Volks - My BB engine saga continues. You might recall that I installed a new BB 2.1l engine with the longer duration cam and polished heads in my '87 Westy, and have been dealing with low power. Tests showed that #3 cylinder was only 110# compression, the engine vacuum was 6#, and fuel pressure from the pressure regulator was too high. An emissions tests showed high HC and CO figures that some thought were too high. Bob was concerned about possible vacuum leaks, valve adjustments, the Temp II sensor, and problems with poor plug wires causing missfiring, so he sent me a new cap, rotor and wire set. My mechanic adjusted the valves, and we both looked for vacuum leaks. An unlit propane torch carefully waved around all of the rubber parts in the engine compartment didn't cause the engine idle to change at all. The brakes work fine, so it's unlikely that there is a significant leak to the booster up front. Others have suggested the idle stabilizer, so I tested it according to Bentley, and drove with it off. Seems to work OK, and there is no difference when it isn't connected, except for the tendancy to die when the wheels are cranked, because the power steering sensor can't boost engine speed to meet the demand. I have a Digitool, and following Darrel's notes that came with it, adjusted the internal gear wheel so at warm idle the AFM reading was 1.5, not the 1.7 it was before. That has made a difference in driveability. Power off the line is up, and the engine seems to run with more power. Before putting the new plug wires on, but after adjusting the valves and AFM, I took a 120 mile trip, and got 18.5 mpg, much better than the 15 mpg I had been getting. The engine still seems sluggish in 3rd and 4th, certainly no better than my old tired 2.1, but it's hard to compare. After that trip, we re-checked compression and vacuum, as things would have settled in. Compression in #3 is up, but still only 120#, vacuum at idle is ~ 8#, instead of the 13# it should be. At over 2000 rpm it goes up to 13#. Then we installed a new Temp II sensor, just because, and I put the new plug wires on. Mark Keller had suggested adjusting the CO by disconnecting the O2 sensor, and using a multimeter to check the output from the sensor. If I understood him correctly, I should have been able to use the idle adjustment screw on the AFM to bring that signal to .5 Volts. I disconnected the idle stabiliser, as Bentley suggested. With the multimeter connected between the spade terminal and the braided ground strap, I got 0 V with a cold engine. As things warmed up, it fairly quickly came up to .7 V. I marked the position of the hex key on the adjustment screw, and tried screwing it first out, then in, and watching for voltage changes. I tried it at idle, and then at 2000-2500 RPM. There were none. After the engine was fully warm, the voltage sat at a steady .8 V no matter where I had the adjustment screw, up to a full five turns in or out from the base position. There didn't seem to be any change in the engine idle,or at 2000 RPM. Remembering that someone had suggested that the O2 sensor could be coated with soot, and be reading rich, I removed it. It was indeed coated with a rich black soot, so I took a torch and heated it up. The metal came up to a cherry red very easily, and after it cooled off, the black coating was gone. I re-installed it, and re-tested. The results were identical. In the interests of experiment, I left the adjustment screw turned out 5 turns, assuming that if the engine were running rich, that might help. Driving around town, it seemed to make no difference. Is it possible that the O2 sensor is shot? It's only a year old, and on the Digitool, once it's up to temperature, the readings swing between a bit negative and .8, so something is certainly changing. Was I testing incorrectly? After all this, I took another 120 mile drive. Driveability was OK, but it still seems sluggish in 3rd and 4th. Mileage was about 18.2, within the limits of error of my previous measurement. The O2 sensor readings seemed to not get over .7, where previously I had been seeing .8 from time to time. (To eliminate some variables on such a short test run, I filled up at the same pump before and after the drive, but .2 gallon error in measuring would have made the difference in mileage.) I'm a bit frustrated. I now have about 1400 miles on the engine. Mileage is OK, but not great. The low compression on one cylinder and low engine vacuum worry me, and I paid extra for a camshaft and heads to give me a bit more power, which my calibrated tailbone, and my mechanic, tell me I didn't get. I've had a lot of advice from some great people, but I don't know where to go from here. I'm not sure if the engine power is related to the control systems or the rebuilt engine itself. I don't know if I need to worry about the low vacuum and compression. I also have another problem, which may or may not be related, so I'm putting it in another post. The engine has take to cutting out very briefly at highway speeds. What fun! - Mike Finkbiner '87 Westy Moscow, Idaho _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com |
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