Thumper Posted November 26, 2005 Share Posted November 26, 2005 I went to tune the car tonight and found that I have an rpm stumble between 4600-5100rpms. It is more pronouced in the 3rd, 4th, and 5th gears. Before and after the rpms it runs perfectly. At the same time as the stumble I also get pinging. Now for the fun part I am tunning with a wideband o2 and it stays at 12.2:1-11.8:1 during full throttle. I have tried less fuel and more fuel. The stumble will go away if I advance the timing in that area by +4 degrees but then it majorly pings. If I retard the timing the pinging is alot better although still there but the stumble is much worse. My IAT's are 75-85 on a 64 degree night. Cylinder temps are 180-210. Also at lower boost I can run more timing so it is not there but the more boost I run the worst it gets because of how much timing I retard. I have also played around with my spark plug gap and it has had little to no effect. Any suggestions? Thanks Quote Link to comment Share on other sites More sharing options...
yo2001 Posted November 26, 2005 Share Posted November 26, 2005 Try BPR7ES gapped around .028" see if the stumble goes away. it sounds like blowing out the sparks. Quote Link to comment Share on other sites More sharing options...
Bernardd Posted November 26, 2005 Share Posted November 26, 2005 What PSI? Original coil? Wires? Sparks Plugs? (heat range, brand) Gapped to _____? Fuel? Which wideband are you using? If it's the LM-1 and you're watching the display rather than reading datalogs, that could be a problem. I can't remember which way the reading went from the datalog but it was different from what the display showed. At first guess I'd say you're ignition isn't up to it, but usually you can tune that out with a tighter spark plug gap. Do you have datalogs you can post? Quote Link to comment Share on other sites More sharing options...
Thumper Posted November 26, 2005 Author Share Posted November 26, 2005 I haven't figured out the datalogging yet on it. But will try today. I have an msd6al and a blaster 2 coil, and magnecore wires. The spark plugs were gapped at .030" and I just moved them up to .043" but have only done one run with it as this setting so I am not sure if it helped or hurt. I did over 50+ runs with the gap at .030" and it happened right around 4600 everytime. And then at 5100rpms it would be ok again and run to redline. I am running bpr7es at .030" The missing will first start to manifest it self at 12-13psi and become more and more of a problem all the way up to 18psi. Below 12psi no problems. The other sympton besides the stumble I'm worried about is the pinging. My car should not ping at all at 13psi with 60degree weather and the timing I am running. Also why would advancing the timing get ride of the stumble if it was blowing the spark out. I'm just trying to see all angles. With my t3 setup I could run the spark plugs at .050" at 18psi with the t3 with no problems. I am going to try new spark plugs anyway just incase. Keep em coming. Thanks Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted November 26, 2005 Share Posted November 26, 2005 Take a look at the plugs and make sur that there are no cracks in the porclein or and other damage that might cause them to not work perfectly. If your getting a slight ping I'm sure the plugs are getting damaged and not working at thier peak performace. Possibly not arching correctly or even at all. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted November 27, 2005 Share Posted November 27, 2005 Also why would advancing the timing get ride of the stumble if it was blowing the spark out. because the mixture is not as dense with 20degree before TDC than 15 degree? that's my guess, but I always cured the stumble with timing and spark plug gaps Quote Link to comment Share on other sites More sharing options...
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