81 FI Idling But...

[hank]

Hello Everyone,

Thank you for the wealth of knowledge contributed here! It has been extremely helpful.

I finally got my 81 FI idling well after years in the backyard. Starts fine, idles smoothly at about 900 rpm. Initial acceleration is a little boggy (in the garage - no load) but great response in the upper end. If I goose it a bit at around 2500 RPM, I can get it to knock and even what I think is small backfire a bit. After a visit to the upper range, doesn't want to idle anymore!

Been through just about everything I can handle without a proper shop. Going to re-check timing and plugs 1st but would appreciate your thoughts!

Thanks again!

[So Cal Mark]

check to see if the afm flap sticks when you open it completely

[hank]

Thanks So Cal. Yes, I've had a battle with that - was sticking all across the sweep. After hours of careful but tedious filing of the door flap edge, I finally got it moving freely. I can see it travel during operation with the black cover off now.

[giuliot60]

I'm just started having a loss of power issue all of a sudden (see "sputtering but not stalling"), and I'm wondering if it may have to do with my afm as well.

Did cleaning yours make a difference?

[hank]

Hey giuliot60,

Yes, it certainly helped. IO wasn't even getting good idle before.

It wasn't really a cleaning though so much as correcting a manufacturing flaw by increasing the clearance between the AFM flap and the interior of the air passageway. There does not appear to be a way to properly disassemble the AFM because the housing is welded or riveted shut on the bottom. I took a very thin long blade with fine teeth off a hack saw and worked away at the gap by hand. Tedious because its hard to get in there while holding the flap in place etc.

Any thoughts on the bogging?

[So Cal Mark]

flaps usually stick due to warpage, not manufacturing defects. The problem with filing the housing is that you create wider gaps around the flap. Any air that gets around the flap is unmetered air and that will prevent the L-Jetronic system from working properly

[hank]

Agreed, not ideal but a few nanometers doesn't seem like a big deal. How would you fix the warp? Is there some way to disassemble the beast?

[divace73]

mine has been repaired by drilling out/shearing the bottom rivets, straightening the door then drilled and tap the spot were the rivets (if that is what they are called) were along with some sealant aroung the edge.

[hank]

Wow, sounds extensive! Thanks Bosch for thinking repairs would never be necessary!

Thanks for the comments.

Unfortunately, my AFM is traveling fine and is not the problem i was originally posting about...

Anyone have any thoughts on the boggy acceleration and the rough idle after hitting high rpms? What would you recommend looking at next?

Thanks!

[So Cal Mark]

rough idle indicates a cylinder not working well, first isolate which cylinder is at fault, then determine why

[Fi8spider]

If the engine was dormant for a while you could have a sticky piston ring(s).
Has it fresh oil?
It could loosen up on it's own after a few heat cycles but if all else fails try some oil additive to help loosen it, same type used for sticky lifters or valves.

[hank]

Thanks Fi8, that is a good suggestion as I hadn't thought of fusing an additive to help de-gunk some essential operations. Will report back!