I spent some time cleaning up the valley of my 6.0 93.5 coupe, changing gaskets, renewing vacuum hoses and cleaning and getting parts powder coated, and on reassembly , the idle is rough, and I get an FF34 error code.
the car seems a bit low on power, but I didn’t want to push it while something is wrong
work done :
replace all water rail gaskets and O-rings,
replace all AAV internal with John_John’s kit
got the cam cover powder coated, fit allumium half moons and replace banjo bolts + gaskets
renew the cam cover gasket
clean all injectors, change their filter and all O-rings
clean and refit the additional air rails, and change all the air hoses
change all the small vacuum hoses
clean manifolds and renew all vacuum plugs and manifold gaskets
I checked the following
all spark plugs and both coils are connected to the right plug, and cords are fully inserted,
all injectors are clicking : I thing one seems to be clicking slightly less strongly than the others
all vacuum hoses are back to their original spot
I cleared the code, tightened the manifold nut, and could move the car a few time without getting the FF34 error code, but it came back when I finally got the car back into the garage
FF34 error code is “injection bank A” problem, but I couldn’t find much about it
suggestions are
air leak in the manifold : I tried to tighten all nuts, none was loose, I couldn’t find any open vaccum port
bad ignition : all sparks were changed 3000km ago, so I didn’t took them out
bad or lazy O2 sensor : they’ve not been touched, may be one got some coolant or other fluid during the cleaning up
ignition amp : I may try and swap those, as I got 2 or 3 cut outs on the road before (rpm drop to 0, then engine restarts and rpm show again, which could be related to the said amp)
Iddle seems to stay a bit high, even with AAV screw full on, I I guess there could be still an air entry somewhere
all suggestion of testing welcome, to try and locate the problem
Code 34
36CU DTC FF34 AND FF36 FUEL INJECTORS (FI)
This DTC uses the HO2S signal. The feedback inegrator has been on the rich or lean clamp on one bank. Changes to the mixture have brought the fueling on that bank back in control.
If your car has catalytic converters, please do not run! You are risking a much bigger problem.
If equipped with air injection, carefully trace the vacuum hose routings because incorrect routings can keep air injection on, which would lock oxygen sensors…ask how I know. Failed diverter valve can do same. Some later cars have an electric clutch on the air pump I understand, which might change diagnostic test. Disable temporarily by removing belt (on my ‘88 also drives a/c).
@Andy_Broadbent
thanks for the suggestion , Andy
my car is still on its original engine / injection harness, but it’s a low miler (75 000km, about 55 000 miles) and the wiring is still flexible
from what I gathered, the 6.0 is less prone to burning its wiring, may be because of a different material
I checked all injectors and they all click (one sounds slightly different, but still clicks)
I tested some ignition wires and all were sending the signal to the plugs @sbobev :thanks Steve : I’ve got the same doc, where I found the diagnostic flowchart
my car is a Japanese version, so has dual catalyzers : I’d rather not kill them nor get a fire
@RGK20m3
as I changed all the small vacuum hoses, I could have mixed up somthing, even if I took great care to mimic the original set-up
here are some pictures I took while doing so :
the red arrow points to the air valve command (EAC 5040), which I tested before refiting (helds vacuum, and opens with depression on)
Is your Japanese model LHD or RHD?
Can you post pictures of a larger viewing area, I cannot quite make it from these close-ups?
From memory, neither the front nor the back vacuum delay valves should be plumbed under the intakes.
One thing you can also check - is there fuel in the vacuum line that connect to the fuel pressure regulator on the A-bank side?
I connected the hose to the air valve to the port which is opened on the picture below, other side to the manifold (I may have reversed the entry and exit of the valve ?)
I found an old post of mine where you can see a description of what’s under the intakes and what is connected to engine vacuum of my 6.0L
As far as the vacuum line that goes to the FPR (with the delay provision), if memory serves right, the tube should be connected to the port which I indicated here:
I will double check, but in the meantime, you can run a test - just connect a strain vacuum line from the said port directly to the FPR and see if it makes any difference.
Also, very important - please verify that the diaphragm of the FPR (fuel pressure regulator) is not leaking fuel into the vacuum line.
Here is page from the JAG brochure. A-bank side, as I described in my 2013 post connects only to the SAV and the part-load engine breather in the eve. B-bank (driver) has only vacuum connection to the part-load engine breather
I’m working during the day so didn’t had time to check the FPR, but it was ok before I took if, then back on : I’ll have a look at it this weekend
re the vacuum hot start system : the vacuum port at the front is capped, and I’m sure it was not connected on my car
using any other vacuum port on the manifold should provide the same result , so one of the bottom ports should be ok, provided I didn’t mix up the sides of the delay valve
that 2 doubt areas are :
mixing the 2 ports controlling the additional air injection
mixing the 2 “bends” of the hot start fuel control
as the later shouldn’t do much on cold start, I’ll look at the potential inversion on the first one :
(swapping them may be the easiest way to check if the result is better the other way round)
OK, looks like we have to wait a bit for new developments.
I just re-read your original post. Spark plugs were not renewed. Cheap insurance - do it!
NGK BR7EF here in the US can be found anywhere for under $2/ea.
Also, the 36CU will be running in open loop until the engine reaches certain temperature. The O2-sensor will not be a factor until that point.
If the problem persists, disconnect the - you will get FF44 and FF45, but the engine should be running very well without them.
Last, make sure the large vacuum tube from the back of the A-bank manifold that turns and disappears somewhere along the firewall and then under the whole body to the boot HOLDS VACUUM.
as the car was running ok before I start, I reckon the spark plugs are ok (I didn’t took them out), but they’re indeed cheap (less than 3€ here), so renewing them is not a problem (except the delay to get them)
good point about the open loop : I 'll look for the O2 sensors connectors to test that
I checked the rear large hose : it holds vacuum (short test during 15 s, but could leave it longer if needed
is there a way to test the delay valve ?
the hoses around it seem to match the diagram you posted, the last unconnected point (circled) on the picture is connected to the manifold
looking at the picture and air injection system diagram you posted up : the solenoid vacuum valve entry from the delay valve is on the end, while the output to the air cut off valve is on the side
which seems to match the connections I’ve done (not sure it would make a difference, as it’s an open /close valve)
The solenoid should have a vent, possibly covered with a cap or filter; the nipple that connects to that vent with no power applied is the side that goes to the diverter valve in my experience.
I checked the air solenoid, and it seems to match the original fitments.
Then I cleared the code, and started again : idle is still rough, but the code didn’t came back (yet) : I’ll take the car for a drive , as it seems to be a bit better after a few starts / stops
I’ll report back how it goes
the throttle plates are adjusted , and links are balanced so the plates open in sync (as much as I can check it)
idle is not crazy high, about 1000rpm, and I did loosen a bit the AAV screw during the last tests, after adjusting the throttle turret, to get it at 2mm from the stop
I need to check the idle from cold , then hot, as taking the engine cover off (or back on) needs to release the throttle cable
