940 2.3 Turbo Fault Finding Start Point??

[Steve 940]

Bought a 1995 940 2.3 Turbo with a known rough idle/running issue as a parts donor for my 940 of better door cards, various clips etc.

Has ticket to June'24 and body issues just pieces of flaking lacquer on bonnet.
Too good to scrap once I've got the bits I need, so was going to do a quick fault find to see if I can get it running better and keep another on the road for someone who wants a cheap motor.

Below is link to thread to previous owner had started, and highlights actions taken so far:-
https://www.volvoforums.org.uk/showthread.php?t=323447

Just want a steer on best way to start, I have spare known good spark plugs/Bougicord leads. Lamda light is on dashboard, car came with code reader that plugs into base of armrest, I believe this may be one from another user on here??

Should I clear codes now, then do a fault code code check, or should I replace plugs/leads first, then clear codes and recheck??

Cheers
Steve

[Forrest]

I should check and record the current fault codes and then clear them and see which ones come back in use.

I have found in the past that new spark plugs, leads, distributor cap and rotor arm work wonders when it comes to smooth running.

From the previous owner's description of the stalling on deceleration I would also suspect a vacuum leak and possibly the one I had on one of my cars - a small hole in the recirculation valve bypass membrane on the turbo. This is easy to check for. Just undo the three bolts holding the triangular cover on the turbo and lift carefully away. Dismantle and hold the membrane up to the light. I'm pretty certain that when I fixed that it improved idle; particularly when holding the car (automatic) on the footbrake.

[Steve 940]

Hi Forrest,

That makes good sense, some good pointers thank you.

The chap had been firing the parts cannon on it as its had various MAF's, a new Fuel Pressure Valve plus some of the small diameter vacuum hoses have been replaced.

Cheers,
Steve

[loki_the_glt]

Originally Posted by Steve 940

Just want a steer on best way to start, I have spare known good spark plugs/Bougicord leads. Lamda light is on dashboard, car came with code reader that plugs into base of armrest, I believe this may be one from another user on here??


Cheers
Steve

Code reader is one that I built; I recognise the box, Dymo labelling and instructions sheet! The downside is that I can't offer to build you one!

[Steve 940]

Right, day off today, so time to look at this 940 rough running.

Having some issues to read the codes using Loki's reader, when I turn the selector to 'F' and 'A' I get the weak led and on pressing the button in either of these positions, I get 1.1.1. codes, so good there.

However in position 'I' ignition and 'C' cruise, I get no led light and pressing the button does nothing????

Have managed to reset lamda/engine management light using the remove fuse 1 method.

Would be good to see if I can get codes for Ignition as could be source of rough running, any suggestions as to what I'm doing wrong??

Cheers
Steve

[loki_the_glt]

Originally Posted by Steve 940

Right, day off today, so time to look at this 940 rough running.

Having some issues to read the codes using Loki's reader, when I turn the selector to 'F' and 'A' I get the weak led and on pressing the button in either of these positions, I get 1.1.1. codes, so good there.

However in position 'I' ignition and 'C' cruise, I get no led light and pressing the button does nothing????

Have managed to reset lamda/engine management light using the remove fuse 1 method.

Would be good to see if I can get codes for Ignition as could be source of rough running, any suggestions as to what I'm doing wrong??

Cheers
Steve

If your car doesn't have cruise control the "C" position won't give you any codes; it's probably a dry joint or disconnected wire that's causing a lack of signal on the "I" (ignition) side, which is Pin 1 on the OBD plug.

[Steve 940]

Originally Posted by loki_the_glt

If your car doesn't have cruise control the "C" position won't give you any codes; it's probably a dry joint or disconnected wire that's causing a lack of signal on the "I" (ignition) side, which is Pin 1 on the OBD plug.

Hi Loki,

Many thanks for that, most helpful. Car doesn't have cruise, so that position I'm not worried about.

I'll try to pop open the box to just see if any obvious solder joint issues.

Quite surprised the check engine light hasn't come back on, but suppose that's good news in one way.👍

Cheers
Steve

[Forrest]

Did you try again after you’d reset the ECU? This might have woken it up. I think from your reply to Loki you’re planning to check the tester for continuity first, which would be my suggestion. But the same applies to the socket in the armrest.

The logic the tester uses is to take +12V from pin 16 and route it to the positive side of the LED. The negative side of the LED completes the circuit to ground via one of the signal pins and/or the momentary switch which, when pressed, grounds both the selected signal pin and the LED via pins 4/5.

I made my own reader which comprises the momentary switch and LED in a small project box but which relies on an OBD II breakout box to select the pins thus keeping me more aware of what it’s actually doing.

[TonyS9]

Exhaust manifold issues and lambda could be an exhaust leak, cracked manifold or gaskets. It will suck air in and confuse the O2. Manifold can be welded fairly easily usually.

Otherwise I'd be looking for an air leak, inlet gasket or split hose.

Stalling on deceleration can be turbo dump valve or actuator pipe.