Rough Running after Timing Belt Install

[kpaske]

OK, I've finally completed my Timing Belt install, but I think I've got a big problem! After it warmed up for a few minutes, the engine runs fairly smooth, but the check engine light is on, and the exhaust is back-firing and smells WAAAY too rich. I took it for a very short drive, and it feels hesitant upon acceleration and there is a lot of vibration when it's in gear.

I'm pretty sure my timing isn't out of phase - I followed the directions that VCrossfan provided me, along with Randy's HowTo, and I thought everything went fairly smoothly. I'm really hoping that maybe the computer just needs some time to readjust, but I don't want to run it too much without consulting the experts here.

Please, any advice would be appreciated.

[raver_boi_88]

well your timing could be off but if it isnt then mabee you have a bent valve? Did you actually break the belt or was it just that time of year to replace it? I know when I broke mine, I had a simalar problem and I had to replace both my timing belt, and three valves...

[kpaske]

I was just doing the standard maintenance. In fact, my original timing belt appeared to be in pretty good shape.

I'm pretty sure I lined up the timing marks how the directions indicated. I really hope that isn't the problem or else I'll have to do the whole job over again. ARG!!

[kpaske]

Just so I'm clear, let me describe how the marks lined up. If you are looking at the motor, and the top center is 12 o'clock, the passenger side pulley lined up at the 10 o'clock mark, and the drivers side and crank shaft pulley's both lined up at the 2 o'clock. Is this right?

[Joe_Black]

Since the 6VE1 is a non-interference engine you at least don't have to worry about bent valves. The timing belt removal/replacement is pretty clearly outlined in the shop manual, including the timing reference marks.



Number 8 on the diagram is a blow-up of the reference marks for the camshafts, numbers 2 and 5, while number 7 is a blow-up of the timing mark for the oilpump shaft, number 1. All three should align to those marks.

Also note, from the manual: When timing is performed, the number 2 piston will be at TDC.

When changing the timing belt the battery should have been disconnected (for safety) which would force an ECU reset as well.

Check your timing against the reference marks and let us know your findings. Good luck!

[kpaske]

Joe -

Yes, I think that is how I did it. The only part that looks unfamiliar is item 8 - I didn't line anything up on the left side of the cam shaft pulley, I just located the notch on the pulley (I'm pretty sure there was only one), and it lined up exactly with the mark at number 7.

Now the instructions mentioned having to crank the pulleys around several times (up to 9) in order to get them to line up. My cam shaft lined up after one rotation. The driver's side took about 3 or 4 full rotations, and the passenger side lined up after 1 or 2. When I say they "lined up", they sort of "popped" right into place.

I really think I lined it up correctly, and the diagram you just showed me is reassuring (because I felt the guide I was using was a little vague about where to line up the passenger side pulley). So why does my VX run so crappy now?? I've had a dead battery before - probably for a week or more when I was out of town - but I'm not sure if it was dead enough to reset the ECU. When I removed the battery to have it tested and recharged, it was probably disconnected for several hours. It didn't seem to have any issues readjusting then, and that was only a few months ago. The only real difference is that the whether was warmer, but this past week hasn't been too bad. This time I had the battery disconnected for about 4 days, so I know for sure that it should be reset. Should I just let it run for 15 or 20 minutes, or do I need to start driving it around? Is it most likely just going to improve with time? The vibration and back-firing have really got me worried.

Kyle

[Joe_Black]

I'm beginning to think one of your cams is out of time. Each cam has a "number 8" reference mark, where the "number 7" in the diagram is for the oil pump shaft (number 1). Did you verify that the #2 piston was at TDC when you rotated the cams to time? That's the crank reference. With all the backfiring and rough running you could have maybe two pistons out of time even, hopefully though it's just a pair of valves. I'm not intimately familiar with the 6VE1's sequence so am just generalizing.

If it were me I'd re-time from scratch using the Service Manual procedure, letter for letter.

[kpaske]

Each cam has a "number 8" reference mark, where the "number 7" in the diagram is for the oil pump shaft (number 1).

Joe, I don't understand what you mean here. The marks that I lined up were:

On the passenger side cam pulley there was a line on the front with a little bit of green paint on the edge. I lined this up with the mark on the block at about 10 o'clock.

On the driver side cam pulley there was also a line etched on the front with green paint on the edge. I lined this up with the mark on the block at about 2 o'clock.

The crank shaft pulley didn't have marks on the front, but a single notch on the back edge of the pulley. I lined this up with the mark on the block at about 3 o'clock.

To line these up, I basically just cranked them clockwise until they "popped" into place, meeting the mark exactly.

Did you verify that the #2 piston was at TDC when you rotated the cams to time? That's the crank reference.

What is TDC, and how would I verify this?

With all the backfiring and rough running you could have maybe two pistons out of time even, hopefully though it's just a pair of valves. I'm not intimately familiar with the 6VE1's sequence so am just generalizing.

If it were me I'd re-time from scratch using the Service Manual procedure, letter for letter.

Well, that's what I have to do if that is really the problem. I just need to understand what my mistake was so that I don't repeat it. I thought I had followed the instructions exactly...

[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