Location of Intake air Sensor 1995 E34 M50

[Pete Lech]

I want to check my intake air sensor, as I suspect it is misreading and causing a pinging problem.

The Bentley Manual 130-7 shows the sensor to the right of the FI intake, but on my car (build date 05-94) there is a hose running to the vacuum booster from that location.

Was there a running change that moved the sensor location?

TIA.

[johnnyBgood]

Seems to be underneath the intake, just to the right.........

link below:

RealOEM.com BMW E34 525i Intake manifold system

jb

[Pete Lech]

Thanks.Attached are two pix - one of the location in my car and one of the Bentley Manual illustration of the same area.

You can see on my car that that particular location has a vacuum hose leading to the (brake booster?) vacuum resevoir

Is it possible that when the head was overhauled 6 years ago that something was reversed?

[Pete Lech]

Update: I went to the dealer and got a diagram of the intake manifold system. The picture you supplied is the same and evidently the sensor location I need is below the vacuum port higher up on the manifold. I was using the cylinder head picture which shows the same parts, but less clearly.

Nevertheless, the Bentley Manual picture is incorrect, as the location did not change for VANOS engines from 1992 - 1995 per the dealer..

Dealer said he doesn't stock the part as there is no demand for them. Maybe I am on a wild goose chase, but am running out of options. I am due for a plug change, and will try a set of NGKs for their broader heat range. I always liked them.

[mrbillhere]

Hey- I was wondering if you ever cleared up the pining in your 95 525i? I have the same problem and have tried a huge amount of fixes. None have worked. Did the air sensor help?

[Pete Lech]

No, I have not. Winter took off the pressure to fix it, and I was dealing with a weird AC problem, finally found to be a bad AC computer. You won't find that part in the Bentley Manual! <

With the used replacement AC computer installed, the pinging actually got somewhat better, for reasons that are beyond me.

I did find the sensor, I believe, under the intake manifold towards the rear of the engine, but I haven't felt like taking all the stuff off that I would need to to get at it to check it. Too bad it was moved from a relatively accessible location to there later in the model run.

[mrbillhere]

thx for the update. I'm changing mine out this wknd.

Just in case it helps, here's what I've done in an effort chase down the pinging:

- O2 Sensor
- Fuel Filter
- Fuel Pressure test
- ECU water temp sensor (I think this may have helped a little, but its still cold out)
- 1 step cooler Spark Plug
- Chevron Premium fuel (so far, this has helped the most) - Shell makes it worse
- ECU reset
- Borescoped the Cylinders (all very clean)
- Drove with BMW Diagnostic Software running. Knock sensors are working fine. Timing is changing as needed
- Removed and examined MAF sensor. Couldn't be cleaner
- Vacuum leak smoke test

At this point, the last thing I'm changing is air temp sensor and rebuilding the vanos. From there, I'm left with the only option but to change the knock sensors just in case and then do an injector spray pattern test. I doubt its any of those.

If the problem still exists, it pretty much has to be late 1990s California change of fuel requirements that mid 1990s high performance cars aren't calibrated for.

My car only does it up a very steep hill at low speed. Other than that, engine is fantastic.

Will post an update.

[Pete Lech]

FYI, I did all of that except the smoke test. 93 octane gas back east was better than our 91, but the car is supposed to run on 89.

I had one shop tell me to upgrade the chip to a performance unit. That seemed wrong to me as I know that these chips typically ADVANCE the timing more to gain performance. I called the maker, Turner Engineering in Mass and asked them. They agreed that the chip would make things worse. Had no suggestions on a resolution to the pinging issue, but did tell me that the knock sensors do not kick in until close to 3,000 rpm, that is why the pinging goes away close to that rpm.

I will be interested to hear how you got access to the air intake temp sensor, as I can't even get my hand on it.

[Pete Lech]

One more thing - when I first got the car in 1998 with 40K miles, I had minor pinging issues on 89 octane fuel when ambient temps got to 95+ degrees. The dealer said he could upgrade the ECU programming. I didn't do so as the car felt kinda doggy and I didn't want it to be any slower. (Since the head overhaul and more mileage, that issue went away.)

Maybe there was a known problem with the ECU program?? My problem didn't get bad for many years and miles later, around 120k. I have 150K now, and engine uses no oil.