'93 Chev Lumina Euro 3.4 DOHC with timing (?) problem

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Old 05-13-02, 04:28 PM
orange_dude_ca
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'93 Chev Lumina Euro 3.4 DOHC with timing (?) problem

My Lumina (W body) with 4 speed auto trans has 65,000 miles and some recent drivability issues. Last week the engine began to stall on idle.

I checked the fuel pressure, EGR valve, spark plugs visually, and vacuum lines visually and found no problems. I then found the secondary timing belt had been wearing and was down to 60% of its orginal width, and bits of rubber all around the sprockets and pulleys. I also saw the cam sprockets (rear bank) timng indicators were not aligned.

After replacing the timing belt and the idler pulleys and resetting the timng, the car no longer stalls on idle. However, the engine does sputter slightly on idle and when highway cruising (2000rpm) up hills (ie. under load) it shudders. There seems to be no problems uner hard accleration.

1. Do the symptoms indicate timing problems or valve problems? Does it indicate exhaust/intake or early/late condidtion?

2. Is it true this engine, 3.4L DOHC, is designed so the pistons do not collide with valves when timing is off?

3. I believe it is a timing problem, but I did align the timng marks as shown in the service manual. Is there a way to confirm cam orientation without visually inspecting the cams. (Compression test?)

4. How accurate must the timing mark alignment be. After all the original timing marks are not that precise.

5. Why does the service manual stress that the crankshaft should not be rotated counterclockwise? (Just curious)

Any help would be appreciated.
 
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Old 05-13-02, 05:12 PM
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Join Date: Dec 2001
Posts: 2,538
you usually have to remove the valvecovers and use a special tool to hold the cams in the correct position to get your cam to crank timing correctly the marks are usually not accurate at all.
counterclockwise is opposite the direction the engine would normally run and turning the engine backwards can cause the timing belt to get off on some models.
 
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