E30 318i M40: Bosch injectors and tips - checking condition

Next on the agenda to find the culprit of the rough running and stalling idle was to examine the injector condition and the plastic tips. The injector bodies are quite rusty and corroded so they could well be the original set, but on closer inspection the tips are fine and they look to be in pretty good condition, so onwards.

To inspect the injectors the lower inlet manifold will need to be removed, which involves de-plumbing the fuel lines and some of the water hoses. 

E30 318i M40: Camshaft and valve condition

I whipped the rocker cover off to check if there was a dropped valve or broken spring that might be contributing to the poorly idle, but no such defect found. In fact, this has to be one of the cleanest top ends I have ever seen. Nice!

BMW M40 Engine - how to check timing, where the marks are located

This must be one of the hardest bits of info to find in the whole world of BMW, but there is a great post on BMW Werks on how to do it [https://www.bimmerwerkz.com/threads/m40-motor-timing-info.59059/].

QUICK TIMING CHECK GUIDE:

** Only if crank pulley has NOT been separated from crankshaft! **

1. Remove the distributor / timing cover at the front of the engine.

2. Check the timing mark on the crank pulley. This is an arrow cast into the block which should line up with the sprocket tooth to the right of the gap in the teeth, as in pic below.

3. Check the timing mark on the camshaft pulley. This is a notch/line mark in the pulley and should line up with the right-angle notch in the cylinder head, as in pic below. If this looks good, your timing is fine.

Thanks again to xdrian on BMW Works for making these pics and sharing this secret!

E30 318i: New Bosch spark plugs + correct coil fitted

With the car still misfiring a bit, I turned my attention to the plugs and HT leads. All appear fine. The coil works because there is a spark. I inspected the plugs, a set of NGK R that don't look particularly ancient, expecting one or more to be wet with unburnt fuel from a combination of misfiring and running an over-rich mixture from tweaking the air-flow meter [AFM]. I noticed that the plugs were in fact all dry and totally black with soot at the tips from over-fuelling, but their condition seemed fine. This matched the points in the distributor-cap, which were also blackened.

The spark plugs were working, but they didn't seem to fully igniting the mixture and performing weakly, so I turned my attention back to the coil. A previous owner had fitted a universal 'Sports coil' and judging by the shiny casing it doesn't look too old, so I couldn't see how it could be at fault. Thats when I noticed the terminal connecting it to the HT lead. It's about 10mm wide and has a metal inner lining. There is a screw at the bottom holding it in. This is obviously designed for a different type of HT lead than fitted to BMW, as the lead has a rubber plug where

it contacts the copper casing of the terminal in the coil. The metal terminal in the HT lead is designed to fit over a stud inside the coil-terminal, which is what I've always seen before, not just in BMW. This means the only contact being made by the main HT lead was its very tip touching the screw at the bottom of the coil-terminal.

I swiftly ordered a used OEM Bosch coil unit from eBay for £15. A 'Sports coil' type with the correct end was about £35, but I figured it was best to go original, at least for the time being while I iron out the M40 engine's running problems. While I was at it, I bought some OEM Bosch spark plugs for £13, which is cheap and I thought I may as well rule out plug condition as a factor with not knowing how long the incorrect coil has been fitted to the E30.