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'84 XJ6 Dark Exhaust Fumes When Cold

'84 XJ6 Dark Exhaust Fumes When Cold

Hal Rogers

Bert Willing wrote:

My Jag ('84 XJ6) more and more shows problems when running cold. It fires up without problem, but then will hardly accelerate. It stumbles and blows dark fumes until the normal operation temperature is reached - then it runs perfectly. When cold, idle is low (500 rpm), sometimes oscillating. The problem used to be intermittent, but now it's every day. I can smell gas sometimes although there's nothing leaking in the engine compartment. And yes, gas consumption has gone up.

OK, it's pretty clear to me that the engine is fed too much gas/too little air when cold. But where to start fixing it?

The most common problems are 1. faulty fuel pressure regulator and 2. faulty air flow meter. Could have other problem but these two things are common. Pressure regulators are inexpensive and fail frequently. If yours hasn't been changed that you know of, just change it. Air flow meters are of course more $ so it is better to be fairly certain of its condition. Bosch sells news ones..but we can also supply remanufactured units too for less than new.

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