I'm with Greg on that misfire, that is soooo Un-Jaguar, and even more so with a V12.

Based on all sorts of what I have read whilst cleaning up last nights mini flood, are an injector being intermitant. Definately in the RH side, so a choice of 6.

My PreHE did similar, and armed with a SFH (Small F........ Hammer), I simply tapped away with the engine running, on the metal section of each injector, FIXED.

That iffy EFI loom section is really worth looking at. But, having said that, the injectors are in groups of 3, and you dont have 3 cylinders out, thats for sure.

I know you have tested it to annoyance, but a flaky TPS will reek havoc. I know they can be fiddly to set at that 0.34v mark, but not that bad. Only ones I have issues setiing up are flaky ones. BUT, again it will NOT cause a misfire on one cylinder.

The V12 is not happy with too much idling, as Greg mentiond, it is designed to be driven, and thrives on it. The "cotton wool" V12's are usually the worst running, in my years with them.

 

This question gives me pause. When pulling the exhaust to clear out the melted cats I noted that the downpipes joint olives were deteriorated. I ordered new ones to replace them with but have not installed them yet. Are you thinking this could be related? Using a pipe to listen, I don't note any leaks at the junction.

Reset TPS and drop the downpipes today? Well, it's been thoroughly fun working on her the last couple days and it needs doing. I'm being sincere too. It HAS been quite fun working on the Jag. Fall weather in winter, engine is so much more accessible than when I got it, the work is actually making her run better, and several times a day I "have to" go for a test drive! All very enjoyable.

 

I'm having the exact same issue on my '88 Lucas V12. I have sorted almost everything except for the vac capsule, coils, O2 sensors, and cats. My misfire seems random since I can't even pin it to a specific bank. I'm wondering if Greg is on to something with the vac capsule. It's the only item in the list that makes sense (in your case since I haven't swapped my O2 sensors yet) considering the conditions.

My vac capsule won't hold a vacuum. However, I'm not certain it's stuffed. I remember The Great Palm saying the later Lucas vac capsules had a small orifice in the diaphragm and wouldn't hold a vacuum. Have you tested your vac capsule?

 

It is stuffed. Change it, obviously, but in itself it will not cause it unless, the many pipes that form part of the system are iffy. That is why a single pipe direct from under B bank throttle body to the capsule is so important, ensuring all the rest are blocked off.
Greg

 

Greg, I'm assuming either banks lower vac tap will suffice. I have dual vac gauges so I can test and see for myself, but can you explain the differences / behavior of the upper and lower vacuum taps on the TBs?

 

I'm guessing "cotton wool" means "coddled"?

I'll be setting the TPS and tapping the injectors shortly. Thanks for the suggestions! Hope the flood waters have receded.

 

I honestly do not really understand, but it is something to do with one being a throttle butterfly edge tapping and the other some other sort of tapping. What is require is a tapping that shows full manifold vac, throttles closed, and responds immediately to throttle butterfly changes. The one under the A bank happens to work is all I can be sure of. Under B bank, if the same as under A, would be just as good.
Greg

 

Ordered a DAC6093. I am suspicious of those coils.

Ok, So I have a new set of NGK BPR6EFSs in. Better! Still missing. TPS set to .326V. Seems steady! Much better! Still missing. Rapped on all the injectors. Yo. Better again! That actually did make a difference. May look at getting a couple new to swap out for testing.

Ran a bit poorly this way, but it didn't alter the missing.

Then I pulled info on properly setting the ECU Idle adjustment. I warmed the car thoroughly, pulled the "Closed loop" jumper and metered the voltage on the Feedback Monitor Socket. Both sides agreed that it was 1.88-1.90V. Not what I was looking for.

I tried adjusting the ECU in both directions, giving it several minutes to adapt. The voltage never varied.

Anyone know what that means? New O2 sensors needed?

 

A vacuum tap ahead/upstream of the throttle blade is exposed to vacuum whenever the throttle is opened. This is often referred to as "ported vacuum".

A vacuum port behind/downstream of the throttle blade is exposed to vacuum at all times. Often referred to as "Direct vacuum" or simply "Manifold Vacuum".

For vacuum advance system you'd typically use ported vacuum. If you use direct manifold vacuum you'd end up with all that advance coming in at idle !

An exception might be engines with vacuum *retard* systems as some engines have...including earlier Jags....but that's a different matter and not pertinent to the HE V12.

Cheers
DD

 

When cold the ECU is providing "cold fueling"....enriched mixture...thanks to signaling from the coolant temp sensor.

To me this suggests a cylinder or two...or maybe a few?....running slightly lean. The lean condition is temporarily masked by the rich fuel mixture when cold.

Personally I would very strongly suspect some injectors not operating up-to-par. Incorrect/weak/blocked flow, poor spray pattern, or, not responding to properly when minimum pulse width ("on time") is called for....as would occur at idle. Again, the forced enrichment when cold masks these faults.

I would suggest having the injectors professionally tested and serviced. A good outfit, such a Jaguar Fuel Injector Service, will test and measure all the injectors and identify any that are out of spec or, even within spec, are too far out of range when compared to the others.

I have injectors cleaned on numerous cars and it has always greatly improved the running

Cheers
DD

 

Now you're getting somewhere !

As you please, but swapping out injectors isn't a 10 minute thing, as you know. No need for new ones. Personally I'd have ALL of them professionally serviced and be done with it. Do it all, do it once, minimize the torment of alá carte fussing ! Just my opinion.

Cheers
DD

 

My interpretation is that the O2 sensors are dead. They DO eventually degrade.....sometimes to the point of simply not responding at all.

When running in open loop did the misfire go away? I wouldn't really expect it to, but....?

In most HE V12 configurations the system is designed to run in open loop whenever the transmission is in "P" or "N". Does the misfire change when in "Drive" as opposed to "P" or "N"? just wondering

Cheers
DD

 

In my experience the timing but be grossly over-advanced to cause an idle misfire


If the base timing was originally retarded, and your "memory reset" inadvertently advanced the timing, you would feel quite an improvement, yes!

Cheers
DD

 

Doug,

No difference in drive, park or neutral or even with closed loop link pulled except engine speed. Always has the miss.

Now, it is greatly imporoved and lessened by recent changes. But still present.

Big news! 40 minute surface road regular route saw fuel mileage jump from 11 to over 14!!! And I was really driving it pretty hard. This is a change I can really appreciate!

 

Well done.

Off air last night, ADSL out country wide.

That hammer fix indicates crappy injectors due to fuel residue. COMMON.

Doug is spot on about cleaning. Or, a good heavy dose of Injector CLeaner works for me. Drive it, and I mean DRIVE IT like ya stole it, works also for me.

A V12 that is treated like a baby os a SAD V12.

O2 sensors are a service item, and 160,000kms (100,000 miles) is the suggested time, HOWEVER, this an advice of late from NTK, Bosch, and is directly related to the newer cars where the O2 sensor is part of the PRIME fuel setting system, and ours are NOT, they are basically a "trimmer".

 

I follow your logic but I don't think I agree with your diagnosis here.

When I first start her she runs perfect. Absolutely perfect. No misses. Just smooth purring.

Within one minute she will miss once and continue purring. Then two, two more then the regular irregular missing sets in for good.

To me that rules out the injectors. They can fire just fine at idle. Given, it is slightly enriched. But one minute is not long enough for the in Enrichment to end. I really do suspect the coil. I think that cold it can spark those plugs consistently. Even slightly warm it can't.

Given the cost and labor involved I'm going to wait for my new Jag coil to come in and see if it resolves this.

I will order O2 sensors.

 

You're probably right, given that the problem occurs after just one minute.

Your original post said "I have a miss that happens when Jessie warms up...." which I interpreted as after having reached normal running temperature



Makes sense to me!

Cheers
DD

 

10 points to Doug and Grant.

Timing grossly advanced.

Miss is all but gone after etarding timing significantly. My concern now is that perhaps the centrifugal advance is not operating properly. It moves freely and snaps back smartly. But grossly advanced caused no knock. Timing was set by driving it and advancing until heavy load up an incline did not produce valve noise. I will put the gun on it at 3000 RPM tomorrow and seeps far I am & was off. Power is down only marginally from the advanced position. Curious.

New Jaguar single coil arrived today. I'll do the timing and test before installing it.

 

Most detonation can never be heard, that's a very poor way of setting the timing.

There are only 2 ways of detecting detonation events: 1. Having a sensor that can detect vibrations at the particular frequency that detonation occurs at in a particular engine family - this is a production knock sensor; or 2. A device that can measure the instantaneous change in crankshaft angular velocity. This is partly how an engine maker can determine what frequency detonation occurs at, as each engine will have a unique frequency. Thus you can't use an AJ16 system on a V12 for instance, as the critical frequency is different..

 

I don't claim to be a certified anything. But I can hear even subtle pinking. Tiny light little things. And this method is definately not a modern tech-savvy solution, but it's been a staple of shade tree mechanics since forever.

The gun will resolve the questions I have.

One thing is for sure, all these individual fixes have done a world of good for Jessie.



City miles.

US Gallons