Electronics Need help wiring something up? Thinking of adding an electrical component to your car? Need help troubleshooting that wiring glitch?

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Old Oct 23, 2005 | 11:02 PM
  #1  
LoudmouthSS's Avatar
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From: West Palm Beach, FL
Car: 1991 Z28
Engine: SBC
Transmission: 700R4
Axle/Gears: 2.73
Ecm

Whats a good indication that the ECM has crapped out?

Because this is what ive got right now as far as problems go..

1. The car runs like ****, but its running on a stock prom with no tuning and a big cam (so i blame that for the ****ty running). But its running really rich...even some blue smoke, but the engines brand new?...and the car has a very erractic idle.

2. The fans wont come on anymore...all the wirings good...i grounded the wires that lead to the relay and the fans came on. THe coolant temp sensor is good and new, fan motors are good and what not.

3. The tach no longer reads that the car is revving so the tach doesnt move

4. Ive read on a post that a guy had his battery unplugged for 4 years and then reconnected it and fired up the car and the ecm was dead?...ive had mine down for about 6 months and then just recently got the car running again..
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Old Oct 23, 2005 | 11:10 PM
  #2  
HalfInchWrench's Avatar
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From: Ajax, ON
Car: 85Z28 87GTA 91GTA 98SS
Engine: SBC, LS-x
Transmission: T-5, 700-R4, T-56
Do you have access to a scan tool? Could look for abnormal readings such as 4200RPM while the engine is off ect.
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Old Oct 23, 2005 | 11:28 PM
  #3  
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From: West Palm Beach, FL
Car: 1991 Z28
Engine: SBC
Transmission: 700R4
Axle/Gears: 2.73
I have a small computer thing that just flashes the check engine light in order for me to get a code....thats all ive got
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Old Oct 23, 2005 | 11:34 PM
  #4  
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From: Ajax, ON
Car: 85Z28 87GTA 91GTA 98SS
Engine: SBC, LS-x
Transmission: T-5, 700-R4, T-56
Try to find someone with one local would be best. Which ever regional fourm that covers your area. Car guys are pretty good at lending a hand when needed.
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Old Oct 24, 2005 | 11:01 PM
  #5  
Crall13's Avatar
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From: St Louis area
Car: 92 Formula
Engine: 5.7 L
I had a similar problem with my tach, my exhaust was really rich, and it ran a little rough. I ended up replacing the Ignition control module and the coil. I'm not sure which was the problem but it works now with no problem. I think this was due to the fact that I wasn't getting fire in the cylinders all the time.
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Old Oct 25, 2005 | 11:08 PM
  #6  
LoudmouthSS's Avatar
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From: West Palm Beach, FL
Car: 1991 Z28
Engine: SBC
Transmission: 700R4
Axle/Gears: 2.73
yea i replaced the ignition control module too and the coil is a brand new msd blaster.
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Old Oct 26, 2005 | 08:41 PM
  #7  
Vader's Avatar
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A stock PROM, with stock MAP and VE tables, and a "big" cam are not always the best choice. A cam with more overlap and less idle vacuum can appear as an engine with more load to the ECM, causing more fuel delivery. Even if/when the ECM achieves closed loop mode, I think the tendency would be toward rich.

Presuming you've checked the ignition, adjusted the TPS properly, have a good set of filters, tested fuel pressure, and eliminated any vacuum leaks, you might assume that the cam is not happy with the stock tuning. The stock tuning probably isn't a big fan of the cam profile, either.
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Old Oct 30, 2005 | 03:08 AM
  #8  
89TA383M5's Avatar
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From: Illinois
Car: 89 TA
Engine: 413 TPI
Transmission: TKO 600
Axle/Gears: 3.42
Hey loudmouth, did you put a MSD ignition on it, 6A or 6AL? I did and my tach was really stupid then I diconnected the tach wire going to the harness and ran it to the tach output on the MSD box and now it works fine.
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Old Nov 2, 2005 | 08:09 AM
  #9  
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From: West Palm Beach, FL
Car: 1991 Z28
Engine: SBC
Transmission: 700R4
Axle/Gears: 2.73
Hey sorry it took so long to get back, no im running an accel 300+ ignition
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Old Nov 2, 2005 | 08:15 AM
  #10  
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From: Illinois
Car: 89 TA
Engine: 413 TPI
Transmission: TKO 600
Axle/Gears: 3.42
Does the box have a tach output?
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Old Nov 3, 2005 | 06:38 AM
  #11  
LoudmouthSS's Avatar
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From: West Palm Beach, FL
Car: 1991 Z28
Engine: SBC
Transmission: 700R4
Axle/Gears: 2.73
i dont think so..ive got the two wires off the box to the dizzy and the black box thing, then i have a fusible link on the box itself.

Ill get a picture of it today and show you...
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