First, the marbly sound. Thats exactly what is sounds like. A marbly sound coming from inside the engine. It doesn't really increase in intensity through the RPM range or load. I was told alotta Vortec motors have this problem. I was also told the timing chain might need replacing? It's a 2.8 V6 with 140K on it. It also feels pretty dang weak (compared to a friends auto V6 in his '91 Firebird) though the trans feels tight, it just doesn't have the takeoff I was expecting (maybe I'm expecting a little too much). The car has only had 3K put on it the last few years, and it's been a long while since the last tune up. Can someone confirm the timing chain thing, or tell me what else it could be?

As for the ECM dirs. You pull both battery cables for a half an hour to reset the ECM. Reattach them and start the car. Do you just let it idle? Or bring it through the RPM range? Or drive it? Or what? I seem to remember just letting it idle, but my memory fails me, and I don't have the manual (yet). Thanks for your time.

 

Xeno,

The "marbles" could be almost anything, but might not be mechanical if it doesn't vary with engine RPM. You might have an internal compression leak, which could cause soem noise and a power loss. I would advise getting the systems freshened up a bit, like new ignition components, filters, and fluids. Set the TPS, timing, and base idle. Clean the TB, IAC, and EGr passages. Check all vacuum hoses for leaks and deterioration. Test or replace the spark plug wires. Then do a compression test or cylinder leakdown test to determine overall engine health. If the timing chain is sloppy, you'll generally notice it when trying to set the timing at a low idle speed.

As for reinitializing the ECM after clearing the RAM, keep this in mind. When you first start the engine after clearing the ECM, the engine will operate with base parameters programmed into the ECM PROM. These parameters may not be optimum for your engine, but the ECM will enter a Block Learn Mode soon after the engine is warm and enters Closed Loop Mode. The ECM will write new data tables specific to your engine and will eventually rely on those tables instead of the base tables of the factory program. You can expedite this process by driving the car for 20 minutes under varying conditions to allow the ECM to initialize. Or you can wait and drive the car normally at your convenience. The BLM tables are constantly being updated as sensor input ranges change, but the greatest change will occur withing the first twenty minutes of Closed Loop operation. Idling the engine will not expose the ECM to the full range of sensor inputs and may not even keep the ECM in closed loop mode due to an inactive O2 sensor.

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Later,
Vader
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[This message has been edited by Vader (edited April 21, 2001).]

 

Hmm, alright. Sounds like a plan. I was planning on doing a full tune-up as soon as I got it anyway. But cleaning the TB, IAC, and EGR passages I don't know how to do. Think you could walk me through it? Thanks again for your replies.