SURGING ISSUES, SC CAR 1k-500rpm, back and forth


New Member
Apr 9, 2003
SURGING ISSUES, SC CAR 1k-500rpm, back and forth

Hey guys,

I'm almost done with fixing up the little things on my car which I picked up about 3 weeks ago.

Its a 505rwhp beast but I'm thinking something is off. It surges from 1000rpm to 700-500rpm with a constant fuel pressure of 39-40 and a vacuum gauge which dips to about 10.

There are trick flow track heat heads on this car with a trick flow track heat intake.

I was told the cam is a trick flow cam as well as has the specs of a 498/512 split.

I am still new to supercharged cars so excuse me if I'm a bit unaware of certain things.

Any clarification would be appreciated. I knew the lope would be somewhat obvious but this seems like something else to me. It has a vortech v-1 s trim by the way.

I set the tps to .99 and the iac is clean. What do I do?

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Do you still have the factory crankcase vent tube hooked up to the TB? Do you use a bypassvalve? Id also try increasing your idle. How many psi are you running? Aftermarket pump? What are you pulling for vac at idle?
post your stats so I/we can get a better idea of what may be to cause. Sometimes the IAC requires a spacer which helps idle quality. I will check back and give a second opinion.
I would suggest not trying to tune it yourself unless you have a wideband setup to monitor your af ratio. If it was tuned properly I wouldnt touch a thing. I am assuming you have the same igntion as me- the MSD 6BTM.... The degrees on the knob signifies the amount of degrees of timing your engine retards upon every # of boost. It is basically an FMU for your ignition system. what size is your Mass air meter? TB? I need more info- the pic was actually blury but it appears to be a nice clean setup! If I were you I would go ahead and try the idle adjustment plate setup behind the IAC and see if it helps idle. There is/was as sticky about rough idle , however Ill save you the time, with a SC this is a good place to start if its already been tuned. GOOD LUCK
to be honest I don't know the sizes of the mass air or tb. I guess I could just take a ruler to it right?

I just did some reading and here are some suggestions I've gotten:

Change fuel filter
drill into iac (don't really like this idea)
flip iac upside down (suggested for aftermarket ones, which mine seems to be)
install idle air bypass kit (where do I buy this)
and lastly, pcv valve.

I guess I'll just try doing some of this.
My 90 GT does the same thing when starting up cold.

I have:
Vortech V2 12 psi
B cam
Power Plus intake
36lb injectors
70 &75 Mass air and TB i think
255 fuel pump
new IAC
TPS adjusted to .95V KOEOff
AC removed
EGR blocked off
No PCV valve, just a breather, throttle body vacuum line capped

Let me know if you find anything.