Heavy Stumble Only After Prolonged Deceleration

[Fulkrum]

I purchased my second speed3 last weekend. 2008 Gen1 CAI, Catless Pipes. When I drove the car a week before it ran really well. The dealer put new lower control arms in the rear last week and i picked it up in Tamps Sunday. I drove the car from Tampa to Savannah (300 miles) and it stumbled horribly most of the way. Strangely it only stumbled after a hard deceleration or braking. It would stumble for 3-8 seconds and clear out fine. Its running on 2-3 cylinders during this time. I initially thought it was some condensation built up in the tank sloshing around and getting picked up by the LPFP. I have since run 2 tanks through her with a can of heat water remover. I investigated the car once i got it home and found that the dealer neglected to plug in the EVAP tube on the canister when they removed the lower control arm pivot bolt. This was loose for about a 300 mile drive. Its the line that goes to the purge valve and into the intake. This may be unrelated to the stumble. I've driven the car about 50 miles with the tube connected and it hasn't changed anything. It is throwing (2177 System too lean off idle) (p2187 system too lean at idle bank 1) (P2097 Post catalyst fuel trim system too rich bank 1) (P0401 Exhaust gas re circulation flow insufficient detected)
I think a few of those were likely from the EVAP being disconnected. Like i mentioned its a new car to me so i'm unsure if those codes were there due to the catless downpipe (which has both 02 sensors in their bungs).

Any help or pointers would be greatly appreciated. I have a perfect running 2009 I wrecked 3 weeks ago so I have parts I can swap from it easily. Thanks

[JSmith]

Catless, and no tune?

[Fulkrum]

It has the CNT Catless. I'm not sure of the tune. Looks like the pipe was just put on, it looks new. Too loud for me though. The torque curves feel a lot different than my mostly stock 2009. This one has the stock plastic intake and a big catess pipe. Factory TMIC. Need to investigate HPFP Internals as described in a million threads. Ive got the original owners name yesterday, ill reach out and see about the tune and HPFP internals. I'm working on getting Torque Pro Setup tomorrow so i can check FP pressures.

[Fulkrum]

Update. HPFP pressure at idle cold 500. 3-7k rpm pull wot ranged from 1650-1780 through the pull. I’m thinking the fuel pump system is working properly. Swapped the maf sensor for shits and giggles. No change. On to the next possibility.

[JSmith]

Do you have any way to datalog?

[Fulkrum]

JSMITH, I’m capable to graph up to 7 sensors. Which sensors would be most valuable?

[Thor Hammer]

Did you clear the codes and see if they come back? System lean code might be resolved with a new purge valve. You can get one cheap on Rock Auto.

A word of caution: do not install any aftermarket MAF sensors. They just don't work in our cars. You must use OEM.

Check plugs and gap.

[Carskick]

Make sure intake & Boost tubes are all tight. Unmetered air getting in or boost leak can cause some of the problems you describe.

Clean or replace MAF with OEM as suggested. A datalog may help determine if it's reading correctly or not.

I'm confused as to how you are getting some of the data, do you have an AP or something? If so, post logs. Otherwise, how do you know HPFP pressure and the like? Can you check for knock, boost cuts, etc?

If you plan on going pro tune, get an AP now, which will help you diag these problems.

I encountered the EGR issue at around 60k, and I thought that was causing power issues, but it turned out to be a leaky intake. I found this out after replacing the EGR, which was expensive. Probably just needed to be cleaned.

Too lean and too rich errors sounds like a sensor is off somewhere. Or there are a bunch of mods and no tune. Or both!

[Jeff23spl]

It is really looks like a modded car that the previous owner removed the AP with the tune and left the parts he wasn't able to remove or stock out easily...

Check maf and map part #. Check the maf hosing internal size.

For sure a leak will affect the fuel trims so a boost leak test is a good place to begin with.

Leaking injectors could also give troubles but it would usually settle back under boost after being worst at cold start.
It isn't bad to install new plugs, a speed need them to be replaced often

[Fulkrum]

Thor, yes I’ve cleared them a few times.
I’ve swapped the following from my wrecked perfectly running 2009.
Maf sensor -factory mazda-
Swapped Coil packs, -changed plugs while I was in there.
Swapped evap Purge valve
Confirmed fuel pressure is normal during the “stumble event”

Any other ideas? Thanks for your help.
Checked for vacuum leaks

I will be swapping the catless pipe for a stock one , 02 sensors, and egr valve this weekend.

Jeff, that has crossed my mind. I have a unmolested 2009 ecu I can swap into it. Do you think that would work or be worth a try?

[Fulkrum]

Carsick- I’m using OBD auto doctor. I can map up to 7 sensors graphically. The attachments -60 mark is second gear shifting into 3r then wot at the -57 mark (3-6krpm). Then a full deceleration off of an off ramp. What sensors would make this data more valuable? Thanks for your help~

[Fulkrum]

Here are some fresh graphs from tonight. Descriptions are in them.
4th gear pull map,rpm,go, afr
4th gear pull with fuel trim and afr
2k rpm cruise
Idle

[Jeff23spl]

the ecu work with cluster and keys so you would need to try all at once or reprog but i would instead just look at your map part # and compare with the 2009

[Fulkrum]

Jeff- both cars have the same map sensor l3k9 18211a made in Germany.

[Fulkrum]

Jeff- I’ve coamfirmed that it was put back to almost stock after modding. The Ecu harness Mount was hacked off to make room for a non stock cold air intake.

I found the issue while installing my CP-E turbo inlet pipe. The last owner didn’t orient the clamps correctly on the cold air intake. The clamp head had literally carved out an wore the insulation off of about 5 wires in the main ecu harness. Rookie fail. This explains why the car only stumbled after deceleration. The engine would move and the clamp would ground out the multiple wires
exposed. Unreal. Car runs great at the moment going to take her out for a cruise and confirm root cause. See pics attached~

Thanks for everyone’s help.

[Jeff23spl]

Glad that you figured out.
It would be hard to imagine this could happen without seeing it.