Boss Lady

I recently had my 1993 LT1 Automatic built to a 383 with all forged internals, LE2 Heads, Ported Stock Intake, Custom 219/227 Cam, Roller Rockers, Mahle Pistons, 58mm TPiS Throttle Body, and updated to the vented Optispark (MSD 83811) with new Timing Gear Set. The car also has American Racing Headers and 3.54 gear. I have 2 problems:
Coming off the highway mostly, but it does it other times too, the idle will surge from 800 to 1400 rpm's when I'm stopped. I had a new TPS and IAC Motor (both AC Delco) installed with the new Throttle Body. I chose the TPiS brand TB because it has the dedicated IAC Passage and is the same diameter for the Intake Tube as stock. The car runs great when you're on the throttle, but when it's surging it will also idle down to a point that it stops running. I opened the Air Screw 1/2 turn as recommended by TPiS, but that didn't help. The other problem is the dreaded Code 36 - Ignition High Resolution or Multiple Low Resolution Pulse. I cleared the Code 36 the first time it appeared and the car ran fine other than the occasional surging. However, I did get the code again before going to work. I'm currently offshore, but I do have a TPiS Mail Order Chip to try. The current chip is from PCMofNC. Hopefully, the Code 36 will not necessitate changing the new MSD unit. (All connections seem fine) Do any of you have any ideas on what might be going on? Also, I would like to get the equipment and software for my laptop to do some scanning. Any recommendations here would also be appreciated. One other thing I failed to mention, the last time the SES Light came on, my tachometer was jumping from 800 rpm's to around 3,000 rpm's. The engine wasn't revving just the tach jumping. I wasn't sure if this might pinpoint the problem I'm having. Thanks.

MrWillys

A idle surge is an indicator of a lean condition. Adjust the throttle blade until your IAC counts at a fully warmed idle are between 20 and 80. Your 93 is a speed density system and should be datalogged so the VE tables can be tuned. The TPIS chip is a waste of money and anybody who says they can tune it without putting it on a dyno or hooking it to a laptop is worthless.

Kevova

I would scope test opti before going to the trouble of changing it. I would deal with the reference pulse issue first, since it can cause the most troubles, and wait for chip related to idle. I would also contact LE for suggestions being that you got heads and cam from them. Low vacuum at idle will play hell with MAP sensor. You will need some kid of scanner to monitor ECM data to provide feed back to tuner or get a burn your own kit.

Boss Lady

I live on the MS Gulf Coast and to my knowledge, there isn't a place to get a Dyno Tune done for an OBD1 Speed Density vehicle. I'd be willing to drive or trailer my car 200-300 miles if you no anyone around where I live. That pretty much limits me to getting a mail order tune, scanning / data logging my vehicle and getting the chip re-flashed. I'm certainly open to any suggestions!

Boss Lady

I just ordered an ALDL Cable and will be looking at what software I can use to diagnose my problem. I've heard TTS Datamaster and Tuner Pro RT are good, but this is all new to me. Do you have any recommendations? Thanks.

Kevova

Really can't help with software, I have always had access to scanners. I also have a 93 speed density car and a stroker to rebuild. Because of limitations of the 92-93 ECM I'm planning to upgrade to 95 or maybe 96-97 obd2. If I don't just carb it.

MrWillys

The 93 can be tuned for reasonable cam changes by tuning the VE tables in the programming. You drive the car while recording its operation and later playback the file using Datamasters Histogram. This gives BLM averages for each cell hit. You then divide that average by 128 and multiply the current VE value to arrive at the new value. By keeping VE values closer to BLM's of 128 smoothes out the engines operation. Also, adding about 2 degrees of timing at and idle can help a lot.

I use Datamaster to record. Tunercat to modify and you'll need a Moates piggyback adapter or my ability to solder in newer EEPROM's in the memcal (AKA PROM) that can be easily reflashed using Moates header adapter in the Burn2.

Boss Lady

I received and installed my Custom Chip from TPiS a couple of weeks ago, and all of my problems went away! After 4-5 starts / stops, no more idle surge and the Code 36 has not come back in over 300 miles of driving. Jim at TPiS apparently knows his stuff and was a pleasure to deal with. I have no idea how the chip apparently caused my intermittent Ignition Code 36 to disappear, but it did. All I can suggest to anyone that is having the surge / ignition problems that I experienced is to give them a try. TPiS's Chips cost a little more, but are well worth it.