RPM Noise Issue
Hi All,
I've had this installed for 2 weeks or so and have one more issue to tackle before I start fine tuning. However, it is kind of a big one. I have the nagging rpm noise issue. Will work perfectly until I get to around 2500 rpm, then engine cuts out as if there is a rev limiter and stutters. When it does this, I cannot accelerate further until I come down in rpm then it is as if nothing has happened. I've attached logs.
My build is an FE 390 with progression ignition HEI distributor
What I've done so far in order:
- hard wired ground instead of using the intake and throttle body - didn't help
- RF shielded the tach wire (from the connector to the HEI) and routed away from all other wires - didn't help log file after this change: https://docs.google.com/spreadsheets/d/1_-M4j0WOqrMyQlekvQ8Xo2qdjgKgsSz5DVkuKW_SDJw/edit?usp=sharing
- Replaced my old 1g alternator with new 3g alternator - didn't help - log file after this change: https://docs.google.com/spreadsheets/d/1-yL2rzlIOFcrvZHElWnKphfxbASrxH1GiI74L8xOkSg/edit?usp=sharing
things I have yet to try:
- Faraday tape the tach wire
- Faraday tape the front of the ecu
- Run w/o the air cleaner as it may be acting as an antenna?
Any of you experience the same thing? I've searched high and low and I don't have the same issues as most with the rpm noise as I'm able to start the car and drive around town just fine. But I cannot get over 50-ish mph as that's when I hit 2500 rpm and the engine cuts out. Thanks in advance.
Sounds like a distributor to me. Which fitech do you have and is it controlling timing? Try a real stock GM Hei distributor and turn off Fitech from controlling timing if you are controlling timing with Fitech. Just did that with a friends trunk this week as the performance distributor was causing all sorts of issues. Now trunk runs great.
I had the same issue, finally got bad enough that it finally did a Code 36. Code 36 is a ignition noise code. Finally boiled down to a bad coil. The coil was little at a time going bad and initially exhibited itself as a occasional random flutter of the tach needle with no code. That flutter got gradually worse until it did a code 36. At the same time it ran extremely rich with accompanying load missing. I replaced the coil with an old Delco coil that I had laying around, and that cured the problem. Maybe just replace the coil with any old 12v coil to see if issue improves. If it does, get a new coil. JWID
Quote from Larry on July 30, 2022, 9:50 pmI had the same issue, finally got bad enough that it finally did a Code 36. Code 36 is a ignition noise code. Finally boiled down to a bad coil. The coil was little at a time going bad and initially exhibited itself as a occasional random flutter of the tach needle with no code. That flutter got gradually worse until it did a code 36. At the same time it ran extremely rich with accompanying load missing. I replaced the coil with an old Delco coil that I had laying around, and that cured the problem. Maybe just replace the coil with any old 12v coil to see if issue improves. If it does, get a new coil. JWID
Be careful on the coil you are using. If you have replaced points with a petronix system , you need a low ohm coil ( 0.6 ohms ) or you will burnt out the petronix electronic points.
Thanks for that, but when sold as a set, they recommend the 1.5 ohm "Flame Thrower" coil, which is the coil that went bad on me. The Delco coil I replaced it with is a 1.2 ohm. I am using it with the 1181LS Petronix. I've used the Flame thrower with the 1181LS for several years before the coil went bad. No issues with the Petronix....knock on wood....
Here is the coil that I was using and is the one that went bad.......https://www.amazon.com/PerTronix-40011-Flame-Thrower-Volt-Coil/dp/B00199F2WW/ref=pd_bxgy_img_sccl_1/147-0490829-8137046?pd_rd_w=Cv7GC&content-id=amzn1.sym.7757a8b5-874e-4a67-9d85-54ed32f01737&pf_rd_p=7757a8b5-874e-4a67-9d85-54ed32f01737&pf_rd_r=2CRX3M2S3J1JXH9N2AAT&pd_rd_wg=2fLwO&pd_rd_r=8d74bc3e-bdfd-4adc-b15a-6c0db471e902&pd_rd_i=B00199F2WW&th=1
Quote from Larry on July 31, 2022, 2:51 pmThanks for that, but when sold as a set, they recommend the 1.5 ohm "Flame Thrower" coil, which is the coil that went bad on me. The Delco coil I replaced it with is a 1.2 ohm. I am using it with the 1181LS Petronix. I've used the Flame thrower with the 1181LS for several years before the coil went bad. No issues with the Petronix....knock on wood....
Here is the coil that I was using and is the one that went bad.......https://www.amazon.com/PerTronix-40011-Flame-Thrower-Volt-Coil/dp/B00199F2WW/ref=pd_bxgy_img_sccl_1/147-0490829-8137046?pd_rd_w=Cv7GC&content-id=amzn1.sym.7757a8b5-874e-4a67-9d85-54ed32f01737&pf_rd_p=7757a8b5-874e-4a67-9d85-54ed32f01737&pf_rd_r=2CRX3M2S3J1JXH9N2AAT&pd_rd_wg=2fLwO&pd_rd_r=8d74bc3e-bdfd-4adc-b15a-6c0db471e902&pd_rd_i=B00199F2WW&th=1
In your case your ohms is correct as you have the original Ignitor which requires 1.5ohms. The Ignitor II requires 0.6ohms and the Ignitor III requires 0.32ohms. I have the Ignitor III in my car and it made a big difference over the Ignitor II I had in there.
For anyone following this - I went on a hunch and replaced the new HEI distributor with my old ready to run small cap one and the problem went away. So for some reason, the Fitech does not like the rpm signal from that HEI distributor.
Quote from waldezy on August 6, 2022, 7:46 pmFor anyone following this - I went on a hunch and replaced the new HEI distributor with my old ready to run small cap one and the problem went away. So for some reason, the Fitech does not like the rpm signal from that HEI distributor.
Fitech themselves recommend using a genuine GM Hei distributor. I have replaced aftermarket distributors with GM distributors and all problems would go away. I can only say this for GM cars, others I cant say. The biggest problem we face today is stuff being made in China.