16197427 on stock 305- runs lean until closed loop...

Long time lurker, new member. I've done a few TBI swaps in the past with the 7747 and had good luck. My daily driver is a 1992 Caprice wagon with a stock 305 and 700r4 with 3:07 gears. I've recently upgraded the wagon to a '7427 ecm and everything seems to be fine after the engine is warmed up. However, for the first couple of minutes of driving, it is a bit on the lean side. It does not bog or backfire through the intake, but just really sluggish and tapping the accelerator to kick some AE into the mix results in the engine smoothing out for a second, and then goes back to feeling sluggish. The O2 shows low, but may not be warmed up enough to be accurately responding. I have the fueling and timing tables pretty close, but just need a little advise on how to get the cold running a little better. Any ideas where to start would be greatly appreciated!
Thanks!

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Originally Posted by Cooter

Long time lurker, new member. I've done a few TBI swaps in the past with the 7747 and had good luck. My daily driver is a 1992 Caprice wagon with a stock 305 and 700r4 with 3:07 gears. I've recently upgraded the wagon to a '7427 ecm and everything seems to be fine after the engine is warmed up. However, for the first couple of minutes of driving, it is a bit on the lean side. It does not bog or backfire through the intake, but just really sluggish and tapping the accelerator to kick some AE into the mix results in the engine smoothing out for a second, and then goes back to feeling sluggish. The O2 shows low, but may not be warmed up enough to be accurately responding. I have the fueling and timing tables pretty close, but just need a little advise on how to get the cold running a little better. Any ideas where to start would be greatly appreciated!
Thanks!

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Is it in Open loop or closed loop when this happens? If its Open loop and you are running fuel with 10% ethanol richen the closed loop AFR setting to 14.1 to help get it more fuel and drop the open loop afr vs coolant table 0.6:1 to match. I would also add 6-10% more AE pulsewidth in both the TPS AE and MAP AE tables. Should help with the lean running and bring the fueling closer to where it needs to be. If you are running a stock engine in that car it should be very similar to the stock fueling of a truck 305. They shared the same longblock minus the fact the trucks used a flat tappet cam with the same specs and the car a roller cam.

Looks like you may have nailed it. I reflashed the chip and took a drive around the block after it cooled down for a couple of hours and it felt better. I'll find out for sure in the morning when the outside temp is in the 40's at startup- it usually takes a couple of miles of steady driving before it feels 'right'. At operating temps, the fueling and timing were really close with the stock program- blms were in the 120~135 range right from the start and it is only picking up a little knock retard at low speed/high load with the converter locked.
Thank you!

Quote:

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Originally Posted by Cooter

Looks like you may have nailed it. I reflashed the chip and took a drive around the block after it cooled down for a couple of hours and it felt better. I'll find out for sure in the morning when the outside temp is in the 40's at startup- it usually takes a couple of miles of steady driving before it feels 'right'. At operating temps, the fueling and timing were really close with the stock program- blms were in the 120~135 range right from the start and it is only picking up a little knock retard at low speed/high load with the converter locked.
Thank you!

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Good deal! How did it end up working out?

With your spark knock on TCC lockup issue, I would honestly bump up the lockup speed before I pulled the timing. A lugged engine will be under much more load than one that is not. If it is loading the engine enough to knock it is also adding stress on the engine bearings as well as the TCC clutch. Also I would do a TV cable adjustment to ensure the transmission is as responsive as it can be. I changed the TV spring in the valve body in mine and was amazed at how much more responsive it was. The spring gets weak after years of use and causes the TV pressure to rise slowly in response to throttle. After changing the spring out my part-throttle downshifts were much easier to obtain and WOT downshifts happened more quickly.

There was frost on the windows this morning, and Moby (the great white whale of station wagon) started easily and drove smoothly without any hint of a lean condition. I bumped the TCC minimum speed up a little and got rid of most of the knock retard. The 2.73 gears are not helping, but I've got a set of 3.23's that will get installed at some point in the future.