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Ccmano · 05-06-2019

I still get the bogging after coasting and stalling when coming to a stop occasionally. Although the car ran good, it was more pronounced on my 1000k mile trip to LA. last week at lower evaluations and higher temps. After I returned I replaced the injectors and coils, this was previously planned, and I’m now finding this condition a bit more often here as well. In doing some research I found this interesting piece from an old 2014 post by Bob, Warp_Ten with a reply from Mark Haibeck. I thought Marks reply was interesting. I’m going to doing more datalogging here shortly. Keeping in mind bogging and stalling could be two separate issues.

“Craig, I ran into the same problem on my 95 about a month or two after Marc Haibeck did his 510 package for me. I remember him attaching his computer to the OBD port and making a physical adjustment near the throttle in the front of the engine but did not recall precisely what he did. So I asked him and he responded with the following; hope this helps:

Hi Bob,

The adjustment that we made is the, "idle air flow". Basically the air flow through the throttle body at closed throttle needs to match the table that the calibration chip uses to control the IAC servo motor. Engine's with stock cams can use the OE table values. The OE IAC count at idle with a hot engine is 10 IAC servo steps. On your engine the IAC count was 30 at idle. That's because my larger 63 mm throttle body is tighter and leaks less air than the OE throttle body. There is another concern, that the IAC count could go to zero. Then the idle speed would go too high. I initially left the IAC at 30 because running out of counts is a more common problem than die out if the IAC count is not perfect. After your engine exhibited the die out problem. I adjusted the primary throttle plate stop screw to open the throttle until the IAC count on the scanner was 10.

An engine with big cams might idle at 850 rpm. Because of the additional air flow requirement, the IAC count is typically 50. In that case the table in the calibration chip needs to be adjusted to what the engine wants, that is 50.

When I figured this out ten years ago I probably spent 20 hours analyzing data to understand it. At first one might think that the problem is related to fueling or spark advance. I spent most of the time determining that I was barking up the wrong tree.

Regards, Marc

05-06-2019	#38
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,843	Re: Bogging after Coasting I still get the bogging after coasting and stalling when coming to a stop occasionally. Although the car ran good, it was more pronounced on my 1000k mile trip to LA. last week at lower evaluations and higher temps. After I returned I replaced the injectors and coils, this was previously planned, and I’m now finding this condition a bit more often here as well. In doing some research I found this interesting piece from an old 2014 post by Bob, Warp_Ten with a reply from Mark Haibeck. I thought Marks reply was interesting. I’m going to doing more datalogging here shortly. Keeping in mind bogging and stalling could be two separate issues. “Craig, I ran into the same problem on my 95 about a month or two after Marc Haibeck did his 510 package for me. I remember him attaching his computer to the OBD port and making a physical adjustment near the throttle in the front of the engine but did not recall precisely what he did. So I asked him and he responded with the following; hope this helps: Hi Bob, The adjustment that we made is the, "idle air flow". Basically the air flow through the throttle body at closed throttle needs to match the table that the calibration chip uses to control the IAC servo motor. Engine's with stock cams can use the OE table values. The OE IAC count at idle with a hot engine is 10 IAC servo steps. On your engine the IAC count was 30 at idle. That's because my larger 63 mm throttle body is tighter and leaks less air than the OE throttle body. There is another concern, that the IAC count could go to zero. Then the idle speed would go too high. I initially left the IAC at 30 because running out of counts is a more common problem than die out if the IAC count is not perfect. After your engine exhibited the die out problem. I adjusted the primary throttle plate stop screw to open the throttle until the IAC count on the scanner was 10. An engine with big cams might idle at 850 rpm. Because of the additional air flow requirement, the IAC count is typically 50. In that case the table in the calibration chip needs to be adjusted to what the engine wants, that is 50. When I figured this out ten years ago I probably spent 20 hours analyzing data to understand it. At first one might think that the problem is related to fueling or spark advance. I spent most of the time determining that I was barking up the wrong tree. Regards, Marc