Tryingtofixit

Hello!

I'm a newbie to this forum. Thanks for being out there to help. This is a bit of a story, so please hang with me.

Bought a 2000 V6, 154K, about a year ago. The check engine light came on shortly after I bought it (or course!) Showed a misfire on number 1. I've changed plugs, put in new wires, new coil pack, carbon clean out, replaced the little hose on top of the fuel tank cuz my mech says the OBD showed an issue with it. All these were done cuz the code kept popping up.

NOW...here's the kicker...after the hose was replaced, it ran for about 15 miles and the check engine light came on again and I felt a real miss. Brought it in and the mech now says it needs a valve job. Some diagnostic tool shows a burned valve. $1500.

NOW! Here's the real KICKER...yesterday, after being parked for an hour, it didn't need the alarm to be disarmed to start. Just turned the key and it started! AND, the check engine light was no longer lit and the engine ran like a dream! No miss, no stutter!*************

SO, I'm think that the whole issue has been in some electrical interaction between the alarm system and the ignition system. Does that make sense?

Any thoughts, hints, experience with this? I'm liking driving the car (convertible in Southern Utah) but this is driving me nuts and I don't want to do a valve job, especially if the issue is electrical.

Help, please! Thanks.

PNYXPRESS

What were the codes being shown? Also I would be curious to know what sort of "tool" can show it needs a valve job with out pulling the heads off.

Tryingtofixit

Thanks for getting back to me. I'm not sure of the code numbers. They showed a misfire on # 1 though

The "tool" he used he describes as a "transducer" that threads into the spark plug hole and takes supper accurate readings of pressure inside the cylinder so he can see on a screen when the valves open and close and what happens to the compression. He says it shows a slight leak in a valve (intake, I think).

I didn't get the name of the instrument, but he says that not a lot of people have them.

Now, today, the check engine light didn't go on when I turned on the ignition, so I'm think that there might be a problem with the light itself. The engine is still running smoothly.

I've got an aftermarket anti theft system. Don't know why the prior owner installed it. I think I'll have it pulled out and hook up the original again if possible or just deactivate it. Thoughts?

Thanks

PNYXPRESS

There is no way a pressure sensor can tell you how the compression is leaking out. As there are three possible ways: intake valve, exhaust valve, or rings.

If there is a misfire on cyl 1 and that is also the cyl that he says needs new valves then I would guess that there is just a carbon build up on the valve and it should clear it self if the motor no longer runs rough.

TfcCDR

The mechanic's ATM.

If the numbers aren't high enough, someone needs a valve job.

Actually, a boroscope can show you burned valves, but it sounds to me like the ATM was the primary diagnostic tool in use here.

TfcCDR

I think I'd give it at least a month before doing anything, to see what happens. If the problem stays away, then I would check into the alarm system to see if it's related.

The transducer will show when valves open, but if there's a leak, it can't say whether the leak is a valve, bad rings, head gasket or even a cracked cylinder head. Even if it's a leaky valve, it can't tell you if the valve is burned or if the valve is bent or the spring is weak.

A leaky valve WILL NOT cause a misfiring spark plug. This is an electrical or electromechanical fault. All a leak can do is reduce compression on that cylinder.

The one exception to the do-nothing-for-a-month rule is to give it a thorough treatment with Seafoam. You can get this at Walmart. Get two cans, use one for the treatment and then put the other in the gas tank at your next fill-up. If, as PNY suggests, it's a carbon build-up, Seafoam will probably solve the problem.

Tryingtofixit

Thanks for the advice. I've done the "professional" carbon treatment where they have a machine that pumps cans of two different cleaners into the intake system. I didn't notice much difference.

I'm holding off on the valve job, for sure.

How much of a hassle is it to replace the "check engine" light. Mine isn't coming on when I turn on the ignition. At least at the moment. Maybe tomorrow it'll work again!

Thanks again for you help.