Hi All,

Quick head scratcher to see what you guys think. My 2010 xkr 5.0 s/c randomly started rough idling as soon as I started it up one morning after being stationary for 5 days. Thought might just need to be run for a bit so started my journey but nope: limp mode after 2mins driving at low revs. Whipped it back home and turned off. Left for rest of the day until I got back from work and started up again but no engine light and rough idle remained. Checked for codes and nothing current or stored. Took it to the garage a week later and engine light came on on the way there. When checking with their reader it showed a cylinder 2 misfire and misfire on startup below 1k revs. The garage put it down to either coil or injector. They replaced the coil but still rough idles and misfire still there. I cut my losses and avoided the Injector replacement (heavily priced quote too). Went to collect the car a week or so later and low and behold, no rough idle or misfire...permanent codes remain stored and can't delete these with my reader bit symptomatically - no rough idling! Any ideas why the problem has suddenly resolved on its own accord???

Thanks in advance :-)

 

What you describe are typical symptoms of a failing fuel injector on the AJ133S.

How many kilometres/miles on the vehicle?

What type of fuel is being used?

During the misfire event(s) does the MIL flash?

 

Hey thanks for getting back. There is just short of 120k miles on the clock. I only ever use 99 octane shell v power. The engine light comes on whenever it wants to be honest! Like I said it went off after it came on initially. Then came on again when I took it to the garage. Now taken it back from the garage today and no light and no rough idle at all!

 

If the injector is partially blocked, it can result in erratic performance.

In my experience, it's best to replace all four injectors on the same cylinder bank if one is beginning to fail due to the labour involved. If one is beginning to fail, the others are not far behind.

If the MIL begins to flash, shut off the engine as soon as possible because catalyst damage is occurring.

 

Thanks for the feedback! I'll keep it in mind. Probably leave it now until its back in the garage and see what their live data shows them and if they concur. If so will replace the entire bank 👍

 

Yes, this is a somewhat common problem, but still isolated to only a few. It's an easy repair, but still quite costly. It'll run maybe $1500-2500 depending what else you do "while you're there".

 

While the coil units and injectors are removed, it's also a good idea to replace the cam cover gasket and spark plug boss seals along with the spark plugs themselves.

If you haven't done so already, replace the heater pipe between the cylinder heads at the back of the engine as it's a known failure point. If either the water outlet under the front of the supercharger, or the heater pipe fail, catastrophic engine damage is the likely result.

 

After taking it to the mechanic, he has checked all live data and faults which shows there's nothing to suggest an injector fault. Instead he thinks it's an air fuel mix issue and there is a distinct rattling from the inlet manifold and he thinks the flap from this has come off and is giving this intermittent rough idle. Any thoughts on this?

 

Interesting... I've never heard of this in these cars. Anyone else?

 

Does your mechanic know about Direct Injectors? That's a whole new sport, not just ball game.
Open your oil filler cap and smell.... do you smell gasoline?

 

Find another shop.

 

Nothing too strong. Obviously doesnt smell of fresh oil its been in there for 9 months but I don't smell any strong stench of petrol.

 

What usually happens with the direct injectors is that one on either the right or left bank gets stuck open and pumps raw fuel 100% of the time, which douses that cylinder and also reduces the fuel pressure for the other three injectors on that side.
The feel is sort of like a V-8 trying to run on only one bank of cylinders, especially obvious when throttle is applied.

 

Ok so from what I'm getting from you guys is change the injectors 🤣

 

Not what I'm saying though. It MAY be one, but may be NOT one. I dunno. It's hard to diagnose from 2,400 miles distant. I'm just throwing out a possibility.

 

​​​​​​​of course! That's understandable. You can only go on what I'm saying subjectively. I guess the general consensus based on what I've described is that the injectors are a strong possibility as culprit for the issue.

 

That is correct.

 

I do believe the only codes that were thrown when my injector stuck open was "Misfire Cyl 3", "Misfire right bank" and "System Rich Right Bank" or some such thing.

 

Yes the stored codes in this case was misfire cylinder 2 or 3 (cant recall which one) and then a p0316 code.

 

Like @Cee Jay , the few times an injector was mis operating, I showed misfires.
And if you let it continue too long, you will enjoy clogged catalytic converters. Then you can replace those too.
And heed the advice from @NBCat , truly.