Hello all
Recently I posted about a no start problem I was having with my 96 xj6. It turned out to be water in the fuel. Once I got that taken care of I starting having a misfire issue. Upon inspection I found oil in the spark plug wells. So I changed the tube seals and the VCG added new plugs and new coils.
The misfire is still present. the engine runs rough and vibrates a little at low Idle RMPs. When I put the car in gear the engine shakes much worse.
Any ideas what else it could be. When I pulled the codes I had a RCM and cylinder 3 misfire (because of a bad coil).
I could definitely use some input here.

 

New spark plug set may fix the problem. If not then you must change the coils high quality set cost 99$ in eBay im using one in my car working great

 

The coils are the obvious starting point. Check the wiring to them, and try switching them around or putting the some of the old ones back in to see if the problem goes away or migrates to a different cylinder.
I take it you are happy all of the water is out of your fuel?

 

Definitely try swapping the coils and plugs around first. See if the the code changes. We had a similar issue with cylinder 6 misfire that didn't move with the coils/plugs. It turned out to be the injector was clogged. Even though the codes pointed to the coil. Since you had water in the fuel, some rust may have accumulated. But again, coils/plugs are the easiest to check/change.

Bobby

 

Are you sure that the system is already cleared of water? Moreover, if you previously had water in fuel, water could have travelled from the rear to the engine, causing rust or corrosion along the way: the fuel rail is a possible suspect, and let us hope it is the spark plugs and not the injectors.

 

Is the car giving you any codes, or does it simply feel like it’s misfiring.

I did not see new oxygen sensors on your list of new parts. They do need to be changed every 100,000kms or so.

 

Is the the misfire at idle speed where the pulse time of the injectors is at it's smallest and critical , a thing that accures is a dragging injector . A fuel tank injection cleaner is an easy try

The quality of the fuel is critical in the idle area so has the bad fuel be used up

In the regime of first shifting out of park it has a history of the the transmission connector being dirty , there is a speed sensor inside the transmission and although the speed sensor does not need to be addressed its connection through the transmission connector can be easily addressed with a trick to remove it . The Transmission ECU and separate Engine CU both dance with each other effecting engine regulation

The rearmost coil connectors # 5 and # 6 can get swapped and there is a color code on the wires to get it straight

In manually rotating the throttle butterfly to the mechanical idle stop do you have a binding throttle cable ?

The injectors have basket filters on each one that can be removed , cleaned or replaced as this wouldn't be a dragging injector but a flow blockage

Does the coolant temp reach the 88 degree C point where The ECU changes from open loop to closed loop using the O2 sensors for full engine regulation?

Does the middle wire ( Green / Yellow ) return wire to the ECU on the TPS read 0.60 volts DC at the mechanical idle stop ?

Is the MAF return wire color X read 1.2 volts DC at the proper idle speed

The proper idle speed can be found on page 90

www.jagrepair.com/images/Training Guides/801S - 2000.pdf

Swapped the fuel pump relay as it may have burnt power contacts inside limiting current to properly fun the fuel pump

Vacuum leak , see page 60

 

Before you go any further about misfires onAJ16 engines have a serious look at the Jaguar service bulletins.
I bought an X300 sport last year which was in extremely good condition but the engine was mis firing and rough. The speedo showed 210 Ks ie about 130 miles
Two cylinders were definitely down on compression and a leak down test showed exhaust valves were the problem .
Jaguar proposed that the problem related to exhaust valves "gumming up" because of being driven around town at low power settings.
There were two suggested fixes
1. Give the engine a hard run on the open road.
2 Change the exhaust valves to a better "cutter" type.
I put a ridiculous amount of upper cylinder lubricant into the fuel tank ie about five times the recommended amount for the fuel mixture.
I then gave it about 80 Ks or 50 miles in intermediate gears generally holding between 30000 and 4000 RPM.
The engine then ran perfectly and all compressions were within 3 pounds of each other..
Bill Mac
MK1
MK2
S3XJ6
X300 (X2)
15 previous Jags MK5 to X308