Hi Guys! Last chain up to 20 with multiple subjects so starting a new chain.

1. Don't think there's a timing problem. Pulled starter and confirmed that 3-hole timing blank at bottom of starter hole with #1 at TDC.

2. Vacuum leaks. Don't think there are any. This is a Regina system and car will start and run all day without pleated pipe hooked to TBA; or, with a big hole in pipe. Same for IAC valve inlet hose to filter box. Inlet air will not be filtered nor will the air temp sensor function but engine starts, runs and accellerates just fine. MAP sensor monitors vacuum on engine side of throttle plate. There is no AMM! Ragina ECU is supposed to adjust for any long term leaks with IAC valve signal.

Besides with engine hot, RPM immediately increases from 800 to 2100 when TPS switch opens. There would have to be a vacuum leak maybe the size of your little finger tip to increase RPM that much that magically appeared when the TPS idle switch opened. Have unhooked and plugged brake booster hose ditto for, heater hose and small flame trap hose and no change.

Last chain I mentioned with duct taped TBA, that it looked like manifold gasket might be leaking. Manifold nuts were snug and snugger now. Suspect most of the decrease reported was due to engine cooling off after previous test and I didn't check it again when hot. Duct tape was deforming into TBA and didn't want to press my luck and have soft gummy tape mess sucked into engine.

There is no vacuum leak that will increase rpm from 800 to 2100 that magically appears when TPS idle switch opens when engine hot.



Think Art on to something re: IAC valve duty cycle (DC). Retrieved Heathkit ID-29 dwell meter. Must be 45+ years old! but like most heathkits was/is good quality.

Here's the readings:

Warm engine TPS closed 770-790 rpm dwell 16.5 on 45 degree scale 36.7% DC

TPS open 1640-1710 18 45 40% DC

3500RPM 22.5 45 50% DC

Hot engine TPS closed 770-790 16.7 45 37% DC

TPS open 2150 18.5 45 41% DC


Warm engine dwell, DC, increased uniformly between 1700 and 3500 RPM

Heathkit dwell meter calibrated to full scale with ground through ECU.


Ragina Greenbook chart on fault tracing with Measurement box: @ idle DC=20%

@2500 RPM <25%


All heathkit measurements higher than chart!! Meter is off? Or is ECU not comtrolling valve per specs?



Again, here's the problem:

1. Keep engine rpm from jumping when TPS switch opens.

2. Determine why jump is greater with hot engine.

Have swapped 4 ecus, 2 IAC valves, 4 temp sensors and 2 MAP sensors and nothing helps!!! Have not changed oxygen sensor.


Would like to solve this problem and am open to ideas and appreciate everyone imput.


Steve in Charlotte.