91 lexus ls400 timing belt question

[jx295c]

Hey gang,

I've recently replaced the timing belt on my LS and suspect my timing might be slightly off. When starting there was an obvious vibration. When I installed the belt I made sure the small groove on crankshaft spindle was aligned with the small nipple on the engine (also the CR mark on the belt was aligned with the dimple on the spindle) and both camshaft pulleys grooves aligned with the marks on the engine and belt (RH and LH). I turned the crankshaft two full revolutions and the marks on the engine aligned with the marks on the camshaft pulleys. Any suggestions on what might be wrong?

 

[Lextreme II]

Double check your spark plug wires.

 

[jx295c]

update

ok, I double checked the spark plug wires and the plugs (brand new-NGK Vpower). I suspect it's something more severe, since there wasn't any misfire issues prior to changing the timing belt. When starting, it doesn't sound like a minor misfire, it sounds more major like the timing (a electrical burning smell is present, and the starter makes some sort of overspeed sound). The camshaft grooves are pretty close to the indicators on the engine when the camshaft pulley is at zero degrees but they are not dead on. I guess I'm going to have to pull everything off and make sure the timing is dead on unless you all can think of anything better....thanks in advance for your reply.

 

[och]

I dont see how improper timing could cause any electrical burning smell. Also, if they are almost dead on, off by maybe a 1/16" or so, then I dont think you should worry about that, its probably just caused by some play in the belt itself. Either way your ECU should be able to compensate for that. Did you use OEM belt?

 

[mshawari1]

Without getting every thing off .. just move the crank to the "0" and check the sign on the two cam pulley ..​

 

[jx295c]

the belt is a non-OEM, goodyear, but the cr, lh, and rh lines were consistent with the marks on both camshaft pulleys and the crankshaft. Probably the belt is OK....

 

[jx295c]

I did a little more diagnosis, and there was smoke that appeared to be coming out of the intake when starting the engine and an advancing sound for a few seconds even when the ignition was turned off. I'll do a tear down and check the timing again, maybe use an oem belt, let you know...

 

[och]

I did a little more diagnosis, and there was smoke that appeared to be coming out of the intake when starting the engine and an advancing sound for a few seconds even when the ignition was turned off. I'll do a tear down and check the timing again, maybe use an oem belt, let you know...

Holy crap, if you have exaust coming out of your intake, then your valve timing is way off. The first time around I installed my timing belt, I screwed up the drivers side CAM pulley by around 5-10 teeth, and the engine wouldn't start, and backfired smoke through the intake. Thanks God the 1UZ is a non-interference engine, otherwise I would end up needing a new engine.

The one thing that I learned from the replacement of timing belt, is that the cam pulleys, or at least the driver's side pulley, has an extra mark on it, and thats where I had it aligned the first time around, and thats why it didn't start. But that's probably not the case with your engine, because yours starts, and runs, although not perfectly well.

Your timing is defenately off - and it could be caused by your cams not being perfectly aligned, and from what I heard, aftermarket timing belts for our cars are a little longer than OEM, and have too much slack in them. You should replace it with OEM belt.

However, if I were you, before I tore everything back apart, here's what I would do. Align the crank pulley to the "0" mark. Remove the timing belt tensioner only and release the belt from the cam pulleys. Align both cam pulley exactly on the marks, put the belt on the drivers side pulley then on the passenger side pulley, make sure there's no slack. Then reinstall the tensioner, and perhaps use a shim between the tensioner and pulley to pick up the extra slack. By the way, you don't need to compress the tensioner as many tutorials/manuals show, just unbolt it, and then bolt it back in.

After that, I would manually revolve the crank, lets say ten times, and see if cam pulleys still align exactly. However, even it corrects the problem, I would still opt for an OEM belt.

 

[jx295c]

nice suggestions "och," I'll give that a try and let you know....

 

[jx295c]

update

Well, it looks like it's fixed! Gotta make sure your rotors are lined up with the cam properly, it was 180 deg off on one camshaft (rh). I did notice a low idle for a couple of starts but I think the ECU eventually figured it out. The idle seems sorta high at 1k rpm but the engine is cold and I won't be able to heat it up until there is coolant (had to drain due to water pump change), maybe the idle will drop when the motor is warmed up. I've heard the correct idle should be around 600rpm.

 

[rivmasta]

I had the engine backfire through the TB after changing the timing belt... turns out that I had the coils wired up backward - IE right bank to left and left bank to right!

Easy fix thankfully! Better labelled now too...

 

[och]

When the engine is cold the idle is suposed to be high, even higher than 1K. But you should never ever, under any circumstances run the engine without coolant - it will overheat and cease in less than a minute.

 

[jx295c]

yeah, it's risky, but I had some water in there. I'm planning to do a flush and fill and wasn't quite ready for the coolant yet. Plan to add the red dexcool stuff specifically for aluminum blocks. Hopefully this will squeeze more life out of the pump and prevent premature corrosion.