Plug gap effects?

[vwjim]

What effects of changing plug gaps would you expect to see?

Had a bad running engine at low rev's but fine at higher rev's / boost so pulled the plugs and the gaps seemed large at 32thou so reduced the gaps on the new plugs to 24thou - NGK DPR9EA-9's.

Now it seems happy at lower rev's with no popping or banging but won't rev up past 4k.

Would the gap size be effecting how good the map on the ecu is for my engine?

Also recalibrated the TPS before the test drive and its at 60% to 100% throttle that the engine isn't happy.

any clues please? thanks.

[miniman82]

Mine had low RPM misfires with .032" gaps as well, close them down to .025 and retune the upper RPM range.

[vwjim]

thanks. Will trial some different gaps and report back.

[Eaallred]

IIRC VW spec was .024" for the carbed engines, .028" for the FI engines.

If you are running stock ignition, stick with .024".

Check your dwell if it is cutting out at higher rpms. Coil might not be having enough time to saturate between firings.

[vwjim]

thanks guys. I reset the gaps to 28 thou and in doing so found out that one of the boost signal pipes had moved ever so slightly. It looked as if it was seated fully, but on re-checking every connection found it was not fully seated into its quick release fitting.

So the MAP sensor and boost sensitive fuel reg' couldn't have been getting a true reading, hence the issue with higher rev' range.

All sorted now.

Thanks again.