XJ6 SIII 4.2 ENGINE STALLS INTERMITTENTLY

[Br1970]

Afternoon,

We have a very frustrating problem on our 1984 SIII 4.2 Daimler , about a year ago it developed an intermittent issue in that , engine starts from cold no problem, car can drive for a few miles and when slowing down say for a roundabout the engine stalls

At times also when the engine is idling ( engine warm ) when D or R are selected it cuts out

Has anyone experienced this issue and if so what resolved it ?

Any advice or suggestions greatly appreciated

Kind Regards

Pat

[Dave Eynon]

Assuming all is correct with the ignition and injection system.
Is your car fitted with aircon? Does it occur when the compressor cuts in/out? Check the tickover speed when in drive and stationary is not too low as the sudden demand of an electrical load, power steering demand (turning the steering) or aircon could drop it to the point the engine stalls.
Too high a tickover when in neutral or park could cause the drive to "thump" when you select reverse or drive though, so you need an optimum setting.

[mike020150]

Typically, stalling when engaging a load, like the torque converter, is likely to be due to a weak fuel/air mixture, assuming the basic idle speed is correct. Have you an Mot emissions test printout which could confirm whether this is possible? Have you checked for induction air leaks? Is the oil filler cap seal in good condition? Has the airflow meter been checked/cleaned? Is the fuel filter blocked? When was the last time the car's spark plugs were changed? Series XJs need regular fresh plugs, unlike their modern counterparts. These are all possibilities which need to be eliminated by methodical checking. Mike.

[Br1970]

Assuming all is correct with the ignition and injection system.
Is your car fitted with aircon? Does it occur when the compressor cuts in/out? Check the tickover speed when in drive and stationary is not too low as the sudden demand of an electrical load, power steering demand (turning the steering) or aircon could drop it to the point the engine stalls.
Too high a tickover when in neutral or park could cause the drive to "thump" when you select reverse or drive though, so you need an optimum setting.

Thanks Dave for your reply :
The AC in the car is not operating , warm idle is about 900 rpm

Rgds

Pat

[Br1970]

Typically, stalling when engaging a load, like the torque converter, is likely to be due to a weak fuel/air mixture, assuming the basic idle speed is correct. Have you an Mot emissions test printout which could confirm whether this is possible? Have you checked for induction air leaks? Is the oil filler cap seal in good condition? Has the airflow meter been checked/cleaned? Is the fuel filter blocked? When was the last time the car's spark plugs were changed? Series XJs need regular fresh plugs, unlike their modern counterparts. These are all possibilities which need to be eliminated by methodical checking. Mike.

Hi Mike,
Thank you for your reply , I will get an emissions check done on the car , would you know what typically the minimum limit should be on the emissions for a correct fuel/air mixture ?
We will smoke test for induction air leaks
Plugs have been changed I would guess < 1000 miles ago , NGK plugs
New fuel filter a couple of 100 miles ago.
Dont quite understnd the comment on the oil filler cap seal ?

Kind Regards

Pat

[mike020150]

For a car of this age, the MoT emission limits are 4.5% CO and 1200ppm hydrocarbons. However, the design % CO range listed in Jaguar manuals is 0.5 -1.5%. A poor or missing oil filler cap seal will allow additional air into the engine, weakening the mixture and raising its idle speed (900rpm is high compared with the recommended 750rpm). From the additional information you have supplied, an air leak of some description would appear to be the most likely cause of stalling and the high idle speed (unless, of course, it's been increased in an attempt to counter the stalling). One thing you haven't mentioned is the distributor vacuum advance. Don't forget to test it for air leaks, the effect of diaphragm failure is a double whammy, an air leak and retarded ignition (poor performance and economy). Mike.

[Br1970]

Hi Mike,

Many thanks for that detailed reply.
We have access to a smoke machine , will test for air & vacuum leaks
Also will check timing

Thanks again

Pat