440 1.8i fuel consumption down, running rough

[twomo]

I have a 96 P-reg 440GS 1.8i, 85k miles.
The fuel consumption suddenly dropped recently from regular 35-36 to 26-28mpg.
Engine has become a bit lumpy and quickly turns juddery when i ease off the throttle, so i have to change down rapidly as revs drop.
Also, engine has started to run on for a couple of turns after i switch off.
Recent history: had to get new stepper motor fitted earlier this year (thanks to chaps at Braydon Motors).
Am getting concerned that it might conk out at any moment, or result in a problem that costs more to fix than car's value. Any suggestions or similar experience?...

[grass hopper]

Hi,worth checking the dizzy cap/plugs and leads.

also check for any air leaks on the induction system,especially the inlet manifold gasket.

also the rubber hoses can split to the MAP sensor on the bulkhead.

also worth reading the ECM for codes.

regards GH.

[twomo]

Great, thanks GH. Air leaks/hoses sounds plausible - had a similar, worse problem when i first bought it 3 years ago which turned out to be two little bits of perished hose somewhere low down.
Sadly i'm a numptie when it comes to engines, but i know a man called Don who's not! He checked over the "dizzy cap" etc while sorting out the stepper motor prob a few months ago, so that seems less likely.
ECM: just found out what it is, but can you tell me where/how to check it?
Many thanks - twomo

[B20F]

Could be a bad lambda sensor. Check this howto:
http://volvo480.dragons.org.uk/forum...ic.php?t=14683

[twomo]

Much appreciated B20F, thanks - very comprehensive info on that link!

[B20F]

1. Fault codes retrieval
Open the diagnostic system's box cover and place the test cable mounted on the side of the box into an appropriate socket #2.
Turn the ignition ON to key position II without starting the engine. Wait about ten seconds.
Press the button once and hold it for more than one but less than three seconds.
The LED lamp will flash in successive series of three digits followed by a three-second pause. If there are no fault codes stored, it will flash 1-1-1 indicating the system being tested is operating correctly.
Count the successive flashes and record the fault code.
Press the button again, as described above.
Record the fault code. If it is the same as the previous one, then no additional codes are stored. Repeat until all the codes stored are retrieved (often a maximum of three).
Turn the ignition OFF and remove the test cable from a socket.


2. Erasing fault codes
Repeat step 1 and read all the fault codes again.
Press and hold the button for more than five seconds, then release it.
When the LED lights, press the button again for more than five seconds and release it. When the LED goes off, the memory is cleared.
Test that memory is cleared by performing step 1. Code 1-1-1 should be returned.

Diagnostic Codes
Volvo
89-93 models
1-1-1 No faults.
1-1-2 ECU.
1-1-3 Fuel injectors.
1-1-3 Heated Oxygen sensor-max enrichment sensed (94-up).
1-1-5 Injector #1.
1-2-1 Mass airflow sensor.
1-2-2 Air temp sensor signal.
1-2-3 Coolant temp sensor signal.
1-2-5 Injector #2.
1-3-1 Ignition system RPM signal.
1-3-2 Battery voltage.
1-3-3 Throttle switch signal (idle).
1-3-5 Injector #3.
1-4-2 ECU faulty.
1-4-3 Knock Sensor signal missing or defective.
1-4-4 Fuel system load signal(missing or defective).
1-4-5 Injector #4.
1-5-3 Rear heated oxygen sensor signal.
1-5-4 EGR system-leakage or excessive flow.
1-5-5 Injector #5.
2-1-2 Oxygen sensor signal(front sensor on 94 and later models).
2-1-3 Throttle switch signal.
2-1-4 Ignition RPM signal erratic.
2-2-1 Heated Oxygen Sensor(Rich mixture/part throttle).
2-2-2 Main relay.
2-2-3 Idle valve signal.
2-2-4 Coolant temp sensor signal.
2-2-5 A/C pressure sensor signal.
2-3-1 Lambdfa adjustment.
2-3-1 Heated Oxygen sesnor(lean mixture/part throttle) 94-up.
2-3-2 Lamda adjustment.
2-3-2 Adaptive heated O2 sensor control (94-up).
2-3-3 Idle valve-closing signal.
2-3-4 Throttle switch signal missing.
2-4-1 EGR malfunction.
2-4-5 Idle air control valve-closing signal.
3-1-1 Speedometer signal.
3-1-4 Camshaft position signal missing or defective.
3-1-5 EVAP emission control system.
3-2-1 Cold start valve-signal missing.
3-2-2 Airflow meter hot wire.
3-2-4 Camshaft position siganl erratic.
3-2-5 ECU memory failure.
3-3-5 TCM request for MIL.
4-1-1 Throttle switch signal faulty or missing.
4-1-3 EGR temp sensor signal incorrect or missing.
4-1-4 Turbo boost regulation.
4-1-6 Turbo boost reduction from TCM.
4-2-5 Temp warning level #1.
4-3-1 EGR temp sensor faulty or missing.
4-3-2 High temp warning inside ECU.
4-3-3 No rear knock sensor signal.
4-3-5 Front heated oxygen sensor - slow response.
4-3-6 Rear heated oxygen sensor compensation.
4-4-3 Catalytic converter efficiency.
4-4-4 Acceleration sensor signal.
4-5-1 Misfire - #1 cylinder.
4-5-2 Misfire - #2 cylinder.
4-5-3 Misfire - #3 cylinder.
4-5-4 Misfire - #4 cylinder.
4-5-5 Misfire - #5 cylinder.
5-1-1 Adaptive oxygen sensor control-lean mixture at idle.
5-1-2 Oxygen integrator at max lean running limit.
5-1-3 High temp warning inside ECU.
5-1-4 Engine cooling fan-low speed signal faulty.
5-2-1 Oxygen sensor preheating-front.
5-2-2 Oxygen sensor preheating- rear.
5-3-1 Power stage-group A.
5-3-2 Power stage-group B.
5-3-3 Power stage- group C.
5-3-4 Power stage- group C.
5-3-5 TC control valve signal.
5-4-1 EVAP valve signal.
5-4-2 Misfire - more than one cylinder.
5-4-3 Misfire - at least one cylinder.
5-4-4 Misfire - more than one cylinder/catalytic converter damage.
5-4-5 Misfire - at least one cylinder/catalytic converter damage.
5-5-1 Misfire - #1 cylinder/catalytic converter damage.
5-5-2 Misfire - #2 cylinder/catalytic converter damage.
5-5-3 Misfire - #3 cylinder/catalytic converter damage.
5-5-4 Misfire - #4 cylinder/catalytic converter damage.
5-5-5 Misfire - #5 cylinder/catalytic converter damage.

[twomo]

many thanks again B20F - will give it a go over the next few days. This is a great site, cheers for christmas!

[twomo]

hi B20F & Grass Hopper, hope you've had a good Christmas!
I've now done the ECM check, and it went as follows:
Socket 1: fine, reading 1-1-1
Socket 3: fine, reading 1-1-1
S5 & S6, seemingly no terminals inside to connect to
S7: no reaction at all
And Socket 2 (the relevant, fuel system one): the LED came on dimly and stayed on when turned ignition to position II; on pressing the button on the ECM it lit up fully, but when released went back to the permanent dim light, without any flashing. It just stayed lit at this dim level until turned ignition off.
Can't see anything like this in the long list of fault codes above, but noticed that these are headed as "89-93 models", and mine is a 96 440 - don't know if this has any bearing at all, or whether it means i have a knackered ECM, or a knackered fuel system, or both...or neither..?...
Worthy of note, the old faithful chariot got me from north kent to newbury and back again happily, if throatily, over christmas, but the fuel consumption has plummeted again to 24mpg - getting very expensive!
Also, presume lambda sensor is OK because the dashboard light has not been lit.
Won't be able to get hoses/air leaks etc checked until Don's garage opens up again after New Year.
Thanks again, looking forward to any new insight you may have...
Twomo

[Darlo 1]

Try having an emissions test done could be your cat is begining to break up.

[carl4u44]

[QUOTE=And Socket 2 (the relevant, fuel system one): the LED came on dimly and stayed on when turned ignition to position II; on pressing the button on the ECM it lit up fully, but when released went back to the permanent dim light, without any flashing. It just stayed lit at this dim level until turned ignition off.
[/QUOTE]

I've noticed this as a downside to the diagnostice system. This happened to me in socket 1 when I was testing the remote central locking. A faulty control box caused this. In your case a spare ecu (as socket 2 is ecu related) to plug in would be handy to see if this led issue in socket 2 was to cease.