1993 SuperSprint Momentary Power Loss

[Tony]

Good Morning,

 

My Seven has developed a curious momentary power loss mostly during warm up, more noticeable at lower rpms.

Accelerating slowly, there is a momentary blip of a power loss.  No sound, no backfire, pop, just loses power for a briefest instant.

Seems more prevalent at lower rpms and smooths out as RPMs increase, but occasionally noticeable.

Not problem on the road, seems to go away when hot, but initially will happen four or five times.

Makes me nervous about longer trips should whatever it is fail.

What would you check or suggest replacing?

Planning on a tune up soon, but would like to figure this out.

 

Thanks much for your thoughts,

 

Tony

 

[Anker]

I suspect you have the idle mixture set too lean. When you accelerate slowly you aren't getting any help from the acceleration pump. The fat that it goes away when warm further supports this thesis.

 

When setting the idle mixture you should put the screw half-way between the points where you notice a drop in RPM.

 

Your idle jets may also be on the small side and going one size up may eliminate the problem. My car was built with too small idle jets and had a flat spot between 2000 and 3000 RPM when accelerating slowly, even when hot. It was cured when I had larger jets installed.

 

Anker 

[Tony]

Thanks Anker,

I'll try richening them up a bit, evenly across the carbs.

When this happens though, it only lasts the snap of a finger.

Like a switch turned off and on quickly.

Initially, at low rpms, you can feel it through the car and hear it cut out for an instant.

Doesn't occur regularly or evenly.

Tony

[Anker]

I suspect they are backfires or spitting through the carbs. A misfire will feel exactly as you described.

[Anker]

Another possibility could be that the advance mechanism in your distributor is sticking. If you have a timing light check whether there is smooth advance of the timing as you advance throttle.