Rough Running after Timing Belt Install

[Joe_Black]

What is TDC, and how would I verify this?

TDC = Top Dead Center. One simple way is to remove the number 2 cylinder sparkplug and use a wooden dowel to "feel" the top of the piston. Using a wrench on the crankshaft rotate the engine until the piston is at it's highest point. Once you have it at TDC, then you align the rest of the timing marks while keeping the number 2 piston at TDC.

Clear as mud?

Do you have a copy of the Service Manual?

[kpaske]

Joe,

Thanks for your help (again... )

No, I don't have the Service Manual, but I do have the manual on CD, as well as Randy's How To and some pages that VCrossfan sent to me.

I guess I'll have to tear it apart and try it again...

By the way, which is the #2 cylinder? And if I've got to turn the pulleys to get everything to line up, how do I ensure that #2 stays at TDC?

[Joe_Black]

No worries, that's what we're all here for!

If you've got the manual on CD, that's the service manual and has all this in there under the engine section. Take a look there at the timing belt procedure and you'll get things right straightaway.

Remember that the timing belt is what turns all these shafts and keeps them in time, so with the belt off you can turn each to where you need them to be. That's one of the many things that make OHC engines such a joy to work on.

Here's the block diagram with the pistons numbered...

[kpaske]

Frustration is setting in now...

I just spent a good part of the day redoing the entire job, and it's still doing the same thing. Joe, just to reconfirm, the diagram shows the engine from above, with the front of the car facing to the LEFT, is that correct? That diagram didn't indicate which way was the front, but from looking at some of the other diagrams on the CD manual I deduced that the #2 cylinder is on the driver's side, nearest the front on the car.

So I took everything apart, stuck a dowel down the #2 cylinder, cranked it to ensure that #2 was TDC, lined up the left and right cam pulleys with their marks, and lined up all three marks on the belt with their appropriate marks on the pulleys. There is no doubt in my mind that I did it correctly this time. (In fact, I still think I did it right the first time too, but there were a few finer details I ensured were correct the second time around). So why does it still run like crap?

I took it around the block one time just to see what would happen, and it had little to no power, and no acceleration. It backfires and sometimes vibrates much more than normal for a VX. Since Autozone is only about 2 miles away, I decided to go get my CEL codes read and here is what I've got:

P0300 Misfire on Cylinder #1
P0300 Misfire on Cylinder #3
P0135 Bank 1 Sensor Heater Circuit Malfunction

Any ideas what the heck is going on??? It was running fine before I started this timing belt job.

[Joe_Black]

I'm going to share this thread with some mechanic friends and see what they think. I feel your frustration!

[kpaske]

Thanks Joe... I have no idea what could be wrong at this point. I double and triple checked to make sure there wasn't something disconnected, but really there wasn't that much to take apart. In fact, the second time around went a lot faster because I found I didn't need to disconnect the lower radiator hose OR the power steering pump, like the original directions told me to. Plus, I already knew all the tricks to getting the different bolts loosened and such. Anyhow, I'll be waiting to see what your mechanic says.

[mbeach]

I've never changed the timing belt in the VXs, so this is just a SWAG:

1. The OHCs are "direct attack" or whatever. The intake/exhaust cams are phased off of a single cog on each side. One whole bank of your engine would be out of time, this would explain the backfiring (exhaust valves open at detonation) and the misfire in cylinders 1 and 3 (same side).

2. If you simply took out (a good, whole) belt, and put in another, why would you have had to rotate the camshaft cog(s) at all? As long as the crank didn't rotate (in the absence of a belt), the camshafts and crank/piston arrangement should have went unchanged.

3. It's apparent that the #2 piston was not at TDC when the belt was originally removed -it's too late to do anything about it. Those timing marks are designed to line up under ONE condition, this eliminates the possibility of installing the belt in a '180 out' configuration.
Remember, during the suck-squish-bang-blow cycle, the #2 piston moves to the top of its travel 2 times. It's possible to locate the #2 piston's uppermost position and STILL be 180* out of phase (in relation to the camshafts' intake/exhaust arrangement). Next time, ensure that the #2 is at TDC AND the marks line up before removing the old belt.

O.K. what to do now:
You can't go any further on your own. Thank Isuzu for building a non-interference engine, because your timing is bonked.
Pretend that you broke the old belt, and take it in to a shop -one that has experience in DOHC V6s.
They will have to locate the correct positions for each of the OHC banks and the crankshaft based off of the firing order and the position of the camshafts' lobes (yes, they will be pulling your valve covers, unless there is a guru there with a fiber optic scope who can look through your oil filler hole (think gynecologist/mechanic) and determine your camshaft orientation).

It sucks that you have to pay some shop to do the work, but hey, your time has value. Think of all of the trial and error work, as well as typing and waiting for responses and it all adds up. AAA and a few (hundred) bucks and it'll be a memory.

RLTW

[AREA 51]

to find the compressiom stroke you'd have to screw a press. gauge into #2 spark plug hole (unless you have really long fingers)and watch for press rise up to about 100 psi while turning the crank (in the correct rotation direction) by hand. Then you could use the dowel to get closer to tdc, and use the marks to finalize.

[VXJIM]

I replaced my belts at 120,134 miles but the dealer said they were in good shape. As the original owner since Aprill 99, except for tires, brakes, two radiator hoses and an EGR valve that's all I've done and it runs great! The VX has been very reliable. Never had an intake manifold problem or break down.