Droops83

Hi Tom,

Thank you for pointing out the counterintuitive fact that a weak spark will cause an oxygen sensor to read lean---because all an oxygen sensor detects (wideband or not) is a lack of or excess of oxygen compared to ambient air. I have pointed this out several times recently on the Facebook group, but I'm not sure it is getting through because most people there seem unable to read more than one short sentence (TLDR .

RGS

I am working my way through this gremlin as well. My 951 is completely stock. Here is what I have done, and what I notice.
Symptoms:
1. Idle is fine, smooth, no miss
2. If I am low in the RPM and I floor it, I get boost and no miss
3. If I am part throttle slowly going through the rpms, I get a lean miss (well feels like a lean misfire), bucking

Car details and what I have done:
1. Car is completely stock
2. I have replaced nearly all vacuum hoses with Lindsey silicone - (1-4 were done at the same time, no change)
3. I have sealed up the IAC
4. I have rebuilt the throttle body seals with Paragon kit
5. I have cleaned the AFM per Arnnworx tutorial - no change
6. replaced the blow off valve/diverter valve
7. I have a new TPS, but haven't test it yet.

Here is my thought process on diagnosis with one key element. I drove the car about 25 miles and finally got a 4-1 code on the blink test. Didn't show up before in all the rest of my short trips. Also the car goes into limp mode after the part throttle bucking. I am thinking it is TPS related. Or as others have said maybe the AFM, but that looked good and was cleaned. It is something in part throttle driving as I can floor it and boost and no misfire. I am not sure if this helps, have you tested or replaced the TPS? How about AFM or do you have a MAF?

markl951

Check the blow off valve. It's easy to get to. A sticky or stuck open blow off valve can sometimes create the symptoms you are experiencing.

spencang

Sorry for the delay in reporting back, I had some issues logging in to rennlist from my work computer.

While changing the FQS settings, I noticed that my A Tune chip was not there from when I sent in my DME to be "renewed" by Focus 9. I have contacted them and they are looking to see if they still have it somewhere (that was 2 1/2 years ago). So I feel like I MUST have that in or switch to different chips before I proceed. I do have Max Hp chips that I got years ago that I really liked, but I'm not sure if I need to take out the other A Tune hardware in order to use those.

When I did to a run yesterday from 2500 Rpm, I had the same cut-out/bog/buck at 3800 rpm. The only difference was that my AFR was now at 12.

I have not capped off my evap system.

Am I correct in assuming that I need to have the right chips in place before I proceed in checking the other possible problems?

spencang

Yes, stock and stock. I guess so!

spencang

Do you know if need to remove the A Tune hardware to put my old Russell Berry chips in? Or should I wait to get the A tune chip back in there?

Tom M'Guinn

What hardware? On Bosch DME's you needed to cut a resistor lead to hook up the map sensor. On that new DME, is there a jumper or something to put it back to stock with the map removed. If so, I'd just do that and eliminate a variable. If you have bigger injectors, or a 3bar FPR, then it depends if the MAX chips are programmed to use them or if they are programmed for stock parts.

You could also just turn the boost down, assuming it's controllable, to see if it goes away. Or check the blink codes -- over-boost triggers a code if memory serves.

spencang

Here's the hardware. There was no jumper or that resistor that I originally cut on the old DME.

My old Russel Berry chips worked very well with the 3bar AFPR that I have had for some years now. I had no issues back then. I just heard about the A tune and the 3D Mapping, so I thought "why not improve what's already good".

spencang

I'll remove the rest of the A Tune and report back tomorrow. Fingers crossed...

spencang

I wasn't rich at all. I was lean. That's why I changed the FQS setting to #3, +6%. I'll know more tomorrow

mwc951

A couple months ago I ordered a F9T DME as part of a winter upgrade project.
Concerned about clipping the resistor, I emailedJoe Baumbach about it before placing the order.
Below is his response.

I clipped a resistor per John’s instructions, I believe this is done with the Rogue kit as well.
How will your DME accommodate for this?

The SPORT DME is designed with MAF and MAP upgrades in mind, it is compatible with these kits out of the box.

spencang

It was the chip all along! I returned everything back to run my Russell Berry chips and it's all good now; bucking is gone!

That's good to know about the F9 DME. I remember a similar response. I'm just waiting to see if he has my chip still, and if not, what he will do about it.

Tom M'Guinn

In your first post, a year and a half ago, you said it "almost feel like over-boost protection...." I guess we all should have listened better. I can't quite explain why ignition parts seemed to clear up the issue temporarily, etc., but I'm guessing you are on the cusp of the limit and things like ambient temps/humidity were helping to push you over/under the limit. I did notice that "most" of your "it's happening again" posts were in cold months, when the motor will see more oxygen/load.

Knock on wood this time the fix is real. Did you change chips in both the DME and KLR? How did the KLR chip get replaced with stock? Or was the MAX chip in the KLR all this time? If the MAX chip was in the KLR all this time, I would have thought that it would prevent overboost protection even with a stock DME chip, but I don't know that for sure.

spencang

The A-Tune runs with the stock KLR chip, so I had the stock one in all this time. When I switched back to the Max chips, I swapped them both out.

What I have noticed so far is that the initial tip in is not as good as it was with A-Tune or with the Focus 9 "stock" chip. So I will definitely be switching to the A Tune once I get the chip back.

Thanks again for your diligence and help in trying to diagnose the "issue" Tom. I'm definitely knocking on wood that this is it....and hopefully this thread has and will help others with a similar problem.

mahoney944

I used vmaf+ and mtune with my ftech9 dme. Works great. No resistor to clip as his design doesn't have that resistor. From my understanding the klr chip doesn't really matter for these kits. Especially if you've switched to an after market boost controller.