Help! My v12 seems a farm tractor
 

Hello!

I've done valve cover gasket job and spark plugs job (new plugs: NGK br7ef).

Today I reassemble the engine, connect all the hoses and plugs and turn it on... HORRIBLE: the engine makes an incredible scrap sound: it almost splits my ears... it recalls a farm tractor or a two stroke engine...

The exhaust gas, then, smells terrible of CO2.

The idle is crazy: it grows from 800 to 1800 in ten seconds without touching the gas.

I turn off the engine and try again but it's the same story.

I can't misunderstood the spar plugs: I've done the job one plug after the other!

What have I done?

Where can I see for healing my poor engine that, before my "jobs", ran smooth?

Thanks and sorry to bother you!

Anything caught in the cooling fan?

Did you have the distributor cap off? if so, is it correctly/securely reinstalled?

Next...and I really hate to mention this....did you drop anything into the engine while the intake manifolds were removed?




Perhaps the fuel injector harness is shorting/grounding out due to damaged/frayed wires? This would make the injectors stay open and cause over-fueling.

Are the fuel pressure regulator vacuum hoses in place?




You have an air leak somewhere.




I'd begin by *very slowly and carefully* inspecting all the work you've just done. You'll probably find where the problem is this way.

As for the engine noise, well, IF you dropped something into the engine, it might be too late. You *could* remove the intake manifolds and look inside. Maybe you'll find something ....

On a happier note, an engine that is very badly misfiring and/or has major fueling problems can sound horrible...so maybe if you find the *running* problem the horrible noise will go away

Good Luck

DD

You are NOT a bother! Thats what we are here for!
Are you certain you put the plug wires back correctly? The idle sounds like you have a vaccume leak somewhere.
The scraping sound is concerning. Others will chime in!

Hi!
Thanks all!
The fan is ok and I didn't touch the distributor
I removed the intake manifolds and there's nothing inside.
The valves body and stem are straight and in place.
I checked the plug wires diagram with the one in this page:
http://www.reopus.co.uk/Original%20Wiring%20XJ12.html
My wires are all in place.
I forgot to tell you that I removed the air pump, the air rail and plugged the holes in the manifolds.
I removed the spark plug on the 1A plug and it's ok... must I remove all the plugs to inspect them?
Any idea on what can I check now?
How can I check if there're sparks in the plugs, in there's a prblem in the distributor or if the fuel inj. work properly?
Thanks!!!

Double check your leads and firing order, did you seal the holes from where the air pump are tubes go in properly?, also a simply thing check to see that your leads are set properly and making contact with the plugs, I just changed my leads and these new ones where buggers to get on, I had to push the the lead through the boot and connect it, or it wouldn't engage properly.
If it was working fine before and not now its got to be something simple. I have also heard that the V12 is fussy on what plugs it uses are they the recommended plug?

Hi guys!

Today I reassembled the engine and.... PUOFFFF it starts and runs smooth without noises!!!!

I don't know what the noise was or what I've mistaken but now the engine is ok... and I'm happy!

Time for oil change....

Thanks!!!

Great news ! :)


Cheers
DD

My 88 XJ-S ran horribly when the auxillary air valve was adjusted for too low air, it would rev up, then almost stall, and when I adjusted it that solved the problem...
I hopd that's all there is to your problem, I would not wish an engine rebuild on anyone unless they $20,000 in the bank to burn!