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Save this 240 from the scrapyard

740atl

740atl

Gear acquisition syndrome
Joined
Apr 17, 2010
Location
USA
Here's the premise. I have replaced everything. LH2.4 240. There are no air leaks, fuel pump, all sensors, gaskets, orings, etc. have been replaced with new or known good units. The CLT resistance is right within range. I have blown out the fuel lines (nothing)... everything. Replaced new fuel pump and known good fuel pump twice. Fuel filter replaced twice, fuel sock clean and intact.

Here what's happening. The car runs like ****. Idle is where most of the problems occur. If I goose the throttle, the engine shakes, stumbles, spits out of the intake, and will probably stall. If I ease into the throttle, the engine rpm will increase normally.

Now, a new problem popped up... A few minutes after startup... the car will stumble, will not take any throttle without backfiring through the intake (this usually happens in the middle of the intersection)... and after another 30 seconds, it will "clear" up and run normally. It will do this every day, typically a minute or two after I start the car. This new problem is actually more than pissing me off, it's downright dangerous esp. on the roads I drive.

I should mention that at higher rpm (above 2500) the car runs like I drove it off the showroom.

It never bucks, stalls, misfires when I have it above 2500rpm.

The wrinkle is this. If I unplug the AMM, the car purrs like a kitten, I can goose the throttle all I want and it just runs... it pegs the O2 at 1v and I can smell the gas out of the tailpipe. Plug the AMM back in and it bucks and stumbles.

I have done this with two known good AMM's and I was able to get ahold of a NEW AMM and it does this with everything.

I am at the "checking wire integrity stage" but I simply cannot invest any more time into this car except this weekend.
 
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Probably help to know the year...

Spitting out the intake makes me question timing. Verified cam timing, ignition timing, balancer hasn't spun, all that jazz? LH2.2, confirmed no bad wiring to the hall sensor in the dizzy? Harness good? LH2.4, suppression relay good, crank sensor good, power stage good? Obviously the powers and grounds, swap the ecu/icu, all that.

Just for starters anyway...
 
Any ideas on what would cause the car to have zero power and lug like it's going to die for 30 seconds or so, then instantly have all the power back?
 
Had the same symptoms when my crank position sensor wiring failed...motor mounts were shot, so the engine had a good bit of movement at idle, but under load, it was _usually_ fine.
 
740atl said:
Any ideas on what would cause the car to have zero power and lug like it's going to die for 30 seconds or so, then instantly have all the power back?
Click to expand...

A couple of things to check are the fuel pressure when operating the vehicle. I've had bad main pressure pumps do this kind of intermittent operation. Also a good time to check the fuel pressure regulator.

Be sure to check the coolant temp sensor at three operation points. Cold, then when slightly warmed up, and fully warmed up. I've had bad ones which have good resistance when cold but open circuit when getting hot which causes a rich running open loop engine that the computer thinks never warmed up.

This winter here in nj both myself and a friend with a 240 wagon got bad fuel twice. So don't rule that out. It ran similar to what you describe. It wouldn't idle or was very rough and you had to rev up to make power. But above about 2k rpms it seemed to be ok and had some power to drive around. It took a couple of days of driving to clear. I also started using luk oil gas because it doesn't have the alcohol in it supposedly.
 
So does the statement everything include the CPS.i had a similar wierd issue and it turned out to be faulty CPS (the wires from the plug to the CPS)
 
SLO240 said:
So does the statement everything include the CPS.i had a similar wierd issue and it turned out to be faulty CPS (the wires from the plug to the CPS)
Click to expand...

I have replaced everything on the engine except the wiring harness, fuel line, head gasket, head, engine block with known good working parts.
 
Have now replaced everything except the wiring harness. I am Chief Joseph of the Volvo 240. I will fight with this car no more forever.
 
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