Engine/car loud?

[usinjin]

Hello all,

Here's a question that a mechanic I went to forgot/didn't know how to address.

My car sounds like it's always cold while driving now, even when it's not.

When I start my car, I of course let the idle drop before driving off. On the rare occasion that I don't wait and drive while it's still a little cold, the engine sounds..loud. It has a sort of loud whoosh/roar. I'm not exactly sure how to describe it. I mostly hear it in first gear, ascending with RPMs, getting louder as I accelerate SLOWLY.

I just got my car back from some repairs..I think it's been sitting a while. Now, when I drive, it's always sounding like it's cold in this manner. It idles very smoothly. Any ideas what it could be?

[PetesZ]

Unplug the secondary air pump.

[az3579]

Yours is automatic, right? I think those are mechanical fans?
If it's an electric, maybe it's stuck at a higher speed. I'd check the fan switch for that. If it's mechanical, then.. I don't know.

[usinjin]

Unplug the secondary air pump.

I think this was it. I unplugged the pump and the noise seemed abated.

This car has always had issues with the secondary air system..more than likely the culprit is yet to be found.

[PetesZ]

The cover plate is $10. You will have a CEL light that can be coded out

https://www.ecstuning.com/b-genuine-bmw-parts/egr-secondary-air-pump-block-off-plate/11121438086/?gclid=Cj0KCQjw77TbBRDtARIsAC4l83lXawdwOI40DO4ysN6 UZS2i5OBma2BQDeCPIWPXOleMNZ5zi_JBi-IaAqk9EALw_wcB

Or you can get a working one to keep it stock.

[Oli77]

Where are you located Usinjin that a secondary air pump would turn on in August?

[fredo]

He's in Austin TX.

[PetesZ]

Yeah. Here in the south it gets down right cold in the mornings was nearly 69 70 this morning.

You can have the one I pulled off the race car for a small fee plus shipping. But I would just put a plate on it. On the cheap you can find those on x3 if you have a u pull it salvage nearby.

[Oli77]

Weird, my secondary air pump turns on ONLY when it's near freezing, it is loud, as op describes and then within a minute it shuts off. Always thought it's rôle was on very cold stats.

[Sockethead]

It's role is to preheat the catalytic converters so they can do their job right away on cold starts. Interesting that with the MS45.1 DME, the SAP has a MAF to monitor air flow.

If you eliminate the SAP system, you'll need to code out the SAP and the secondary O2 sensors... same as if you were putting headers on the car.
Also, If your state has emissions tests, It will most likely fail even though you have cats due to the fact that those two entries will be non-functional when they read from the OBDII port.

[usinjin]

It's role is to preheat the catalytic converters so they can do their job right away on cold starts. Interesting that with the MS45.1 DME, the SAP has a MAF to monitor air flow.

If you eliminate the SAP system, you'll need to code out the SAP and the secondary O2 sensors... same as if you were putting headers on the car.
Also, If your state has emissions tests, It will most likely fail even though you have cats due to the fact that those two entries will be non-functional when they read from the OBDII port.

In Texas, it varies by county. I am in a county that does a safety-only inspection (no emissions).

Mafia, I am not sure if this is the same subject or not, but maybe someone would help me to understand something. My understanding is that the SAP system is only there for emissions reasons--feeds air into exhaust manifold on cold starts and runs for just a minute or so. There are many, many explanations of this system on the internet and I've read many of them.

However, a new shop I recently took my car to said that the slight engine roughness that has plagued me for so long is due to the fact that I most likely have carbon buildup on my SAI valve. I take this to me "secondary air intake valve". But again, isn't the functionality of this valve limited to the few minutes of the car warming up?

Is it possible that the shop means the Idle Air Control Valve?

[PetesZ]

I’d check that or the disa.

May also be time to clean your mass air.

Typical issues with your ccv should show smoke and or lost oil

[usinjin]

I’d check that or the disa.

May also be time to clean your mass air.

Typical issues with your ccv should show smoke and or lost oil

I'll check my DISA. MAF was just replaced. No smoke or oil loss from what I can tell--indy shop is insisting carbon is built up in the engine. They quoted $2200 to pull the head to scrape it out (ahhh no!) or just cleaning the "check valve". Still not exactly sure what they mean by this.

Is it normal to have to do a "carbon scrape", or could that be solved with Seafoam?

[Sockethead]

If there is enough carbon buildup on the valve they talk about, it could keep the valve from closing all the way letting air back into the engine. You could temporarily remove the SAP, block off the hole in the head with a block off plate and see if your problem goes away. You'll get a check engine light but if you put the SAP back in after the test and clear the codes you should be good.
When was the last time you changed your spark plugs? This can cause rough starts too...

[Newjack]

If there is enough carbon buildup on the valve they talk about, it could keep the valve from closing all the way letting air back into the engine. You could temporarily remove the SAP, block off the hole in the head with a block off plate and see if your problem goes away. You'll get a check engine light but if you put the SAP back in after the test and clear the codes you should be good.
When was the last time you changed your spark plugs? This can cause rough starts too...

This is good advice, I would start here.

[usinjin]

If there is enough carbon buildup on the valve they talk about, it could keep the valve from closing all the way letting air back into the engine. You could temporarily remove the SAP, block off the hole in the head with a block off plate and see if your problem goes away. You'll get a check engine light but if you put the SAP back in after the test and clear the codes you should be good.
When was the last time you changed your spark plugs? This can cause rough starts too...

I understand your test, and I want to understand why it would lead to sub-par engine performance--if the valve doesn't seal correctly, does this mean exhaust gasses could leak from that intake line back into the engine?

Edit: also, evidently our cars don't come with the vacuum line on the check valve (from what I see at realoem). Why is this?

[Sockethead]

That valve hanging open would be the same as having an exhaust manifold leak. Not only would that make the engine louder, it could potentially throw the mixture off since the air leak would be before the O2 sensors

[usinjin]

Well, I replaced the valve with a new gasket and the Turner Motorsports stop plate, and the problem and noise persists. Seems like it might be something else.

The noise sure sounds like some sort of leak. It's not constant, but it gets louder at times under low/moderate acceleration. I'm definitely feeling a loss of power as well, and my fuel economy has dropped about 5 mpg.

I ran a Seafoam treatment through the brake booster and the intake. This seems to have helped smoothed the car somewhat, but it's not the root of my problem.

Interestingly enough, when I pulled the brake booster line, the engine seemed to run BETTER than when it was connected. It idled slightly faster and stronger. I thought it was supposed to idle worse when disconnected with such a large vacuum leak??

[PetesZ]

Try a smoke test. Did you pull the electrical connect to the SAP?

[usinjin]

Try a smoke test. Did you pull the electrical connect to the SAP?

Smoke test is next, as soon as I can rig something up. SAP connection was disconnected.