Hi Everyone,

I recently fixed the stubborn P2188 (system too rich at idle) code on my 152k mile 2008 R56 Cooper S (JCW Package). The worst part about this code was every 50 miles (or 3 engine warmups mostly) my mini would turn into a base mini past 3500 rpm. The turbo became non-existent you couldn't hear any spool. I had the code for about two years due to trying to fix/replace parts, still having the issue, feeling defeated and giving up and repeating that cycle. What ended up fixing the code for me was replacing the upstream o2 sensor (of course the last of MANY fuel components I replaced!)

Anyways, car now has no codes and I have boost all the way through, but I get some fuel stumble or "hiccups" on wide open throttle. I have replaced a lot within the past 20k miles:

(132k ish)
- Thermostat and Housing
- HPFP (still reads 750psi at idle and 1700psi underload)
- Water Pump
- Brake booster pump
- Oil pump chain and Sprocket
- Oil Filter Housing Gaskets
- Turbo oil feed and return lines
- Turbo Coolant feed line
- Timing Chain, Guides, Tensioner
- Hardened Turbo Vac Lines throughout
- Diverter Valve (Upgraded to revised Pierburg OEM)
- VANOS Sensor
- Bosch Iridium Plugs and coils (ran bosch iridiums since I got the mini at 98k miles)
- Downstream o2 sensor
- Cam position sensor
- Forge charge Pipes all Around
- Turbo Inlet Pipe (Just have MAF and K&N Filter coming off of this, but had this intake setup for years since I got the car before getting P2188 so don't think it's worth going to stock box)

(142k ish)
- Valve Cover and Gasket
- Intake Valve Walnut Blast at Dealer

(Very recent, past 3k miles)
- MAF Sensor
- Throttle Body
- Intake Manifold Gaskets
- Upstream o2 sensor
- Fuel Filter and Fuel Filter Assembly (Because Fuel Pressure Regulator is built in)
- New Plugs (Again, Bosch Iridiums)

Regarding fuel system, the only components that haven't been replaced are in tank fuel pump, fuel rail pressure sensor, and injectors. I'm doubtful it's injectors they don't tend to go bad. I'm also doubtful its the fuel rail pressure sensor if I'm getting proper readings on my scanner for the HPFP idle and load pressure readings, but I suppose it could maybe be throwing off readings for such a short amount of time my scanner doesn't pick it up, but it affects the car trying to maintain proper air to fuel ratio. My scanner is cheap I can't log the data.

I'm thinking the in tank fuel pump or the spark plugs are my issue. I've ran bosch iridiums for years with no issues but some people on this forum say the N14's are finnicky and swear by NGK's.

Any thoughts or insight on why I'm getting this fuel stumble is highly appreciated. Thanks!

Jordan

 

I had high boost fuel stumble due to a clogged fuel filter. It’s possible your in tank pump is starting to slow down, and can’t provide the fuel volume needed

 

Like you, I have had 6 months of exactly the same issues regarding p2188 and I replaced many of the same parts.

I replaced plugs, coil packs, thermostat, water pump, valve cover, upstream and downstream o2, checked the timing chain, cam timing, MAF sensor, did a compression test and all of these did nothing to stop the code and the limp setting kicking in, usually after a couple big stumbles at WOT or if it idles a long time.

I started to look for vacuum leaks and did find two big ones, one the intake hose to the turbo had a crack at the clamp, and another was an extra hole in the intake manifold that had nothing hooked up to it (looks like the intake manifold was made for a different version of n14). This solved a few things but not the p2188 and limp mode.

I thought maybe to try disconnecting the evap hose from the manifold and plugging it so that there was no chance at a vacuum leak anywhere and voila, no more code. The problem is I don't think it is actually solved, just a close enough mixture that the computer can sort of keep up enough to not code out anymore.

I get -.25 at idle and between -.21 and +5 short term fuel trim, 0 long term, when driving, and at highway cruise right around 0 trim on both, so at speed it runs properly. Still get the hard stumble off idle while the car is luke warm, not cold not hot, or just after starting it when it is warm. Occasionally it idles at around zero, but mostly -.25 which is the limit the system can handle.

The only thing weird is my high pressure fuel pressure is at 925 at idle. Other sites say it should be 750ish. Occasionally the idle is at 750ish but it is sporadic. The idle and mixture are always pretty close to correct. Any of this sound familiar?

 

Keeping things simple, the two most likely causes of this are poor fuel or bad plugs. Reasonably simple to eliminate both of those before moving on to other causes

With plugs, there are a lot of fake plugs around on the internet, a real problem. You have to buy them from a very reputable place, even if it is not the cheapest. Most people don't ever know they have been stung, because the fake ones work ok for cruising around lie 99% of drivers do.

 

^^ +1 Yep and make sure the gap is correct on the plugs, most come pre gapped but they can get knocked around before install.

 

Appreciate the input. However. Plugs are installed by the dealer as are the coil packs and I run Shell 93 octane fuel. The motor runs hard and smooth to redline. This is an intermittent issue not related to performance, mileage or even idle. The -.25 short term fuel trim at idle tells me there is an issue, but idle is smooth and mixture around 1.00 all the time far as I can tell. The stumble at WOT while the car is say 170 degrees F that seems to go away at full temp also appears occasionally after the car has been idling for a while. Another oddity, I have had several instances where the short term trim at idle is 0, so this makes me think a faulty sensor?

 

Hi

Did you mange to find the issue. im sitting with the same problem

 

^^