Check Engine Light, Rough Idle, Air Intake Manifold Rebuild, Bad PCV (OSV) Valve - DI

[rimasl2]

I would like to post some observations and results regarding the rebuild of my air-intake manifold on my 1995 740i (E38 body ; M60 engine). A lot of the info. about what to check came from this board which I appreciated greatly. Its why I thought I would write this up so that maybe it can help add to the knowledge base.

While there are differences between the M60 engine and later M62's, the similarities are greater than the differences. As near as I can tell, the M62 engine was put into production in February of 1996 for the E38 body. All E38 bodies manufactured before that date were M60's.

In case anyone is wondering what the air-intake-manifold is, click here and check out part #1.

ONE NOTE: There are many references to the "OSV valve" or "OSV Plate" thoughout the forums where the reference is to part #2 in the diagram above. Its really incorrect to call the plate by that name. The OSV valve is located inside the crankcase of the engine at the front. The plate everyone refers to at the rear of the air-intake-manifold is really the PCV valve (positive-crankcase-ventilation). In this writeup, I refer to that plate by its correct name, the "PCV valve".

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Symptoms of My Car
==================
I've got 112k miles on the car. Generally the car ran well, but things didn't feel right. The car didn't have the instant power from a stop. Instead there was a very very slight lag when the accelerator was hit. Gas mileage was OK, about 16.5, but I think it had gone down about a mile/gallon over the last several years.

Recently, the check-engine-light (CEL) had begun flickering on and the idle was rough with some misses when cold. When cold, the CEL would generally flicker on when de-accelerating from about 30mph. If I gassed the accelerator pedal, the light would go off. Once warmed up, I'd never see the CEL. Error codes from a PEAK showed 0065 (output stage group #2), 00C9 (Lambda Control #1), 00CB (Lambda Control #2). If I reset the codes, they wouldn't re-appear until the next morning, when the car started from cold.

I did a couple of things:
1. replaced both my O2 sensors (the M60 engine only has 2, M62's have 4). This seemed to pick my gas mileage back up to 17.3 or so.
2. I could flick my finger against my Mass-Air-Flow sensor (MAF) and cause the car to stall (at idle). I replaced the MAF and could no longer stall the car, but it didn't seem to fix anything with regard to the running of the car. Also, I performed ohm checks on the good and "bad" MAF. This is what I observed:
(checks performed at about 65 degrees F)

MAF pins
=======
1-3 good MAF = 1.58K ; bad MAF = 1.62K
3-1 good = 1.58K ; bad = 1.62K
2-4 good = 241.2K ; bad = 300.5K
4-2 good = 238.2K ; bad = 294.1K

I can't say that ohm checks are necessarily a good indication in my case of a bad MAF.

After replacing the two items above, I was still left with the CEL light flicker when the engine was cold and the rough idle.
The next step was to look at vacuum leaks.

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Some Vacuum Leak Diagnostics
============================
Here is what I observed in finally deciding to rebuild the air-intake-manifold:

1. Oil dipstick test: I had a very slight amount of air being pulled into my dipstick tube. Some posts I had seen seemed to indicate that if you had an air-leak, or a bad PCV valve, that the air being sucked into the dipstick tube would be very dramatic and noticeable. Mine was barely noticeable. I wasn't sure there was a problem, but I wasn't sure it was correct.
2. PCV valve test: This test was one I came up with on my own. There is a small air breather hole on the bottom of the PCV valve plate (see photo #1). You can cover it with a single finger. When I covered this hole while the engine was running, the engine would shake convulsively and accelerate, then slow down to almost a stall and cycle like that very rapidly. This didn't seem correct, and in fact when I did have everything back together again with a new PCV valve installed, the engine remained rock-steady when that hole was covered while idling......so I think covering the hole is a good indication of an overall vacuum leak somewhere in the system. Possibly it is only an indication of a bad PCV valve, but when I did finally take it apart, the PCV valve looked whole, but it was very carboned up.

photo #1 - PCV Valve Test - you can cover this small vent hole with the engine idling by reaching in back of the engine. If, when you cover the hole with your finger, you get a lot of engine surging, it is a possible indication of either an air-intake-manifold leak, or a bad PCV valve....disclaimer: this observation is a sample of one only (my car before and after an air-intake-manifold rebuild)


3. Carburetor Spray test: I could not get the engine to change idle speed with carburetor spray.
4. Cold engine test: I already mentioned this as a symptom, but it needs to be placed here. For sure if you're seeing a CEL light flicker when cold along with rough idle, its a pretty good bet, that there is a vacuum leak somewhere. Early vacuum leaks, will seal once the engine warms up. When they go really bad, they won't seal at operating temperature either.
5. Slight Lag when accelerating: The very very slight lag wasn't even a symptom I was sure about. Only after the rebuild, could I confirm that I had had a slightly lean condition from a vacuum leak.

Finally, I decided to take the plunge and do the rebuild. There was no hard evidence of a failure, just an accumulation of observations. The one condition that forced me into taking action was the CEL and rough idle when cold as I really wanted to get that fixed.

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A few easy checks before starting a rebuild
===========================================
As I did the rebuild, I saw a few things that could be done, or checked, without a rebuild. Maybe some individuals will only have one of these issues and so its worth checking first.

1. Rubber cap on throttle body: see part #8 here. This is a rubber cap about 1/2" in diameter. It actually faces to the front of the car (unlike the diagram) and is located at about 5 o'clock below the main 3" throttle opening. Mine was hard as a rock (oxidized) and had cracked and I am sure was causing a small vacuum leak.



2. Carbon buildup on the throttle intake: The 3" opening on the throttle intake body as well as the idle intake valve (part #9 here) can get very carboned up. You can remove the idle intake valve and clean it with carburetor cleaner. The 3" throttle throat can actually keep the throttle plate from closing as was the case with mine.

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Verbal description of disassembly of the air-intake manifold
================================================== ===========
That's about it. Below is a verbal description of taking apart and cleaning the air-intake manifold. There are also some writeups at e38.org. Look for either "OSV" or "Oil Separator".

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Items replaced:
===============
1. Rear cover PCV valve on air-intake manifold (see #2)
2. Vent pipe see #7
3. rubber cap on throttle body (part #8)
4. 4ea. "eyeglass" gaskets see #9
5. front and rear gaskets on air-intake-manifold
6. replaced all E30 torx head bolts on front and rear with 6mm x 25mm (1mm pitch 10.9 hardness) hex bolts
7. had fuel-injectors cleaned at http://www.witchhunter.com/ this really seemed worthwhile. turnaround was about 5 days (my ship to my receive). they cleaned, checked and replaced O-rings and gave a full report. My fuel-injector fuel throughput differed by almost 5% when received by them and differed by < 1% after re-build.

=========================
some notes on the rebuild
=========================
1. the removal of the 13ea E30 torx head bolts, that are located on the front and rear of the air-intake-manifold, are a bitch. Clean the inside of the heads with a knife and engine de-greaser first to get the tool seated. If all else fails, buy a good vise grips.
2. the removal of the small wires holding the valve electronics boxes to the fuel-injectors is very diffcult. If you just pull, they will come off and break some of the plastic while doing it. You need to remove by grabbing their ends where they loop around the plastic and separating and lowering them toward the fuel-injector body or pulling them toward the electronic boxes.
3. I tightened the front and rear bolts on the air-intake manifold to 140 inch-lbs as well as the 10ea nuts holding the air-intake manifold to the engine block

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Disassembly
===========
Taking the manifold off requires the removal (in order) of:

1. front MAF air duct to throttle, and idle-control-valve assemblies
2. fuel tank breather hose on front of the throttle assembly (just a 1/8" fuel pipe that sits at about 8-o-clock relative to the 3" throttle input).
3. throttle cables (removing the bracket holding the 2ea. throttle cables does the job)
4. 2ea. electronics boxes on each cylinder head. Pretty straightforward. You need to remove connectors all over the place. Just remember where they go back. When you finally get to the point where you're going to lift the boxes up from the fuel injector connectors, be careful. There are small metal wires which need to be removed from each fuel injector connector 1st. When all is said and done, the two electronics boxes will fold over to the passenger side of the engine compartment (they will never be removed completely from the car).
5. auxiliary brake vacuum pipe on rear of intake manifold as well as the fuel pressure regulator overflow pipe on the passenger side of the fuel rail going to the same rear plate
6. fuel rail and fuel injectors
7. 10ea. air intake manifold bolts.
8. once the air intake manifold bolts are out, the air intake manifold can slide to the rear of the engine compartment about 1/2" and clip #10 here can be removed. After the clip is off, the air intake manifold can be lifted off the engine.

Photo - engine compartment with air-intake-manifold removed
Notice the two each electronic boxes that mount to the valve boxes are pulled to the passenger side of the car.



======================
Some results after the rebuild
======================
1. No air entering the dipstick. Actually, I think the air is very slightly positive now.
2. When I cover the small hole at the bottom of the PCV valve, the engine idle doesn't change at all.
3. The CEL and rough idle when cold are gone. In fact the engine is silky smooth at idle when cold.
4. Power from a stop is instantaneous. No lag whatsoever.
5. Overall glide of the car, is more positive. Before I seemed to have engine de-acceleration when I took the foot off the pedal. Now the engine seems to allow the car to glide along more or less at speed.
6. Beautifully smooth idle overall.
7. Gas mileage ???? will post with an update.

In the end, I can't say what exactly was wrong, but I believe it was just an accumulation of small things in a 11 year old car that included:
1. Bad rubber cap on throttle body
2. gummed up PCV valve
3. 2ea. rear most eyeglass gaskets on the air-intake manifold were definitely leaking as there was oil in the valley.
4. very gummed up fuel injectors and uneven spray
5. carboned up 3" throttle body opening that wasn't allowing the throttle plate to close
6. possible gummed up idle control valve.

[ghoster]

rimasl2,

After reading your entire post, twice, I think I want to kiss you. ok, maybe not. I have the exact symptoms you described. I also was guessing I had a vaccum leak somewhere. I purchased a used manifold with the throttle body and the injectors still on it. I haven't begun the task of cleaning it up yet for a couple reasons. 1) I haven't figured out how to get the injectors out yet. And 2) it looks like a messy job. With the pics you posted and the instructions you gave I think I can pull this off without any major problems now. I appreciate your help!


One other question. The inside of the air intake I got has a pretty heavy coating of oil and gunk. How would you recommend cleaning this out? I am a little worried about using a heavy degreaser on a plastic intake. Any suggestions?

[rimasl2]

Hi ghoster,

Glad it helped. I couldn't have done it without a lot of info. gained from this board and also BimerBoard.

re: "1) I haven't figured out how to get the injectors out yet."

This post on BimmerBoard has some good photos even though he's going farther than I did. The hardest part of the whole job was getting the metal wires off the fuel-injector electrical connectors. His photos really helped me: BimmerBoard Link

re: "How would you recommend cleaning this out? "

I'll have to get the name of the degreaser I used and will post it later today. But it is relatively mild. I bought a large plastic tub at my local hardware store for $8 and soaked the entire manifold in the water/degrease mix for about 3 days. Cleaned out the interior air channels and main body beautifully.

[rimasl2]

Just to finish up the last post regarding the degreaser used:

The name of the degreaser was "Simple Green Max - Pro Series". Found it at Kragen Auto here in San Jose, CA. Biodegradeable. Which I figured meant it was milder than the hard solvents.

Used a gallon and added water to the tub until the manifold was submerged. Probably was about 4 or 5 parts water to degreaser.

[ghoster]

I think my local parts store carries the simple green stuff. I am going to use the same method to clean mine out. The stupid little wires just about drove me crazy. I got all of the electronics out of the way today. getting to the back side of the manifold is next to impossible. I do have a question about one part. On the bottom side of the throttle body, you had a black plug covering a vacuum point. Yours was dry rotted and probably leaking. Mine has a line connected there! What is that connection for?

[rimasl2]

re: "Mine has a line connected there! What is that connection for?"

I looked at realoem.com here: (part #8) for a 1993 740i, and it shows the same cap as mine so I'd be guessing.

Probably best if you can trace it back and see where it's coming from. Then check on http://realoem.com/bmw/select.do for your year/model and see if you can figure it out.

EDIT: Just had a thought: There is a tube that connects into the throttle body at about 8 oclock which is a fuel tank breather hose. The cap is located at about 5 oclock. Just wanted to log that in case you've overlooked something.<!-- / message -->

[ghoster]

I just looked again. I have a hose coming off of there. It is run to something under the master cylinder. I can't see down there to even guess what it is.

[Ratfink77]

I have exactly the same symptoms on my 95 540i. Tried all the easy stuff. Engine acts all weird when I cover that hole in the back too. Now I can detect a faint whistling sound coming from somewhere in the engine bay. Definite leak. Guess I'm ordering parts this week.
Will report back on the results.

[crewdog843]

Is there any possibility that you can get this write-up included in www.e38.org?

Information like this is invaluable and should be included in a central database which is easy for everyone to find.

jake

[Nash740I2000]

Wow....
Awesome write up,

I ordered my rebuild kit from AutoHausAZ earlier this morning and I am looking forward to this project. My car hesitate and idles a little rough.

I replaced the EGR recently.

I also shined a light at the rubber hose connecting to the throtle and noticed major oil leak.

Thanks for the post...excellent write up

[likedatyall]

Wow....
Awesome write up,

I ordered my rebuild kit from AutoHausAZ earlier this morning and I am looking forward to this project. My car hesitate and idles a little rough.

I replaced the EGR recently.

I also shined a light at the rubber hose connecting to the throtle and noticed major oil leak.

Thanks for the post...excellent write up

If you haven't done it yet, get a CPS [Camshaft Position Sensor (or two depending on your year 7 series)] from the dealer as well.

[Ratfink77]

Ok, finally got around to starting the intake rebuild on my '95 540i two weekends ago. Got the intake off, no problems. Then I noticed one of the knock sensors was in pieces. The rest were in horrible shape. (If you are thinking about doing the intake reseal and your M60 engine has 188,000 miles on it like mine, get the knock sensors.) So I ordered four, and Saturday I went in to finish the job.

I had read on the various forums that you must remove the water distribution assembly to get two of the knock sensor mounting bolts out.

Here's a little trick to avoid removing the water distribution assembly, and get the two bolts on the left side out.

Loosen the bolts as much as you can until they almost touch the pipe. Once you break the bolt loose it turns easily.

Then we used an air powered hack saw that looks like a miniature sawzall to cut off the bolt heads.

Then you can loosen the bolts the rest of the way with needlenose pliers and your fingers, and remove the old sensors.

To reassemble, use 25mm length bolts. They will fit in the space available and still have plenty of threads to hold the sensor.

Anyway I got the intake back on and she started right up.

Sunday morning it was cold enough to see if the fix worked. She started up and idled like a kitten right away.
The car runs much smoother and no CEL!

I highly recommend this procedure for rough idle on an M60.

[Nash740I2000]

Guys,

Again, nice write up..........helped me a great deal............I couldn't do it without you...

I am happy to inform you that I finished the project and my car runs GREAT. I replaced the V pan, water pipes gaskets, belts, etc.......it took me over 9 hours (first timer) ...

Now I am waiting on complete set of hoses to arrive.

Will keep you posted

Thanks again

[Nash740I2000]

If you haven't done it yet, get a CPS [Camshaft Position Sensor (or two depending on your year 7 series)] from the dealer as well.

Thanks for the advice.

Well, I ordered CPS s from AutohausAZ and had to return them for full vresit. I ended up paying $129 each plus tax from the local dealer. It runs good now.

Thanks

[hairtrigger]

Great info.
Shoulg go on E38.org

[Jonny bravo]

Hi Rimasl2 Thankyou for your detailed post,I think it could be the answer to much of my head scratching.

I believe I have the same problem.
Rocking idle and just of recent smoke on start up. oh and a possible warning light but looks like the bulb has been removed

Only thing is I recently brought the car and in the paper work is reciepts for the end of last year showing the purchase of the pcv valve and all inlet gaskets and pretty much all of the stuff quoted in your repair scheme. No reciepts for work carried out though.

My question is how do I find the hole on the pcv valve that you covered/ uncovered with your finger to whitness the erratic idle etc, the pic is missing from the post. well as far as i can tell and im at a bit of a loss???

I have had a feel around the back of the pcv and can't seem to put my finger on it!

I would like to see if this can direct me in the direction of wether i need to carry out the repairs as you have stated or look for another cause. As the gasket replacement may or may not have been done???? Or done well!!!

Any help would be much appreciated, oh nearly forgot I have a 1995 740i with 88k on the clock

Cheers again to Rimasl2 and anyone who may be able to help me