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Join Date: Sep 2003
Location: Los Altos, CA
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Low idle speed...please help

We just finished rebuilding our engine and it started right up the first time...

We set the timing at 27 degrees with both hoses removed at 3500 rpm. After the engine had warmed up and the aux air valve shut (even tested by plugging air inlet to valve), we tried to set the idle.

The idle is way too low, about 500 rpm max. The adjustment screw is making almost no difference. I played with the mixture screw on the ECU both directions (refresh my understanding, it is backwards, right? CCW is leaner, CW is richer). Adjusting this did not make a huge difference. I adjusted this to achieve highest rpm and richened one click (CW).

We cleaned out the air bypass hole to make sure it was not plugged.

We also played around with the TPS by shutting the butterfly valve all the way to make sure the ECU "thought" it was in idle mode.

I also have another question about advance. I have been told that we should see a total advance (with hoses on) of around 33-36 degrees. We checked our's after setting the 27 degrees the normal way, it was around 35 degrees. Does anyone have any specs on the mechanical advance and vacuum advance (retard as well, I guess)? My understanding is that at WOT that vacuum advance should be close to nil. We should basically only see the mechanical advance. However, we are seeing about 8 degrees advance due to the vacuum advance (35-27=8). Does this make sense?

We played with the advance all over the place and were not able to get the idle to go higher.

Please help me with these questions.... Your help is much appreciated.

Yes, it is running on all cylinders.... Hoses connected properly..

Chris
Old 09-08-2003, 11:49 AM
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Distributor info:
http://www.dgi.net/914/tech/distrib.html

First things first--you want to run the motor at 2000 RPM (or more) for 20 minutes to break in the cam.

Then shut down, change the oil, and the next day (or after everything has cooled off) adjust the valves.

The low idle could simply be from the parts not having worn in to each other.

--DD
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Old 09-08-2003, 12:00 PM
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I was going to ask on the other board about the valves, watch the tight ones at this point.


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Old 09-08-2003, 12:11 PM
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Thanks Dave. It was actually only a top end rebuild with new P&C so the cam is good. We did as you suggested anyway...;-) Do you really think the valves being off by a little would cause this? When we set them we set them all, then spun the engine around a few times (maybe 5) and then re-checked the adjustment. We re-adjusted a few. they shouldn't be that far off...

Chris
Old 09-08-2003, 12:15 PM
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