Cam timing question

[cat007]

Howdy all

My car is feeling significantly sluggish. Feels like the ignition timing or cam timing is retarded somewhat.

Poking a long screwdriver down the #1 cylinder and lining up the crank pulley with the TDC mark, I've noticed something odd....

Going from about 15 degrees BTDC towards 0, it feels like the screwdriver is at it's highest at around 7BTDC and by the time the crank pulley gets to 0 the screwdriver appears to be starting to go down....

My understanding is the piston should be at it's highest point as the crank passes TDC - not before?

[holden_fan2005]

Checked the timing with a timing light?

[cat007]

Checked the timing with a timing light?

Yeah just checked the ignition timing with a timing light and it's spot on...

[QikStarlie]

sounds like you need to find true tdc. get you a spark plug. weld a bolt to the end of it, just long enough to get the piston to come to rest against it, when rotating the engine towards tdc. jam it in number 1 with engine away from tdc. rotate engine by hand until comes to rest. mark where the crank pulley mark lines up. spin engine back the other way. mark again. true tdc is half way between both marks.

better if you do it with a degree wheel. but should be able to get it pretty good without.

[cat007]

sounds like you need to find true tdc. get you a spark plug. weld a bolt to the end of it, just long enough to get the piston to come to rest against it, when rotating the engine towards tdc. jam it in number 1 with engine away from tdc. rotate engine by hand until comes to rest. mark where the crank pulley mark lines up. spin engine back the other way. mark again. true tdc is half way between both marks.

better if you do it with a degree wheel. but should be able to get it pretty good without.

Thanks for that. I don't have a spare spark plug - but have tested again with a screw driver and the #1 cylinder is definitely at TDC at the 5 degrees mark on the timing cover. By the time the crank gets to 0 it's started moving downward...

I don't think the cam belt is off by a whole tooth - the cam gears are lined up with the markings fine - so not sure how the cam timing is out by such a small amount. And is 5 degree's much or anything to worry about?

Actually now I think about it - it's probably not the cam timing that's out? Maybe it's fine - but the ignition timing is out by 5 degrees because I've been going off the timing cover marks, which appear to be out by 5 degrees....

[Grrrrrrr!]

If piston is at TDC and the markings aren't lined up something is wrong with the pulley/cover/crank combo. Cam timing has nothing to do with when piston is at TDC, nor does ignition timing. No point going any further till you figure out where TDC actually is, otherwise everything is going to be out by however much your index marks are out by.

[cat007]

If piston is at TDC and the markings aren't lined up something is wrong with the pulley/cover/crank combo. Cam timing has nothing to do with when piston is at TDC, nor does ignition timing. No point going any further till you figure out where TDC actually is, otherwise everything is going to be out by however much your index marks are out by.

I think it's something to do with the lower plastic timing cover being wrong for some reason. If I were to move the cam timing by a tooth it would definitely be out - even if the lower timing cover is mis-aligned by 5 degrees, moving the intake and exhaust cams by a whole tooth would be too much

The only thing I can think of is if the lower timing cover is reading 5 when the crank is actually at 0, then the static ignition timing (which is configured in the ECU by setting the timing to 'static' in the software and taking a reading then inputting that into the ECU software) would be out by 5 degrees - so the ECU thinks it's applying, say, 15 degrees timing, but really it's only giving 10 degrees.

If this is the case, would 5 degrees ignition timing affect how the engine performs to the point where it feels noticeably sluggish and lazy?

[Grrrrrrr!]

When you checked your cam timing did you check it against true TDC or the 5 degrees offset TDC marks on the pulley/cover?

[cat007]

When you checked your cam timing did you check it against true TDC or the 5 degrees offset TDC marks on the pulley/cover?

Well the difference between 0 and 5 degrees on the crank pulley is so small - it's less than the width of a tooth on the cam gears....

[Lloyd]

Crank pulley and/or timing covers aren't the original off that motor? Key or slot isn't worn in the crank/pulley that locates the pulley?

Short of those couple of things the marks have to line up when you're on TDC unless there is a big mechanical issue internally. If you're really concerned then pop the cambelt covers off so you can see the actual timing marks down at the crank pulley and see where those line up.

And 5 degrees ignition timing can make a huge different.

[cat007]

Crank pulley and/or timing covers aren't the original off that motor? Key or slot isn't worn in the crank/pulley that locates the pulley?

Short of those couple of things the marks have to line up when you're on TDC unless there is a big mechanical issue internally. If you're really concerned then pop the cambelt covers off so you can see the actual timing marks down at the crank pulley and see where those line up.

And 5 degrees ignition timing can make a huge different.

I can't remember for sure if the crank pulley is off this motor. I have a feeling I used one off another 1G-GTE engine I had - but not 100% on that.

The same goes for the lower timing cover - I have a feeling I changed that as well for one that's in better condition....

Is there markings on the block to line up the crank pulley? Rather than just the ones on the plastic cover?

Not sure about the crank pulley keyway - I haven't got a pulley puller - will try and source one and take a look.

[Lloyd]

There are marks on the block, but they'll be the ones in behind the cam covers for lining up the cambelt. If you have a little time/space to play with then it couldn't hurt to pop the pulley and covers off just to be 100% sure.

[strx7]

could have spun the outer parts of the pulley on the rubber harmonic balancer part, seen this happen on lots of different engines, mechanics are bemuzzed at why the timing checks out fine but vehicle runs like a sack.

[jondee86]

This ^^^^ certainly can happen. But unless the outer rim of the pulley has
a wobble on, the easy fix is to set the engine to TDC using the best estimate
from the screwdriver down the plug hole. Then make a new mark on the
crank pulley rim opposite zero degrees on the timing cover.

Time everything to the new mark and you should be away laffing

Cheers... jondee86

[Lloyd]

Until half the pulley walks off one day

[cat007]

Trying to source a pulley puller - and another crank pulley to see if mine has spun the rubber a little.

Thanks for the help

[strx7]

has your engine got a cam angle sensor or distributor? if either of those, check to make sure the bolt hasn't come loose and it has retarded itself

[cat007]

has your engine got a cam angle sensor or distributor? if either of those, check to make sure the bolt hasn't come loose and it has retarded itself

Has a cps. Have confirmed static timing is set correctly in the ecu software.

[allencr]

....to see if mine has spun the rubber a little.

Didn't the screwdriver prove that?
Only use a timing light to check that the ECU's ignition advance is working, that's all.
Time it by its performance, fast & smooth idle and only pings/detonate/pinks/spark knocks a little when abused with the octane of your choice.

[cat007]

....to see if mine has spun the rubber a little.

Didn't the screwdriver prove that?
Only use a timing light to check that the ECU's ignition advance is working, that's all.
Time it by its performance, fast & smooth idle and only pings/detonate/pinks/spark knocks a little when abused with the octane of your choice.

Smooth idle is a little tricky as without a IAC valve the idle is tricky to get right.

Trying to track down a pulley puller and a 1G crank to confirm the current one has spun the rubber.

Almost impossible to hear the pings/detonation when under boost by ear.

Dam I need to get it tuned properly again