Timing...Off by one tooth..What to do?

[alice]

So I have had about 10in/hg vacuum, about 10MPG and really rough idle/low power since I bought the car. I did a boost leak test at both the turbo and the TB, checked out good. I also did a compression test and had 180's across the board so thats good. So, today I decided to check timing and the cam sprockets never line up at the marks and when the exhaust cam dowel pin is straight up, the intake cam dowel pin points towards the rear of the car, not straight up. Basically, the cam shafts are one tooth out of alignment. In turn, is there anyway to correct this without actually removing the timing belt or should I just follow the tensioning part of the VFAQ? Any help is greatly appreciated.

 

[alice]

So how far should I adjust the cam sprockets to make up for the fact the tensioner is going to make the belt tight and in turn, turn the cam sprockets?

 

[GVR4592]

I think you need to read the vfaq again and follow the instructions step by step, if you do it correctly the cam's won't move when you tension the belt. I wouldn't trust the TDC marks on the timing cover either.

 

[alice]

So I got everything timed properly and put everything back together, started it up and.....my vacuum is at a steady 17in/hg and the engine runs so smooth, it's just great. However, I didn't really feel a great increase in power like everyone else does. I set the crank to TDC on the timing cover and followed the tensioning steps, but everywhere I have read, including on the badge under the hood, it says "timing should be at 5 degrees BTDC," which I can clearly see that on the timing belt cover. I put it to the "T" on the cover. I have not checked it with a timing light yet but does the car automatically adjust to the 5 degrees, or how does that work?

 

[steve]

SI set the crank to TDC on the timing cover and followed the tensioning steps, but everywhere I have read, including on the badge under the hood, it says "timing should be at 5 degrees BTDC," which I can clearly see that on the timing belt cover. I put it to the "T" on the cover. I have not checked it with a timing light yet but does the car automatically adjust to the 5 degrees, or how does that work?

The word timing gets used for many different things on a car.

The timing belt controls the timing (relationship) of the crank to the cams and the balance shaft making sure that they all work together in the right order.

Ignition timing is electrical and controlled by the engine computer (ECU) but it needs a reference to work from. The CAS or the crank and cam sensors on a 2G provide that reference. "Setting the timing" on a 4G63 is actually adjusting the sensor to the correct position so the ECU knows where the engine is in it's cycle. The specification is to adjust the CAS using a timing light until the crank pulley timing mark is at 5* BTDC on the timing belt cover while the engine is up to operating temp and the timing adjust connector is grounded.

The CAS is attached to the back end of the intake camshaft so any errors in the timing belt between the intake cam and the crank will also show up as errors in the ignition timing.

Steve

 

[alice]

Thats the thing is that with a 2g 7 bolt engine, there is no adjustable CAS so here in lies the problem. So how do I adjust the timing to get the ECU reading the right time in the cycle? How do I adjust the sensors?

 

[steve]

If it doesn't read correctly then it's a mechanical problem.
The most common problem is the crank pulley coming apart so that the timing mark on the outer ring has moved and won't line up anymore.

Steve

 

[ekanddsm]

Did you get the cams lined up right, did you check to see if the crank was at TDC, did you pull the thing apart or did you jump the belt like someone suggested? If you had 17 in, after and 18 in of vacuum before, and compression was 180, it doesnt sound like much of a mechanical problem.

But did the belt line up perfect after you worked on it both top and bottom?

 

[alice]

I got everything in line, cam shafts, crank, oil sprocket, and proper tension. The vacuum before I did the job was at 10in/hg now after doing the job, it is at a steady 17in/hg. The reason I did this job in the first place is because the guy I bought the car off of had some crappy garage to the timing belt and when I checked the cam sprockets on Sunday, they were about on tooth out of alignment, now they are dead on. I am just confused about this 5*BTDC thing. Here is my thought on it. I get everything marked up right and in time at TDC, then the ECU should read the sensors signal and adjust to 5*BTDC?