picked up fc and now i feel im in for it "problems"
Joined: Feb 2001
Posts: 29,798
Likes: 128
From: London, Ontario, Canada
Also check the wiring around your primary injectors. If you have access to a scope, scope the lines and be sure they are receiving a pulse train. It does sound oddly like the primaries are having issues so you can try swapping the injector positions and see what happens.
Rotary Freak
Joined: Jun 2004
Posts: 2,718
Likes: 1
From: Ames, IA
I would agree with the analysis of primary injector issues, but it could also be a vacuum leak.
Take a can of carb cleaner, spray around the engine bay while it's idling. If the engine sound changes, you've found a vaccum leak (the carb cleaner getting sucked in will affect how the engine runs). If it's running as bad as you say, it would require a large vacuum leak, and the change would be really obvious.
My guess, though, would be badly clogged primary injectors. The engine runs on just the primary injectors up to 3800 RPM (technically, I believe it's 3644 RPM, but with the stock tach, 3800 is close enough). At this point, it transitions over to using the primary & secondary injectors both, at an even split (half primary, half secondary).
This would explain why it rips nicely above 3800 RPM - the primary injectors aren't having to do as much, and so bad flow has less of an effect on how it runs.
And, injectors *do* go bad (usually from sitting with fuel in them). I spent several days working on a FC that absolutely wouldn't start - after eliminating a bunch of other things, I purchased a set of 4 used (but still good) injectors. 15 minutes later, it was running. An hour later, after fixing the timing (retarded by a full tooth) and the vacuum leaks (kinda forgot to plug a finger-sized hole while bypassing stuff to get it running), it was running halfway decently.
The first thing I'd try would be swapping the primary & secondary injectors, though I suspect they're all in similar condition. A better option would be to wander over to the "Parts for Sale" section, and buy a set of 4 new NA injectors - you shouldn't pay more than $50 or $60 for a decent set. Alternately, you could pull yours & send them in for professional cleaning (Cruzin Performance & RC Engineering are well liked around here). You can't clean them effectively yourself, don't even try. It takes some reasonably specialized equipment, but most of the time can restore older injectors to a like-new flow pattern.
-=Russ=-
Take a can of carb cleaner, spray around the engine bay while it's idling. If the engine sound changes, you've found a vaccum leak (the carb cleaner getting sucked in will affect how the engine runs). If it's running as bad as you say, it would require a large vacuum leak, and the change would be really obvious.
My guess, though, would be badly clogged primary injectors. The engine runs on just the primary injectors up to 3800 RPM (technically, I believe it's 3644 RPM, but with the stock tach, 3800 is close enough). At this point, it transitions over to using the primary & secondary injectors both, at an even split (half primary, half secondary).
This would explain why it rips nicely above 3800 RPM - the primary injectors aren't having to do as much, and so bad flow has less of an effect on how it runs.
And, injectors *do* go bad (usually from sitting with fuel in them). I spent several days working on a FC that absolutely wouldn't start - after eliminating a bunch of other things, I purchased a set of 4 used (but still good) injectors. 15 minutes later, it was running. An hour later, after fixing the timing (retarded by a full tooth) and the vacuum leaks (kinda forgot to plug a finger-sized hole while bypassing stuff to get it running), it was running halfway decently.
The first thing I'd try would be swapping the primary & secondary injectors, though I suspect they're all in similar condition. A better option would be to wander over to the "Parts for Sale" section, and buy a set of 4 new NA injectors - you shouldn't pay more than $50 or $60 for a decent set. Alternately, you could pull yours & send them in for professional cleaning (Cruzin Performance & RC Engineering are well liked around here). You can't clean them effectively yourself, don't even try. It takes some reasonably specialized equipment, but most of the time can restore older injectors to a like-new flow pattern.
-=Russ=-
Rotary Freak
Joined: Jun 2004
Posts: 2,718
Likes: 1
From: Ames, IA
Originally Posted by fast86rx-7
so you think it might be the coil i checked both and they seem to be ok
when useing a timing light is it normal for it to stop flashing when you give it alittle throttle?
when useing a timing light is it normal for it to stop flashing when you give it alittle throttle?
-=Russ=-
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