Tough TPI problem
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Supreme Member
iTrader: (1)
Joined: Jul 1999
Posts: 1,334
Likes: 1
From: Key West, Florida!
Car: 89RSconvtZZ4TPI
Engine: ZZ4TPI
Transmission: 700R4 TRIPP TRANNY
Tough TPI problem
I posted this on the TPI board but they are to busy arguing about TPI-vs-Mini-Ram-vs-torque blah blah blah.
Engine is a ZZ4TPI, Edelbrock intake/SLP runners/ported plenum. SVO 24lb injectors, stock 48mmtb. New TPS and MAP sensor. All other sensors appear to be working properly on my autoxray. In the morning or at various times the car starts and runs very rough. These are the symptoms on the scanner:
Desired Idle 925rpm
BLM 128
Open Loop
Spark Adv 18 deg
Idle Air Mtr position 40 steps
Injector pulse 2.4ms and higher up to 3.7 at idle.
MAP 1.80 volts.
Learned Idle 59 steps.
If I step on the gas in this condition, the pulse climbs to 3.4 4.4 6.6 etc. Climbs with just a slight blip of the throttle.
The injectors are just dumping fuel.
Now...When the car decides to run properly, here are the readings:
Inj Pulse 1.7ms
O2 cross counts climb from 0-254
Map 1.72 volts
Learned IAC Pos 57 steps
TPS .54
Fuel Pump voltage 12.6
BLM 108
Spark Adv 14.7 deg
Idle air mtr position 0 steps
The idle will stay high for a few moments when the car goes "normal" Idle about 1200rpm then the Idle air mtr postion goes from like 33 down to 4. I stop the motor, restart and idle air mtr position goes to 0.
CTS and MAT sensor appear to be working fine.
WHen I blip the throttle at idle or in drive, the injector pulse width barely climps over 2.0. Something is telling the injectors to dump fuel. Could this be a lazy IAC, allowing too much air and causing the engine to dump fuel to compensate. Of note, Since the ZZ4 TPI conversion the car has always had a closed loop BLM of 108, thats with a stock L98 chip and the Street and Performance Chip. My stock L98 chip has the egr function off, fans on a little sooner, and 24lb injectors instead of 22lb. The car has ran perfect with both chips before. I have two computers and she does the same on both. The problem seems to abate now once the car warms up or after multiple stops and restarts.
Any ideas?
p.s. No Codes. Fuel pressure has been varied between 38 and 50 with no affect.
------------------
Rob P
89RSconvtZZ4TPI Edelbrock Intake
SLP Dual Cold Air Intake 1 5/8" Headers Semi-Siamesed Runners, IROC
suspension, alum shaft. Numerous mods.
92Z28convt5spd (stock)
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!
Engine is a ZZ4TPI, Edelbrock intake/SLP runners/ported plenum. SVO 24lb injectors, stock 48mmtb. New TPS and MAP sensor. All other sensors appear to be working properly on my autoxray. In the morning or at various times the car starts and runs very rough. These are the symptoms on the scanner:
Desired Idle 925rpm
BLM 128
Open Loop
Spark Adv 18 deg
Idle Air Mtr position 40 steps
Injector pulse 2.4ms and higher up to 3.7 at idle.
MAP 1.80 volts.
Learned Idle 59 steps.
If I step on the gas in this condition, the pulse climbs to 3.4 4.4 6.6 etc. Climbs with just a slight blip of the throttle.
The injectors are just dumping fuel.
Now...When the car decides to run properly, here are the readings:
Inj Pulse 1.7ms
O2 cross counts climb from 0-254
Map 1.72 volts
Learned IAC Pos 57 steps
TPS .54
Fuel Pump voltage 12.6
BLM 108
Spark Adv 14.7 deg
Idle air mtr position 0 steps
The idle will stay high for a few moments when the car goes "normal" Idle about 1200rpm then the Idle air mtr postion goes from like 33 down to 4. I stop the motor, restart and idle air mtr position goes to 0.
CTS and MAT sensor appear to be working fine.
WHen I blip the throttle at idle or in drive, the injector pulse width barely climps over 2.0. Something is telling the injectors to dump fuel. Could this be a lazy IAC, allowing too much air and causing the engine to dump fuel to compensate. Of note, Since the ZZ4 TPI conversion the car has always had a closed loop BLM of 108, thats with a stock L98 chip and the Street and Performance Chip. My stock L98 chip has the egr function off, fans on a little sooner, and 24lb injectors instead of 22lb. The car has ran perfect with both chips before. I have two computers and she does the same on both. The problem seems to abate now once the car warms up or after multiple stops and restarts.
Any ideas?
p.s. No Codes. Fuel pressure has been varied between 38 and 50 with no affect.
------------------
Rob P
89RSconvtZZ4TPI Edelbrock Intake
SLP Dual Cold Air Intake 1 5/8" Headers Semi-Siamesed Runners, IROC
suspension, alum shaft. Numerous mods.
92Z28convt5spd (stock)
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!
Joined: Jul 1999
Posts: 10,950
Likes: 26
From: Orange, SoCal
Car: 1990 Pontiac Trans Am
Engine: 355 TPI siamesed runners
Transmission: Tremec T56
Axle/Gears: 12-Bolt 3.73
I think you need more tuning with your chip. Its running really rich. Try setting the injector constant to 26 lbs and see if that leans it.
------------------
1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH (2.10 60')
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-
------------------
1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH (2.10 60')
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-
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