93 Legacy 2.2L rough engine idle, replaced intake manifold g
Posted: Mon Sep 02, 2002 12:53 am
--- In BC-BFLegacyWorks@y..., "illanrob" <illanrob@j...> wrote:
93 Legacy 2.2L L 5speed 130kmi rough engine idle, replaced intake manifold gasket BC-BFLegacyWorks@yahoogroups.com
Problem solved, there was a leak from the intake manifold gasket. I had help from a mechanic to identify the problem. This is my first experience fixing fuel injected engines, carbureted engines are easier. The fact that the air/fuel mixture was rich is contrary to a carbureted engine with the same vacuum leak problem, it should run lean and maybe stall after a while. It seems that the Engine Computer purposely enriches the mixture too much even when the O2 sensor is pegged at 100mV, the too much fuel limit. Enriching the mixture may prevent the engine from stalling, but it surely confused this operator from thinking vacuum leak.
After replacing the intake manifold gasket the idle became smooth, I recreated an intake manifold leak by removing the brake power assisted vacuum hose to the manifold and the same scenario with the engine rough idle/near stall and high rev surges repeated.
The intake manifold gasket has 4 screws holding it to the head, 2 short at the ends torqued at 25ft/#, 2 long between the two air ducts torqued at 4ft/#. Yes, 4ft/# that is really low, my torque wrench with a half inch drive doesn't go that low. My gasket leaked on the middle near one of the low ft/# screws. Only one head was bad, only one air duct leaked, this one had two hair line cracks, each crack cut into both side of the gasket. These cracks do not look that big, perhaps the 2 low torque screws on the inside could have been tightened more than 4FT/# to help locate/exonerate the problem.
Replacing the gaskets and inspecting the intake chambers of the heads is difficult. I was trying to follow a Chilton manual. Chilton wanted the steering pump and alternator removed to help with clearance, I did not move either. The AC compressor caused more clearance problems, as well as the hill helder cable which loops to/from the firewall and between the fuel rail and the left air intake manifold. The fuel injector cabling crossing over the fuel rail was equally bad. I only lifted the manifold 4 inches up and 3 inches to the right to inspect heads. The Subaru shop manual did not describe how to remove the manifold to replace a gasket. Took 1.5hrs to free the gaskets, 1hr more to raise the manifold 4in. to inspect heads, 1.25hr to replace all connections, refill fluids. Looks like a 2 hour job next time.
Explanation of problem/investigation before solution:
Three weeks ago had some poor engine idling, three days later it got
much worse. I have the shop manual for the car so I read about
the different causes.
-1)NOW Managed to reset the engine computer driving the car and the
Codes for Knock sensor 2-2, and ignition switch 1-2 were reset. Did
get a Code 3-2 for Throttle body sensor. Tested sensor out of car in
the car works fine. Found error on Pg 76 of Section 2/3 Manual pins 2
and 4 wrong on E8 connector.
0) the engine runs rich in fuel and soots the plugs; NOW have seen
more evidence of this soots new plugs (3 of the 4) in 20 min
1)THEN engine always starts on second or third start, will stall
unless the AC is turned ON; NOW this is no longer true, now more
difficult to start (possibly more soot on plugs) and the AC ON trick
looks awfull in the way the compressor clutch cycles ON-OFF as engine
is near stall, so I'm not running AC anymore
2)THEN the engine takes 5 min to stabilize such that it is driveable,
I am not driving it any more; NOW the engine now takes 10 min to
stabilize if I increase RPMs to 850 900 with Throttle body screw, the
engine runs fair
3) idling or driving at 2000 RPM or more; its not too bad, no smoke
from exhaust; NOW I can see the O2 sensor output start at 0.100V
700RPM idle rich/rough to 0.040V 2000RPM idle steady; some black smoke
at idle
4) driving 20 to 40MPH has normal power, the higher RPM always better,
never back fires, could go for many more miles; NOW the engine
backfires when starting from cold and I open the throttle
5) Timing at #1 cyl 20 deg BTDC steady
6)NOW If I pinch the hose to the Air-Bleeder-Valve the engine starves
for air and stall. Less so now that the TB screw is set to higher idle.
7) NOW measured the pulse width to injectors from engine computer
reads 6mS ( milliseconds) at idle, the shop manual says 3.0 to 3.7mS
in Mode F11 for non turbo Section2/3 pg 107 of 1992 Service manual.
Can't figure out why doesn't the ECU cut this 6mS down to 3.0 if the
value is indeed correct? This could be a mayor problem the longes time
dumps more fuel.
7a) Listen to injectors with sthetoscope all four click about the
same, not sure if I could pick out a marginal one.
NOW replaced with new fuel filter, pumped gas out of old filter
canister a lot of black dirt comes out.
9) Time to take it to a shop and do an inductive cleaning, mechanic
claims it cleans fuel injectors, MECHANIC found intake manifold vacuum leak.
THEN: Early during the 5 min warm up, AC on, it looks like it may
stall anytime, some black smoke from exhaust during the 5 mins. The
engine surges to 3000 RPMs for say 3 seconds in 1 minute intervals.
So I know the idle air valve is working some. Then after 5 mins I can
drive it around a city block and gets me home, glad to be home in the
garage after that ride. The pattern repeats the same way.
THEN So far here is what I have done to stabilize, fix the problem:
Adjusted screw, 2 turns CW, in throttle body to raise idle RPM to 850.
This level is similar when AC is ON
Replace original spark plug wires No Change, Replaced plugs with 20Kmi
No Change on engine
Tested cylinder compression cold then warm then hot all 4 cyl read the
same. My gauge reads 190-195PSI and 210PSI adding a teaspoon of oil.
Engine is 9.5:1 so the gauge reads high.
Changed the Knock Sensor the engine computer indicated bad sensor, a
lot of engine pinging with old sensor when climbing a hill, can't
really remember now if this is better until the mayor idle shaking is
resolved.
Why is the AC helping to prevent engine stall, well the load forces
idle air valve to pass more air and it gets more fuel?
> Robert Illan
> 93 Legacy L 5spd 130kmi
93 Legacy 2.2L L 5speed 130kmi rough engine idle, replaced intake manifold gasket BC-BFLegacyWorks@yahoogroups.com
Problem solved, there was a leak from the intake manifold gasket. I had help from a mechanic to identify the problem. This is my first experience fixing fuel injected engines, carbureted engines are easier. The fact that the air/fuel mixture was rich is contrary to a carbureted engine with the same vacuum leak problem, it should run lean and maybe stall after a while. It seems that the Engine Computer purposely enriches the mixture too much even when the O2 sensor is pegged at 100mV, the too much fuel limit. Enriching the mixture may prevent the engine from stalling, but it surely confused this operator from thinking vacuum leak.
After replacing the intake manifold gasket the idle became smooth, I recreated an intake manifold leak by removing the brake power assisted vacuum hose to the manifold and the same scenario with the engine rough idle/near stall and high rev surges repeated.
The intake manifold gasket has 4 screws holding it to the head, 2 short at the ends torqued at 25ft/#, 2 long between the two air ducts torqued at 4ft/#. Yes, 4ft/# that is really low, my torque wrench with a half inch drive doesn't go that low. My gasket leaked on the middle near one of the low ft/# screws. Only one head was bad, only one air duct leaked, this one had two hair line cracks, each crack cut into both side of the gasket. These cracks do not look that big, perhaps the 2 low torque screws on the inside could have been tightened more than 4FT/# to help locate/exonerate the problem.
Replacing the gaskets and inspecting the intake chambers of the heads is difficult. I was trying to follow a Chilton manual. Chilton wanted the steering pump and alternator removed to help with clearance, I did not move either. The AC compressor caused more clearance problems, as well as the hill helder cable which loops to/from the firewall and between the fuel rail and the left air intake manifold. The fuel injector cabling crossing over the fuel rail was equally bad. I only lifted the manifold 4 inches up and 3 inches to the right to inspect heads. The Subaru shop manual did not describe how to remove the manifold to replace a gasket. Took 1.5hrs to free the gaskets, 1hr more to raise the manifold 4in. to inspect heads, 1.25hr to replace all connections, refill fluids. Looks like a 2 hour job next time.
Explanation of problem/investigation before solution:
Three weeks ago had some poor engine idling, three days later it got
much worse. I have the shop manual for the car so I read about
the different causes.
-1)NOW Managed to reset the engine computer driving the car and the
Codes for Knock sensor 2-2, and ignition switch 1-2 were reset. Did
get a Code 3-2 for Throttle body sensor. Tested sensor out of car in
the car works fine. Found error on Pg 76 of Section 2/3 Manual pins 2
and 4 wrong on E8 connector.
0) the engine runs rich in fuel and soots the plugs; NOW have seen
more evidence of this soots new plugs (3 of the 4) in 20 min
1)THEN engine always starts on second or third start, will stall
unless the AC is turned ON; NOW this is no longer true, now more
difficult to start (possibly more soot on plugs) and the AC ON trick
looks awfull in the way the compressor clutch cycles ON-OFF as engine
is near stall, so I'm not running AC anymore
2)THEN the engine takes 5 min to stabilize such that it is driveable,
I am not driving it any more; NOW the engine now takes 10 min to
stabilize if I increase RPMs to 850 900 with Throttle body screw, the
engine runs fair
3) idling or driving at 2000 RPM or more; its not too bad, no smoke
from exhaust; NOW I can see the O2 sensor output start at 0.100V
700RPM idle rich/rough to 0.040V 2000RPM idle steady; some black smoke
at idle
4) driving 20 to 40MPH has normal power, the higher RPM always better,
never back fires, could go for many more miles; NOW the engine
backfires when starting from cold and I open the throttle
5) Timing at #1 cyl 20 deg BTDC steady
6)NOW If I pinch the hose to the Air-Bleeder-Valve the engine starves
for air and stall. Less so now that the TB screw is set to higher idle.
7) NOW measured the pulse width to injectors from engine computer
reads 6mS ( milliseconds) at idle, the shop manual says 3.0 to 3.7mS
in Mode F11 for non turbo Section2/3 pg 107 of 1992 Service manual.
Can't figure out why doesn't the ECU cut this 6mS down to 3.0 if the
value is indeed correct? This could be a mayor problem the longes time
dumps more fuel.
7a) Listen to injectors with sthetoscope all four click about the
same, not sure if I could pick out a marginal one.
NOW replaced with new fuel filter, pumped gas out of old filtercanister a lot of black dirt comes out.
9) Time to take it to a shop and do an inductive cleaning, mechanic
claims it cleans fuel injectors, MECHANIC found intake manifold vacuum leak.
THEN: Early during the 5 min warm up, AC on, it looks like it may
stall anytime, some black smoke from exhaust during the 5 mins. The
engine surges to 3000 RPMs for say 3 seconds in 1 minute intervals.
So I know the idle air valve is working some. Then after 5 mins I can
drive it around a city block and gets me home, glad to be home in the
garage after that ride. The pattern repeats the same way.
THEN So far here is what I have done to stabilize, fix the problem:
Adjusted screw, 2 turns CW, in throttle body to raise idle RPM to 850.
This level is similar when AC is ON
Replace original spark plug wires No Change, Replaced plugs with 20Kmi
No Change on engine
Tested cylinder compression cold then warm then hot all 4 cyl read the
same. My gauge reads 190-195PSI and 210PSI adding a teaspoon of oil.
Engine is 9.5:1 so the gauge reads high.
Changed the Knock Sensor the engine computer indicated bad sensor, a
lot of engine pinging with old sensor when climbing a hill, can't
really remember now if this is better until the mayor idle shaking is
resolved.
Why is the AC helping to prevent engine stall, well the load forces
idle air valve to pass more air and it gets more fuel?
> Robert Illan
> 93 Legacy L 5spd 130kmi