Hi everyone, just wondering if any of you have encountered a situation where your car gets hiccoughs (I assume it's a misfire) at idle. It seems to happen intermittently, only when warm, and tends to go away if I put the car in neutral when idling (though not always). The car pulls away cleanly and the hiccoughs disappear when driving. It seems to get more noticable when I've been pottering through the daily traffic, and if I get the chance to give the car some real welly through the gears it seems to go away for a day. Any ideas? Thanks!

 

Do you have a scanner? It sounds like a coil collapsing, but it depends on if it is a random or consistent misfire. If it's random, it could be any number of things. If it's always on the same cylinder it is likely a coil or even just a spark plug. A scan might lead you right to the problem. It might be easy, or it might be a nightmare! Start with the easy stuff first. Pull the plugs then go from there. Note the condition of each cylinder's spark plug. They should all look about the same. A bit more detail on maintenance and history would also help a lot.

Cheers!

 

I have the same problem. She is smooth as butter cold and when the car warms up a get a slight miss. I'm guessing either fuel injector or coil. The have changed the plugs twice and still the same. I don't think these car detect misfires that well. So far no codes for me yet.

 

I'm leaning towards an injector problem.

If nothing concrete comes of your checks I'd had the injectors professionally cleaned and see what happens.

FWIW, every time I've had injectors professionally cleaned on *any* car I've noticed an improvement in idle quality.

Cheers
DD

 

Turftech, Drew, Doug, thanks for your comments. The car is probably way over-serviced - I only do about 8,500 Km p.a. and it's serviced twice a year by a Jaguar mechanic. The plugs were all changed about 2,500 Km/3 months ago but I'll whip them out and have a look and see if they are all consistent in colour. Since I had a slight trace of the same problem before the last service (and no codes came up) I suspect you may be on to something with a coil or an injector issue. I had a much more severe version of the problem with my wife's old P**g**t a couple of years ago and that turned out to be a failed coil (also a coil per plug on that Pug's V6 motor) - I didn't think of that first up as this is so much milder, a bit random and only affects the engine when idling warm. The Pug was spluttering and losing power (and belching fumes) whereas the Jag runs perfectly as ever except when idling. My car has only just clicked over 72,000 Km (~45,000 miles) as I drove to work today, so has very modest mileage for its 13 years. I don't have a scanner myself so if I can't identify anything on any one cylinder from the plugs I'll have to take it to the workshop. I hate intermittent faults - they are so hard - and therefore cost a fortune - to pin down, even if the ultimate solution tends to be something cheap and simple to fix!

Thanks again guys.

 

lol The aj16 leaves little behind in redundancy. Tends to make it persnickety! You will feel any and all imperfections no matter how slight. I would also have someone "sniff" the coolant for hydrocarbons; just in case. It may just be that it is getting a bit "unbalanced" as it ages? Tends to thump on the weakest cylinder? Who knows... I have also noticed that this engine loves quality high octane fuel! Hard to know what you get these days. It might also be revealing to watch the O2 sensors outputs on the fly. Maybe your garage can do a road test at the next service?

Hope you get a handle on it!

 

I'm isn't constant and only when warm. That's what leads me to believe it's a coil. Heat is bad for eletrical components and the coil will swell slightly from heat and cause a issue in the core winding or connections. A clogged or stuck open fuel injector will usually be a constant miss. Unless the clog or impurity is small enough that during warm up fuel passes because of the fatter fuel curve(choke), but should return when at temp. I have learned over the years that you need to classify issues, it reduces possible solutions. For engine....it's one of 3 things 1. fuel 2. ignition 3. compression. For all others, I think about if the issue is a mechanical failure or eletrical failure. A mechanical failure is USUALLY constant while electrical can be intromittent. This works under the 80/20 rule.

 

Coil is a good guess. When you pull the plugs, inspect for oil on them. The spark plug boss seals leak and allow oil in the holes. The oil can cause a misfire.