Hi,I have a 2002 S 4.0 with 79900 miles on it. It began to miss at idle and low power requests. Fault code indicated 303 misfire. I changed plugs to same that was in it (ngk platinums) changed fuel filter, checked and moved coils around, added injector cleaner and some fresh gas. Still Missing and showing 303,lean condition, and engine light came on. I took it to the pros. They have checked fuel pressure, cleaned (and moved to different holes)1-4 injectors(slight rust in screens), checked spark signal, checked injector signal and done a running and nonrunning compression check in #3 cyl(good, and similar to the ones next door). They don't know what is causing the lean condition miss. It used to come and go but steadily got worse. In the shop now for 3 weeks. Any ideas?

 

Welcome to the forum tonykart,

I've moved your question from General Tech Help to S-type forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Thanks Graham. I just posted a short bit on the New Member forum.
Gil

 

May be the wrong plugs? But... things to check
timing - have you changed the tensioners & guides?
fuel trims - what are they?

 

I did change the plugs to the same NGK that was in the car (NGK platinum 13.00 each). The old plugs looked good. Not over carboned even on cyc 3. We did a compresssion check and it was good, the engine sounds correct when cranking. No I haven't changed the tensioners yet and I don't think the previous owner did. The way the miss came on and got worse with time ,I don't think it is valve timing. Spark timing was checked and appears correct.
Gil

 

I don't know anything about fuel trims and need to research those. I thought they were set by the ECU and unchangeable. Maybe my trim for cyc 3 has gone walkabout?
Gil

 

OK I did some fuel trim research. Looks like they are left and right bank controlled,not per cylinder. Why would I only have a fault in cyl 3 if it was fuel trim? I will ask my pro to check all O2 sensors to confirm they are OK.

 

Here's another curious bit. My CEL strobed for a short time. If that means that too much unburned fuel is going to the cat, is that consistent with an indicated lean condition on cyl 3?

 

Come on Jag. I'm leaning on you to think outside the box as to this persistent miss. Not bad plugs, not bad coils, not bad injector, good compression, apparent good signal to coil and injector. Good rail pressure, new fuel filter. Clean spark plug tubes. Only cyl 3? Am working on fuel map.

 

Don't be silly. Go with the obvious. Any/all of what you've already been told.

 

I don't think it's something obvious, I think we've touched those bases.

 

Ignored some. Your call.

 

If your repair facility has the equipment to find vacuum leaks, such as by means of a smoke test, you can determine the cause of the lean condition. They should also check the fuel injector to that cylinder to see if it is functioning correctly.

DTC is P0303, not PO303. Are there any other DTCs stored in the system?

Do not operate the vehicle under any conditions that cause the MIL to flash as catalyst damage is occurring.

 

Sad but true, resources demand that some things be ignored so prioritized items can be investigated. Perhaps the fuel trims are involved,We'll be looking at those, the rest referenced in the string has been confirmed as OK. 3 Mechanics with combined fuel injected engine experience exceeding 50 years and 600.00 of diagnostics in a high tech shop tend to indicate this is not an obvious problem. Again, why would fuel trim affect just one cyl? Don't the trims control a whole bank?

 

Hi NB, yes they know leaks, they found none(nor have I). The injectors on the right bank were removed and sent to be cleaned and flow tested, They were reinstalled with the one from 3 going to number 1 cyl, the miss stayed in hole 3. There is one other code beside the 303 code, I don't know it's number but I was told it referenced the missfire as due to lean condition. I'll find out what that is and see if I can get my fuel trim numbers. The total time of flashing engine light is less than 30 seconds.

 

Fuel trim does indeed affect the cylinder bank and is used to determine if there is an over lean or over rich condition to that cylinder bank thereby narrowing the cylinders to be checked.

Are there any other DTCs other than P0303 stored?

 

doesn't that mean that cyls 1-4 would be affected by an incorrect fuel trim, not just cyc 3? Yes there is one more code, I'll get that soon as I can.

 

If there is misfire on one of the cylinders the exhaust contains oxigen that has not been used to burn the fuel in that cylinder. That is why the o2 sensor thinks the engine is running lean when in fact it does not.

 

My mechanic says that there is only the 303 code. He has checked the signal to the injector, it is correct. He says that the valve train is currently tight and by all indications is OK. The indication that it is lean is coming from an analyzer that he is using, not from a fault code

 

Fuel trims are close to 0 on left bank, 10% on right bank. ??