My 2000 LS has been diagnosed with two very different problems from three different mechanics and I need help figuring out what to do. You should know the car has 149K miles, a new rebuilt trans a month old, a slight knock and a rough idle. I thought it was the notorious coils. The first mechanic told me I need a new engine, I declined the work and went for a second opinion. The second mechanic told me diagnostics came up with four bad coils. I opted for that and had them replace them. The car came out the same way I drove it in, the mechanic told me I need a new computer because there is no power going into four of the coils or one side of the engine which tells him there is a problem with the computer. He suggested I take it to the dealer to check the computer. So I did, the dealer hesitated to just check the computer so they did a full diagnostic for engine and electrical. Their diagnosis came back with needing a new engine, internal mechanical, faulty with cylinders, timing chain failed. I went back to the mechanic who diagnosed the computer problem and he insists its the computer. Please help advice what route to take or whether one or the other is steering me wrong. Is it possible for the computer to get fried and not send signals to four coils? Should I just replace the whole engine, even if that may not be the problem, the car other than a rough idle and a slight knock seems to be running fine.
Calling all LS mechanics
- Thread starter rrrick
- Start date
nearlyhalfamile
Active LVC Member
What engine???
It could easily be that the timing chain tensioner failed, at least briefly, causing the chain to jump a tooth. This would cause the engine to have a rough idle, make a knocking sound, but also drive ok and rev fine. It would probably also make the computer think that a couple coils have gone bad on that cylinder band because of the misfire because the cam timing is off.
However, it could also be a computer related problem or with the wiring, or the plugs, or maybe even a fuel problem.
It could easily be that the timing chain tensioner failed, at least briefly, causing the chain to jump a tooth. This would cause the engine to have a rough idle, make a knocking sound, but also drive ok and rev fine. It would probably also make the computer think that a couple coils have gone bad on that cylinder band because of the misfire because the cam timing is off.
However, it could also be a computer related problem or with the wiring, or the plugs, or maybe even a fuel problem.
97stscaddy
Dedicated LVC Member
I think you might be looking at a jumped timing chain. You'll probably have to remove the valve covers and check the allignment marks on the cam gears to be sure though.
Whichever side the coils were replaced on is probably the side that's jumped.
I certainly wouldn't drive the car until you find out whats wrong with it though.
Whichever side the coils were replaced on is probably the side that's jumped.
I certainly wouldn't drive the car until you find out whats wrong with it though.
Theres too many possibilities. Should I just replace the engine? Or will I be wasting my hard earned money and find out that the first guy was right and I have to replace the computer.
Here's what I'm being told about possibilities.
1. Bad engine needs new engine
2. Bad coils (four were replaced)
3. Bad computer
4. Bad Timing Chain
Here's what I'm being told about possibilities.
1. Bad engine needs new engine
2. Bad coils (four were replaced)
3. Bad computer
4. Bad Timing Chain
97stscaddy
Dedicated LVC Member
Well you dont go fly off the handle and start replacing things without TESTING them first, which it appears your mechanic DID NOT do with those 4 coils.
Unfortunately a Lincoln dealer is going to be the only place that can test the computer for you.
The timing chain can be checked by removing the valve covers and lining up the timing marks on the camshaft gears. If they don't line up then its jumped timin and needs new tensioners and a chains. You'll probably need a service manual to figure out where the marks are supposed to line up at.
The next thing to check after cehcking the timing, (assuming that it is off) is to reset it to the correct spec. briefly, and do a leakdown test on the affected cylinders to be sure there are no bent valves, before you go buying the new chains. If there are any bent valves the new chains wont do you any good without pulling the cylinder head and replacing the bent valves.
If its still at the dealer, you might be better off to just have them pull the valve covers and check the timing before you go any further.
Unfortunately a Lincoln dealer is going to be the only place that can test the computer for you.
The timing chain can be checked by removing the valve covers and lining up the timing marks on the camshaft gears. If they don't line up then its jumped timin and needs new tensioners and a chains. You'll probably need a service manual to figure out where the marks are supposed to line up at.
The next thing to check after cehcking the timing, (assuming that it is off) is to reset it to the correct spec. briefly, and do a leakdown test on the affected cylinders to be sure there are no bent valves, before you go buying the new chains. If there are any bent valves the new chains wont do you any good without pulling the cylinder head and replacing the bent valves.
If its still at the dealer, you might be better off to just have them pull the valve covers and check the timing before you go any further.
If the timing chain has jumped, it's possible that you've not only bent a valve stem or two, but also damaged the pistons and valve seats, possibly the heads too. The piston clearance at the top of it's stroke is thousands of an inch at the the smallest gap with the head and less than an eigth inch directly beneath the valves. The 2nd gen pistons have relief cut in them for valve clearance because the VVT holds the valves open longer and the clearance isnt enough.