2000 LS Issues

[schaebo]

I have a 2000 LS V6, with 105k mi., with a variety of perplexing issues. It misfires occasionally on cyl #1, always when warmed up, never cold. It runs very rough during the misfire, but then eventually levels out and runs just fine. The check engine light does not come on but it is working. Over the last 9 months, due to oil leaks and my washing the engine, all of the wires, plugs & coils have been replaced, along with the valve cover gaskets and oil pan gasket (not excatly cheap fixes, any of them). The cooling fan is also running very slowly, but if the power is hooked up directly to the hydraulic pump, it runs just fine. It only recently showed that it was running a bit hot via the guages or idiot light (only once or twice just above the mid-point on the guage for a very short period). The car is at my mechanics place now as it has been for a few days, but he is having difficulty diagnosing what all is wrong with the car. He seems to think maybe the head gasket is leaking a bit, but I have had no noticable loss of coolant. He also thinks that maybe the computer is faulty causing the cooling fan not to run properly. The car runs very well when cold, as long as you don't stop it. But when it is warmed up, and you have been stopped for 10 minutes or so and then restart it, that's when you get the rough idle (misfire), and even that only sometimes. I love the car and have owned it since it was new. It has been very well taken care of. I'm (we're) kind of lost on what to check next (fuel injectors, timing belt tensioners, O2 sensors, PCM, MAF, ?????)

Please help if you can shed some light on any of this.

 

[joegr]

There's no timing belt, so no timing belt tensioners. You do have timing chains, but the V6 doesn't seem to have much trouble with that.
I would also completely discount the leaking headgasket theory and look elsewhere.

For the rough running when hot, the first thing to check is the rubber elbow at the PCV valve. They are bad about collapsing (and splitting) when hot after they get old. This may also be the cause of the misfire (due to lean mixture).

The fan issue may be a PCM fault, or the wiring between the PCM and the solenoid. If the mechanic has an oscilloscope, it will be easy enough to see if the PCM is correctly PCM'ing the solenoid.

 

[schaebo]

Thanks Joe. I'll pass this along to my mechanic when I talk with him this afternoon. If you think of anything else to check, I would appreciate any additional thoughts. I'll also pass along any new information from him.

 

[schaebo]

My mechanic just reminded me that he changed the PVC connection hoses late last year (2011). He has a scope so he's going to check PCM / soleniod wiring. He says he still thinks that maybe there's a head gasket issue of some kind though. They've been running it around town today to warm it up, so that they can let it sit and then try to get it to misfire after start-up, but so far that has not resulted in any further misfiring. Let me know if you think of anything else and I'll pass it along.

 

[Lincolnls00arturo]

I have the same problem with the missfire here n there with no light on. I chage all coils n sparkplugs even tho they were new. I went to do the smog n it didnt pass. I dont now what to do, need help lol... My 00 ls is not given me no codes. At high rpm it runs like a champ, but on regular driving 55 to 60 mph it seems like is running with 7 pintons. if I floor the pedal it hasetates for a split second n it runns like a champ again. What to do? Any sugestions?

 

[schaebo]

My mechanic changed coil #1 (under warranty as it had been changed only a few months ago). Car will run fantastically for days, then it will suddenly overheat (it has never run above the halfway mark on the temp guage) at first only slightly, then all the way up to the 3/4 mark on the temp guage. Stays around there for 2 - 3 minutes, then comes back down to either normal or nearly so. During the high temp and sometimes afterwards, it runs very rough like its missing badly. Seems to happen more in warmer weather and only after the car is warmed up and restarted like when you've been on an errand. Next day, everything's great again. Very inconsistent, very sporatic. It also sometimes has a "gassy" smell coming through the inside vents, but only sometimes. And just to make things more confusing, the CEL comes on for a couple of days, then it goes off for a day or two. Right now, we're just continuing to drive it around town (but not out of town) to see if we can get it to hard fail, like fail and continue to do so rather than fixing itself.

Sounds like yours is a V8 though, where mine is a V6. Wish I could help you, but the LS issues are very perplexing until you finally find them. It is still a great car and I love mine. Good luck. Maybe Joe can shed some light; he's pretty good and well respected on this site.

 

[joegr]

The overheat problem is (unfortunately) not an uncommon one. You have one or more leaks in the cooling system (cracked plastic parts) that are letting air get into the system. You'll have to fix those and bleed all the air out.

Don't worry at all about the rough running when it over heats. It's supposed to do that. It has fail-safe cooling to reduce the amount of damage done to the engine. What it does is intentionally misfire (or not fire) each cylinder every other time (fuel is cut). This pumps air through the cylinder to cool it. Your six cylinder running as if it were a three cylinder will be rough.

You should fix the cooling system problem before you have head damage to deal with.

 

[schaebo]

Could this be why my mechanic said that he noticed white smoke coming out of the car one day when he was running it at the shop trying to get it to fail? He was thinking some kind of head gasket issue, but it only happend that one time, never again. I've been driving it almost every day (just around town) with no smoke issues, only the occasional overheat and then back to normal again.

 

[joegr]

Could this be why my mechanic said that he noticed white smoke coming out of the car one day when he was running it at the shop trying to get it to fail? He was thinking some kind of head gasket issue, but it only happend that one time, never again. I've been driving it almost every day (just around town) with no smoke issues, only the occasional overheat and then back to normal again.

Another problem that is not unheard of on the V6 is random oil leaks from the IMRC o-rings in the intake manifold. (This causes random smoke from under the hood.) I would suggest changing those o-rings out.

 

[schaebo]

I'll talk to him this afternoon. Would a cooling system pressure test show the cooling system leak(s). He tested the cooling system for carbons (it came up negative), but I don't know if he pressure tested the cooling system.

 

[joegr]

I'll talk to him this afternoon. Would a cooling system pressure test show the cooling system leak(s). He tested the cooling system for carbons (it came up negative), but I don't know if he pressure tested the cooling system.

Often, but not always. Sometimes the leaks only happen at specific pressure and temperature combinations. If you haven't replaced your degas bottle in the last three or four years, you need to. It will be cracked. All the old ones that I have seen have been. Other plastic parts should be suspect too. Either replace them or check them all very carefully for signs of dried coolant.

Have you tried bleeding the system? You should get some air out and the overheating should be resolved (until you let it cool off and restart it), but it will come back.

 

[schaebo]

Thanks Joe. I'll keep you posted.

 

[schaebo]

The Final Resolution

Well, finally after weeks of limping along using my LS only on short local trips where it ran great for awhile and then overheated by varying degrees, along with rough running, missing, etc., etc, etc., we decided to begin changing out the most likely/least expensive culprits in order until the problem went away. That led us first to the thermostat.
When my mechanic took the car out to test the new thermostat, it completely crapped out (overheated). After he let it cool down, he went back to the shop and found that the hydraulic fan unit had completely stopped running. Interestingly enough, this was the first thing that he looked at way back when, but the problem was so intermittent that the fan unit ran fine every time it was tested. Not to mention that the hydraulic fans tend to be VERY reliable, except of course for this one.
Anyway, the car is running fantastically now. NO problems, no issues, no overheating, no rough running. In fact the Lincoln parts guy mentioned (at time of purchase of the new fan unit and soleniod) that when the Lincolns begin to overheat, even just a bit, it affects the emissions controls and the cars "do some very funky things". Now he tells us.
But all is well now. The repair was very expensive ($1300), but well worth it in hind sight. I hope this information helps someone else out there who might be having similar issue(s). Good luck everyone and thanks for all of your suggestions and insights.