E30 318i: Replaced AFM (Air-Flow Meter)

I’d been messing with my AFM in order to get the car running ok when cold and when I finally fixed the massive air leak on the inlet manifold I then struggled to reset the AFM back to standard. 

In order to get the M40 to idle ok while the engine was cold I adjusted the mixture setting to run richer. Obviously this was providing enough fuel to stop the engine cutting out while the plenum was filling with as much air as the cylinders could gulp through the gap in the manifold gasket. It runs and drives ok in this setting, but idles quite high (about 1100rpm) and you can smell the stink of neat petrol out of the exhaust. Ok for short trips shunting the project car around but will need addressing to enjoy it before summer ends!

The real problem began when I had repaired the gasket, got the engine running smoothly and then tried to reset the AFM back to a stock, or near stock value. To begin with I had been putting marks and taking photos to recall where the settings were before I started messing, but you know how it is, once you get immersed into a several day long tweaking session (take that as you will!) the tendency is to get lost along the way.

I gave up trying in the end and decided the only way to dial this engine in and be sure I was not fighting with a dodgy AFM was to buy one that had not been messed with. This is in my interests anyway, as I got one from a car with far lower miles on it so the carbon-track is less worn and I know the air-temp sensor is OK too, which was a doubt with the original one.

E30 318i M40: GUIDE - Replacing lower inlet-manifold gasket - rough idle and stalling fixed!

After all the diagnosis and testing from THIS POST, I found the cause of my rough idle and stalling out when cold was a damaged paper gasket on the lower inlet-manifold allowing unmetered air to be drawn in to the plenum at will and confusing the AFM and DME over how much fuel to deliver. 

The engine just about ticked over when warm, albeit with a slight misfire. On cold startups however, the misfire was a lot more severe and at low revs the engine just couldn’t hold on, stalling out due to a way over-lean mixture. It would drive though, but there was no throttle response until about halfway up the rev range and power would arrive with a bang. It is amazing how sensitive these older engines with analog electronics are to unmetered air leaks!

IF YOU HAVE THESE SYMPTOMS, CHECK HERE!

I ordered a new gasket from eBay, it was a snip at £6.88. Be careful when ordering, older M10 engine gaskets are far more plentiful, so ensure yours is the right one for the M40... they have a funny shape which is quite distinctive. Choice was limited, in fact I could find one more gasket for sale of the right type and that came with a full £30 set including a head gasket, so be sure to check out carpartsinmotion, they have rare-fit stuff.

GUIDE:

1. Undo the jubilee-clip and disconnect the large rubber duct from the throttle-body using a flat screwdriver or 7mm socket.

2. Unclip the throttle-cable from the throttle-linkage and remove the two 10mm screws holding the metal plate to the throttle-body so the cable assembly can be moved clear.

3. Remove the wiring connectors from the throttle position sensor [TPS] and idle control valve [ICV].

4. Remove the rubber hose from the bottom of the ICV.

5. Remove the vacuum air hose from the front side of the throttle-body by undoing the jubilee-clip and teasing it off carefully with a flat screwdriver.

6. Remove the two coolant hoses from either side of the throttle-body by undoing the jubilee clips and teasing them off with a flat screwdriver. 

7. Remove the six nuts from the upper inlet-manifold using an 11mm wrench [9 in diagram] and two locating studs in the centre with a 10mm wrench [13 in diagram]. 

8. The upper inlet-manifold can now be lifted out of the engine bay.

9. Remove the wiring connector from the fuel-rail / injectors. 

10. Remove the metal fuel send and return pipes from each end of the fuel-rail by undoing the jubilee clips. (This is where it gets messy, you may wish to plug or clamp the ends of these hoses). The send pipe is attached to the fuel pressure regulator [FPR] at the front of the fuel-rail and the return pipe is at the back of the rail.

11. Remove the five nuts holding the ports of the lower inlet-manifold to the head using an 11mm socket [4 in diagram].

12. Remove the two bracing bolts from the lower inlet-manifold using a 13mm socket. (They point towards the right side of the car) [11 in diagram].

13. The lower inlet manifold is now free to be removed. This can be a bit tricky as the rigid fuel pipes are routed through one of the gaps in the manifold ports. Also make a note of how the hoses to the throttle-body are routed through around the lower manifold, as it can be confusing once the upper manifold is bolted back in.

14. Clean off the mating surfaces of the cylinder head and the inlet manifold.

15. Carefully fit the new gasket to the studs on the head. It only fits one way round.

16. To refit reverse the above steps.

BMW M54 Engine Wiring Harness Diagram Illustration

Illustrated diagram showing the engine wiring-harness configuration on BMWs with the M54 6-cylinder petrol/gasoline engine family, showing connections to the Vanos, GCV, DISA Valve, etc.

“TIP: Ensure your CCV system is properly connected to the underside of the intake-manifold (and it is not damaged) before connecting all of these harnesses. It’s a huge pain trying to reach through all the wires to adjust or properly connect it.”

A different take on a wiring-harness diagram done in a hand-drawn artwork style, but useful none-the-less, so it had to get catalogued. Originally posted by u/feedthedonkey on the r/BMW Tech subReddit, who claims credit for the artwork.

E46 Clubsport: Quick rev and exhaust burble...

Quick rev of the CS as we stave off real work by fiddling with Beemers. It finally has that proper vanos whoosh and exhaust note, though there is still a bit of a misfire / bogging down under acceleration and no fault codes are coming up on Autocom GDP, but DIS will find something and I will post the results. Shame, as this is delaying that front bumper splitter...

E46 Clubsport: Nathan's split rubber + other issues.

More big spending as the Clubsport gets back on the road with a new MOT, starting with 4 new Maxxis tyres for the refurbed split-rims. It's been running a bit rough, but as he started it for the first time in a month it ran a bit worse and began producing a lot of white / blue smoke from the exhaust. Fearing the head-gasket he started dismantling and found it was just one of the profile-gaskets in the rocker-cover [16 in the bottom diagram] was split and hadn't seated in the head properly the last time it was replaced and was allowing oil to spill down into the chamber and was causing the smoke. This, he assures us, is a common problem in 6-cylinder BMW petrols and had nothing to do with any 'engine-weld' products he may have also added. Never the less, with a new rubber-gasket the smoke has ceased. During the job he found the rubber intake hose was also split in two places, clearly contributing to the lack of smooth acceleration suffered since he got it, so he treated the 330 to a new one of these as well.

The MOT threw up borderline high emissions, which was waved, and both front lower ball-joints were knackered. These are usually replaced as a whole control-arm, so that's what was done and finally the Clubsport is back on the road, looking and sounding as it should with better pull and a really raspy vanos exhaust note. Next up comes replacing the lower bumper splitter sorely missing from the front end.

E46: Inlet full of oil! Re-con time.

Removed the inlet-manifold to check the CCV [crankcase-ventilator], crankshaft-sensor and main wiring-loom / connections. It didn't look too bad underneath, though there are some signs of a stuck CCV valve. I put the manifold down next to the car while I was working and after 5 minutes I noticed a large pool of dirty oil had run out of the throttle-body, so I placed that end in a bowl, jammed the butterfly open and leant the manifold on its end. Another 1/4 pint of oil ran out of it and today I removed the throttle-body entirely and managed to get about half as much again. More is coming, so I've blasted carb-cleaner back through the inlet-ports and left it to run down.

So either the piston-rings are completely shot and are leaking that much oil back up into the inlet, in which case the engine wouldn't run... or it's one heck of a stuck CCV. In this case, it would appear the crankcase-vent valve has stuck closed, which is allowing pressure to build up and pump oil back through the clean side of the CCV-system, dumping it right into the top of the throttle-body! Rather than creating a vacuum in the air-inlet that keeps the car at a decent idle, the CCV is pumping combustion pressure instead and covering all the sensors with hot oil. Not good. This is the most poorly engine I've ever seen.

While the throttle-body is off I may as well give it a good clean, along with all the sensors that had filled up to the wiring-connector with the pressurised oil. Even if this doesn't completely clear the rough running faults, it has certainly given the engine a new lease of like and it never does any harm to flush everything out and eliminate any further problems in the inlet.