So, I have a '91 240 that seems to go into this 'run like crap' mode after a few minutes. Sometimes it waits till its warm, and sometimes it starts doing this immediately. It hesitates to rev and bogs down if I can get up to speed. It will idle up and down and die.

I have already replaced plugs, wires, cap, rotor, tested coil, checked 25amp fuse, tried unplugging MAF, tried another ignition control module, tried cleaning MAF, tried cleaning idle air controller, tested TPS, cleaned throttle body, replaced ECT, replaced throttle body gasket, and do not see or hear any large vacuum leaks. Coil is a little off but not enough to cause a problem I wouldn't think.

I can hear both fuel pumps running. I tested fuel pressure and it was jumping from 25-35, so I replaced the main pump. The in tank pump was replaced by previous owner. Replaced injectors too with new Bosch ones. no leaks, and new fuel filter. (Have not retested yet)

The only code I am getting is 'lean/rich at idle'

What am I missing? What would be malfunctioning and not throwing a code? Should I try ordering a new ECU?

I appreciate all input

mvh Trenton

 

No OBD codes?
Since you replaced the coolant temperature sensor (ECT), I'd try a different MAFS, a tricky customer! Swap it with a good known one first--testing it is useless and many "new" MAFS are apparently bad...

 

The only code I have been getting is “lean/rich at idle”. When I unplug the MAFS it still bogs down and doesn’t rev well so wouldn’t that rule out a problem there?

Thanks

/Trenton

 

What's the fuel pressure? What's the fuel volume? Is it a stream if fuel or are there air bubbles in it? Is there more than 1/2 tank of gas in the car? If not, it's possible the feeder pump hose has a problem (short 2 inch hose from feeder pump to pipe on sending unit) If that hose is missing/broken/whatever and the fuel level is below 1/2 tank or so - the main pump will suck air and the car will run bad or not run.

 

No! That MAFS "test" is not realiable. MAFS seem to be causing all kinds of driveability issues such as what you describe. Another poster, Edvard, just went through a long ordeal, finally a decent MAFS fixed it... Seems like whenever all issues are exhausted (believing the MAFS is OK) and nothing else works, in the end it's the MAFS!

 

Sorry did not see this earlier - NO It's not the ECU

And the "I unplugged the AMM and it _______________ " really has no bearing on what's really wrong with the car or is a reasonable diagnostic process - but I agree my techs got into the habit on trying that - then giving me some bullcrap story about needing XX. So I would get them a new or known good XX and then they would find the real problem.

 

Hey folks--

I tried a brand new MAFS, with no change. I had the battery disconnected for a while for another reason and the code seems to have gone away too. It also started feeling like it is misfiring, which is probably unrelated. Haven't figured out why yet.

I guess now I need to find out why it's misfiring and then maybe try a 3rd MAFS just to be sure. This one had bad reviews but it was the only one available that day.

/Trenton

 

It is getting low since I haven't run the car much recently, probably below 1/2 tank now. I took out the in-tank pump and made sure it was running. That hose looked fine too. I still put some more gas in it, like 5 gallons and it still hesitates.