one I pulled from a junkyard and tested, so it *should* be good. I think that I have something else messed up that the ECU freaks out when it sees and it's not in "limp home" mode. Any ideas on good places to check? I'm about to go out and see if there are any blown fuses that would be preventing the ECU from seeing what it expects...

- Jack

mountainredneck · Post by **mountainredneck** » 29 Dec 2012, 15:38

for what its worth, and I am somewhat new to volvo. I had the same issue with my very first 1989 volvo 240dl. It would start up and somewhat limp with it disconnected. With it connected it wouldnt start at all. I bought a NEW maf and it worked like a charm.

Post by **billofdurham** » 30 Dec 2012, 12:03

How did you test the MAF from the junk-yard?

Bill.

Krampus · Post by **Krampus** » 31 Dec 2012, 00:50

Checked the resistance at the yard across two of the terminals (forget which ones, it's late.

) to make sure they were within spec. Then brought it home and tested it on my bench using a power supply, a hot air gun (without the heat) and an oscilloscope to make sure that the signal generated varied with the amount of air being pushed acrossed it. I didn't verify that what it was putting out made sense, but I figured if it did that much it was probably good enough.

Another thing that occured to me was that I might still have a vacuum leak that I had missed. And I think my oil breather box (below the flame trap) is clogged, since my oil pressure is somewhat high and there doesn't seem to be a vacuum in the crankcase. I was going to shoot some carb cleaner down through it when i did an oil change. The vacuum leak I'd think could pretty easily confuse the LH computer. Would a clogged PCV system do the same?

- Jack

Krampus · Post by **Krampus** » 05 Jan 2013, 17:28

Changing the oil (and clearing out the oil separator box by spraying a bunch of carb cleaner down it) made a world of difference. I can now start it with the MAF sensor attached and the timing seems reasonable, although it still idles rough, stalls, and I can't seem to set the baseline idle correctly. I think I also probably still have a vacuum leak somewhere.

With regard to setting baseline idle and rough idle/stalls, could vacuum leaks account for all of that? While some of the hoses could almost certainly do with replacement, I want to try to address one problem at a time. To check for vacuum leaks, would spraying starting fluid around the hoses be the easiest way to detect?

Krampus · Post by **Krampus** » 12 Jan 2013, 20:41

In case anyone has similar symptoms, this was a combination of a stuck idle air controller, a groady throttle body, a hole in the air intake hose, and a busted climate control check valve (with presumably other leaks behind it)! Cleaning the first two and replacing the second two made this *MUCH* better and I think I may even be able to drive it tomorrow! I told my friend that I bought this from that she needs to find a new mechanic, since she's had these problems for years without them repairing. Maybe they saw it as good guaranteed future business.

Post by **billofdurham** » 13 Jan 2013, 11:44

Too many mechanics think that women drivers make for easy pickings. My daughter, who uses repair shops very rarely, can baffle most of these easy money merchants by asking several searching questions showing she knows too much about the workings of her car for them to try to con her.

Thank you for the update.

Bill.