| Tach Noise [message #319646] |
Tue, 27 June 2017 07:50  |
Jon payne
Messages: 495
Registered: May 2008
Karma:
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Senior Member |
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Hi Guys!
Need you help please. Last fall I installed the FiTech EFI. Only put on around 300 miles on the system since then. When I first took the GMC out this past April it was the first time I had the handheld controller set up where I could monitor some parameters like AFR, RPM, Coolant temp, etc while driving. One thing I noticed right away was the RPM would spike to 3000 to 5000 randomly and the AFR was really rich, around 10.8. The RPM spike would last 1 second but no obvious affect on the engine operation. This also happens during idle including the very rich AFR. I performed a data log and noticed that when the RPM spikes the fuel pressure spikes to 100psi and the injector duty cycle spikes as well. This only lasts 1 second and I think this is the reason the AFR is really rich. The ECU might think there is a mis-fire and is trying to adjust.
Anyway, I spoke with FiTech and they said there is noise getting into the tach wire so I isolated the tach wire and put braided shielding the length of the wire but no help. During further trouble shooting, while the engine was running attempted to move around the tach wire and when a touched it I got a huge shock so for sure there is noise in the tach signal. I then put an alligator clip on the tach wire, about 5 inches from the distributor, touched the other end to ground and the engine quite. Moving the clip another five inches or so away from the distributor, touched ground and had no effect. For the heck of it I swapped out the coil with a spare, made sure the installation was correct but no change.
Not positive if what I am seeing is normal or not with the tach wire but if it is not could it be the RF capacitor is bad? I know that is for RF noise but not sure if it helps to keep noise out of the tach wire??
Hoping for some ideas here as I am really lost on this one. Got a big trip to Sleeping Bear Dunes next week and got to get this sorted out ASAP. Any help would be greatly appreciated as always!
Jon
Jon Payne
76 Palm Beach
Westfield,IN
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