911S MFI Top-End Sputter

Did you do the lines at the same time?

Did not touch the lines. I did reuse my old (original) in-tank strainer so will order a new one and replace.

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Originally Posted by Brbrbr

Thanks for all the helpful tips here. I'd have assumed my mechanic would have flagged any broken springs when he did the valve adjustment but I'll double check. Fuel pressure definitely a question.

Another odd thing about this issue is that it is not always present. Sometimes it will rev freely through the power band without a hiccup, and others it sputters like its missing spark/fuel.

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Then it won't be a valve spring. That doesn't come and go.

Open the tank and run compressed air through the lines from the engine side. You can also run weed eater line through and see if it comes back clean. Should have done the lines with the tank out. Those are not fun connections.

A quick easy check is to measure resistance across each spark plug end. They should all be close to each other. Weak spark, caused by a bad plug end, usually shows up with high rpm and high engine load. Rob

Thanks all for the great tips. Running through some trouble shooting and will report back if any success.

Just changed plugs from BR8EIX to BPR7EIX. The 8’s are pictured for any thoughts. Ceramic looks okay but ends are a little sooty. Thinking the hotter plug will be beneficial.

Attachment 636601
Attachment 636602

BPR6's would be fine in an E , the difference now will be using a BPR instead of a BR . The P's were noticeably better running in my S .

I plan on stopping by the shop tomorrow and will look at mine. My recollection is 7's for myself.

I run BPR7ES plugs (NGK part #5534) in my ‘69S MFI and am very happy with them.

Alan
N.J.