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Did timing chain replacement with both dots at the 12 o’clock, car ran great afterwards during test fire. Threw the water pump back on and now it won’t run. It will “sort of” idle but at ~400 rpm and with massive backfires to the point it blew my TPS sensor clear out the throttle body. I’m concerned it may have somehow jumped timing after the test run. What should the rotor position be in the opti? I positioned the balancer so the point is straight up to make it easier to observe the rotor position. I just can’t find any info about what the rotor position SHOULD be, only stuff about the splined shaft which appears to me to be normal. Current rotor position With balancer straight up and down.
Last edited by Z28gr.mans; Dec 14, 2021 at 10:04 PM.
In stock configuration the damper (not “balancer”) hub is not keyed to the crank, and not necessarily a valid reference. Could have slipped, or not been reinstalled correctly if it's ever been removed.
In stock configuration the damper (not “balancer”) hub is not keyed to the crank, and not necessarily a valid reference. Could have slipped, or not been reinstalled correctly if it's ever been removed.
car is a 1994. My apologies, the damper was reinstalled (by me) within 5 degrees of “correct” spec. Hard to eyeball it without the key way but I did my best. I suppose I should refine my question to, should the Rotor align up and down in the same way that the spline key does on the cam gear? Based on shoebox’s info and assuming the damper hasn’t slipped to much should I assume I’m off xx degrees? Looking at his pictures the number 1 TDC position should have the rotor pointing straight down. I suppose I should check actual TDC at this point.
will add a sig asap
Last edited by Z28gr.mans; Dec 14, 2021 at 09:59 PM.
I can't remember how many teeth there are on the splined shaft. I think there are 16. That means being “off” by one tooth would create an error of 22.5°. Each slot on the outer edge of the disc is one cam degree apart. Your rotor appears to be (roughly) 1/16th of a cam rotation off, which would be 22.5°.
I helped someone with the cam dowel pin driven Opti diagnose a crankshaft position error diagnostic code (P0336). In OBD-2 there is a measurement in the “advanced parameters” PCM data stream that shows the crank position read from the crank sensor did not match the crank position measured by the cam position sensor in the Opti. I told him the Opti was probably not indexed correctly, He was skeptical because the engine seemed to be running OK. When he finally pulled the Opti, he found the dowel pin was a shade on the short side, and had slipped out of the index hole in the Opti. We were both surprised the engine ran as well as it did (at least what he described to me).
I can't remember how many teeth there are on the splined shaft. I think there are 16. That means being “off” by one tooth would create an error of 22.5°. Each slot on the outer edge of the disc is one cam degree apart. Your rotor appears to be (roughly) 1/16th of a cam rotation off, which would be 22.5°.
I helped someone with the cam dowel pin driven Opti diagnose a crankshaft position error diagnostic code (P0336). In OBD-2 there is a measurement in the “advanced parameters” PCM data stream that shows the crank position read from the crank sensor did not match the crank position measured by the cam position sensor in the Opti. I told him the Opti was probably not indexed correctly, He was skeptical because the engine seemed to be running OK. When he finally pulled the Opti, he found the dowel pin was a shade on the short side, and had slipped out of the index hole in the Opti. We were both surprised the engine ran as well as it did (at least what he described to me).
interesting. I got it running again today and it ran a little bit better after I cleaned the optical sensor but there’s still a serious miss on one or more cylinders. Okay I can’t really fathom how the shaft could be indexed incorrectly considering it only fits into the cam gear one way, but I guess the new chain may have jumped a sprocket or two.
In theory, the shaft can only be indexed one way. In practice, based on doing this for 20+ years on this site (and several others), I would estimate that about 10% of the Opti installs end up with the shaft in the wrong position. Unfortunately, it is possible and does happen.
