2003 X-Type is either misfiring or has an intermittent fuel injector problem. Occurs at low RPM under a load but has been doing it for 4 months without throwing a code. Getting to be a real nuisance, any ideas?

 

I hope you get a reply to this. I've experienced the same thing and I've gone as far as replacing plugs, coils, upper plenum gaskets, IMT Gaskets, Crank Sensor, Fuel Filter, MAP and MAF sensors. It helped a lot, but the sense of sputtering or misfiring underload is still there. I'm curious what you find out. It didn't occur to me it could be an injector.

 

You don't mention checking the air inlet trunking for splits between the MAF and the Throttle Body. Same check for the underside of the crankcase breather pipe from front cam box cover to inlet manifold.

 

Ah, yes, I forgot that. That breather hose has indeed been replaced with the ribbed version as well.

 

I just realized you mention the articulating vent hose between the MAF and TB. Thought you were talking about the breather hose. I'll double check that.

 

It never does it at or above 2000rpm, all the hoses seem good. I am now getting a code P0420 occassionally. I am at my wits end with this car, it is a beautiful black car with a classy front end but it frustrates me.

 

I replaced the 6 upper oval seals on my intake manifold, and the misfire returned a few months later. Only then did I find out that there are 6 oval seals further below; I changed these and have no problems in last 2 years - now at 305,000 km = 190,000 miles.

 

Rjcl004, a P0420 generally indicates that the catalyst system for bank 1 is not operating within factory thresholds. Since it is intermittent I tend to agree with John that it is possibly your lower manifold gaskets or you have a vacuum leak in the intake manifold area causing the slight misfires an error code. Bank 1 is the firewall side of the engine. A bad injector or leaky injector can cause a P0420 code as well as it could also be your 02 sensors or a bad cat converter, but the latter would be more contingent on how many miles you have on your Jag. I think you should dig around the Intake area for leaks and/or replace the lower manifold gaskets.

 

How can i check the injectors, there are no codes other than P0420 and it comes and goes. It will likely show up again on the day I take it in for emissions testing. It just rolled over 100,000 miles, I have put the last 13k on it. I know how to get the top cylinder o-rings replaced as I have replaced the plugs and one coil on the back side.How difficult are the bottom ones? Where should I get them and about how much are they? Anything else I should replace while I am in that deep? Thanks!!!!!

 

I've not actually replaced my lower plenum gaskets. I believe the lower manifold is secured to the block by bolts so I haven't had to. If I'm wrong about that, then so far I've been lucky in not having to do it. There's probably a less expensive option, but I bought my set of upper and lower gaskets off of Amazon. Here's a link.


As for checking the Injectors, someone else will have to chime in on that. I haven't had to do it, I don't know how to do it, and I haven't read a 'How to' on it yet. I'd say search the forum. I'm sure it's here.

You say you've replaced the plugs and reported bad coil, did you make sure to gap the plug properly and what plugs did you go with? When I replaced my plugs I was told that the splitfires and other plugs with dual prongs were problematic. I went with NGK Laser Iridium and gaped them at .052 which was exactly within the recommended tolerance.

In response to your last question of whether there is anything else you should replace. There's a write up or thread on the forum about replacing the O2 sensor(s) on Bank 1 while you have the manifold off. I don't know if it was just the Upstream, Downstream or both but it might be of some use. Here's are links to the O2 sensors you'd need.

(Upstream)
(Downstream)

 

I looked at post about a misfire and most things had been checked from induction air leeks to ignition components.
This got me thinking about a car I had that would though up a fuel mixture code on warm up.
The long term shrift of the fuel mixture was not good. The reason for all my trouble was a hair line crack in the exhaust near the cat. The Lambda sensor pre cat and after cat new there was a problem. It all so easy when you find the fault.
I would be looking again at diagnostic for fuel trim with your misfire. The engine temp sensor, Lambda sensors are important to fuel trim any exhaust system manifold needs to be good.