Hi and welcome back

Quick question: does your multimeter have a dedicated position for Hz - like mine - or is there a separate 'Hz' button? What make/model is the meter?

Sorry that's 2 questions.

 

This is the meter I'm using.

 

Auto range: that should work fine. Somewhat better than my $15 Amazon special...

I wonder if it might be easiest to check on the injectors first. Choose a cylinder we know is firing (so any of 1A 2B 3B 4A) and connect the meter +ve to the Black/not red) wire, -ve to ground.

With the ignition on & motor not running, you should read B+ with the meter on Volts. Start the motor and switch the meter to Hz. Do you get a steady reading now?

I had to probe around a little with the blunt needle in the back of the injector plug to get proper contact.

 

I see we are at it again.

Gus
JagRepair.com - Jaguar Repair Information Resource

 

I'll try this tomorrow. Thanks.

 

I had to take more time of than I was planning. Now I can get back to frustrating myself

 

I did a quick video to show what reading I was getting. This is injector 1A, key on, engine off.

 

Hi - it sounds like the engine is running?

Set to AC volts with the engine running I'd expect an inconsistent reading.

 

No, engine not running, just key on. Solid ground.

 

OK, perhaps I can hear the TB or some other background noise.

That wild variation doesn't make sense
The meter should strictly be on DC Volts, but that wouldn't explain the erratic readings. Switch it to DC just to make sure.

Can you get a stable display by moving the probe to the Brown/Red wire on the injector plug? I'd expect a steady B+ there.

What is the symbol on the very top left of the meter display?

 

The symbol on the top left shows it's in auto mode. I think I figured out that the auto mode was not going into the right setting. Using the range setting I was able to get a steady reading. I'll give the readings from all injectors.
1A- 3.6
2A- 0
3A- 3.1
4A- 3.1
1B- 3.1
2B- 3.1
3B- 3.1
4B- 0

 

Was this on the black/not red wire for each injector? I'd expect the full B+ on both injector plug wires with the motor not running:- not quite sure why it's reporting 3.1/3.6

If so, can you probe the black/red wire for the two reporting 0 to see if there's B+ there?

 

The meter should be on DC...
Poke the black lead into the little crevice in the springed hood latch where the hood/bonnet locks down. There is a spot where you can PIN the lead and leave it there so you have a ground and can use your other hand and move around... You have to find a good ground point.

Then, if you can, remove the connectors and take the readings from the connector contacts. You need to be seeing a solid steady battery voltage or youre doing something wrong.

 

So sorry, trying to do to many things at one time. The last set of numbers were with the engine running. I'll do it with just key on tomorrow.

 

No worries
We're trying to confirm that we can get a stable Hz reading from the meter.

To recap, we want to 'see' the injector firing approximately 5.75 times each second, and we know that the ones for 1A 2B 3B 4A are good since the car isn't reporting any codes for those cylinders.

With the ignition on, motor not running, I'd expect to see B+ or around 12V DC on both the black/red and black/not red wire on an injector. Choose one of the above working cylinders, and place the meter probe at the black/not red injector connection. You should see B+.

Now switch the meter to 'Hz', start the engine and note the meter reading.


If you don't see B+ on the black/not red wire in the first step, move the probe to the black/red wire and check for B+ again (meter on DC volts). This should confirm whether or not the injector is receiving power.

 

How about just swapping the injectors from the suspect cylinders around? See if the problem follows the injectors.

edit:

I plowed though some of the original posts and did find the injectors were replaced.

The problem arose with coil replacement and now three cylinders show consistently misfire and a couple others occasionally. Since injectors, coils, plugs, ECM and even harness have been replaced, about the only two original items remaining are the engine and chassis. The resistance from the coils joint grounding point is 0.1 Ohms, What is the resistance from that lug to the battery ground? I have added ground wires on engines and chassis that did resolve problems numerous times. You might take a few minutes out to wire brush that lug and terminal then add a temporary ground wire from that ground lug directly to the battery terminal.

 

Wiring harness replaced. Did that include the injector and coil harnesses, too?

 

So as not to complicate things, I'm working on only injector 1A, right side first cylinder. Key on, I get 12v on both black/not red, and black/red. Switch the multimeter to Hz, engine on, I get no reading. The probe is working because I get 12v with key on, engine off, as well as engine on.

 

Yes - hence the snips from the 1999 EG rather than 2000. Jaguar likes to keep us on our toes by shuffling wiring colours around

I couldn't find any 'banana skins' where Jaguar had changed the pin-to-pin wiring between the two years.

We are trying to establish whether the injectors on the 'bad' cylinders are firing. One of the default actions taken by the ECM when P035x codes are thrown is to inhibit injector firing for that cylinder. My take there is that if the ECM can't detect a sucessful spark, it will shut off the injector to the offending cylinder to prevent raw fuel being dumped out the exhaust and into the cat.

The codes indicate a coil or spark feedback issue, yet moving the coils around makes no difference. The grouping of the three failing cylinders suggests to me that there is a problem with the spark 'OK' signals getting back to the ECM (or, for some reason, the ECM isn't responding properly) since they are aggregated into two groups of four:- two from each bank per group.

 

Sounds like you're doing everything right. I'd expect 12V on both wires to the injector except for when it is actually firing. Why won't the meter detect the 'fire' signal on the black/blue wire. 1A is one of the good cylinders - at least, the car isn't throwing a P0351 code for it?