Welcome to the Cadillac XLR Forums!

Coil and spark plugs recommendation


Seasoned Member
Jul 7, 2017
My XLR/V(s)
2004 Thunder Gray
Hi folks,

after sitting for about 3 months during winter I startet my 04 diva yesterday
and ... rough idling. Looks like misfires I thought and plugged in the Tech2.

And yes, but only P0300, no specific cylinder and strange U0101 / U1024 codes
about losing communication to TCM.
I'm wondering why no specific cylinder is marked.

As these are still original spark plugs and coils (30k miles) I thought I would put in new ones first of all.

What was your experience? Go ACDelco or better NGK, Bosch etc?

That's a good hint, I will look after. Should I get new seals for the intake too?

I hope it's not the injectors or even worse a loss of compression.
Thanks, I have the repair manual and think I will find it.

Did you have the same issues and it was the intake ?
yes .I work on several cars and the loose manifold is a known problem and throws a couple of codes . I am just in the habit if I am under the hood on and 04/05 and know I have not worked on it before I just check the bolts to start with. Remember the setting is inch pounds
Ok I will try this today or tomorrow. Thanks.
In my manual it is "Nm" and says 10 Nm.

That would be an easy fix.

I'm a little bit afraid of a worn injector that keeps on dripping fuel into the cylinder.
A friend of mine bursted his engine that way (not a XLR or Northstar)
Hi Sammy, My intake loosens itself from time to time, easy to properly torque. Careful to not over tighten, plastics are unforgiving. If your X was good before storing, rather than suspect ignition I would suspect Critters. Your description sounds like damaged wires, shorted or open circuit will create those codes. Remove the engine cover a look closely for any signs of invaders. I didn't have to look far, he chewed thru my Brake Master cylinder, Overflow Rad cap, Windshield washer cap, corner of the air induction near the MAF and various wires. Codes galore. If you do replace parts, I suggest ACDelco all the way, keep your GM Car all GM.
Yes thought about that, but my garage is really closed.
I will take a closer look these days.
Thanks for advice.

Worst case would be a compression loss - but never heard of this on a XLR.
Ok finally weather and time was right to look after my XLR.

Things seem even worse.
First of all: no invaders, bolts on intake were fine - although it's not possible to check
torque on every screw I checked it with a small wrench that fit into the tiny places.
Spark plugs fine, coils fine.

BUT: As I registered a drop of oil coming out of the cables coming from VVT solenoids / magnets I pulled all plugs and connectors and there is oil everywhere.
I know this is a common problem with Mercedes but never heard of it on Cadillacs.

Looks like a mess that will cost me a lot of money?!

valve cover gaskets are not real hard to replace plus the oil leak on the vvt is pretty command not expensive or hard to replace .they usually throw a code if the oil leaks bad enough to short them.
No oil leaks on valve covers, but oil in every cable of 4 VVTs.
U0101 / U1024 codes about losing communication to TCM - I think thats because of the oil.
But how to drain it all cables?
It moved far upwards under intake manifold, maybe moved into ECM.

Cadillac XLR Forums

Not a member?  Join now!  It's Free!

Learn more about Supporting Membership

Win 2 Supercharged Cadillacs!

Win both supercharged Cadillac Vs!

Supporting Vendors

Taput Tunning LLC

Top Hydraulics

Cadillac XLR Registry

Click here to enter the official Cadillac XLR and XLR-V Registry
Top Bottom