Yesterday I decided to start wiring up my Zex wet nitrous system. I decided to use an MSD window switch in conjunction with it. First I drilled the hole for my fogger in the side of the intake duct. Then I stuck the bulkhead fitting through that hole. Then I ran the nitrous line from the backseat to under the hood. Then I unscrewed the Schrader valve and hooked up the fuel line to the Nitrous Management Unit (NMU). All the braided lines are connected except to the bottle itself.

Then I wired part of the system. The MSD window switch came first. I wired the positive, the ground, and ran the yellow wire to a relay attached to the NMU. Finally I go to tap into the ECU for the tach sensor. My friend that was with me told me to tap into this white wire:



(this pic is after I discover the problem and try to get everything back to normal)

I trusted him instead of checking to see if this was routed into Pin 35.

Throughout this process I'm starting the car to make sure the fuel line wasn't leaking. It started and ran fine the first 2 times. Then after tapping into the white wire, I start up the car again. This time the car stutters and the engine shakes pretty violently. Without revving it, the car dies.

Here is a youtube vid of how the car sounds and shakes:

http://www.youtube.com/watch?v=nTiw5FtBdak

This morning I went to start the car again after putting everything back to the way it was. It starts and idles without dying. The engine still shakes pretty bad and gets worse when I shift into R.

My guess is the white wire we cut into isn't the tach wire at all and is causing problems. That or I didn't clean the shavings off the intake duct and debris has entered the intake. I'm at a loss for what to do now and need some more opinions.

 

Rpm signal is pin 35 on the blue connector. Its a white wire.
Tps signal is pin 12 and is a dark blue wire.
Remove the plastic snap caps off the connectors to the pcm. Every pin is labeled with a number. This should of been done when it was installed.

 

The screw must have been stripped becacause it would not come out. I knew the wire was white. At first glance, it seemed that there was only 1 white wire. Later I pulled back more wire loom and found another white wire.

Even after I reconnected the wire I cut, the car still won't run right.

 

The screw isn't suppose to come out. It will come out once you unscrew it and unclip the plastic covers that proctect the wiring.

 

Let's just hope you didn't tap into the wrong wire and cause some kind of damage to the computer

 

Does anyone have a pinout of the ECU handy? I'm almost 100 percent positive I tapped into the wrong wire and would like to know what wire I connected to.

 

http://shbox.com/1/4th_gen_tech2.html#1995_pcm_pinouts

 

whoops, thats a link for LT1... hang on I'll look for the LS

 

Try this one...

https://ls1tech.com/forums/conversio...swap-faqs.html

 

I think its pin 10 you are looking for tach.

 

You could always come take a look at mine Matt.

 

Fix that wire properly and try swapping out the PCM with someone elses to make sure you didn't fry the thing.

 

You need to do a visual insoection first and make sure everything is correct. Watching the video, the first thing i saw was you have the nozzle just sticking out. thats unmetered air getting past the MAF. You need to plug that hole.

 

Problem was simple and that's how it usually is. Didn't tighten down the lower section of the ecu. Whoops. Runs perfect now and IDed the correct wires for the tps and tach.

 

great. were you able to use the pin out to find the right wires?

 

Found the correct wires this time. For future reference, if anyone owns a 98 F-body, the wires you want are in the upper PCM. Pin 12 (DRK BLU) is TPS. Pin 35 (WHT) is Tach.