Diagnosing Hesitating/Misfiring X35i with No Codes

[andrewwynn]

Originally Posted by 740iS

Forgot to reply the other day, but the rebuilders for most auto parts chains, especially O'Reilly and Autozone out here, are NOT using Valeo or Bosch internals. The rebuilds, regardless of who the original manufacturer was, are all using the same aftermarket internals on their rebuilds.

That would explain the quick failures. You can get a new Bosch from O'Reilly for barely more than the rebuilt and from the way they handled my exchange I think they will replace new for new.

[ClutchKickChris]

Hey Guys,

I really appreciate all the ideas and feedback!

It's still not fixed but some progress has been made. Since my first post I have done the following:

• Removed and flushed clean the vanos solenoids.
  They weren't too dirty. Idle feels a bit "crisper".
  
• Ran a bottle of techron concentrated fuel injector cleaner through a tank.
  No change at all.
  
• Replaced the waterpump
  This actually cleared all of the false DME DTC's! Now the waterpump doesn't run with the engine off, the alternator, oil level sensor, battery sensor etc. all report and function correctly!
  
• Double checked that the trans fluid was properly filled.
  Around a year ago I had flushed the trans fluid and replaced the trans filter. Somebody told me that torque converter shudders can feel a lot like a misfire, usually caused by not enough trans fluid. This got me thinking and doubting that I had filled it correctly or not. Well after getting trans up to temp and following the fill procedure again it was filled perfect. I also reset the trans adaptations and went through the re-learn procedure. No change in driving.

So today I had my wife drive the car while I monitored different variables, especially the "Rough running value" for all 6 cylinders (I believe this is the "run unrest" test that ard mentioned). Unfortunately all cylinders seem to randomly show high/low values so it's not very conclusive as far as I can tell. I screen recorded this and more off of my phone and uploaded it to YT:



List of theories:

• Broken oil filter cap - I'll be checking this tomorrow.
• Alternator - I highly doubt this as I have a battery monitor and it shows the alternator charge amps and volts to be correct and working normally.
• Low or High pressure fuel pump
• Bad Injector
• Some rogue intermittent bad sensor (timing or pressure)
• Somehow still a bad coil or plug
• Bade DME?

[andrewwynn]

The sensory that detects misfire is the crank position sensor. If a cylinder misses, the math doesn't work out for the expected position of the crank. I think that's where the smooth operation values come from that's just educates guess.

Since you aren't getting codes, you made be in a similar situation to me when I first bought my X5 but in my case was the intake cam position sensor.

No codes never drove funny but would stall with increasing frequency when moving short distances eg pull forward to turn left when the light turns green.

I would get codes but just random cylinder misfire nothing CPS related.

I think you may be experiencing a very similar thing.

Imagine if you will, the cpk is reading but adding or subtracting milliseconds from the timing of the crank. The car will have fits trying to figure out when to send the fuel and spark and will definitely mess with performance.

I forgot if you said you changed cam position sensors. That could also cause performance degradation.

[ClutchKickChris]

Originally Posted by andrewwynn

The sensory that detects misfire is the crank position sensor. If a cylinder misses, the math doesn't work out for the expected position of the crank. I think that's where the smooth operation values come from that's just educates guess.

Since you aren't getting codes, you made be in a similar situation to me when I first bought my X5 but in my case was the intake cam position sensor.

No codes never drove funny but would stall with increasing frequency when moving short distances eg pull forward to turn left when the light turns green.

I would get codes but just random cylinder misfire nothing CPS related.

I think you may be experiencing a very similar thing.

Imagine if you will, the cpk is reading but adding or subtracting milliseconds from the timing of the crank. The car will have fits trying to figure out when to send the fuel and spark and will definitely mess with performance.

I forgot if you said you changed cam position sensors. That could also cause performance degradation.

No, never changed the cam sensors, is it recommended at a certain mileage?

[andrewwynn]

Originally Posted by ClutchKickChris

No, never changed the cam sensors, is it recommended at a certain mileage?

Usually when you start getting random weirdness a prime suspect is cam sensors. Usually they last 120-150 k miles

[SB1120]

I have a 12 35i 185k, almost identical issues.

The water pump “waking up” and other shadow codes were definitely that water pump. The oil sensor, water pump, alternator, battery management (IBS) all share a serial bus interface wire ( think party line). When one component fails and pulls the bus wire down, the other items either can’t communicate or start doing funny things until the failed component is fixed. In this case, the most likely is the water pump because the electronics are all housed within the case where coolant eventually leaks.

Here’s what I have done to “save” this e70. The thing was a steal so I wasn’t too worried about spending the money on parts. I started with what I knew to be broken or overdue and later just started throwing parts at it.

-Valve cover- ruptured diaphragm and rotten valves within the valve cover
-Valvetronic motor (I did this while I had the valve cover off. I DO NOT recommend this unless you’re prepared to replace the eccentric shaft, bearings, etc at the same time. The shaft wears a pattern into the bearings and gears wear a pattern into each other. Once disturbed, valvetronic motor current sensing is too sensitive and a run in cannot be done. Ask me how I know)
-Plugs and coils (Delphi)
-Intake Vanos solenoid- present code
-Intake valve cleaning, intake gaskets (including the gasket for the DME), sealing rings on charge pipes, cleaned maf
-A/F sensor- just because
-Injectors and coded them- shot in the dark. The plugs were pretty darkened and at 184k, I figured why not.
-Cleaned exhaust Vanos solenoid
-Oil filler cap gasket- any air leakage into the crankcase is a vacuum leak. The valve cover is a very integral part of the intake system, to this engine’s detriment.
-Reset adaptations each time something major is done.
-Battery (Age)

I’ve gotten to the point that I’ll live with it for now until something actually breaks. It’s strong at WOT like the op’s and it’s just partial throttle where I feel a mild bucking sensation. I grabbed Carly to see some live data that I couldn’t see on other tools but I haven’t had an ah-ha moment. High pressure fuel reading looks fairly normal, throttle input, advance/retard of cams, MAP and MAF readings..

OP- a new thing I have noticed is that at night with the dome/map lights on, I can see some flickering from the lights that seem to be influenced by the engine operation and speed. Do you notice anything like that?

[ClutchKickChris]

Originally Posted by SB1120

I have a 12 35i 185k, almost identical issues.

The water pump “waking up” and other shadow codes were definitely that water pump. The oil sensor, water pump, alternator, battery management (IBS) all share a serial bus interface wire ( think party line). When one component fails and pulls the bus wire down, the other items either can’t communicate or start doing funny things until the failed component is fixed. In this case, the most likely is the water pump because the electronics are all housed within the case where coolant eventually leaks.

Here’s what I have done to “save” this e70. The thing was a steal so I wasn’t too worried about spending the money on parts. I started with what I knew to be broken or overdue and later just started throwing parts at it.

-Valve cover- ruptured diaphragm and rotten valves within the valve cover
-Valvetronic motor (I did this while I had the valve cover off. I DO NOT recommend this unless you’re prepared to replace the eccentric shaft, bearings, etc at the same time. The shaft wears a pattern into the bearings and gears wear a pattern into each other. Once disturbed, valvetronic motor current sensing is too sensitive and a run in cannot be done. Ask me how I know)
-Plugs and coils (Delphi)
-Intake Vanos solenoid- present code
-Intake valve cleaning, intake gaskets (including the gasket for the DME), sealing rings on charge pipes, cleaned maf
-A/F sensor- just because
-Injectors and coded them- shot in the dark. The plugs were pretty darkened and at 184k, I figured why not.
-Cleaned exhaust Vanos solenoid
-Oil filler cap gasket- any air leakage into the crankcase is a vacuum leak. The valve cover is a very integral part of the intake system, to this engine’s detriment.
-Reset adaptations each time something major is done.
-Battery (Age)

I’ve gotten to the point that I’ll live with it for now until something actually breaks. It’s strong at WOT like the op’s and it’s just partial throttle where I feel a mild bucking sensation. I grabbed Carly to see some live data that I couldn’t see on other tools but I haven’t had an ah-ha moment. High pressure fuel reading looks fairly normal, throttle input, advance/retard of cams, MAP and MAF readings..

OP- a new thing I have noticed is that at night with the dome/map lights on, I can see some flickering from the lights that seem to be influenced by the engine operation and speed. Do you notice anything like that?

Nice to see I have a buddy with exact same issues lol. Yes replacing the waterpump fixed all those canbus devices!

No I have not noticed any flickering lights at all.

I'm going to try replacing the camshaft sensors next, ordering them tonight.

[Mackskibum]

CBU?

[ClutchKickChris]

Originally Posted by Mackskibum

CBU?

Yup carbon buildup was my #1 theory before starting this thread. They were just cleaned less than a month ago.

[Ryansbmw1]

I’m having similar issues on my 35i but mine only manifest at cold start, especially on colder days in he winter. Upon start, the engine will be stumbling for 15 sec and sometimes stall out. Restart the car and runs smooth. For the longest time, no codes. Just recently I got a code for VANOS intake that would clear itself after 10 min. Cleaned both solenoids and switched positions. I had one day where the same VANOS code popped up again but again cleared itself. Strangely enough, the idle is normally fine when the code pops up. Now it’s just back to no codes, but rough idle.

Had a smoke test and no leaks. Plugs and coils are new enough not to be the issue. If it’s not the solenoids, is it the actual VANOS unit? Can a camshaft sensor somehow throw off the VANOS? Trying to think of other potential issues before diving into that expensive repair