Misfire. Help needed please

[Acousticplayer]

Hello all. 1999 2.8 roadster. Approx 80,000 miles. I appear to have an intermittent misfire. Scan first showed a misfire on number one cylinder but it now shows misfire bank one on 1 2 and 3 cylinders. I've checked all the coils and the plugs all look ok. Can anyone indicate the likely cause please.

 

[Sajk]

Could be o2 sensor for that bank. Try swapping plugs from not misfiring bank with misfiring bank one plug at a time. Sometimes the detection is not exact. If the miss does not move I would suspect the o2 sensor. What are the code numbers?

 

[Acousticplayer]

Thanks for that. Can't report the codes as I deleted them to see if they would repeat,but will check again and come back. The car is at present being used by my Grandson who is destined to inherit it in my will. He has suddenly taken a liking to it.

 

[Grumps]

The only problem I ever had in 7 years of owning my 2.8 was the crankshaft sensor which caused a misfire. I changed both that and the camshaft sensor and never had an issue going forward.

 

[NZ00Z3]

Misfires are caused by Electrical and Mixture problems:
Electrical

• Misfires on one cylinder tends to be electrical
• Plugs and coils. Swap with another cylinder to see if fault follows
• Harness. Dirty connectors, damaged wires, faulty coil earthing resistor
• DME. Inspect the 2 sets of 6 MOSFETS (Black boxes) around the outside of the DME PC Board for damage. Inspect for PC Board track damage. Any damage will be obvious.

Mixture

• Misfires on multiple cylinders tends to be mixture
• Too rich. Too much fuel, not enough air. Faulty MAF or Pre-Cat sensor fooling the DME into thinking 1 or the 2 prior causes is happening, blocked Cats, if the problem is bank specific, a leaking injector.
• Too lean. Too much air, not enough fuel. Faulty MAF or Pre-Cat sensor fooling the DME into thinking 1 or the 2 prior causes is happening. Vacuum leaks
• The DME has a performance tune. The DME tables may not match the MAF or injectors fitted. The Air/Fuel tables have been incorrectly altered. Put the DME back to its original tune and see if the problem is fixed.

 

[Devon Z]

Always suspected my TU engine had a slight misfire from new but dealer couldn’t find anything wrong, once the warranty ran out and following advice I replaced the inlet cam position sensor with a Febi unit and all has been good ever since.

I also replaced the exhaust sensor.