Z4MC Hesitating

[BGR]

Car has ESS tune on it, aftermarket secondary air pump, possibly the Motorsport thermostat, stock air box/filter but has a charge pipe. This is how I bought the car and it has been hesitating and throwing codes since day 1 (it came with a tune for a supercharger on it but no supercharger so I reflashed it with the ESS NA tune).

If I go full throttle, regardless of the RPM or speed I'm at, I get a little hesitation for about .5 seconds, then it seems to clear itself and accelerate normally. During the hesitation, it almost sounds like it is bogged down and there is an audible change when it picks up (it sounds happier).

Here are are the codes it is throwing. If I clear them, they all come back. The first code won't clear, so I suspect there is an actual failure, but I can't imagine it would be causing this issue.

// 1) 2E7C bit serial data interface, signal (BSD wire failure)
// 2) 2C92 EGT sensor, electric
// 3) 2C9C Output heater 02-sensor before catalyst
// 4) 2C9D Output heater 02-sensor before catalyst (bank 2)
// 5) 2C9E Control heater sensor after cat
// 6) 2C9F Control heater sensor after cat (bank 2)

Any thoughts/guesses/pointers/suggestions would be appreciated.

Thanks.

[Westersund]

Afaik the secondary air pumps only feature is to heat up the cats faster to decrease the polution, shouldn't effect the way the car drives. Given it's an older car, but my E34 M5 doesn't have the secondary air pump anymore and it runs great.

Maybe it's the O2 sensor that's bad? Seems to be quite a common problem. Or some wiring/connectors have gone bad.

[Vanne]

it aint the egt sensor, car will happily run without that

[bignosejim]

Here is a link to BMW fault codes.

https://www.google.com/url?sa=t&rct=...02537793,d.eXY

Post #23 has the fault codes your car is throwing. It looks like maybe both O2 sensors/EGT sensor might not be hooked up? the first one means that a connector is not connected and the other one's are probably what is not connected. If you have the stock tune you can always flash that and see if the problem follows. If a supercharger was connected they probably didn't use some of those instruments.

[BGR]

Let's just say the O2 sensors were bad or not hooked up, could that be causing the hesitation?

[Westersund]

As the ECU adjust the air/fuel ratio based on the values it gets from different sensors I'd say yes. Hesitation is common if the MAF is bad, hence it giving the ECU bad readings. But since you get fault codes on the O2's they're likely to be the cause of the problem. Check if everything is connected first before you replace parts.

[inTgr8r]

Does the hesitation occur at a specific RPM?

[BGR]

Originally Posted by inTgr8r

Does the hesitation occur at a specific RPM?

Doesn't matter the gear or rpm, but it seems to be more pronounced if I floor it at a lower RPM (2k) vs higher (4k+). I can definitely still feel it at higher RPMs though.

[tiltmode43]

When your car still had the ESS S/C tune on there, was SES light on/any codes thrown? Wondering if turning readiness on/off had an effect on how the car performed.

[BGR]

Originally Posted by tiltmode43

When your car still had the ESS S/C tune on there, was SES light on/any codes thrown? Wondering if turning readiness on/off had an effect on how the car performed.

I'm 95% sure the check engine light was on. I did not pull the codes or clear them though.

[pokeybritches]

Did the car have aftermarket headers that were swapped to stock?

[BGR]

Originally Posted by pokeybritches

Did the car have aftermarket headers that were swapped to stock?

At one point, the car had euro headers. My plan is to crawl under tomorrow to confirm what is on there now, but I'm fairly certain they are stock US headers currently.

[pokeybritches]

I ask because some of the sensors could have been swapped around.

[Steeler]

Originally Posted by pokeybritches

I ask because some of the sensors could have been swapped around.

I have this situation and my reader returns a ghost code for "mixed up O2 sensors"

Haven't got around to reversing yet

[Vanne]

The egt will throw a ses. Though will happily run without it..just not at optimum.

Edit, stock tune will throw ses, mine dident, and discovered later it had a non stock tune.

[BGR]

Well, more issues.

I got the stock DME flash file from ESS to help with diagnosis when I bring the car in. Except when I tried to flash it back to stock, it gave me an error message "error initializing crypto routine". It wouldn't install the stock file. So I reinstalled the ESS tune file (without issue, it took it right away) and started it up...

-Started find
-Idled fine, although smelled rich
-But if I gave it any gas, the RPMs would climb to about 1,500 then cut out and fall down to about 1k, then climb, then cut out over and over again. When I let off the gas the car would die.

No check engine light came on, and by this time I was frustrated and the mosquitoes were trying to take me to their home base so I didn't check for any stored codes.

Not sure if the DME got fried or what. So far this car has been a problem child.

[Westersund]

Originally Posted by BGR

-But if I gave it any gas, the RPMs would climb to about 1,500 then cut out and fall down to about 1k, then climb, then cut out over and over again. When I let off the gas the car would die.

This sounds exactly like a bad crank shaft pulse sensor. Had it on my daily, but the problem wasn't permanent yet it would just come and go.

[BGR]

Originally Posted by Westersund

This sounds exactly like a bad crank shaft pulse sensor. Had it on my daily, but the problem wasn't permanent yet it would just come and go.

Did you get any error codes indicating that was bad anywhere along the way?

[BGR]

I got the stock version of the tune on (still wouldn't accept actual stock tune so had to flash a stock parameter tune).

Still does the cutout under any throttle.

It's interesting you mention the crankcase pulse sensor... The oil fill cap was leaking (has since been replaced) and oil ran down the top and right side of the engine... Right in the area of that sensor. Not sure if it could have fouled something up.

[BGR]

This is the part I was referring to as possibly being subjected to oil. After doing some reading, it doesn't appear this is the crankshaft position sensor/pulse generator. Which I suppose still could be bad, but does anyone know what the circled part is?

[BGR]

[RobMCoupe]

I believe that is wire connection to O2 sensors.