FZJ 80 unsolvable running lean condition please grab a beer help (1 Viewer)

[fz1boxer]

4.3 negative on the timing. Am I understanding that correctly?

That type of timing will cause it to run lean.

Should be 5-15 positive or advanced. Either the computer is retarding the timing or it is set incorrectly.

If the computer is retarding the timing look for a faulty input from a sensor such as the knock or temperature sensor.

the ignition timing shown is before TDC so it is advanced,that is where mine is at idle -4.3 to -5.6

 

[fz1boxer]

your VAF voltage is low

 

[baldilocks]

I missed this from my list
I has been replaced 2times with different makes
Last one is a Denso

Strange thing is I dont fell difference in performance with a disconnected sensor

My next question was going to ask whether or not you used dielectric grease on the sensor connector (not a good idea for the O2 sensor connector) but you pretty much rule out that as possibility here. Or ........?

 

[fz1boxer]

if you go over to the obd1 Facebook page and look at where a majority of the users show a screen shot of the display the lowest VAF voltage i saw was .97,yours looks way to low for idle,what does it do when the rpm's go up.

 

[Tedward]

This thread is great, with what I think is solid tech stuff. Gonna help me with with motor adding 30+% fuel at idle. Is or thinks it is running lean.

Thanks to all who contribute to this thread!

Hoping the OP keeps plugging along till its solved!

 

[Viktor84]

Injectors all plugged in and running right? My buddies was running on 5 cyl, cause one plug wasn’t seated to injector so not firing

Yes injectors connections are all ok

Can it graph just the o2 sensor voltage?

It says it's reading rich, but I can't make out the voltages on the graph.


I had the oposit problem with my o2 sensor where it was reading wrong and adding way to much fuel.



You could try uplugging the o2 sensor. Reseting the ecu and driving around for a bit to see if it's better. It won't be perfect but it will be close.

I will do a test drive like that and will upload the readings

That thing is running lean as hell!

The exhaust valves are WHITE! You're lucky you didn't actually burn a valve!

Things that will cause it to run lean:
Timing (Must be PROPERLY set)
O2 sensor
Knock Sensor
Temp Sensor
Low fuel pressure
Leaking air (Unmetered air entering the system)

Since you have changed all these sensors, I would look at the Unmetered Air.
Oil cap
Spark Plug Tube Seals
PCV Valve system
Vacuum brake booster check valve and booster
All vacuum hoses
EGR Valve
PAIR unit? (If equipped)
Intake air hose cracked
AFM/VAF/MAF unit. Does this have the MAF of the US97 model or the AFM or the US94 model? Check to make sure the wiring harness on this item didn't get yanked and broken.
Intake manifold leak or plug missing
Valve gasket cover leak

How was the LPG system installed? You said it was 100% removed. Did ALL ports get properly plugged?

Oil cap good
Spark plug tube seals replaced
PCV valve, hose, grommet new
Vacuum booster check valve ok as per FSM, not sure how to test the brake booster itself but will look into it
EGR fine and no difference if I plug it
Intake air hose new
PAIR unit, I dont know what this is, I dont think I have on but will look it up
All vacuum hoses replaced on and around the manifold
This car has a MAF, the wiring however is not part of the engine wiring harness as it is routed differently coz it is a RHD car, I will look into how to test the wiring. If you have any suggestions or a link please let me know
All gaskets are new on intake manifold, when it was apart I inspected it for cracks as I was cleaning the 2 parts but all looked ok
LPG system ports are plugged properly, there were 6 for the injectors +1 for evaporator vacuum

My next question was going to ask whether or not you used dielectric grease on the sensor connector (not a good idea for the O2 sensor connector) but you pretty much rule out that as possibility here. Or ........?

No grease used, if I remember correctly this is a water proof plug

if you go over to the obd1 Facebook page and look at where a majority of the users show a screen shot of the display the lowest VAF voltage i saw was .97,yours looks way to low for idle,what does it do when the rpm's go up.

Good point, I look into this

Thanks for all the input

 

[BILT4ME]

PAIR unit, I dont know what this is, I dont think I have on but will look it up

This car has a MAF, the wiring however is not part of the engine wiring harness as it is routed differently coz it is a RHD car, I will look into how to test the wiring. If you have any suggestions or a link please let me know

Your truck may NOT have the PAIR unit. Was installed on US 1993 and 1994 models, but those were OBD1 trucks in the US.

If it has a MAF, but is "not part of the engine wiring harness" is it plugged in properly and allowing correct readings? If not, then it is not reading the incoming airflow properly and it is adjusting your injector timing accordingly and leaning out, causing your O2 sensors to read low.

Look into the proper wiring of the MAF. I am not sure RHD/LHD would have anything to do with that.

 

[Eicca]

Subscribed out of interest.

 

[Viktor84]

Hi, havent had time to do any testing in the past days
It looks like the machine shop messed up something with the valve clearances
The valves are ticking very loudly, I would say it is louder then the diesel
I dont think the hardened valve seats making the noise, what do you think?

Anyways I was stupid not to check the valve clearances before putting it all back together, I will take the valve cover off to check it by the weekend. Before the head job the exhaust side clearances were too tight due to original valve seats not liking the LPG. It was out of the tolerance by 0.05mm which is not much but still not good. It was whisper quiet. Now its very LOUD so it must be off, I was trying to have a listed with the screwdriver in the ear and it is definitely valve train. Another issue to deal with...

I took some other reading on different engine load/throttle input, does this look right to you?

 

[fz1boxer]

let me see if i can pull up injector percentages for my 94 through a specific rpm range and see how close they are to your,maybe tomorrow before i can post them

 

[Viktor84]

I am struggling to find the right instructions on how to test the MAF and the wiring on the FZJ80
Could you give me some recommendations please?
I would like understand and rule out that this is 100% ok since this is one of the most important reading that the ECM uses for AFR

 

[fz1boxer]

Your VAF/MAF voltage looks low at idle and your timing looks wrong for the given rpms.
If i can find it there is a couple of threads here on VAF to MAF conversion which may help you trouble shoot the MAF.
I am not familiar with overseas version but i thought OBD1 was VAF.

 

[Proven]

I had a Tacoma where one of the pins in the MAF sensor backed out and wasn't all the way clicked in place on the harness side. This cause my truck to run crazy.

 

[fz1boxer]

93-94 truck VAF to MAF conversion project
this thread has some values to look for in checking your MAF

 

[Viktor84]

Just a quick update

After the head job, I checked the valve clearances

It should be 0.25-0.35mm on the exhaust side
I have 0.70 on average, closest is 0.60mm, worst is 0.80mm !!!

No idea how they managed a f@ck up like this at a well reputed machine shop but they will have a bad Monday for sure...

Anyways I will carry on with the testing once this is fixed, I dont feel the point before this is put right

 

[fz1boxer]

Well that will make it rattle like a diesel,i would check your timing chain/gears indexed properly as well.