So I have an 87 IROC-Z TPI 5.7, The vehicle is having an issue with Idle Surge when in park and when the vehicle is in drive but stopped.
It acts as if it is trying to find Idle and surges between 550 to 750 RPM.

So far I have replaced the ECM with a CARDONE Reman., changed stock PROM to a HyperTech, Pick up coil in the distributor, Complete Tune Up, O2 Sensor, Replaced Throttle Body that was confirmed good and working with sensors, replaced ALL Intake gaskets, replaced Injectors to BOSH 3's from SouthBay, replaced Fuel pressure Regulator, Fuel pressure is reading 42 KOEO, Running it reads 36. Have even replaced MAF to Delphi (No change), Confirmed EGR is good and working properly, Compression test (145 Cold +) Checked Battery and Alternator, voltage is good. No codes or Engine Lights. Timing is set at stock 6 degree and also running with 18-19 vacuum.

Vehicle runs like a race car down the highway, not a single issue, no delay in throttle response, runs like its brand new BUT only at idle and when the car is at a full stop it will start to surge, after changing all these parts there has been no change. Every time I replaced any electrical components, I disconnected the battery and followed all the steps. I just cannot figure out what is going on and what to look for next.

The only other thing I can think to do is find a BOSH MAF and go from there. Anything someone can advise would be greatly appreciated.

 

What changes were made RIGHT BEFORE this idle issue appeared?

 

I got the car about 4 months ago, the car only had 38K miles when I got it and ive only put 600 since then.
Nothing was done or changed except for just a routine tune up due to it being hard to start. (Distributor cap, rotor button, plugs and wires was the only thing that was changed)
I put a accel cap and rotor button, AC Delco plugs and a set of NAPA wires.
After this was when the surge started. But I changed out caps to try and troubleshoot the issue some and it still happened.

 

Have you smoked tested the intake for leaks ?
Adjusted battery voltage offsets for the D3 injectors ? The d3 can cause a lean surge

 

Bingo. Your answer lies somewhere in there. IF your idle issue appeared immediately after that it was one of those new components or something you touched (either intentionally or unintentionally) while you were doing said work.

IF the idle issue actually started immediately after that you can ignore advice about troubleshooting other stuff later, like the new injectors. Chasing your tail troubleshooting components you replaced that did not cause the idle change will drive you crazy and drain your wallet. Focus on what happened RIGHT BEFORE said idle problem.

 

Yes the car has been smoked.
Just recently purchased a MOATES ALDL cable and have the TunerPro and WinALDL software to better understand the data log and trends.
If I need to adjust the voltage through the tuner, what should I set it to?

Thank you again for the advise.

 

https://www.thirdgen.org/forums/diy-...0-voltage.html

if blm/int are high in closed loop I’d try these offsets.

 

Thank you for that information!
Will I need to purchase additional hardware to make these adjustments? (i.e. Chips, chip burner etc..)
Or can I make all the adjustments I need just with TunerPro?

 

You would need a moates.net g1 and burner and eeprom . If you like the Hypertech a hdr1 to read it or upgrade to $6e aujm at gearhead efi.

 

An alternate to to get a PROM reader/writer and use TunerPro. Finding the hardware is a little easier than it was in the past, and they are out there in many versions. Getting those to work with the tuning software is a different chore, however.

 

Just curious any updates?