Maf sensor emissions

Afternoon to you all, I am having emission problems thinking it may be the maf sensor, symptoms are black sooty water from the exhausts, from start up hesitation and not a lot of power, it’s definitely running rich spark plugs with soot deposits and high levels of carbon monoxide emissions, rough idle, tried testing maf with multi meter but not sure of what I am doing as on YouTube all videos have 4 and 5 wires, as you know the x300 has 3 have found the positive wire and ground but not sure if the supply wire to ecu is giving me correct reading, any and all help would be greatly appreciated
Thank you in advance for any help



Need more data.Model, year, engine and maybe more details,mileage etc.

Source a cheap code reader and report the codes.

If you really believe the MAF is bad try unplugging it and see what happens.

Thank you for your reply, it is a 1995 4.0ltr sovereign and has done 155,000 miles, I bought an obd2 code reader but doesn’t show anything, apparently on the 1995 model Jaguar Ford had’nt finished the software, I have tried testing the maf with multi meter but all the videos on tube show 4 or 5 wires, I have unplugged the maf sensor when engine is running and continues to run, unplugged before start up and it turns over and starts, I have driven with maf unplugged also driving with the maf connected, it is the same rough idle, black sooty water from exhaust, sometimes I have grey smoke from exhausts other times it is black, I don’t have any misfiring, I recently change spark plugs air filter, prior to that it would not start called green flag and he said I probably have oil in one or more spark plugs, I removed on coil plugs and spark plugs to find oil in one of the wells, I soaked up best as I could and replaced the whole rubber gasket set including the six rubber seals where the spark plugs are, i am using e5 fuel although prior to all of this I used e10 and after a day out it stopped running and would not start, the car was recovered by mechanic who flushed it through and fitted new spark plugs, apologies for the long winded reply hopefully it will help, I have had the car since 2002, my grandson once said jokingly “ grandad loves that car more than you Nan” so any hope will be great, thank you again for taking the time to reply

Regards Steve

If there’s no difference between driving with or without a MAF, then you may have solved your problem.

I would suggest getting an ELM27 dongle, WIFI only with iPhone, android can use either WiFi or Bluetooth. Then download an app.

We need to know if your car is getting into closed loop. The car needs proper readings from four key sensors in your car before agreeing to use sensors for fueling direction.

  1. TPS - let’s assume that’s good for now.
  2. O2 sensors- when was the last time these were replaced? If you don’t know, it’s time.
  3. Coolant Temperature Sensor- a $20 part that takes 5 minutes to replace. Let’s do it!
  4. MAF sensor…You can look up for the wiring diagram to read what’s going on.

Hi Veekay

Seems the 95 X300 did not have a fully functional OBD ll port plus it may not have the diagnostic trip computer like the XJS has. Not sure where to go from here. Thanks

Leaning towards number 3 as a good candidate.

Thank you

Regards Steve

Thank you for your help, will look at prices for o2 sensors

Regards Steve

The jag repair link is great thank you

ELM27 dongle is about $15-$20 on eBay. Software probably comes with a free trial. I say it’s worth a shot. The risk is cheap compared to the reward.

The price of a CTS is also very cheap risk for the reward. If you’ve never replaced the CTS, it’s probably overdue anyways.

1 Like