cory_jackson

Car: 1996 Del Sol Si SOHC D16Y8 MT 300k no major overhauls (head never removed) all maintenance performed per factory manual with OEM parts. Very good condition.

Synopsis: When installing timing belt per factory manual cam pulley alignment mark is always half a tooth off. Which is correct?

Details: First pic proves the crank alignment is perfect.



The manual says that the cam pulley alignment mark should align with the arrow approx 4 mm below the valve cover gasket plane molded into the plastic but I cannot install the belt this way because t's half a tooth off. First guess is as shown with the cam mark below the mark on the plastic cover. In this pic I have rotated it several times to ensure proper seating and tension. Of course I did not feel any valve collisions. Using a straight edge I have projected the mark from the head out to the front of the pulley being very careful to get it perpendicular. The black mark is the alignment marks projection. I'm sorry but I couldn't get the camera in low enough to show it straight on. It didn't occur to me to use a mirror until just now:-)



When I ran it this way it had a notable purr and pinged. IE really sounded wrong. I moved on at this point assuming that was a negative result but this is the second time I've replaced this belt over the car's life and it's possible I got it wrong before and I did not correct the timing. Next I moved it up a notch.



Here you can see it aligns almost perfectly with the top of the head. I know in years passed Civics were supposed to align this way so I am beginning to wonder if the manual is wrong. Here again I have projected the mark on the head to the pulley with a black line. Here you can see it's now a half a tooth above the mark on the head.



Now I run the car and it runs fairly normal so I think this is the correct guess.

Why am I asking? I am not 100% certain exactly when but around the time I replaced the belt I began to get CEL with P0301-4 and P1300 with rough and low idle. I don't know exactly because it's the wife's car. A good example is I can drive down the freeway and the car runs smooth and normal. As soon as I exit and stop at the light the idle drops to about 800 and is fairly smooth although I can feel a little vibration. After a few seconds the idle plummets to around 5-600 and is very rough. I tried adjusting the manual idle bypass per the manual but even screwed all the way down cannot get the idle low enough. So I removed and thoroughly cleaned the coke from the throttle body and inlet to the IAC valve. Now I can get the idle circuit to work better but when I try to adjust it down to the 470RPM with the IAC disconnected it's really stumbling. With IAC back on it idles normally. With the idle working more or less I adjusted timing. It was slightly off and when I move it a little the engine stopped. Restarted OK and was able to adjust. Later I was looking at other things like PCV and without doing anything it stopped again. Like one turned off the key. This time it would not start at all and had no spark. TS ignition circuit and fount the coil was getting pulse but no spark coming out. Replaced ignition coil and it runs again but I still have the idle symptoms and DTCs.

So now in the back of my head I keep wondering if it's related to the cam alignment/timing issue. Is it possible that I have it on the wrong tooth? Perhaps the misfire DTCs are because the crank flux sensor is not jiving with the TDC or other sensors and the ECM thinks it's misfiring?

PS: The other symptom that flies in the face of the idea of the cam timing being wrong is that when it first falls to idle it holds the correct RPM. But then something changes and the RPM drops. Often I can hear a low guttural purr from the air intake and I have no idea what that is. Perhaps a PCV or Evap valve has opened so I'll be checking that next.

thesmogman

If you can get the timing correct then it is not off. My T-belt was replaced and I checked the timing (spec is 18 for my motor)I could only turn the distributor to 20 degrees. I moved the belt one tooth and then I could only get it to 16 degrees. Turned out that the cam gear was worn down so much that I could not get my timing to spec. Something to check.

So if you can get it to your spec then it should be correct. Sorry about the long story!!

Also the plastic timing cover that has the arrow on it might have shifted up or down on you Take a peek at this too!

cory_jackson

I was trying to remember why on the last timing belt change I decided on this timing and I recalled exactly that. When I selected the advanced timing I couldn't rotate the distributer enough or it was just at the adjustment limit which looked wrong.

cory_jackson

In case anyone reads this later a compression test revealed that cylinder 3 was only 80PSI and 4 was 120. Leaks were the exhaust valves.