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Matt
Matt, Mechanical Engineer
Category: Jaguar
Satisfied Customers: 22153
Experience:  BEng hons Mech engineering, in auto industry 22 years
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2001 S-Type, 82,000 miles - 2 issues! 1. Starting from cold

Customer Question

2001 S-Type, 82,000 miles - 2 issues!
1. Starting from cold there is an irregular misfire, and hunting rev counter, but no problem once it reaches operating temperature. O2 sensor? Dirty throttle housing?
2. Intermittent gearbox fault - absolutely fine around town, but on a single long run (>40 miles) it stays in 3rd once I've slowed down and accelerate again. I can 'cure' it by switching off the ignition whilst moving and then starting the engine again immediately. My local indy supposedly changed a solenoid a couple of years back but it only ran properly for a couple of months.
Could the two be related? Have you come across either before? Any guidance (before I get the codes read) would be great.
Submitted: 7 months ago.
Category: Jaguar
Expert:  Matt replied 7 months ago.

Hello

I'd 1st replace the spark plugs if any of them fail this checklist:

https://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/how-do-i-read-a-spark-plug

You can also try spraying some water on the coil packs with the engine running. It is possible the coil is faulty and causing the misfire. If you see sparks arcing with the water, then replace the coil.

I'd check the condition of the injector plugs / connections as this could be a lean misfire if an injector isn't firing properly - the best way to check this is with a 'noid' light

http://www.noidlight.com/

Then check all the connections to the engine sensors one at a time, remove each one and examine for signs of corrosion or damage and a squirt of contact cleaner ( not WD40) will also help.

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine - although this last is unlikely if the engine runs fine when warm

Expert:  Matt replied 6 months ago.

Hi
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