Car Gets Weak Under Load - Vanos Seals?

[nnamssorxela]

Hello All,

Slowly working my way through the car and years of neglect, and I think the last big fix is the vanos seals. The symptoms are that the car runs best when it's first started and "cold," then seems to lose power. Once the car is warm it is intermittently fast. Sometimes it pulls hard, and others it just falls flat on it's face. Occasionally it will pull hard then noticeably become weaker throughout the pull as if it's going into a limp mode of sorts.

Vehicle is an OBDI 318ti swapped with an M50. So far (as a part of replacing failing items and a little maintenance) I've replaced my single O2 sensor, the MAF sensor, both coolant temp sensors in the head, air temp sensor under manifold, and checked for vac leaks among a few other things. I'm not sure where the best place to smoke test the system is, and I suspect I'm missing a leak somewhere.

One strange thing I've noticed is that the MPG gauge shoots up to max (40+) as soon as the vehicle is moving, then is pegged at zero once the vehicle stops. Not sure if that is just a side effect of the swap though.

All of the threads I've read say that the vanos only affects engine performance below 3k RPM, however I've experienced a loss of power above that as well. Should I be looking only at my vanos seals, or am I missing something obvious?

-Alex

[AlpineM3OldAsMe]

Does it feel like it is missing at all? I would check your plugs and coils and maybe look into replacing the fuel filter if the mileage/age is unknown

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[vmbray]

Hello All,

Slowly working my way through the car and years of neglect, and I think the last big fix is the vanos seals. The symptoms are that the car runs best when it's first started and "cold," then seems to loose power. Once the car is warm it is intermittently fast. Sometimes it pulls hard, and others it just falls flat on it's face. Occasionally it will pull hard then noticeably become weaker throughout the pull as if it's going into a limp mode of sorts.

Vehicle is an OBDI 318ti swapped with an M50. So far (as a part of replacing failing items and a little maintenance) I've replaced my single O2 sensor, the MAF sensor, both coolant temp sensors in the head, air temp sensor under manifold, and checked for vac leaks among a few other things. I'm not sure where the best place to smoke test the system is, and I suspect I'm missing a leak somewhere.

One strange thing I've noticed is that the MPG gauge shoots up to max (40+) as soon as the vehicle is moving, then is pegged at zero once the vehicle stops. Not sure if that is just a side effect of the swap though.

All of the threads I've read say that the vanos only affects engine performance below 3k RPM, however I've experienced a loss of power above that as well. Should I be looking only at my vanos seals, or am I missing something obvious?

-Alex

Check your camshaft sensor wiring. Even if you put a “known good” sensor on, when you move the wiring around it will fall apart internally. Take a look here.

https://r.tapatalk.com/shareLink?sha...3&share_type=t


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[nnamssorxela]

It does not seem to miss, hesitate, bog, etc. I do on occasion get one "bounce" of the idle when I come to a stop when the car is warm. Plugs were also replaced recently, and the PO claims there is a new filter installed. Filter exterior appearance looks better than if it were 20 years old, so I may believe him.

I would think that if the CPS wiring was bad, I'd get a nasty misfire or stalling. Is that the case? Fuel pump, VC gasket, and that air pipe connection under the manifold are also new.

EDIT: I also get 20-22MPG in a completely gutted 318ti. That's not horrible considering I drive the car pretty hard, but I'd think it would be better given the low weight of the car.
Also, the CPS ohmed out within spec when I checked it last.

[vmbray]

Power loss, hard hot starts, and vanos jammed errors. Depending on the day it might run pretty well but will lose power at higher rpm. If sensor hasn’t been changed there’s no harm in peeling back the jacket.


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[vmbray]

Yeah your first paragraph sounds like this problem a lot. Also vanos seals is a more subtle issue and will be a consistent issue, not fine sometimes and not others.


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[nnamssorxela]

Weird, I replied to this last night, but it's not showing up. It said:

Well, curiosity got the better of me and I went out and cut off about 1.5" of the shielding near the sensor and the wires looked great. I'd assume that would be the offending end as well. I didn't check resistance again, but it tested fine last time. I may replace it for peace of mind....now that I hacked it up.

Any more suggestions?

[nnamssorxela]

Slight update. I've been getting an intermittent cel that comes and goes every few minutes. Initially I thought it was just a 1263 (fuel evap), but I finally figured out how to read all the codes....oops.

I'm getting 1262 (idle speed control), 1263 (fuel evap), and 1264 (O2 circuit).

I have my fuel evap valve disconnected from the lines, but the plug hooked up to the electrical connector, so I'm not very worried about that code, but I'm concerned about the other two. Does the obd1 m50 just have the one O2 sensor?

[nnamssorxela]

Replaced the evap valve and drove it pretty hard all weekend. No check engine light and plenty of power up top. Not sure why the evap valve would put the car into "limp mode," but it seems fine now.

[jc43089]

If the lines were disconnected that would be a significant vacuum leak.

[nnamssorxela]

The line into the manifold is plugged, and the line from tank is vented to atmosphere. The valve is only connected to the electrical plug and does absolutely nothing but prevent a CEL as far as I know.

[jc43089]

That is fine then, as long as the manifold line is plugged. And electrically the valve is connected. If you have all of the parts though why not have it hooked up properly? There is no performance gain by removing it.

[nnamssorxela]

So far this is the second valve that has failed in a year of ownership. When they fail they can allow constant vacuum to the tank. This creates a host of problems (car stalls, poor power, collapsed gas tank, etc.), and it killed my last fuel pump because it had to fight the vacuum constantly. I also think that as long as my car is running there is constant power to the valve (this is not how it is supposed to work), which basically makes it perform like a broken valve.