MAP sensor

Hi,

you should start from engine mechanics basics: Valve timing and false air. A car that needs such igntion timing has serious other problems.

My next stage of investigation is to eliminate all of the H/T ignition system piece by piece and if after that it still misfires under load then I guess potentially I have mechanical problems!
Things like valve timing are difficult to check without complete engine dismantle and I've already done compression checks and discovered nothing to cause alarm - false air I have struggled to test with any success, historically when I've encountered air leaks they wont idle very smooth and mine idles good, but what ever I do next I'll feed back and try and close this thread.
Just to try and justify my reasoning for such advanced ignition timing, I have read something on a different forum that suggests that when an engine is running really rich you may need to advance the timing by anything up to 10 degrees to allow enough time for complete combustion of all the fuel, so maybe if I get to the point where I have cured the misfire I'll try reducing the ignition timing to reflect VW's intentions as now I've hopefully fixed the FI issues with a new MAP sensor and repaired temp sensor wiring so hopefully it isn't running too rich!

Thanks for all your help so far, Doug.

Hi,

Quick update on the above, I've replaced some of the HT ignition system with new parts with no success but I'm still waiting for the new distributor cap and rotor arm to arrive before I can say for definite that the cause is or isn't ignition related.
If the cause turns out to be mechanical internals worn out and I decide to re-build the engine does the D jet have enough scope to cope with either extra capacity or bigger cam shafts etc. to try and gain a little bit of power or should it just be re-built totally stock?

Thanks again Doug.

Hi,

as D-Jetronic is an open loop control system you should stay with stock versions.

Hi,

Ok thank you I thought as much!

Doug.

Hi,

Hopefully the last update for a while, the cause of my high load misfire turned out to be nothing more than the simple distributor cap and rotor arm, whilst these parts were probably about 7 years old they had only done approximately 3000 miles so I was very surprised to discover they had failed so early!

Thanks for all your help, Doug.