I built up a 454 to replace my 350 in a GMC Suburban

[SkyCapt]

I built up a 454 to replace my 350 in a GMC Suburban 4WD and was told that re-programming the ECM was a simple thing 5 years later I'm still having issues with the system despite sending it out to several tuners. It runs too rich at low power settings 13.8 and too lean at high power settings 16.0 or there about till RPMs catch up. Seems to throw the Code 13 when the mixture at low power ticks 14.0 or lower. It runs fine but the check engine light will fail my emissions. I monitor with the Wide Band Innovate system. I monitor fuel pressure and its rock steady. I have the larger TBI and new injectors. The gear ratio is 488, I pull a big boat up long high passes. The O2 sensor seems to work, monitor with a meter it swings high with a rich mixture .900VDC and Low with a Lean mixture .400VDC. Any ideas? My last tuner was at a loss but doesn't specialize in OBD1 systems. It's mostly stock 1987 vintage 9.1 compression, 500CID RV cam, Edelbrock TBI Alum, manifold no EGR, Headders, High Flow Cat, Heated 02 Sensor. How touchy are the OBD1 systems?

[dave w]

The 1993 - 1995 Second Generation TBI computer has more tuning parameters than the 1987 - 1992 First Generation TBI computer. The second Generation TBI computer is about 50 times faster, 8192 Baud rate vs. the First Generation running at 160 Baud rate. Memory size of the Second Generation TBI is 64K vs. the First Generation 4K.

The Second Generation TBI can be wired so the WBO2 data will show up in the TunerPro RT data log.

What is your computer part number?

dave w

[1project2many]

How touchy are the OBD1 systems?

Welcome to the forum.
"Touchy" isn't a word I would use to describe the early systems. Tuning early TBI could be likened to crop dusting. You try to get everything covered but at the end of the day it seems there are some areas that still need attention.

Tuning without a tool to monitor and record data for later review is an extrmely challenging task and requires a large investment in time and patience. Tunerpro RT is a one of several good tools to monitor and record how the engine is running. Data from Tunerpro can be input into a special tool that will help generate corrections for you or your tuner to apply to the chip to help adjust the calibration values.

In order to tune the calibration completely the vehicle needs to be operated under conditions similar to thiose in which you are experiencing problems. If you're seeing lean or rich operation with the vehicle loaded and climbing hills it may be tough for a tuner stationed in a shop in town to realize what the problem is.

Can I ask how your tuner(s) have asked you to collect data so they could see what changes could be made?

[SkyCapt]

The CPU Part number is a 777747. The CALPAK is from a 350 CDI but from what I understand shouldn't affect anything, it runs in limp home ok. I don't have any software and wondering whether of not to invest in the whole shebang or bail and order the Holley System. I have 2 CPUs one with the standard 26 pin EProm and one with the 28 pin Flash. I purchased a performance 454 26 pin chip from Summit but it runs terribly with that setup (very lean). I had a tuner with a dyno set up the 28 pin flash chip and as far as drivability goes it runs great, my Check Engine light comes on after the truck runs 10 minutes or so in a light cruise. I haven't actually checked the emissions, I might mod the light and just see. Is it worth the time involved with the OBD1 system to get it right?

Thanks

[SkyCapt]

The Tuner drove it around some and pulled data from his equipment to look at. I don't have anything. But might consider ordering equipment if the OBD1 can be made to work.

[1project2many]

Is it worth the time involved with the OBD1 system to get it right?

I would think it will take less time to make these corrections than to start from the beginning with the Holley system. Have you spoken with the tuner who used the dyno about making small corrections to fix the c/e light? That should require a minimum investment in time, money, and hardware. Tunerpro is $30 and you can buy a cable for around $10-$15.

[dave w]

I'm not sure if the 1227747 TunerPro RT screen shots below will be confusing or helpful.

I posted the TunerPro RT screen shots to show the "tuner" data available with TunerPro RT.

TunerPro RT is a very good "Scan Tool" also.

dave w