Tuesday, 5 October 2021

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.

Wednesday, 29 September 2021

BMW E21 323i Baur wins HERO-ERA Summer Trial

I've been interested in HERO (The Historic Endurance Rallying Organisation) since owning my red E21 and had intended to enter that car in one of the smaller events, as they host a few throughout the year. The big one is the Summer Trial in June and it was nice to see another E21 taking first place this year. A Baur cabriolet no less. Better late than never to throw up a pic of Angus McQueen and Mike Cochrane's HERO winning 323i...

Pic: Classic & Sports Car Magazine, Aug 2021

HERO EVENTS & ERA EVENTS - The Original Classic Rally - https://www.hero-era.com

Sunday, 26 September 2021

E30 318i: Replacement Speedometer/ Odometer

Had to bite the bullet and bu a replacement speedo / pro for project E30 this week as after many different attempts to fix the original one [THIS POST], I had to declare it totally junked. These are not cheap and sit around the £65-70 region, but I got a deal on one for £59... still an unwanted cost but at least I no longer have to tape an old iPhone to the dash with a speedo app!

Now the question is, do I swap in the number row from my old odometer or leave the ones in from this one, some 100k miles less.... Hmmm.

As per the pics, the areas of concern on my old speedo are not problem on the replacement, with resistors, capacitors and other components all looking mint. There is also no charring to the back of the PCB, so no sign of this unit overheating in the past and the odometer gearing is perfect. This unit has still covered 154k miles over the last 35 years, but has clearly had an easier life than the one from my E30!

Showing the healthy resistor on the newer speedo on the left and the burnt out one to the right.

E30 318i: Speedometer / Odometer faults + check list

If your E30 speedometer is broken, your odometer isn't turning or both, then here is a troubleshoot check list to find and fix the fault. Doing the work yourself is a bit fiddly, but totally doable if you are handy with a soldering-iron.

** A more detailed guide / thread all about E30 speedometer / odometer faults by 03IRM3 on r3vLimited.com is here - https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/59019-e30-speedometer-repairs-failure-modes, which was a great help. **

NOTE: If your speedometer is not reading, before starting to diagnose the instrument the first thing to check should be if there is a pulse being generated by the speed-sensor in the differential, see E30Zone Wiki here.

Broken Odometer drive gear.
This is the most common problem when the odometer has stopped turning. The drive gear from the stepper motor that turns the larger cogs tends to split on higher mileage cars causing it to skip teeth and not turn the odometer gearing. Replacement gear sets can be bought from eBay for a few quid.


Burnt out resistor.
This is the main power resistor on the 12v + input to the PCB and it's never usually failure of this component that causes it to burn out. Instead, failure of a component further upstream is usually the culprit by drawing way too much current, causing the resistor to work double-time and overheat. This one was still working amazingly, given the heat it had been producing that charred everything around it, but I threw a new one in anyway. The value was about 150 ohms, so that's what I went with.



Blown capacitor.
Sudden failure of both speedo and odometer can often be down to the main power capacitor blowing. This is visible in the above pic to the right of (and next in sequence to) the burnt out resistor. It's a basic 220uF electrolytic capacitor and is very simple to replace with only two pins needing de-soldering, so should be the first step in troubleshooting a dead unit, even if the cap itself doesn't appear blown. Mine had been scorched by the overheating resistor, but seemed ok. I replaced it anyway, but it did not help with mine.


Snapped wire on Odometer stepper-motor coil.
This is rare, but does happen as 03IRM3 has seen one and mine had this too so I guess it does happen, where one of the single strands of copper coil for the stepper-motor snaps off its pin on the PCB. It’s possible that this happens due to time/age and vibration in the vehicle, but could likely be due to manhandling the unit while it is out for other repair work. Either way, it’s an easy fix to just solder it back in place and will be stronger than it was before at least.


UAF chip blown.
If none of the above fixes have worked and both speedo and odo are still not working, the likely culprit is that the UAF I/C chip has malfunctioned and is not processing inputs and outputs correctly, which leads to the resistor burning out, caps blowing and the odometer coil overheating. These UAF2115 chips are common, used in many speedo/odo units, taxi-meters, tachographs etc., so replacements can be found on eBay or electronic component sites for a few £/$, but this is probably the most advanced fix needed for these units and the question at this point is whether it's worthwhile. 03IRM3 has replaced chips as a last resort only to find the unit still won't work, so I decided that with all other fixes not working and my odometer still needing new drive gears that it was time to junk it and seek a replacement unit... [THIS POST].

Wednesday, 15 September 2021

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.

Sunday, 5 September 2021

E46 318i Touring: Replacing leaky Oil Cooler gasket [N42]

After fixing the major oil leak from the rocker-cover gasket [THIS POST], I noticed there was still some oil pooling on the under-tray and a fews spots dripping onto the road. I traced the source up the right side of the engine (looking from the front) and could see oil filling up some cavities in the cylinder-head to the left of the oil-cooler / filter housing, so determined this to be the culprit... yes, another common one, especially if the filter-housing has been removed for previous engine work.

A replacement gasket was just £6.59 from eBay and comes as a two piece set including the main gasket that sits between the housing and the cylinder-head, as well as a smaller gasket that sits between the oil-filter housing and the coolant fed heat-exchanger. This latter one hardly ever leaks, as it's very rare to find a filter-housing that has been split apart during engine work, but it's nice to have one anyway and you may find it worth the time to replace this one while the housing is removed, though I could not see any signs of leakage so didn't bother.


GUIDE:

1. Remove the lid to the air-con ducting that sits atop the firewall at the back of the engine by undoing the clips a quarter-turn, take out the pollen-filter and remove the weather-strip seal from the firewall.

2. Remove the air-con ducting itself by undoing the four screws using a T30-Torx socket and lifting it out.

3. Remove the rear right-side engine cover by undoing the two stud-nuts using a 10mm wrench.\

** Make sure you have a cloth / plenty of tissue to catch any oil that runs from the housing. **

4. Remove the three screws holding the oil-filter / cooler housing to the cylinder-head using a 10mm socket with a long extension bar. One is clearly visible in front of the housing, the other two being hidden down the back.

5. Lift the oil-filter / cooler housing upwards out of the head, catching any wayward oil and lift the housing clear, rotating it so as not to put too much strain on the coolant-hoses. The hoses do not need removing or any coolant draining for this job.

6. Remove the old gasket and clean both mating surfaces with a cloth and I find it always worth scraping any crud off with a razor-blade.

7. Insert the new gasket to the housing. A lug on one side sits in a notch in the housing so the gasket can only fit in one way. [If it's an older engine or the housing has been removed a few times before, it might be worth taking a belts-and-braces approach by applying some gasket sealant to the mating surface on the head, as I did with some white Corteco.]

8. Carefully place the filter/cooler housing back onto the cylinder-head, trying to spill as little oil as possible on the mating surface and reverse steps 4-1 to refit.

Monday, 30 August 2021

E46 318i Touring: Handbrake / parking-brake repair + adjustment

The handbrake (e-brake) wasn't working properly on the left side of the E46 Touring, which I assumed would either just need adjusting or at worst the spring mechanism had failed. BMWs of this era have a drum-brake mounted inside the hub of the disc-brake that is used only for the parking-brake. It turned out that the sprung stud that holds the lower brake-shoe in place had come loose, worked its way round the drum and partially jammed the mechanism, as in top picture.


The slot that the stud locks in to is part of the backing plate for the disc and it had bent outward and rounded off over time, no longer giving enough metal for the stud to hold on to. I managed to build the slot back up using a cole-chisel and there is just about enough metal left to hold the stud firmly. If it happens again in the near future then a new backing plate may be required, but this is a hub off job and a whole load more work, so lets hope it doesn't. 


Annoyingly, I had to crack open a new £13 handbrake spring assembly kit just to use the one sprung retaining stud, guess I have some spares at least. With the left side now working correctly, I gave both sides of the handbrake a quick tighten up using the rotating adjuster inside the drum.