I'm not new to engines and performance, just fairly new to TPI. Currently I'm just starting on a 85 IROC I just bought. The engine is a 350 L98 from a late 80's IROC, although it was claimed it was a 383, I have no way to verify that without pulling it apart. At this point that's not an option.

Anyway, as purchased, the car was getting audible spark knock, and when this happened it was setting a code 42. I found out the car had a Hypercrap chip in it, and luckily I got the original with the car, so I swapped back to the original chip, and reset the stored codes by killing battery power.

Results... car runs GREAT!! Still needs a tune up, but NO spark knock ( At least audible ) and it pulls like a horse, even with stock manifolds ( this thing could be a 383 by the way it pulls on the bottom end ). I can already tell that traction is going to be my biggest hurdle.

Anway, with the stock chip back in, it "hunts" and idle, now granted this thing does have a bigger than stock cam in it...I can clearly hear and feel the lope... very evident through the exhaust at idle.

Now it is idling too low with the stock chip. I plan on cleaning the TB passages w/ some carb cleaner, as well as the IAC passages, then do some basic checks to make sure all the hoses are correct and there aren't any vacuum leaks etc.

Next I planned on checking / setting the TPS voltage, then setting the IAC, and if necessary, bumping the idle up a tad. I'm thinking that just cleaning everything up will probably help the idle problem.

I also plan on checking and setting the timing.


Any other things I should be checking out while I'm doing all the above? I'm still waiting on my GM service manual to get here.

If time permits, I'm going to go ahead and do the TB coolant bypass mod, as temps here where I live hardly ever get below 35 degrees...if that.

New dist cap, rotor, plugs are going on, and I'm going to ohm out the wires to make sure they are okay as well...

Any suggestions here GREATLY appreciated.

Chris
85 IROC

 

Change the thermostat to stock if not already. I think hypertech chips work with a 160* therm. and the stock chip doesn't like it very much.

 

Thanks, I hadn't thought about that..it does have a 160 thermostat it.

It's still gettting audible spark knock w/ the stock chip, but ONLY when the car has been run ( @200 w/ stock gauge ) and ONLY if you tip it in from 4th, or if you're not turning many RPM at all, then you hammer it...it will spark knock waiting on the downshift.

I'm wiring up a cable to be able to plug the laptop up to it as I type this...I'll run WINALDL and be able to see what everything is doing before I go any further. And my 85 Helms is on the way.

As a stop gap, I'm going to retard the timing a few degrees...

I adjusted the idle up, and it helped, and this thing definitely has a good size cam.

thanks for the post


Chris

 

fuel pressure.....air/fuel ratio..

 

Switch to the 165 ECM and start burning proms. If as you say this isn't the engine that came in the car you need to burn your own prom.