I don't know if Jaguar has published a specification on air flow readings for the AJ16 engines, but my impression is that 0.5 grams/second at idle seems low. I recall a rule of thumb that a healthy MAFS reading at idle in grams/second will be approximately equal to the displacement of the engine in liters.

I can't remember if you've cleaned the MAFS, but a dirty or contaminated platinum wire can make it run hotter than it should, causing the MAFS to underestimate the volume of air flow.

This might coincide with your P1178 code.

Cheers,

Don

 

Hi to confirm I have cleaned maf when I had low rpm misfire and cleaning made the misfire go away.

ive connected the solus on another xjr same yr and funny enough same colour!! And had the same reading give or take1 g/s. So maybe scanner not reading correct.

Filled the car up yesterday £60 and drove 125 mile trip drove ok no problems and I have yet to try and work out how much fuel it's used 1/4 tank left so I would assume about £40 as a guess.

when arrived home. late last night getting slight ruff running but no misfire on idle.whilst driving home on motor way felt like car was missing at 70 mph on and off could feel car holding back then free for about ten minutes then drove ok..

When home scanned ecm and p1178 present again I have found a leak at the servo to intake connection but have temporary sealed so it should not be leaking when on the drive.

Fuel trims are still not equal on each bank.

 

I too have the irregular miss when my 1996 XJ6 is warmed up. The only time I have no miss is when I turn off the air conditioning system. Is this extra load causing the miss?

My Jag has 345,000 miles on it and the only repairs have been condensers on the plugs and 3 air compressors. I cannot complain but would like to eliminate the miss.

 

If you're not sure of age of coils or replaced them a while ago with cheapies, I recommend changing all 6 plugs, with correct Champions, and 6 new coils even if aftermarket. Total bill, $60.

 

Hi Steve,

I just happened to run across this table that shows approximate air flow in grams/second under various conditions. This is from pdf page 1241 of the X308 Workshop Manual, but I think it is safe to assume the X300 specs should be similar:




I still think your reading of 0.5 grams per second at idle is much too low.

Cheers,

Don

 

Hi going by the above chart and working out my readings seem correct if you move my decimal point it's the way the scanner is reading it ie.
I get 0.04= 4.0 g/s ..iI done the above and the make sense I have checked this on a duplicate car and I get same readings.
My syptoms are changing and gettingworse.like a hesitation type misfire if you try to blip throttle more noticeable from cold but still there when hot.and a rough idle.
Drive car no faults to mention.
Fuel trims on idle bank 1 -25
bank2 +25
Rev car trims both react and go low-3 even 0 runs smoothly the as trims go back to high25 numbers runs rough again.

Check for air leaks found one the other day that might explain the p1178 servo Pipe connection yet to buy need correct part number.number.but temp sealed up.no air leaks at present.i don't believe it's maf.
Maybe coils but why are my trims like that..

 

Well after removing the ecm cleaning all the ground points and cleaning the maf I run the car up..from cold it was fine.when hot and 02 sensors on solus bank 1 -25 and bank2 +25 on idle and running ruff and with the he added interintermitant misfire.
Now the next thing I done was to swap the 02 sensors over on the harness connectors which I have done a thousand times over the last 2 months since replacing them and monitoring the data on solus.

Turned off ignition re started guess what running smoothly both bank 1 and 2 come both down to around 0 +- 7 to 8 on both Banks. Still had the little misfire so bit the bullet and fitted new oem coil packs and misfire not returned so now one happy smooth running jag....

I suspect speaking all the earth's have had an impact on the o2 sensors.and cleaning maf as well has helped...

Thank you for your help Don and others

 

Top marks Stevie and Don for perseverance!
It is good to see a happy ending, and the saga highlights again how sensitive these cars are to coils, and how logic and science aren't always friends when it comes to diagnosis.
I sometimes wonder whether there should be a new opening chapter to the workshop manual: "If there is anything wrong with your X300 engine, replace the Crankshaft position sensor. If that doesnt work, replace plugs with the correct make. If that doesnt work, replace all coils. If none of the above work, read remainder of manual."
I wonder what percentage of cases would need to look at the rest of the manual...