Baffled by Acceleration Problem (12A, Nikki)
 

Alright, I've been fighting issues with my 7 since I bought it (as many of you have =) and I've hit a wall on my last problem.
(Summary below, for those of you that don't want to read this whole mess)

Idle is beautiful (well, close enough) and I run just fine when accelerating as any normal driver would (hehe).

However, when I put the pedal to the metal, so to speak, I lose all engine power for a moment (this has been as long as half a second-- and when I say I lose all engine power, I mean that I literally cannot hear the engine and the car decelerates).

If I continue holding the pedal where it is I start accelerating again and have beautiful power on the high end.
(On an interesting note, I appear to not have the buzzer at redline that everyone speaks of)


This used to seem to occur around 4500 rpm (although it could have been due to the way I was driving)....

So I inspected the secondaries, which seem to be moving freely, and appear to be operating how they should. (Mind you, I didn't try to force them open in my driveway while the car was running).

The problem persists.


I changed the fuel filter before that, and the fresh filter improved the situation, but it still happens when I really gun it.


Summary: (for those who don't like to read but want to be a good pal and help me out =)

- New fuel filter
- New plugs, cables, dizzy cap, rotor
- I'm assuming fuel flow is fine since it's ok once I pass the loss of power
- Coolant & Oil are beautiful (although I'm losing oil kind of fast... I plan on changing the o-rings at the fuel filter soon)


Any ideas?
Thanks in advance for your help,

Matt

Accelerator pump maybe momentarily flooding the engine? Sounds possible.

Yup! Sounds like the AP to me too. 'cept it's not flooding it's momentary fuel starvation. Replacing just the AP might solve the problem but I'd recommend a complete carb rebuild if it's never been done. Good luck!
.
http://www.mazdatrix.com/c-3.htm

--Bob

When you say replace the ap do you mean the diaphram?

yes

how often should that be replaced. I replaced mine about 5000 miles ago and im havin the same symptoms?

So, is it better to get the $60 carb rebuild kit from Mazdatrix or the $20 one from VB that looks the same in the picture? =)

I found a few complains about the VB kit in past posts... But I suppose there very well could be complaints about the Mazdatrix kit too.

More likely its out of adjustment. If the AP diaphragm was torn it would be leaking fuel. The AP should shoot fuel into the carb IMMEDIATELY after the butterflies move. You can easily test this with the engine off. Look into the carb and move the throttle linkage. There should be no delay in the pump shot.

Should I move the linkage fast or slow-like?

And I'm watching the jet-like-things in the center, yes?

You can move it slow so you can see if the butterflies start to open b4 the fuel starts shooting.

Yes the AP nozzle is in the middle of the carb. It has a brass colored screw holding it down and the 2 little legs on either side should squirt.

Thanks a bunch, I'll check it out tomorrow afternoon!

Alright-- I'm reporting in again!!

I checked out the AP this weekend and it *appears* to be working okay... (keep in mind I'm no carb expert =)

On another note, I swapped the wiring of the plugs on my front rotor and the problem seems to have lessened, but still occurs under hard accleration (i.e., pushing the pedal to the floor)

Any more ideas? Or should I just buy a kit and redo the carb?

Ok, another possibility(s). Your secondary spring may be missing and/or its wired to be mechanical secondaries. From the description, it sounds like this may be the trouble.

You swapped the spark splug wires and it ran better? Dat not right :confused: Here's how they should go.

T1 = front Top plug (T for Top)
L1 = front Leading plug (L for Lower)

T2 = back Top plug (T for Top)
L2 = back Leading plug (L for Lower)

Another possibilty is that you have a blown or marginal ignitor. Leading ignitor would be my guess. The Mazda shop manual describes how to test an ignitor with a light bulb. Jeff20b has a method too, check it out: http://www.geocities.com/cd23c/test.html

Good luck!

--Bob

Yeah- leave the carburetor alone till you at least sort out which plug wire goes where!

If the AP was working and you have a fresh fuel filter, the way you describe what happens is just like what Carl says- You may be missing the secondary spring located in the square box (toward the passenger headlight), or the linkage might be disconnected and wired together by hand for mechanical operation.

Grab that damn linkage and spin it right round! Do ALL the butterflies open eventually? They're not supposed to. If the secondaries (larger holes [venturis]) open too, then it has been converted to mechanical operation.
The missing or cut spring can only be certainly tested by removing the cover from the vacuum box. If you had more experience, you could open up completely the primary shaft, and the operate the vacuum box linkage to see what kind of resistance is there- but even that's "iffy" for experienced guys.
There's nothing to fear- just don't lose anything, don't force anything, work clean, and take your time. People get too freaked out about this stuff. The key is relaxing and working slowly.
Now check for that spring, and if it's not there, it means you need to replace it, or learn to drive the engine.

Learning to drive the "engine"- I gotta do a write-up on this cause I find myself repeating this whole thing and I just can't stress these points enough! (Damnit!:))

When you drive you are operating the metering unit that feeds a specific amount of air/fuel mixture to your machine. Of all things, you're using your FOOT!- one of the clumsiest parts of your body to operate what SHOULD be concidered the most delicate part of engine control.
With mechanical secondaries, (or with the spring removed, though the results of that method do vary) you are in complete control of now much mixture is fed into your engine no matter what the load on the engine is.
Examples of load are inclines, to high a gear for the speed/incline you're going, and flat straight road acceleration.
For any given load, there is a PERFECT amount of mixture for your engine to perform to it's maximum potential. Our Nikki carbs won't go to that point without alot of modification, but they will meter out the closest to 'perfect' that they can get.

A perfectly tuned (there is no such thing) stock Nikki carb will try to meter out the nearest to perfect amount of mixture that it can to your engine under any load condition all by itself. That's the whole reason for vacuum operated secondaries.

I'm not going to go off on a rant- soon enough I will in a seperate thread. But the whole reason for vacuum operated secondaries is NOT fuel economy as everyone likes to believe, it's because with MECHANICAL SECONDARY OPERATION, you can't simply jump in the car and expect to nail the piss outta the pedal and burn the tread off the tires! It's gonna bog unless you use a little finess, and I don't know any driving schools save the likes of Skip Barbers that will demonstrate this as a fact. FACT!
These cars are not V8s with automatic trannys. Those cars are like lounge chairs with steering wheels- everything is done for you- you can be a clumsy ox and make those cars drive fast.
Our cars (with mechanical secondary carbs) will perform very very well if you don't slam the pedal. If you slam the pedal, you're trying to feed the car faster than it can eat in this atmospheric pressure.
If you want it to eat faster, you have to change the atmospheric pressure. (not likely, however you can change the CARs pressure.:))

It is my belief that with practice, you can learn to operate your mechanical secondary carb MUCH better than the automated vacuum secondary system. It can't possibly see and feel the up-coming loads that you the driver will be able to anticipate.

Oh God- I did go off on a rant. What the hell's wrong with me?!
;)

::claps::

I like rants, hehe.


Anywho, The linkage for the secondaries seems to be acting within the parameters you've specified.... It doesn't appear that it's wired for mech. secondaries either...

I didn't check for the spring inside the square box.... Is there a diaphram in there? If so, am I ok to open that without having rebuild parts handy?

I hear a swooshing sound when I push on the linkage to open the secondaries... Is this normal? (It sounds like something vacuum related) And I can't move the linkage once the engine is running (There's a strong resistance to me doing so =)


I havn't checked igniters yet but I'll be sure to check that tomorrow!
(I actually had everything wired correctly in the first place-- so I'm really confused as to why it ran better with the leading and trailing wires on the front rotor swapped!)


Thanks for your help everybuddy... I'm still pluggin' away at this extremely annoying problem..... =)

Yea what Sterling said! Why do you think they wont allow mech secondaries for us in IT race cars? ;) Cause we'd whoop ass! Anywho, Yes you can open the box to look for the spring, no worries. Check the diaphragm while your in there. The whooshing is the air moving from the diaphragm moving, perfectly normal.

Well, crap.

You'll never guess what seems to have been the problem.


The "engine" fuse was blown.

After replacing that fuse, I don't seem to have this accleration problem anymore.

What was that powering that was causing me problems?


Thanks for all the help everybuddy!

Good question... :confused:

~T.J.

Probably the emissions computer, which cuts spark advance at certain conditions, among other things. Glad you got it fixed. :)