regarding lack of power above 3k rpm, MC-1 engine

[Eric]

Are you sure on your cam timing?  This can cause backfiring even just a
few teeth off.  I suggest the cam because I have done it before.

Is the cam one you have any history on?  I had the lobes on an
aftermarket solid lifter GTI cam get wiped off on a drive home from work
and the car would not rev over about 3500 rpm even if floored in
neutral.  After tons of troubleshooting I changed to a new copy of the
same cam and it still turns 8000 rpm to this day.

Good luck.

-Eric


Michael S. Williams wrote:

> hey everyone... urq list, you've already heard about part of this
> anyway... main list, hey... long time no post... if you are on the
> main list, can you make sure to reply to me directly, as im not
> currently receiving emails...
>
> ok, on with the story.
>
> i just finished replacing the head on my urq w/ an mc-1 engine and
> k24 turbo (the turbo was changed way before the head, so it isnt a
> "new" component in this equation).  the head is shaved, as well as
> ported and polished (not sure about how many angles on the valve job,
> though), i also replaced the exhaust manifold, and pretty much every
> fastener in between... i also completely drained the fuel tank (cause
> the gas got way too old) and filled it yesterday, completely, w/ high
> grade gas...
>
> the car runs, but idle is very iffy at first.  it is very very lumpy,
> but after a minute, it'll stabilize to about 900rpm... before it will
> idle with any sort of stability, if i hold the revs up a bit, i can
> hear it missing slightly every couple seconds or so (but this was
> about what it would do before i did the head...it always idled like
> this when cold....i think it has to do with a faulty isv control
> module...but there are new components to this problem which i'll get
> into in a second...)...
>
> anyway, if i hold the revs, let off, and then give it gas again, it
> will backfire (this is new)... the backfiring will also happen once
> the idle has stabilized, but not as badly...
>
> so, i checked the timing, and it is spot on... i even tried moving
> the cam a tooth (counterclockwise), and that made it even worse...
> so, i checked again, and the timing, is set according to spec...
>
> so, i took it out for a drive... from idle - ~3200 rpm, it is like it
> should be... i can feel the boost build up like it should... but as
> soon as i hit that point, the acceleration completely flatlines... it
> pulls a little, but nothing like i know it should... it's like
> there's no difference in acceleration between 6psi and 12 psi... its
> really strange...
>
> it feels like the timing is being WAY retarded, or, again, the timing
> is off (but i keep checking it, and it isnt...), or it feels like not
> enough fuel (makes no sense as the fuel pump is new as of maybe 6
> months before i started the head replacement job), and i just
> replaced both fuel filters as part of this whole project...  the
> injectors, i will admit, are not new, and they were in my garage for
> the 2 years that it took me to get this project situated and
> 'completed'...
>
> i pulled input and output codes, and NOTHING... got a 4444 on the
> output, and went through the whole sequence of input, and everything
> works....
>
> so, the question is, what is going on here? im stumped...
>
> does anyone have any idea?
> --
> MswmSwmsW
>
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