Hello everyone

I have a 96 VDP with 170K miles and it started missing bad, had to have it towed home, it appears the front bank is not firing, as the plugs get wet with gas. it will start and idle but only on the back 3 cylinders, I had put 6 new coils in the car a month earlier. So I assumed the new coils had fried the ECU. so I got another ECU, put some older original coils back in. same thing the front 3 cylinders are not working, I can disconnect the coils while running and it makes no difference. So, I know it may have taken out the 02 sensors, but it should still run, as it is getting gas ( the plugs are wet ) so even if the 02 sensors were shot, wouldn't the ECU shut down the injectors not the spark?

Thank you for your help

Darryl

 

Hi barchettaboy,

Your symptoms sound a lot like the ones dealt with in one of the longest forum threads in the history of forums:

X300 Mystery

Post 623 (out of 644!) suggests your first suspect may be the crankshaft position sensor (CKPS).

Cheers,

Don

 

I would check the tone wheel as it will start on all 6 cylinders but when the ecm does not see a valid signal from both reference marks ecm can shut down that bank as it does not know where tdc is.. same would happen if cam and crank out of sync.i had tdhat before on a crysler timing was out due too incorrect timing Mark on cam pully would not fire up disconnect cam sensor fired up..check for damage or slippage ..then crank sensor but crank sensors work or don't and if fail temp related I my experience as a technician.

 

Have you checked the wiring going to the coils to make sure they're getting a signal? If they are then you've got a few bad injectors. I'd work from that point back. It could also be a bad connection/corrosion at the ECM connection.

 

I did swap out a CKPS ( used ) that I had it did not help.

I did go look at the link you sent Don, that has to be the longest ( like you said ) but also the most depressing post I have ever seen. After what looked like a couple of years, the poster had a major bought of depression and had to quit on the car and eventually scrapped the car. That does not bowed well.

Like I said, I did replace the ECU which looked great ( no corrosion ) I have not checked to see if the front coils are getting 12 volts yet or checked the crank wheel.

I will let you know, but to be honest after reading that other post, I do not want to focus too much on this car, Luckily I have other Jags to use, and I did not pay much for it. I would hate to scrap it out, as it is a fairly nice car. But I am not going to let it break me.
I have customers cars that I need to be working on, that pay money ( Dino, Bentley and Lotus )

Darryl

 

Here's something you may want to look into.....I remembered reading something about the harmonic balancer slipping??? Maybe this could be the cause of your issue? I'm sure there are posts somewhere within the forum.

 

That's an interesting thought. I don't know if it's possible for a failing harmonic balancer to cause the engine timing to shift, because I believe the sensor timing ring is fixed to the core of the damper that is keyed to the crankshaft, so it cannot spin on the crank, unless the Woodruff key broke (not impossible). When the harmonic balancer failed on our '93, the end with the drive belt pulley could slip, but the timing ring never lost its proper orientation.

But it would still be worth ruling out. The most common symptom of harmonic balancer failure is a loud screeching sound at start up or sudden engine acceleration which prompts the outer part of the damper to slip in relationship to the inner part, causing a noise something like a loud slipping belt.

Have you had any symptoms like that, Darryl?

Cheers,

Don

 

I know all to well about failing harmonics, as some of you may remember, I also have an 95 XJR that had a long standing no start issue. That car stumped me for ( I am embarrassed to to admit 3-4 years ) What I found was the crank key had sheared and spun the harmonic balancer 100 degrees. What I also found when I took it off, was ( you are correct Don ) that the timing wheel is connected to the internal part of the balancer, that is keyed to the crank, so even if the rubber fails and spins it will not effect the timing. However mine had failed and a previous owner had welded the timing gear to the outer part of the damper because it was slipping. Which maybe would kinda work, but on the supercharged car especially, there is a hell of a load of that crank key, so it sheared that baby good. I will say that the key if very undersized for the load that is put on it on the XJR. I am suprized that there are not a lot more failers on the supercharged cars with the wimpy keys they used.

Darryl