4GTABODT

Installed a cam, new 2.02 heads, 1.6 rockers, 30 over pistons and now car won't idle. All the parts came from TPIS and they burned a Level 5 prom for me to support all the new goodies. The guys there have been great but I must admit I am getting frustrated (they swear up and down its not the chip)

TPIS has told me because the car is overcammed, I need to open the TB blades with the adjustment screw so that my IAC steps are between 20-30 at idle...currently they're at 145!! Each time I adjust the blades, I re-adjust the TPS so that the voltage is around 0.52 My buddy and I are running out of alternatives

I've set the idle using the IAC motor (you know, the 30 second thing) and while its a bit better, the car is still VERY rough. I'm considering getting a new chip burned...any suggestions as to who I could use. I'd like someone in Canada but realize I may have to send to the US to get it done

Thanks guys...

tjwong

What are the cam specs that you installed into the engine. Depending on that if the cam specs are not to radical you may have other problems causing the idle problem. And if that is the case, burning a new chip is like putting on a bandaid.

chriswtx

Some of the guys with bigger cams are removing the IAC and blocking the port on the throttle body, leave the IAC coneccted to the computer so it sees it(and wont throw check engine lights) and lay it to the side. Then set the idle with the blades. You might want to try it.


[Modified by chriswtx, 11:40 PM 6/9/2004]


[Modified by chriswtx, 11:41 PM 6/9/2004]

tequilaboy

You may want to try more initial spark advance, like 12 degrees. This should raise the idle rpm for a given throttle opening.

With this timing on my 88 and my throttle stop screwed all the way in, and tps adjusted to 0.54 volts, 145 counts will support 1600-1800 rpm idle speed in neutral. 20 counts supports 900 rpm (my normal target idle custom tuned to compensate for underdrive pulleys)

Side note: I have played with chip tuning various idle speeds alot and use high idle as a crude launch control with the a/c button adding as much 1100 rpm, with the compressor disconnected.

You should have plenty of air flow at 145 counts, unless your IAC is plugged, or you vacuum is extremely low due to your cam or leaks.

Regarding a new chip, you may need to re-calibrate you MAF tables in the idle airflow regions to clean up the mixture. This eliminated all of my rough idle issues. With a scan tool Check your blms if you can establish closed loop idle. If not around 128 then your mixture is way off, and closed loop can only compensate for limited errors.

Low vacuum will also increase your fuel pressure which will tend to richen the mixture, so reducing the MAF calibration (meaning less air flow gm/sec per counts) can help to compensate.

A custom chip calibration is probably required, using the TPIS chip as a base.

87NassauBlue

I just installed a ZZ9 cam and used their chip. I have 1.5 rockers. My idle counts don't go over 20 and sometimes go down to 0. I also have a 58 mm BBK.

What cam did you put in? The 1.6 rockers may be too much with a really hot cam. I would tend to agree with the TPIS boys. 145 counts seem aufully high to maintain idle. Each time you change the throttle blades, you know your moving the TPS. You may want to try removing the TPS and taping the wiper in place at .62 volts and adjust your throttle blades to get the Idle air control counts down in a normal range, then reinstall the TPS and readjust it.

VetNutJim

You haven't given enough information for anyone to even venture an educated guess.

What are the cam specs????????????????????

Duration at .050 ???
I/E Lift ???
LSA ???

Edit:
The FIRST poster to your message is one of the most knowledgeable guys around. But you have to provide data to get answers.


[Modified by VetNutJim, 11:38 AM 6/11/2004]

Oden

I've just tuned in my 230/244 112 0,544/0,576 at idle at 900rpm(N)

Need more input on cam and comp ratio, my guess is more timing.......


/N.