2.5T (S60) Observation regarding engine vibration Topic is solved

[mrbrian200]

Update-- Still chasing this.

Problems have progressed it is no longer drivable (limp mode at startup, sometimes). DTC for gas pedal triggers that randomly, also low maf and LTFT random DTCs. Discovered erratic cycling in several sensors data at 15-20hz that seemed to correlate with excessive ripple from the alternator. alternator rebuilt (local pro shop). Stabilized B+ but erratic sensor readings persist, particularly between 1500-2500 RPM. Hunts and sputters at idle. Hold it at high idle once in awhile it clears up and runs like new with expected, stable sensor readings. 10 seconds later it wont rev past 1500 and runs extremely rough with sensor data that looks like a seismometer. Shut off and restart it's maybe, maybe not.

List of things replaced, tested or rebuilt is getting extensive.

[mrbrian200]

Battery ground plate on firewall (horizontal when parked flat/level). Holds water in a small puddle with wire crimp/bolt partially submerged in rain/wet weather. I would say either add a drain hole or bend it down to at least a 15 degree angle from level. Or treat that connection point as unreliable and add redundant jumps from that terminal up on the firewall and/or fender with ring terminals soldered together and soldered wire crimps. The horizontal plate OE attachment point as it is down low in the salt zone, and relatively unprotected spot... not the best place I would personally think to put it. I'm not sure attaching a redundant ground to chassis at the battery is adequate (too much resistance through the body all the way from rear to front).

[mrbrian200]

Ground fixed with -zero- chance of it ever being a problem. Almost 2 hours to rework that. Fortunately there's extra length on that cable shortening by an inch doesn't render it unusable.

Starter cranks a bit faster. Still doesn't run right.

Vida now shows 925C - Throttle signal high.

[mrbrian200]

Removed ETA. Internal reduction gearing worn (specifically the gear attached to the throttle plate with the pot sweeps). Binding at part throttle. Not far away from stripping completely out by the look of it. Throttle plate doesn't return to idle stop with middle gear installed... with the gear installed it wants to return back "open" about 10 degrees.

No rebuild kits for these anywhere I deduct, or does somebody know a source?
..also.. Ive seen pictures on google with newer design units that use a contactless position sensor but I'm not sure those apply to Volvo parts - or is that the difference between the older OE/Bosch p/n 0280750103 I have and a the newer p/n 0280750131 listed for these vehicles?

[mrbrian200]

It should be noted regarding ETA internal plastic gear wear: during key on engine off sweep test (on mine) it will appear to function properly every time. It sticks/binds while engine running when the throttle plate is loaded with pressure/vacuum. Engine running I observed it getting stuck/not reponding to minor changes. Once at 7%, another time at 30%, then at 10% at which point I pulled the ETA to physically inspect. Major changes (kick the throttle past 1/3-1/2 it would free up, then have a tendency to stick again at when releasing the accelerator pedal slowly, at startup it would sometimes get stuck at idle position (no initial high rev or fast idle when cold), or rev up then stick part open (sputtering idle). ECM throws DTCs for lean condition and (occasionaly) MAF but not for ETA/throttle plate itself.

I mentioned earlier virtually ALL the S60s I looked at in October/November (between '05-'08s between 50k-100k miles) exhibited the "droney idle" (excessive vibration felt through the steering wheel/chassis). I would venture to say the ETA is at the heart of it on most of them (throttle plate doesn't return fully to idle stop position. ECM compensates to bring the idle speed down but things aren't optimal (lean, retarded). I'm sure somebody at Volvo knows about this, but fixing them would amount to a prolific expensive recall. Volvo relied on RB-GMBH to supply them with quality reliable engine management components. RB let them down. New Chinese owners I wouldn't be surprised they're looking to dump RB like a hot potato. If I were in their shoes...

Looking at this thing the difference between what I see and a quality part that would be 99.999 trouble free the life of these cars (aside from an occasional throttle plate cleaning) is about $2 in a volume production scenario (alloy gears and a squirt of synthetic+PTFE grease), assuming a contactless position sensor found in the newer/replacement ETAs.

[mrbrian200]

I'm also noticing a design flaw in the way the return spring is attached to the throttle plate gear resulting in around 2-3 degrees of freeplay on the throttle plate (also a potential issue when air loaded/engine running). I could picture this "fluttering" under certain conditions.

[abscate]

Nice troubleshooting and it sounds like you've nailed it. Can you get some pics of the offender?

[mrbrian200]

Nice troubleshooting and it sounds like you've nailed it. Can you get some pics of the offender?

Yes.

For those still paying attention to this thread,

See picture attached.

I can now explain what is happening, with conditions for resulting DTCs "LTFT Rich" and "Low MAF", Drivability symptoms, and likely reason(s) why the ECM didn't spit the ETA specific DTC until after ECM adaptive values were reset.

As the internal gears wear they no longer mesh cleanly but instead develop a tendency to bind, sticking the throttle plate mechanism at certain positions (roughly 10 degree increments as it corresponds to physical spacing of the gear teeth).

They bind under air loading (engine running). Not necessarily during KPII/engine off (sweep test looks good).

Attached pic (green arrows) shows that the throttle plate doesn't always return to it's idle/closed position (sometimes it does, sometimes it doesn't!) In addition there's increased resistance and a tendency to stick at those same positions while opening. However, it will near consistently close to the stop if you hold it open then allow it to "snap" back by the return spring, such as kicking/releasing the accel pedal quick (symptoms may easily be misinterpreted as a leaking/stuck injector when it happens at startup, ah hem, I went down this path)

DTC: "LTFT Rich" Occurs at idle or part throttle cruising. In these conditions you're either sitting at idle stop or (while cruising) flirting in the neighborhood at times. But the plate wants to stick open at approximate positions 15% and 25%. Too much air, lean: DTC LTFT rich.

DTC: "LOW MAF" Usually occurs on cold starts, sometimes while cruising and under light acceleration. Resistance to opening of the throttle plate-> not enough air. Poor econ. However under hard acceleration the stepper motor overcomes the physical resistance, past the first few teeth that are worn, and delivers appropriate higher end torque with proper A/F.
I suspect the ECM is performing some pretty crazy workarounds with fuel metering and ignition advance to deliver the requested torque. Result: poor highway econ, atrocious part throttle econ. Hypermiling doesn't work: I discovered I actually got better stop-n-go mileage by accelerating hard, then snapping back on the pedal when reaching the desired vehicle speed. Yes yes! I now know why.

What I am not sure about: The gear attached to the throttle plate is actually two pieces incorporating the return spring. I can't tell if about 5 degrees of play between them is by design or due to physical wear as the play is spring loaded. If it's a wear issue then I can say a brand new ETA has the idle position set with the plate about 3 degrees from fully closed, and the wear over time adds around 3-5 more (droney idle/vibration absent of issues above?). I was seeing some unusual/crazy fast cyclical readings off sensors, specifically the MAF at certain RPMs (Play= throttle plate "fluttering in the wind"?). I will be able to assess this better when I receive the new ETA in a few days as I can examine for this play before installing on the car. It may be by design, and for reasons I'm not aware.

Why ETA specific code not set until after adaptation was reset? Analog POTS. Pots of this nature may have a tolerance +/- 15% or more and are affected by temperature drift. ECU has to account for this normal variance...so...over time it learns/interprets a consistent part open reading as closed, and uses these values. The ECU *should* catch when changes that are commanded don't physically occur raising the possibility that somebody hath designed the ECU program to hide problems that might result in warranty/recall work. My opinion is it's probably a little bit of both.

Contactless sensors also have angular variance, so an updated sensor design doesn't necessarily solve the problem of (with absolute certainty) knowing the true throttle plate position short of a contact switch (at idle stop, at least).

Note the VW/Audi TDI emissions fiasco vehicles also run on Bosch management. I would imagine Bosch being very protective of their ECU software code. VOLVO and VW/Audi may not even be privy to much of its inner workings. I'm not sure it's appropriate for regulators to pin TDI emissions fault solely on VW, just as I'm not sure I'm willing to pin this solely on Volvo, because so much of the rest of the car is so very very solid.

[mrbrian200]

Engine RPM, 668 r/min
Vehicle Speed, 0.0
Timing Advance, 5.0 deg
Intake Air Temperature, 37F
Air Flow Rate (MAF sensor), 0.6 lb/min
Absolute Throttle Position, 13.7%
O2 Sensor 2, Bank 1, 1.275 V @ -92.19% s.t. fuel trim

Guys, am I wrong, or is that idle speed hinky?

Add that to the list of symptoms. Hinky idle speed (slightly elevated or slightly low) I think its supposed to be around to 600-620

Adding oil to my sisters '02 Jetta before we drive to a Cubs game... low and behold (I never really noticed before) a Bosch DV-E5 gen ETA (at a glance they look identical, just with different dimensions for mount and a PCV hose connection). That car has 200k miles on it and the throttle assembly is dandy fine. So what could be the difference between the one on the Jetta and the one on my Volvo? Is it a matter of being a simple crapshoot for inconsistent nylon formulation from day to day or does the turbo pressure on these Volvos put more stress on the mechanism and it's just not up to the task?

From vehicle history I've been suspicious the previous owner got rid of it at 1.5 years because they couldn't get it to pass emissions in IL- which is about how much time you get before your plates get suspended. Owner before them shows it came from out of state(subject to tailpipe test not just quick pass on readiness state).

[mrbrian200]

I figured out more:

That two piece spring loaded mechanism of the throttle plate gear is a damper mechanism designed to cushion the mechanism at the idle stop (such as when releasing the pedal quickly). However, the vacuum pressure behind the plate is not a constant flow, but pulsates with opening of the valves (this is normal on any engine, I'm thinking it's more pronounced on these engines possibly related to being turbocharged, or a mechanical resonance that occurs at specific flow/rpms. This pulsation acts on the damper mechanism and induces a vibration in the throttle plate, as designed, gets transferred to the internal nylon gears resulting in excessive wear on the gear teeth. The damper mechanism also wears resulting in the throttle plate at the idle stop sitting further and further open over time (Droney/excessive idle vibraton felt through the car, usually blamed on various bushings!)

Those nylon gears are infused with Teflon to "self lubricate" as they wear down. But that's not enough...

What sounds (at a glance) as excessive top end/valve train noise (but doesn't really sound like it's coming from the engine) is throttle plate "flutter" and noise induced into this gear/damper mechanism inside the ETA. And this vibrational movement accelerates the wear of the mechanism progressively as the gear teeth wear.

Now this is my idea for the a fix, but involves a physical redesign of both the throttle plate mechanism -and- the ECM software.

Get rid of that spring loaded damper mechanism. Instead use the ECM to apply current to the stepper motor as it approaches the idle stop to slow it down. One point of wear eliminated. Because the vibration is being induced by changes vacuum pressure behind the throttle plate there really is no way to get around using -something- more durable than nylon to fabricate those gears.
If the problem is due to a mechanical/sonic resonance, are redesign of the intake would be in order. Possibly a spacer between the plenum and ETA (changing the effective volume of this internal space) might do it, but that's hard core engineering that would have to be addressed by design engineers under simulation.

Making the teeth longer only would extend the service life, but the underlying issue remains (play would still develop, just take a little longer to become a problem). Some sort of alloy or stainless would provide the longest service life, but still eventually wear and UNLESS it is greased. Because of the pulsations in the manifold air flow, these design Bosch ETA, as is, might simply unsuitable for this application in my humble opinion, or, there's an engineering failure (hydraulic/mechanical resonance).