uneven acceleration

[funky technician]

I had my festiva out for a test run the other day and I noticed that if i floor it and let it come up to red-line, the entire way through the power band, the engine output is in waves, like, if you were to compare it to a chart, the thrust would look like a sign wave with 3 humps, I don't know how else to explain this, um like........waaAAAaaaAAAaaaAAAAAA. weird eh? thoughts?

[ajb999]

does the power seem to level out or is there a big drop or even a small drop?

[lilred]

mine and my budies does the same thing i think it just has a wavy power band

[darkdan]

Mine does it, kicks in at about 2500 rpms, kicks in again at about 4300.

[oxbrain]

My 93 does the same thing. I figured it was a clogged fuel filter, but I haven't really thought about it much.

[packrat427]

Every now and then mine will do it on a hot restart ,seem sluggish ,and feel like it pulls hard then not so then hard again , like you said wavy,on a fast scale ,it usually does it a few times then quits after a few blocks .
It does not do it all the time , I have never worried about it , I have always blamed it on poor quality fuel .

[funky technician]

I'm going to do some more tests to see if I can narrow it down, I suspected the tranny, but if people are getting this problem with MT's, then I guess its an air or fuel problem because mines a 3 speed auto.

[funky technician]

Perhaps the shudder inside the mass air flow box is sticking from age and as the engine draws more and more air throughout its power band, instead of the shudder fluently moving open according to air demand, it is sticking and un-sticking as the engine goes through its power band. Any thoughts on this theory guys?

[bluemissil]

just before it went out it was running nicely then all of a sudden it started reving up at like 4500 rpms ideling i replaced the throtal positioning sensor cost 60 bucks but this did not help. at all it jsut high reving really bad still with this new part any body got any suggestions on this

[packrat427]

Have you checked to see if there is something caught in your throttle plate , like a chunk of build up or a foriegn object , holding the plate open .

[kirko]

Ive been in about 4 festivas and 2 aspires, they all do this. I believe reason for is that there is basically a defined preset fuel map, and what you are feeling is the fuel map changing through the rpm's. I wouldnt worry about it, i think it is normal. My 97 does this as well. I would almost put my money on the ecu fuel map.

[packrat427]

Not 4,500 RPM's at a idle .

[FestYboy]

it happens with carbed engines as well... it's how the intake and exhaust are tuned that causes this phenom. for the FI engines i suspect the intake side is felt first and then the exhaust at higher rpms. when i had my stock B3 carb setup with stock exhaust, i used to feel a slight kick at 3800 and then it would fall on it's face, this due to both short intake runners and exhaust manifold. when i switched to the long tube headers, i started getting 2 humps of power, once at around 2500 and then again just after 4000.

for you FI guys, it's just the opposite... long intake runners and short exhaust, but the same principals apply.

[kirko]

Not 4,500 RPM's at a idle .

no, not that