So I found out I had a bad alternator in my 99 XJ and replaced it this weekend. After doing so, I seem to be noticing something, but am not sure if itÆs something I THINK I am noticing or something that I ACTUALLY am noticing. So I figured I would get your thoughts on if it is even possible.

So the jeep now feels like itÆs idling a little smoother, and feels like it transitions from between idle and off idle smoother. And when driving previous if I shifted early I often heard what sounded like a couple pings, like the fuel grade was not correct, right when I let the clutch out on the higher gear. Well that seems to have stopped too.

Like I said I donÆt know if any of this is real or just something I THINK I am noticing. The only rational I have is I know the old alternator had a bad diode, and it was putting out lower voltage, and I assume a lower current as well. Do you think the bad alternator that was still limping along, just at a diminished state, could have been caused any of what I think I felt/ heard? I am thinking the decreased output could have affected possibly affected the spark strength, and possibly contributed to the issues, but like I said, what do you all think?

Thanks,

Sean

Sean a bad diod will cause the alt to put out less than 11V which won't charge the battery. Bad diods are found very shortly as the battery goes dead real quick.
As for the spark... if it runs smoothly without jumping and humping the spark is good enough. Sparks either spark or don't! Remember a small yellow spark is just as serviceable as a giant blue one.. The fuel don't know the difference. Once lit (no matter what lights it) the fuel burns the same..
You've heard of "buyers remorse" Well the opposite occures when a guy buys something and gets real giddy about his purchase!! Examples could be pooty-poot mufflers, cold air systems, throttle plates or even new shocks.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Thanks for the input Jim

Generally I donÆt go in for any of the gimmick type items, and I wasnÆt trying to drive this question in that direction at all, I am not thinking of making any ignition upgrades right now, and I am not looking gain performance, the Jeep is a blast as is for now, it may be getting a very little lift this summer, but thatÆs another story.

I was only trying to rationalize what I thought I was feeling with the operation of the jeep. I am fully aware of people thinking they are going faster because their wallets are lighter, and I donÆt think thatÆs the case, but the rational side of my mind needed to ask.

The diode may have just finally failed, I am really not sure, but I have been picking up noise (whine) on the AM radio since I have owned the jeep (~3 years), which is gone now too. The old alternator was still putting out around 14 volts with jeep just running around 1500 RPM with no load, but as soon as I flipped on the high beams the volt meter I had hooked to the battery dropped to around 12.2 volts, and when I went to start the jeep in the morning it momentarily dropped to 7-9 volts, but if the jeep had been running, and then was started again while everything was warm the voltage only dropped to about 11V when started. As soon as I put the battery on the charger it acted like the battery was low on charge, and it spent half the day Saturday charging up. Initially I was thinking both battery and alternator, but I am thinking now the battery might be ok. IÆll keep an eye on it, but its turning right over now, just like everything was brand new. Obviously I checked every connection for corrosion and tightness prior to anything else, and all were excellent.

Anyway I was just thinking the alternator with one bad diode would have one of the three windings operating at a different voltage/ current than the other two, and that momentary interruption or pulse in the voltage/ current might be affecting the operation of something else on the jeep, my first thought was the ignition system, but really I suppose even if it was affecting anything in the computer / feedback system it could have had an effect in the Jeep's operation. Unfortunately my understanding of electronics is not as strong as my understanding of mechanical things.

Like I said I am more just thinking out loud here, rather than looking to change anything it's running great now. It sure is nice to have these forums where we can openly discuss topics

<img src="/forums/images/graemlins/cheers.gif" alt="" />

Sean

In modern cars with a great deal of electronics low battery voltage can cause all sorts of problems. The magic voltage seems to be around 10.5 vdc to 11.0 vdc, at that voltage computers, ignition, fuel pumps, and etc can become a little nuts, and then you throw in even lower voltage at idle or very low engine speeds and your car can do a lot of strange and wonderful things.