Throttle body limited to 40%

L

limesta

Greenie N00B Member
Year/Make/Model: 2006 speed6 GT
Mileage: 250,000
Location: SW MI
Concern: TB
Modifications: CP intake, HPFP internals, EGR delete
ECU/Tuning Software: stock
Is the concern intermittent? constant

So this post is somewhat of an extension from this previous thread, and it just died with no resolution.
https://mazdaspeeds.org/index.php?threads/possible-throttle-body-issue.12176/page-2
I have had the same issue for a few months now, nothing was done to the vehicle for this to happen.
only additional repairs done was an alternator replacement, but it didn't seem like that effected anything at the time.
I went ahead and replaced the throttle body, and did my HPFP internals, and nothing has been fixed.
My throttle body seems to only open to ~40%, and just stops.
My logs are extremely similar to the ones posted in the linked thread, so far I cleaned the grounds and nothing has been fixed, anyone have any troubleshooting ideas or suggestions?
I have an EGR delete, and no boost/intake leaks, vacuum leak-down seemed to hold pressure.
I also reset the battery, and tried opening the TB w/ acc and it hardly moves in that state., cleaned the MAF and cleaned the TB, connector was corrosion free.

Pretty much just lost on this one chasing gremlins, looking for diagnosing suggestions and ideas to pinpoint this ongoing issue, maybe the TB isn't getting enough power from the ECU from a damaged wire? No limp mode or anything to that degree
 
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Throttle body gasket fail.jpg This may help. In my complete rebuild process when I removed the throttle body I found this gasket failure by PO. After rebuild I was having odd throttle results, finally figured out the throttle body actuator motor was sticking in various areas in the total butterfly movement.
Vid attached is a recording of key on and key off. The ECU will cycle the throttle body butterfly then turn off relay removing power to ECU after the actual key position is off. The high frequency "hum, sound is the throttle body motor holding the position of the throttle butterfly in the ECU commanded spot. The (power off cycle) movement is likely a validation of the stroke operation before shut off. Then next key on the ecu remembers the last key off status. The audio recording is a key on then a key off you coordinate that sound file with the video and if yours is different the replacement throttle body is part of your problem. Hopefully you can find a known good throttle body to test with.
 

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Definitely try a new tb. I gave mine away when I went corksport.
 
So went through and inspected my TB and nothing, already replaced, I cleared codes and after discharging the car I went ahead and tried driving, and noticed a small stutter when the VVT typically actuates from full retard to advance (IIRC ~3k RPM under WOT), and then the fuel trims are a little weird for idle after that.

I am suspecting this may be the symptoms of a bad OCV, there are no DTCs, this may be automated ECU behavior based on OCV operation.
I have to replace some gaskets (OCV seal, VC gasket), so I will go through and inspect the OCV using this guide. I will report back this weekend, a replacement has been preemptively ordered.
Car has missed a few oil changes between me and the previous owner, so I will inspect the filter before the OCV and inspect for a clog there as well. Will inspect resistances in the morning as well and also report.
Additionally why I suspect this is because of my mileage, I found this video on YT, and they specified they did not notice the failure until they logged and went through advanced diagnostics, assuming they had no DTC pop up, I may be in the same boat, I noticed some minor unusual fuel trim behavior, and from other resources, it directs to poor OCV performance.

The weird fuel trim behavior was also noted in the linked thread above when I went through their logs, I am suspecting they had suffered the exact issue I am dealing with as well, I am hopeful this is the solution.
 
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That thread was not me, but I got my logs here, I reset the PCM w/ forscans' tool, anything with "d2" is after the PCM reset and the one called pcm reset idle and drive is as well, everything else was warmed up and before the reset
I have a couple of WOT pulls, if you want me to do any other runs, lmk.
I logged a value as well called "VVT DIFF" (degrees) that shows the difference in VVT intended position and actual position.
I also ran KOEO and KOER and no results.
Parts should be coming in tomorrow, assuming Fedex doesn't lose them I should have that at the very least done.
 

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