1988 928 Stalling below 1200 RPM-HELP!!
02-04-2012, 12:17 PM
#17
As it turns out, the problem was that the crank shaft is moving, even though my mechanic told me it is not moving out of the path of the sensor. He said the prior owner must have changed the torque tube and they did an improper job because the fly wheel jumped back 1/2 inch when they tested it. Any thoughts on how this should be repaired? My mechanic is going to replace the LH engine harness in the hopes that this will do the trick, but he seems to think that we may need to replace the engine? Any ideas? Your comments are appreciated
02-05-2012, 12:55 AM
#19
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When the ISV began to fail on my first 928 S4, it only stalled when the engine was warm.
When the TPS failed on my current S4, the engine did not stall - it just didn't idle smoothly. Again, this only showed when the engine was warm. However, I don't know, if that's a typical symptom of failure of the TPS.
When you wrote that 928 International told your mechanic the engine is toast, my first thought was - they probably asked some good questions and determined that your engine suffers from the dreaded Thrust Bearing Failure (aka TBF). This is a result of too much pressure on the flex plate and subsequently on the crank, which destroys the Thrust Bearing and subsequently the block. By the time you experience symptoms as the ones you describe, the block is destroyed (it cannot be repaired). You probably have plenty of metal in the oil - an oil analysis could confirm. Once you remove the oil pan, you'll have a good view of the mess.
I encourage you to search here for "TBF" or "Thrust Bearing Failure" - there are many past discussions, some with great pictures of the damage.
Your only option is to look for a new engine. However, you still need to figure out why there was so much pressure put on the flex plate. How many miles are on the car? Was any work done on the transmission or torque converter?
Once you have a new engine installed, make sure the pressure on the flex plate is checked and released regularly. You may also consider upgrading the clamp that connects the shaft and flex plate to Constantine's Super Clamp.
My condolences for the death of your engine, and best of luck in getting this shark roaring again!
When the TPS failed on my current S4, the engine did not stall - it just didn't idle smoothly. Again, this only showed when the engine was warm. However, I don't know, if that's a typical symptom of failure of the TPS.
When you wrote that 928 International told your mechanic the engine is toast, my first thought was - they probably asked some good questions and determined that your engine suffers from the dreaded Thrust Bearing Failure (aka TBF). This is a result of too much pressure on the flex plate and subsequently on the crank, which destroys the Thrust Bearing and subsequently the block. By the time you experience symptoms as the ones you describe, the block is destroyed (it cannot be repaired). You probably have plenty of metal in the oil - an oil analysis could confirm. Once you remove the oil pan, you'll have a good view of the mess.
I encourage you to search here for "TBF" or "Thrust Bearing Failure" - there are many past discussions, some with great pictures of the damage.
Your only option is to look for a new engine. However, you still need to figure out why there was so much pressure put on the flex plate. How many miles are on the car? Was any work done on the transmission or torque converter?
Once you have a new engine installed, make sure the pressure on the flex plate is checked and released regularly. You may also consider upgrading the clamp that connects the shaft and flex plate to Constantine's Super Clamp.
My condolences for the death of your engine, and best of luck in getting this shark roaring again!
