1985 240 Stumbling on acceleration

newmex999 · Post by **newmex999** » 28 Apr 2014, 12:57

My 85 240 wagon stumbles bad on acceleration. Tried replacing fuel filter, plug wires, AMM, checked for vacuum leaks. Once I reach cruising speed, absolutely no problem at all. The car has also developed an idol surge when I am stopped(replaced IAC valve already).

Any ideas would be appreciated

Post by **rgk** » 29 Apr 2014, 06:08

I had this problem and it turned out to be the rubber hose between the primer fuel pump and the sending unit in which the pump is housed. This entire assembly is located in the gas tank.

The hose had split, allowing air to enter the fuel line. You may have to check the hose very carefully - I removed the assembly three times before I realized the hose was split. Try bending and rotating it to get a view from all sides. As long as you're in there, you may want to replace the hose even if it's in ok shape.

I knew this was a fuel issue by the fact that the problem went away after filling my gas tank at least halfway full, but reappeared once fuel level dropped.

newmex999 · Post by **newmex999** » 29 Apr 2014, 06:32

Hello- I ruled that out, because the car does it even when the tank is full. I also replaced the fuel relay.

Post by **rgk** » 29 Apr 2014, 19:04

According to Haynes, an engine stumbling on acceleration is caused by one of the following:

fouled spark plugs
fuel injection system malfunctioning
fuel filter clogged
incorrect ignition timing
intake manifold leak

when is the last time you have changed your plugs, your intake gasket, and your fuel filter?

newmex999 · Post by **newmex999** » 29 Apr 2014, 19:08

Plugs and fuel filter a couple of months ago.

Post by **rgk** » 30 Apr 2014, 05:59

Go ahead and pull your spark plugs to see what they look like. If they look anything but normal, that will give you a clue to the car's condition. Also, try checking your intake nuts and bolts for tightness. Then try checking the gasket. Finally, you may need to begin to troubleshoot your fuel injection system.

LikeAGloveBox · Post by **LikeAGloveBox** » 04 May 2014, 11:34

I had this problem on my 1990 240 DL sedan. It was a fuel injector. I replaced them all. One was cracked and one was clogged so not sure which was the problem, but that did the trick.

joe_pinehill · Post by **joe_pinehill** » 05 May 2014, 20:36

when was the last time you cleaned the throttle body? Fouled TB caused those symptoms on my old 240

jotzgr · Post by **jotzgr** » 10 May 2014, 16:52

Having a similar problem with my 85 240 and am stumped. You'll be accelerating or just going down the road and it's like you hit a brick wall, all of a sudden nothing, just for a second, and then is fine, like a big hiccup almost. Come to think of it, doesn't usually happen once you are up to highway speed though. Some days it never does it and then the next time it will be quite often. Just started all of a sudden. I have replaced fuel filter and checked most everything else. I bought in-tank fuel pump thinking that might be it, but haven't got around to putting it in yet.

newmex999 · Post by **newmex999** » 11 May 2014, 16:19

Yes. Sounds like exactly the same thing. I guess if one of is geuss to the bottom of this the other will luck out. Let's keep in contact through this board. I have tried many things and am at the point now where I may bring it in for diagnosis and then do the work myself.