Hey all,

My wagon up and decided to be a pain today, and now has no power above 2k RPMs and is limited to 90 km/h down hill haha. It starts and idles well, no sputtering or anything of that sort.

So far I have replaced the fuel filter with no result. This seems like a timing issue to me, is the computer able to retard timing? What are some of the factors that contribute to it? My temp gauge is reading as it should, is there a secondary coolant temp gauge that the ECU reads?

As usual, thanks for the help in advance.

 

the timing on a LH2.4/EZK116 car, which your 1990 240 is (1989+) is entirely electronic, using a crankshaft position sensor as the primary input for both the ICU Ignition Computer, and the ECU fuel injection computer.

the dashboard coolant temperature gauge is on its own sensor in the engine block. the ICU and ECU share another sensor, which has two outputs, one for each ICU and ECU.

I'm much more inclined to suspect your problem is air leak based. any cracks or openings in the air pipes between the intake manifold and the MAF (Mass Air Flow meter) can cause these sorts of problems.

 

Thanks for your rapid input, Pierce, I won't be able to look at this issue again for a while but will be sure to report back with my findings.

 

I took apart most of the fittings between the MAF and the intake manifold, and didn't find anything really obviously broken or leaking. Several vacuum lines don't have clamps to secure them, but I don't think that much air could be getting by.

One thing I did notice was that the MAF plug had some moisture and corrosion inside of it. I cleaned the contacts off and sprayed it out with an air gun, but still no luck.

There is definitely a specific spot in the throttle that it starts to bog badly, and now that I drive it again it seems to be much less RPM dependent. Any more suggestions?

 

If you can track down another MAF to "borrow" for a test drive, that might help. Just be sure it is out of an LH 2.4 system. Also, does the OBD unit give you an codes? that can help narrow things down a bit.

 

Alright, a 85 240 came up in the junk yard recently and if the weather cooperates I'm going to go pilfer some things from it, including the MAF. How can I tell if the car I'm looking at has the same fuel system? I know there must be a breakdown of years in the 240 history but I haven't found it yet.

 

an 85 ls LH2.2, your 90 is LH2.4, not compatible.

basically any 240/740/940 non-turbo Bosch 1989+ or 740/940 turbo 1990+ has the right MAF. some 7/9 non-turbos are Regina instead of Bosch and don't have a MAF at all (and there's some rare 240s that are LH3.1, and use a different MAF unique to LH3.1)

 

Peirce, thanks very much for that info. As you probably already know, there was in fact a crack in the hard plastic intake hose between the MAF and the throttle body. I used a flashlight on it, and saw a hair line crack around one of the hose nipples. Have some caulking drying on it now, will report results. I suspect this will solve the issue.

 

No such luck, still bogging at half throttle and above. I'm off to search out a replacement MAF, not so keen on spending the $200 after tax and shipping for a new one but there are no compatible ones in the wreckers that I have found.

 

RGuy here. Try cleaning your throttle body. Disconnect big hose going into the throttle body. Get a can of throttle body cleaner not carb cleaner. Open the butterfly insert cleaner end into the throttle body and spray liberally. Car should not be running. Let your brick sit for about 5 or ten munutes, then start up it will be hard starting but no worries. Repeat if not satisfied!

 

Thanks for that RGuy, gave it a go this morning but no such luck. Out of curiosity, whats the difference between carb and throttle body cleaner? Just effectiveness?

Broke down and ordered a MAF/Air Box Thermostat today, not very confident that it'll work but worth a try.

 

carb cleaner tends to be a lot harsher. the spray stuff is likely OK, its the stuff in the soak can you don't want near anything involved with a EFI system

 

Could be a clogged catalytic converter.

Attach a vacuum gauge from the intake manifold on a warm engine at idle. Blip the throttle and hold rpms steady at about 2500- 3000rpm. If the vacuum begins to drop, then bad cat, bad cat. Could be just an exhaust restriction, too, inspect the exhaust.

Or get a backpressure test from the O2 sensor bung.

 

my turbo 740 went through a problem where I'd lose power under heavy throttle acceleration and higher RPMs and speeds, suddenly it would cut out and drop power, then if you took your foot off the gas it woudl come back.

the first time this happened, it was the in-tank pump. it was OK with a full tank, but below 1/2 tank it got worse and worse.

the second time, it was the silicone turbo air intake pipe had a airleak under high suction, that would bypass the MAF, so the EFI wouldn't provide enough gas. this only happened under basically max boost at mid-to-upper RPMs where the B230FT pulls hardest. now, of course, this 2nd couldn't happen to your non-turbo, but an air leak after the MAF could have similar symptoms.

 

Looks like the cat may in fact be the culprit. I started taking the exhaust apart last night in an attempt to delete the forward muffler, which is rotted out. After cutting it off, I fired up the car and it was not much louder. I smacked the cat a couple times with a hammer, and the idle went all over. Then I put my hand behind the exhaust to see what the flow was like and it got covered in reddish black liquid. Looks like that half can of intake cleaner and the half can of sea foam before that never made it out of the cat. Going to take it into the muffler place on tues and have them delete both the cat and the forward muffler, see how she goes after that.

True to form, the replacement MAF shipped yesterday. Will probably just throw it up on ebay if this fixes the problem.

 

Back on the road again! Cat and resonator deleted, can't say I notice the difference from before the cat failed haha. I asked the guys at the muffler shop to do it cheap and they did not disappoint! Thanks for the help!