hey guys,
this past weekend i installed a manual boost controller in my 93 fd but didnt really get a chance to "tune" it until today. First i did a 2nd gear run from 3000 rpms with a boost pattern of 10-12-10 but somewhere between 6k and 7k rpms it stops accelerating for just a second then comes back. then i did a run in third gear with another 10-12-10 boost pattern and it did the same thing right at 6k rpms. is this a fuel cut or something? anyone have any ideas?
thanks,
Craig

 

could be fuel cut, but doubtfull since your boost is in relatively good shape. Most likely I think may be some ignition breakup at high rpm's.

Maybe change your plugs and wires for starters if they haven't been done for a while. I believe that the break-up is fairly common once people start tuning their cars.( be it on the roads or dynos) A dyno would give you a good diagnostic check of the ignition,a/f ratio, and of course RWHP and Torque. That would be my guess on your situation. Anyone else?

 

anyone else have any ideas?

 

10-12-10 ?

 

Were you low on Gas? Possibly a sloshing problem?

 

no, i wasnt low on gas, i changed my plugs but not my wires yet, i was gonna take of my UIM this weekend to check for a vacuum leak i think i have so i will replace the spark plug wires then. the car still does it since the plugs. im gonna take my car to mazda to replace the fuel filter soon too. anyone else have any ideas?

 

It shouldnt be fuel cut, thats at 8200 i think. So I have no clue!

 

its not a vacuum leak. search for vacuum leak if you want to learn what that is. however, the 10-12-10 is odd. list your mods and tell us how many miles on the wires.

 

i think i have a vacuum leak because of my 1500 rpm idle, not because of the wot problem, but my mods are apexi intake, hks dp, hks carbon ti, efini y-pipe, hks bov, and manual boost controller. i have not replaced the wires since i got the car, which was last May.

 

Two random thoughts. Have you replaced the engine top ground wire-a common problem know as the 3000 rpm hesitation that can take on its own life - drove me crazy for years and once mods are made it can be more bothersome as removing the clip during mods makes contact break down. The replacement is about a $12 wire part from Mazda, takes about 2 minutes to install and eliminates the plastic clip for a real ground point. Search the TSB and you can get the exact part number. 2nd - double check your vacuum hoses, all of the small ones on top of the engine. Look for any signs of loose connections or breakage and consider an upgrade.

 

Hmm, does your car idle rough now. If it does you may have chipped an apex seal. You may want to start saving for a new motor. Get a compression test asap. Sorry if my post gets you worried.
Adam

 

no it doesnt idle rough, it just idles high, i tried messing around with the air bleed screw and the idle screw but that didnt help.

 

anyone have any other ideas?

 

If you suspect a vacuum leak.....my question is always, have you checked using the carb cleaner trick. It will tell you in 5 seconds, but no-one seems to do it, I'll be ripping my LIM and UIM off this afternoon because I found out this way that my LIM/eng gasket has a small leak.
the high RPM stuff does kinda sound like ignition breakup though.

 

what is this "carb cleaner trick"? I am interested in trying this. I believe I have a vacuum leak but I cannot find it.

Mitch

 

ahh grasshoppa....
all ya do is start the car, with it idling spray carb cleaner around any are where there could be a leak....manifolds, vacuum lines, hoses. If the car starts to die or does then it sucked in the carb cleaner causing it to stall. Area your testing has to see vaccum is the only stippulation..ie, doesnt always find leaks in the IC pipes, but around the manifold it works like a charm.

 

i dont think a vacuum leak could cause it to stop accelerating for a second at wot would it? i said i think i have a vacuum leak because of high idle, i dont think it has anything to do with the acceleration problem.

 

Eek, make sure to do this only on a COLD engine - carb cleaner is more than a little bit volatile.

 

here is a little short clip of what its doing, it does it right at 6500 rpms, you might have to turn the volume up a little to hear it. sounds like a "booo" i guess. i know i should have put the windows up when i filmed it. i havent changed the plug wires yet but i plan to soon, not sure if that will fix it or not

http://www.arctiq.net/media/uploaded/rx7%20cut.zip
the video is a zipped avi file.

any ideas?

 

If you have a stock ECU, I'm fairly certain that is the boost-triggered fuel cut. See if it goes away when you turn the boost down.

-Max

 

if it was a fuel cut, why would it go back to normal after it does it, and is fine until redline?

 

Boost drops, fuel cut is over, resume revving to redline. That's how it works.

-Max