Engine: 2.3 F/Inj B23E/B230F: '91 240 issues

[Grahambharper]

I have tested the 02 sensor again and it seems to be working, as far as the MAF sensor goes when I unplug it the rpm Increases at idle but bogs as soon as any throttle is applied.

[Bugjam1999]

How did you test the o2 sensor?

Next suggestion- partially blocked exhaust pipe from the cat disintegrating inside. Hard to know what to suggest to test this- undo the exhaust after the downpipe and go for a drive? The lack of backpressure might mean it’s down on power anyway. And it’d be really loud of course.

Cheers

[Dirty Rooster]

Originally Posted by Grahambharper

... as far as the MAF sensor goes when I unplug it the rpm Increases at idle but bogs as soon as any throttle is applied.

So is that different to your plugged-in-MAF state?

Another thing to look at, possibly, since we're going through everything ;
remove the cam cover and manually turn the engine, check all the valve buckets are depressing and raising correctly.

[Grahambharper]

With the MAF unplugged the idle rpm is higher then with the MAF plugged in, but the engine bogs at a much lower rpm then with it plugged in.
I have had the exhaust flow tested and that's not it.
As far as testing the o2 sensor goes it creates a voltage that is supposed to "sweep" between parameters when it is sensing o2. The old o2 sensor was not doing that which is why I thought it was my problem, the new one does, however the problem persists.

[Grahambharper]

I have also done a valve adjustment and replaced the hushers and checked the timing (don't know if I mentioned the timing before or not).

[Nicholas Lewin]

Graham - sorry to ask the obvious, but I am a fellow 1991 B230F owner with engine speed management problems (different tho')

Have you got a throttle switch problem? Reading the thread, you are being offered electrical and fuel (and engine mechanical) solutions...

I am wondering whether your throttle switch or some other element of the fuel injection electrical circuit is actually causing the problem?

Thinking aloud - keep us posted! Nick

[Clan]

Originally Posted by Grahambharper

Hello all,

I'm having a problem with my 1991 Volvo 240.
During normal driving it seems to not be getting enough fuel at higher speeds. Right now the car does not have a lot of power and will not go faster than 55mph. If I clamp the fuel return line it will easily hit 80mph but then (predictably) is getting to much fuel in the lower speeds and idle. I am at a total loss as I have already cleaned out the fuel lines, changed the fuel filter, changed the fuel pump and changed out the fuel pressure regulator.

Any ideas?
Graham

I forgot to mention, this is a B230F engine with a Bosch fuel injection system, the ECU and in tank pump have both been swapped with known working ones.

what is the fuel pressure when it plays up? you really do need to know or you will be fighting up the wrong pathway .. A lambda probe should not make any difference to the power it just trims the fuel mixture at idle at low rpm on these basic fuel injection sytems . Fuel pressure should be about 3.5 bar and if you clamp the return line briefly should go up to about 5 to 6 bar
Do you have the main pump under the floor ?

[Grahambharper]

When I run the OBD throttle position sensor test (the one where you plug the probe in to socket #2 then hit the button while the accelerator is to the floor) the ECU says the throttle position sensor checks out, but is there another way I can back this up?

[DW42]

I don't know another way to test the throttle position sensor, but it may be a good idea to clean the throttle body/IAC. It's my understanding that this can be the source of driveability issues. Does anyone on here know whether the TPS picks up its signal from the position of the butterfly valve in the throttle body? If so, it seems like a clean throttle body could be important if you suspect poor TPS function. 240s also seem to go through distributor caps and rotors -- have these been replaced recently?

[Clifford Pope]

Originally Posted by DW42

Does anyone on here know whether the TPS picks up its signal from the position of the butterfly valve in the throttle body?

From the black box mounted on the other end of the butterfly spindle from the one with the link rod.
It does relate to the position of the butterfly valve, but only if the adjustment is correct. It should click the instant the butterfly moves from the idling position, and reliably click back again on release. Don't go by the movementof the rod or the wire on the wheel - there will be a bit of slack there - it's the valve itself that matters.

Haynes gives directions for testing the terminals on the TPS. I think on this model it's only a micro-switch, it only became a variable resistance with LH 3 ?


People sometimes move the throttle stop screw to adjust the idle, wrongly compensating for dirt in the throttle body. Moving the stop screw upsets the TPS setting. Clean the body and valve, check the stop screw is at its original standard fixed setting, then check the TPS.
Idling is controlled entirely by the Idle Air Valve, very prone to sticking from dirt.


You can check the fuel pressure with an ordinary tyre gauge, but be prepared to sacrifice an old one as the seal inside doesn't like petrol.