

| Subject: | Re: tantalum cures for mysterious IMB |
| From: | Larry Alofs |
| Date: | Sat, 13 Jan 2001 21:27:37 -0600 |
David Luddy wrote: > Thank you... > to all who pointed out this possibility in my new Intermittent Miss > Behavior "IMB". > However there is some conflicting info on what size capacitor, and which > direction it should work in. > its either 1. 25volt 10uF + side to pin 4 of AFM connector , other side to > pin 2 > -or- > 2. 25volt 22uF + side to pin 2 of AFM , other side to pin 4 > soooooo... > Is there a majority vote on this? > tanks > <bugle> Check your Bentley. On the 91, pin 4 (brown and white wire) goes to ground, negative. Pin 2 (blue and red wire) was at about 4.5 or 5 volts positive when I measured it with a DVM. Someone in the archives felt that 10 mfd was insufficient and recommended 20 mfd, so that was what I used. More capacitance is more effective in preventing voltage fluctuations, but too much could keep the voltage from changing quickly enough when you press the accelerator. A rough calculation of the RC time constant, seems to indicate that we could probably use 100 mfd with no problem, although its physical size might make it more difficult to fit inside the boot of the connector. Radio Shack sells 10 mfd tantalums off the rack; I hooked two of them in parallel (+ to +, - to - ). Tantalum capacitors are generally smaller physically than other types and of higher quality in other ways. The voltage rating of the R.S. ones seemed a little low to me until I saw that the voltage from the ECU was apparently 5 V or lower. Since the intermittent power loss in my 91 only happened after an hour of driving at speed in cold weather, I am not sure if the fix has been effective for me. Installed it a week ago. It may be my imagination, but the idling seems smoother and slower when cold now. Good luck. Larry Alofs Chicago
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