E30/E28: Adjusting AFM (Air-Flow Meter) - change air/fuel rich/lean mixture

 ** ADJUST YOUR AFM SETTINGS AT YOUR OWN RISK **

This is for BOSCH AFM units, fitted to most E30 and other BMWs fitted with Bosch Motronic or Jetronic injection systems.

The AFM, or Air Flow Meter, is a metal flap that is drawn open by air entering the engine and the position of the flap tells the ECU how much air is coming in so it can inject the right amount of fuel. The stock parameters for the AFM are set at the factory and unique to each car and BMW recommend that these settings should NEVER be adjusted... so do it at your own risk!!

Why would the AFM need adjusting??

• You have done a ‘gas-test’ and the results show your car is running rich (too much fuel for amount of air) or lean (too much air for the fuel being supplied) and wish to adjust for emissions / fine-tuning purposes.
• You have an air leak after the AFM, so more air is getting in than the ECU is supplying fuel for and the engine won’t run, especially when cold.
• You have an over-fuelling problem where too much fuel is being supplied for the amount of air and flooding the engine.

Adjusting the AFM in the second two instances is a quick and dirty way to get your car running well enough to drive it, but is not a long-term fix for an underlying problem, so bear this in mind before messing with the AFM.

E60: Replacing Rear Rose-Bushes / Lower Ball-Joints

These are the main joint where the rear wheel-hubs attach to the trailing-arms and are a pretty common replacement on high mileage 5 and 7 series. They were the advisories I got on the MOT in February, so thought I should get them done before the nice weather ends.

DIFFICULTY - 6/10 This is not a long or complicated job, but is quite labour intensive.

** YOU WILL NEED: A dedicated removal / installation tool. These are available on eBay [here] for just under £40 and work for all modern 5, 6, 7, X5 and X6 rose-bushes. These are all copies of the BMW special tools listed here on TIS.

The rose-bush is item 2 in the diagram.

1. Lift car, remove rear wheel, support on axle-stand.

2. Unbolt the anti-roll bar link from the trailing-arm using an 18mm open/ring spanner on the nut from underneath, while holding the stud from turning using a T40 Torx socket through the centre of the spanner.

3. Loosen the long bolt that holds the trailing-arm to the wheel hub [5] using a 24mm wrench on the nut and an 18mm wrench on the bolt head. [A long breaker-bar is advisable on the nut.]

4. Loosen off the eccentric-bolt on the trailing-arm [11] using an 18mm wrench on the bolt head and a 21mm wrench on the nut. [Be careful not to turn the bolt and alter the alignment as it's hard to get back.]

5. Loosen off the other bolt on the trailing arm [9] using an 18mm wrench on both the nut and bolt head.

6. Fully remove the 24mm nut [6] and long bolt [5] from the wheel-hub. [The bolt will likely need knocking out with a drift.]

7. Remove the bolt holding the push-rod to the wheel-hub [7] using an 18mm wrench.

7a. (O/S trailing-arm only) - Disconnect the suspension-angle sensor from the trailing-arm using a 10mm wrench and 10mm open-end spanner.

8. Lever the trailing arm down so it is clear of the wheel-hub and the push-rod [4] can be removed.

9. Remove the retaining-ring [3] from the rear face of the rose-bush. [It will likely be well seized in place and need splitting with a grinder / cut-off tool before knocking out in two pieces.]

10. Set up the removal-tool either side of the rose-bush with the largest mandrel on the receiving side and the smallest mandrel on the pushing side, ensuring the pushing side is completely flush to the rose-bush face. [Some of the rose-bush rubber boot may need cutting off to ensure this.]

11. Tighten up the removal-tool using a 19mm wrench on either side until the bush pops out of the wheel-hub. [Rotating the receiving mandrel round so the notched area can be viewed from underneath shows the progress of the bush coming out.] [The bush may well need some heat treatment if it is seized, or you can have a go at splitting it if you are brave enough.]

12. Place the new rose-bush into the hub, ensuring it is straight to the collar and will go in evenly. [The bush always slots it from front to rear, with the retaining ring on the rear face.]

13. Set up the removal-tool on the new rose-bush with the largest mandrel on the receiving side again and the mid-sized mandrel on the pushing side. [The notched side of the receiving mandrel will need rotating so it fits flush past the back of the brake disc. This is essential to keep the threaded-bar / bush straight.]

14. Tighten up the removal-tool with two 19mm wrenches until the bush is fully seated in the collar. [The bush should slide in pretty easily, if it resists then it is not going in straight. A small amount of copper grease can be rubbed round the bush to aid it, but be very sparing.]

15. Fit the new retaining-ring to the rear face of the rose-bush.

16. Refit the push-rod and trailing arm etc. as a reversal of steps 8 to 1.

** For correct re-alignment of suspension geometry see this post. **

E60: Replacing the Rear Trailing-arm / Bushes

REMOVAL:

1. Jack car, remove wheel.
2. Remove anti-roll bar link [14] by undoing both the upper and lower nut. Upper nut is 16mm and you need to hold the threaded-bolt by inserting a T30-Torx socket down the end of bolt itself. Lower nut is 18mm and the bolt-end is held by a T40-Torx. Use an open-ended spanner or place a ring-spanner over the Torx-socket before inserting it.
3. Loosen the eccentric-bolt [11] that aligns the rear suspension, making a note of its position. This is the bolt connecting the trailing-arm to the subframe lowest to the rear of the car. The bolt-head is 18mm and the nut, to the rear, is 21mm.
4. Loosen off the front bolt [9] connecting the trailing-arm to the subframe using an 18mm socket and spanner. You do not need to remove the hard plastic cover next to it, there is just enough room to hold the obscured bolt with a spanner.
5. Loosen off the long bolt [5] connecting the trailing-arm to the wheel-hub. The bolt-head is 18mm again and the nut, to the front, is 24mm.
6. Fully remove the 3 bolts and wiggle the trailing arm out, usually from the subframe end first. The bolts may need helping out with a drift and hammer.

REPLACING BUSHES:

Replacing the rubber-bushes and refitting your existing trailing-arm is the cheapest option. The bushes are really tight in the arm and the old ones can be removed by any means necessary - cutting, burning, whatever gets them out. The new bushes however, are nigh on impossible to fit and will likely need shoving in with a hydraulic-press. Your local garage or mechanic mate will do this for buttons. If your on your own at home, as I was, then replacing the whole arm with bushes already in will save a lot of hassle.

REFITTING:

1. Offer the trailing-arm up, wheel-hub first, and reinsert the long bolt [5] through the hub, loosely screwing the nut [6] on a few turns.
2. Manoeuvre the arm up to slide the foremost bush back into the subframe mount and reinsert the bolt [9], screwing the nut [10] on a few turns. The arm may need a bit of twisting and jimmying to get in due to the geometry of the raised suspension.
3. Manoeuvre the trailing-arm up to fit the rearmost bush back into the subframe mount. This will be difficult and you will likely need a second car-jack and a fair bit of working to get it in so the eccentric-bolt will slide through. Reinsert the eccentric-bolt [11] and tighten it up so it is reasonably tight.
4. Tighten up the other two bolts s they are reasonably tight.
5. Replace the wheel and lower the car off the jack to rest the weight back on the axles and reset the suspension geometry.
6. Fully tighten all the bolts while the car is not raised off the wheels. The correct torques are [5] - 240Nm, [9] - 100Nm, [11] - 165Nm.  [BMW recommend tightening the bolts while the car is under 'normal load'. This involved placing 50kg weights on each of the seats. ** on ** used multiple bags of cement to properly set his, but if you consider this going too far then just tighten them with the car sat on its wheels as I did. You will need to back the car onto ramps to get access to the bolts without removing the wheel, so if you absolutely can't do that then just tighten them as much as possible with the car raised.]

E60 530d MOT Fail - Brakes, Trailing Arm

After the horror of the swirl-flap failure and engine swap, the E60 went off the road again at the start of December after an annoying MOT fail on imbalanced brakes, likely discs and pads, and split trailing arm bushes on the N/S. The tester also failed it on a bend in the rim of the N/S/R alloy wheel, which is reasonably bad, but enough to be an MOT fail I am not too sure.

This is the bush on the offending arm with the most play, but I still can't see a major split as I have with other bushes.

Closer inspection reveals what could be a split on the right side of the pic, but it's still not a shut case. Maybe the rubber has separated from the metal outer and is moving around?

Ok, so it's no small dent. The inner rim is bent, where the tyre sits, but I've had similar sized ones before that have been no problem. 

Is it repairable? Perhaps, but I have no spare wheel to use and a replacement is £200. Maybe the MOT tester was having a bad day?

E36 Compact: E46 Driver's Arm-Rest Retrofit

Just as on E46, the two bolts holding the handbrake down hold the right side of the arm-rest bracket. The third threaded-hole is covered by putty a bit further down the left side of the trans-tunnel.

The three existing holes fit the E46 arm-rest bracket, longer 13mm bolts and shims perfectly.

The rear roll-down ash-tray trim screws to the rear of the arm-rest bracket.

The centre-console trim took a bit of getting in under the gearstick trim panel, but fits the rear and arm-rest pretty well.

As does the handbrake handle and leather gaiter. Just deciding now whether to retrofit the gearstick trim panel and window-switches from the E46, or cut the centre-console trim to fit the E36 better. Hmm.