Any LH-2.2 experts?

Still battling a severe fuel consumption problem on my 89 740T wagon.
Have done pretty much everything that can cause excessive consumption
from full tune up, new ECT and fuel pressure regulator, intake tract
leak repaired, new O2 sensor, AMM, everything cleaned, etc, etc,
Nothing has improved mileage from the 13-15 mpg one bit. Not in the
slightest.
I'm pretty much stumped but thinking about it yesterday I have a
thought. When I replaced my ECT I found it had a black one for an
LH-2.4 instead of the blue for LH-2.2. Figuring that has to be the
problem I replaced it with the blue one but nothing changed in the
slightest. Mileage and performance remained exactly the same. After
thinking about it and doing some more research I don't see how changing
the ect could not have an effect one way or another. Their values are
completely different and having the wrong one should create havoc with
the ecu. So I'm thinking maybe there is a problem with either the
wiring or the ecu itself. If its getting completely different readings
from the ect and it is processsing it as designed I don't see how it
could not affect the cars performance. Is my logic sound here? Is there
a way of testing the ecu or a good source for testing info? My Haynes
manual doesn't say anything about it. The car has 180K and this is my
first brick. It was bought a few months ago and I have no knowledge of
its service history whatsoever but it seems to be reasonably well cared
for. It runs fine. Starts right up, idles good, pulls hard, runs smooth
with no hesitation or driveability problem with either ect. If not for
this gas mileage issue I would be using and enjoying the car much more.


Dave

 

http://www.brickboard.com/FAQ/700-900/FAQSummary1.htm

Link to a good source of info not in the manuals.

 

Thanks. I have checked them out before and there's lots of great info
there. Couldn't find what I was looking for on actual troubleshooting
procedures though.

Dave

 

If your car came with a LH2.4 ECU as original it should have an LH2.4
replacement. Have you checked the Ignition Control Unit and circuitry? IIRC
should be EZ116. Timing and spark quality also play a part in good mpg. Did
you clean the throttle block thoroughly?

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

The car came with a black LH-2.4 ECT (FI coolant sensor) instead of the
blue LH2.2 unit. My car is an 89 740T and is definately an LH2.2 and at
some time in its life incorrectly had the LH2.4 ECT installed. As for
the ECU, its a Bosch 541 which based on my research is the correct one
for the car. So basically I had the right ecu but the wrong ect in the
car but it still ran fine, other than the gas mileage issue. I just
don't understand how replacing the wrong ect with the correct one not
have any effect on the car. Thanks

Dave

 

Have you had the CO value tested?

If the engine is running to rich - this value is too high.

If the engine has vacuum regulators, check the vacuum tubes,
I once had problems with these giving me 15% better fuel economy
after changing.

Are brakes hanging incl. handbrake?

What oil grade are you using?

/Per

 

What is the bosch number of your AMM. I was just thinking if previous owner
could mistakenly change the ECT to an LH 2.4, maybe also the AMM.
Maybe you could try to disconnet the ECT, and see if cold start and driving
is affected. If it is you'll know that the ECU at least get some kind of
temperature indication from ECT.

Regards

Per Hauge

 

Thanks for the suggestions. The AMM is a Bosch 007 which is the correct
one for an LH-2.2. I did disconnect the ECT and it was much more
difficult to start and when I reconnectted it with the car running the
idle smoothed out. So apparently the ECU is at least responding to a
signal from the ECT.
I have not had the exhaust tested but have not seen or smelled anything
not normal. Of course that doesn't mean all the exhaust readings are
fine, but it is not exhibiting any of the usual symtoms.
The engine does have a vacuum tank which I have not checked. I have
replaced all the narrow vacuum lines and cannot find a leak. Brakes are
fine, not hanging and tires are new running at 35psi. I've been running
Valvoline Syntec Blend 13-30 oil and flushed the A/T and replaced the
rear end oil with Syntec 75-90. This is driving me crazy!!!

 

You can test the engine vacuum with the engine idling by loosing the
oil cap and then putting it on without tightning - the oil cap should now
stay on without the tightning. If not check the flamme filter if your engine
is equipped with such else check the tubes.

Did you replace the tubes with the original tubes and in correct length?

If you disconnect the AMM - what happens then?

By the way - you wrote that the car was equipped with a LH 2.4 - maybe
your car has a bigger cc size injector than normal? LH 2.4 is only used
with bigger size injectors eq. up to 370cc. The standard green injector
on B230FT engine has 300 cc/min. Bosch #0 280 150 357 (Volvo #133233)
- this is the one to use with LH 2.2

/Per

 

This problem seems to be something to do with the changeover date from LH
2.2 to LH 2.4. The 1986 model was equipped with LH2.2 with EZ 117K Ignition
for B230F and FT engines. There were also options for CI (K-jetronic) and
Motronic systems. The 1989 780 using B230FT also uses LH 2.2 with EZ 117K
Ignition. However the 1991 740s and early 940s use LH 2.4 with EZ 116K
Ignition. The difference ignition wise is the trigger sensing for the
ignition. EZ 117K uses Hall sensor in distributor, whereas EZ 116K uses
flywheel pick-up sensor. On the LH 2.2 system the Idle Air Control valve is
driven from different pins on the ECU (23 & 10) and powered via the Fuel
pump relay, whereas on LH 2.4 it is driven by the ECU using pin 33 with
power via the fuel pump relay using the other coil to the LH 2.2 system. LH
2.4 also has a temperature sensor feed to the ICU which LH 2.2 does not. The
temperature sensing on LH 2.2 feeds pin 2 on ECU, but pin13 on LH 2.4 ECU.
LH 2.2 does not have a cold start injector, LH 2.4 does. So if your car has
a cold start injector it should use LH 2.4 and if it does not have a cold
start injector it should use LH 2.2.

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

I definately have the LH-2.2. Its got the 007AMM, green top injectors,
no cold start valve, and distributor Hall sensor instead of the Crank
Sensor on the bell housing. The only 2.4 item on the car as far as I
know was the ECT which easily could have been installed in error. I
have read and have been told though the 2.2 ect feeds pin 13 on the ECU
while you indicate it should be pin 2 and the LH-2.4 feeds pin 13. I am
about to check to see what signal it being sent to the ecu. Are you
sure of the pins? Thanks again.

Dave

 

Maybe you could check the ECT according to following. But anyway I would
think your temp gauge at the instrument panel would give indication of
whether it's working correctly or not. It should be vertical at normal
driving.

Engine coolant temperature (ECT) sensor

1982 - 1986
TemperatureResistance sensor
60°C 217 ± 35 ?
90°C 87 ± 15 ?
100°C 67 ± 15 ?

1987 - 1993
TemperatureResistance sensor
60°C 560 ?
90°C 206 ?
100°C 153 ?

Have you considered things like a leaking fuelline or even tank leak?
Also I have heard that leaking injectors can give poor mileage. But this
would probably also give poor/erratic idling.

You changed the fuel pressure regulator, but did you check that the
returnline to tank was not obstructed?

Regards

Per Hauge

 

Just realized.
That the sensors for ECU and temp gauge are not the same.

Per Hauge

 

I have replaced the ect and tested it before putting it in. It should
be good but I am going to test it again at the ecu plug. I know the ecu
is getting and reacting to a signal from it since the car is much
harder to start and does not idle as well with it unplugged.
Leaking injectors it a possibility but it idles and runs fine so it
really isn't showing any symtoms of that.
I'm sure the return line isn't clogged. I did a fuel pressure test and
it was fine and when I replaced the FPR I started the car with the
return line in a container and it dumped lots of fuel in strong steady
stream.
I see no signs of a fuel leak. I do notice that the needle seems to
start lower after the car has been sitting than when I shut it off. I
have crawled under the car to look but find no leaks anywhere.

Dave

 

When the ECU (behind the passenger side outer footwell panel) is
disconnected the car will neither start nor run. What are you plugging
and unplugging/testing?

Bob

 

When I unplug the ect (temp sensor) at the sensor the ecu reacts. I
plan of unplugging the ecu and testing the resistance from the temp
sensor to make sure there's not problem with the wiring from the sensor
to ecu but I don't really think its a problem.

Dave