I cranked up the car today, and a few (7ish) seconds after it started, the RPMs dipped down to 0, then went abruptly back up to 900. Then it happened again. What on earth is this, its a bit worrying.

It didn't die, but it wasnt running correctly. It drove allright about 1 mile and havent started it since. No warning lights or anything. The engine was 1 line above "C" on the temp gauge.

 

Is your battery weak? After I disconnect and the reconnect my battery, my rpm dips to about 350 rpm before it picks back up to a normal idle. It feels like it will stall in the process but it doesn't.

 

How long has it sat, unused, or at least without a good, long drive?

 

Well, about 50 miles a week of highway driving is what I do, plus the odd 50 on surface streets... Monday I went 30 miles round trip on the highway, and then last friday 40 miles highway to the dealer, so it's been nice and warmed up plenty. I wouldn't let a Jag just sit there dis-used. I know what goes wrong when you leave a car and never drive it. I haven't driven it since the near-stall, I don't know what to think. Maybe it won't happen again.

Side-note, the car just passed 50,000 miles and seems to have opened up a treasure-trove of small issues. Maybe a lot of routine maintenance is in order (and it's had oil changed, 4k ago Mobil1 Synth.)

 

Just wait until you break 100k miles. You will be greeted with many surprises! Some with a price tag that includes a comma.


Have you read the codes/pending codes if there are any? Are you worried its a timing chain issue? Have they been changed? Is a 2002 at risk for the timing chain issue?

 

PO172, Po175. I drove the car today, and got the same old codes... she's going back to the Jaguar dealership monday. They replaced an MAF for the same problem 7 days ago. The timing chain is not an issue I don't think is prevalent on a 2002. Tensioners, maybe, but I'm not looking at replacing those anytime.

 

I meant the tensioners. The timing chain by itself wasnt a problem on any of the years. I wouldn't think driving while running rich in the short term would cause a problem. If it is misfiring, however, then you could cause damage.

Are you paying full price at the dealer or do you have a warranty/hook up? I want to know how much they are charging. Its $140/hr near me.

My car was running lean with misfires and restricted performance. The issue went away when a missing coil cover screw was replaced. It makes no sense that this cured it.

Maybe an oxygen sensor, MAF or leaking injector is the problem?

 

I would clean the throttle body/butterfly valve with spray cleaner and the part load breather tube orifice before I took it anywhere. Clean the area where the valve meets the throttle body. Gunk elsewhere is only an appearance item.

$3 vs $300+.

The part load breather tube can be found on a search.

 

The dealer said the MAF was the prob, paid 80 for a diagnostic so if the MAF was wrong, they should eat the MAF cost not me. I am paying normal rates, but its only 100/hr here. The throttle body looks clean btw. Its not misfiring, so I'm fine driving it until monday.

 

Sure it does. The coil was not staying completely seated on the plug. The spring contact is quite tiny.

 

Would that cause it to run lean too?

 

Maybe ... indirectly.

The unburned fuel is seen by your O2 sensors, the ECM will then (probably) try to trim back the whole bank if not the whole engine. If it does that, then yes, it will go lean because of the attempted compensation.

Someone else may chime in and say this is all wrong.