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Not too long ago I bought a nice '92 ATX off Craig's List in St. Louis. The car has 251000 miles. The engine started and ran good. The distributor was positioned in full static advance allowed by the slot. The engine had no power though and acceleration was 0 to 60 by next Tuesday. I was able to drive it home, 1/3rd Interstate, 2/3rds city streets.
The previous owner said loss of acceleration happened all of a sudden. Maybe it did, maybe it didn't.
I've been tinkering with it off and on trying to determine what was up.
Vacuum testing indicated a valve timing problem. After looking at the marks, I tended to agree something was amiss. I moved the cam pulley one tooth toward advance. Engine operated same as before. Start, run, no power.
I built a compression leak-down tester and found the cylinders showed some leakage past the rings, the cylinder leakage indications were however, reasonably evenly matched. Actual gauge readings are ambiguous at best, but leakage appears to be about 20% to 25% down from the starting point. Not bad for that kind of mileage.
The biggest revelation was the position of the TDC mark on the crank pulley in relation to the TDC timing pointer on the lower cover. After determining the "actual mechanical position" of the piston in the cylinder at actual TDC, I could see the factory timing marks on the crank pulley were not consistent with what's in the shop manual.
The photos show the crank pulley, painted white for visibility, off the engine, and on the engine. The timing marks are identified in the pulley-off pix as 1.-TDC, 2.-10° BTDC , and, 3.-The actual mechanical TDC.
In the pulley-on pix, these same marks are A.-Factory TDC, B.-Factory 10° BTDC, and 3.- Actual mechanical TDC. WTF?
I reset the timing belt in accordance with the newly found TDC mark, reset the distributor to mid-way in the slot, reinstalled enough parts to start the engine, and by golly, it started, and revved as I think it should - with some authority.
Without pulleys and V-belt installed, I wasn't able to drive the car. Nasty rainy day here today but should be able to give a report later. If things work out, I'll re-notch the pulley with a file on the true TDC mark, install a new timing belt etc. and go from there.
Usually when I post, the thread dies. In this case, any comments, related experiences, or even "theories" will be appreciated. Especially from the "tech guys."
Charlie Z
The previous owner said loss of acceleration happened all of a sudden. Maybe it did, maybe it didn't.
I've been tinkering with it off and on trying to determine what was up.
Vacuum testing indicated a valve timing problem. After looking at the marks, I tended to agree something was amiss. I moved the cam pulley one tooth toward advance. Engine operated same as before. Start, run, no power.
I built a compression leak-down tester and found the cylinders showed some leakage past the rings, the cylinder leakage indications were however, reasonably evenly matched. Actual gauge readings are ambiguous at best, but leakage appears to be about 20% to 25% down from the starting point. Not bad for that kind of mileage.
The biggest revelation was the position of the TDC mark on the crank pulley in relation to the TDC timing pointer on the lower cover. After determining the "actual mechanical position" of the piston in the cylinder at actual TDC, I could see the factory timing marks on the crank pulley were not consistent with what's in the shop manual.
The photos show the crank pulley, painted white for visibility, off the engine, and on the engine. The timing marks are identified in the pulley-off pix as 1.-TDC, 2.-10° BTDC , and, 3.-The actual mechanical TDC.
In the pulley-on pix, these same marks are A.-Factory TDC, B.-Factory 10° BTDC, and 3.- Actual mechanical TDC. WTF?
I reset the timing belt in accordance with the newly found TDC mark, reset the distributor to mid-way in the slot, reinstalled enough parts to start the engine, and by golly, it started, and revved as I think it should - with some authority.
Without pulleys and V-belt installed, I wasn't able to drive the car. Nasty rainy day here today but should be able to give a report later. If things work out, I'll re-notch the pulley with a file on the true TDC mark, install a new timing belt etc. and go from there.
Usually when I post, the thread dies. In this case, any comments, related experiences, or even "theories" will be appreciated. Especially from the "tech guys."
Charlie Z
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