2003 knocking = broken rod ?

[First_bug]

We just bought a 2003 1.8 turbo on Saturday - from private party. Car ran great, love it. On Sunday it started to misfire and check engine light came on. Codes said misfire on cylinders 1 & 2. We took it to the dealer and found that it was covered by a recall - great.

After the new ignition coils it made a knocking noise and shook. Now the dealer says it's probably a broken rod or bad main bearing.

Suggestions from this forum? I'm not afraid to do the work myself, including an engine swap, but how can I make sure this is really the problem?

[simonsi]

Originally Posted by First_bug

We just bought a 2003 1.8 turbo on Saturday - from private party. Car ran great, love it. On Sunday it started to misfire and check engine light came on. Codes said misfire on cylinders 1 & 2. We took it to the dealer and found that it was covered by a recall - great.

After the new ignition coils it made a knocking noise and shook. Now the dealer says it's probably a broken rod or bad main bearing.

Suggestions from this forum? I'm not afraid to do the work myself, including an engine swap, but how can I make sure this is really the problem?

Well is it throwing any codes any more? New coils shouldn't have caused a rod to fail or a bearing to fail so if it wasn't making such noises before what else have they done??? You can confirm the pistons are moving as they should by removing the plugs and putting a length of stiff wire (welding rod) down each plug and seeing if the movement is correct when you rotate the engine by hand. Use a temp gauge to check the actual oil pressure to see if there is a problem with the bottom end, else pull the sump and check for play.

[dhc8guru]

If you have a broken rod, its not likely the engine would even turn over. A bad bearing is more likely the problem.
Bad rod bearing would develop over time, so I am wondering how you didn't hear it when you bought the car? The rod knock wouldn't have happened over night. Unless you drove it with no oil then more than likely you would have several bad bearings.

[First_bug]

Sorry I took so long to reply. I had the car towed home and tried starting it myself. The only code was a misfire on cylinder 4.

The car runs, although rough, and occastionally there is a knocking from under the valve cover. Definitely NOT from the lower part of the engine.

I'm not sure what the dealer tech's were thinking, but it sounds like there are still coil pack or ignition problems.

I removed the battery and have it on the charger. I also bought 4 new plugs to go with the new coil packs.

Tomorrow I'm going to reinstall everything and see if there are still codes. I'm going to reset and try again.

[First_bug]

Another followup. I have low compression (below 100) on one of the cylinders. The CEL light only indicated a misfire on one of the other cylinders.

[simonsi]

Originally Posted by First_bug

Another followup. I have low compression (below 100) on one of the cylinders. The CEL light only indicated a misfire on one of the other cylinders.

Hmmm, the noise may indicate a lifter problem which may in turn be causing the low compression, you would need to do a leakdown test and/or remove the valve cover to be sure.

[dhc8guru]

Funny story about rod knocks. I bought an old Toyota 4 runner turbo years ago that had a rod knock. It had 250k miles on it. when I tore down the engine I found one of the oil galley's had a coiled up metal chip stuck in the galley left over from when the crank was machined at the factory. Over 250k it slowly starved that rod for oil.
Anyways back to your deal. A misfiring cylinder can cause a large enough pre-ignition which creates a large backfire and causes a dropped valve seat. Now you end up with a valve that is dinking into the piston because the valve can't fully close. Another tale tale is low cylinder pressure and high crank case pressurization. Pull the valve cover and look for a valve bucket not retracting when the cam rotates to a closed position.

[Loosenutbehindthewheel]

Originally Posted by First_bug

We just bought a 2003 1.8 turbo on Saturday - from private party. Car ran great, love it. On Sunday it started to misfire and check engine light came on. Codes said misfire on cylinders 1 & 2. We took it to the dealer and found that it was covered by a recall - great.

After the new ignition coils it made a knocking noise and shook. Now the dealer says it's probably a broken rod or bad main bearing.

Suggestions from this forum? I'm not afraid to do the work myself, including an engine swap, but how can I make sure this is really the problem?

It had no rod knocks before you took it to the dealer. And they did a repair under recall? Sounds like to me some dealership kid was out there rodding on it.

[Too Cold NB1.8T]

Although possible, I do not believethat a failing rod bearing would cause a misfire code, sounds more like something electrical.

Sometimes the actual coil plugs can go bad, in this case a new coil on that cylinder would do nothing to resolve the issue, a rough idle would be a symptom here.

[First_bug]

I have changed the spark plugs and check the coil packs. The car will start, idle really rough for about 30 seconds then cough and die. This time I did hear what I would call an occasional ping from the bottom.

Next step is pull the valve cover and oil pan and see what it looks like. It may be a while, but I'll let you know what I find.

[simonsi]

Originally Posted by Too Cold NB1.8T

Although possible, I do not believethat a failing rod bearing would cause a misfire code

Assuming the rod BROKE it may well give a misfire code assuming it was running on three, the ECU uses the knock sensors to detact misfire. I can't see it running so quietly with a broken rod though, and a failing bearing wouldn't cause a misfire as the piston is still pretty much moving as it should and doing its compression job...

[First_bug]

Well, valve cover is off and everything looks great. I haven't put a wrench on the crank to rotate it thru a couple revs, but so far so sign of wear.

Hopefully tomorrow I'll pull the oil pan. then I'll crank it through a couple revs and see what happens.

Might this all be an ECU problem? I think the battery shorted because it won't hold a charge.

[dmbluebeetle]

Check your timing belt marks and see if they line up.

You have a 1.8T which is an interference engine, if the belt jumps you can bend/break valves as they bang into the pistons.

[Fl_bug]

I'm curious, but what kind of oil are you using?

[D2Beetle]

I'm thinking bad head gasket. Perform the leak down down mentioned in an earlier post.

[First_bug]

It is a 1.8 turbo. The day we brought it home I changed the oil and put in a synthetic blend and new filter. The vw dealership told me the timing was not off, but I don't know how they could tell given the way it runs.

Yesterday I drained the oil thru a filter and a magnet and pulled the oil pan. No dirt, metal or shavings. Oil looked as good as when I put it in last weekend. I put a socket on the crank and rotated it through several revolutions. I didn't see any sign of bent rod or loose wrist pin ( I realize I may not notice unless it's really bad). I used a stethoscope to listen at the top, by the valves and couldn't hear any kind of contact.

I think I will now replace the gaskets, put it back together, fill it with oil and perform the checks recommended leak tests. I haven't done that before so I'll have to search for some instructions.

The thread continues ...

[Too Cold NB1.8T]

When you changed the spark plugs did you keep the old ones, if so what did they look like?

Did the plugs look the same or did the plugs from the misfiring cylinders look different?

[simonsi]

Originally Posted by Too Cold NB1.8T

When you changed the spark plugs did you keep the old ones, if so what did they look like?

Did the plugs look the same or did the plugs from the misfiring cylinders look different?

Cool reminder, we often overlook "old school" diagnostic techniques....

[sb_beetle]

Check the harness on the coils?

[First_bug]

Plugs on misfiring cylinders were wet with fuel but ok otherwise. I've been away for a few days. I just finished putting the oilpan back on. Tomorrow I'll put the valve cover back on, fill with oil again, and proceed with more testing.