hadams42

'84 N/A 13B. My first rotary. Good with computers. Not so swell with vacuum lines

I got the car and it idled at around 2,500 RPMs. Coasting or slow driving was terrible. Basically had to be ripping it or it felt like it would stall, but never actually would. Seems emissions, including air pump, etc. are removed. A/C is disconnected. Power steering pump came to a clattering end (I cut the belt and continue on).

Checked the timing. It looked basically correct with random advancing occurring. Seemed to even out after warming up.

I followed the Fuel and Emissions section of the FSM for the most part (so many parts are missing on this car). I've tweaked everything back to what seems like something close to normal. Idle is just under 1,000. Drives like a "normal" car, etc.

The remaining issue is, say after pulling into the garage after a short drive, it will idle up down, bouncing predictably...and then clear up on its own. When driving this translates to similar issues when coasting, etc. But it starts bouncing easily enough it seems to be an issue.

I checked timing and the bouncing does not exactly coincide with timing changes, but it does appear that if it bounces too high or low an occasional change occurs. I am assuming the change is the vacuum advance. The fixed timing finger moves away from the yellow mark, further away from the red mark, when timing the leading side.


Here is what I know:

* Tested the airflow sensor. Everything checks out except was just not able to get a real solid resistance curve. I didn't have a 5-volt supply handy, so figured my procedure was bad. So I assume this sensor is fine.

* Did my best to calibrate the TPS, although seems I chase my tail around. The sensor tests fine electrically.

* Fiddled with the variable resistor, as it was screwed to the max right position I believe. It is not more centered. I followed the procedure in the FSM--but once again, I feel like I am going in circles, that there is another variable acting on the system that I am missing.

* The test that seem to totally fail are under the BAC system check. The Vent Solenoid Valve and the Air Supply Valve tests require RPM changes to occur when the units are disconnected in relationship to the A/C or headlights being on. There is no A/C. Headlights work fine. I can plug and unplug these connectors, switch the lights on, etc. and have no change in RPM. Are these potential causes of my issues?



On a side note, when it idles it is relatively smooth but there is an occasional (a second or two between) bbdup, bbdups from the exhaust. Plugs? Wires? Something worse? I have read about the dangers of preignition, so if somebody can describe what that would feel/sound like that would be helpful.

Thanks for your help!

Cheers