another egine miss - Page 3

randy wilson · 07-02-2012, 10:19 AM

Thanks Ralph, didn't think of that. Was a little lean.

Michael Compton · 07-02-2012, 11:32 AM

When I had a miss, mine was at the top of high gear and you could hear the miss and see it on the racepak graph. It was crazy. Turns out we had a regulator and fuel pump going south. When under extreme load, the regulator and pump were causing flucuations in the fuel and making the motor miss because of no fuel. Might be something to check out.

randy wilson · 07-02-2012, 12:09 PM

Thank you! Will do. The fuel pressure on the graph never flucuated though.

FED 387 · 07-02-2012, 01:20 PM

just remember that there is a difference between volume and pressure!!!! FED387

Sean Marconette · 07-02-2012, 01:57 PM

FED 87 hit the nail on the head! I had the same thing happen this year at Great Bend. Data logger showed no fluctuation in fuel pressure, I pulled the fuel filter to see if that would make a difference. None. My engine builder suggested it was probably the pump. I replaced the pump, and checked calibration of fuel pressure sensor, it was within .5 PSI of a calibrated instrument. Next time out my car was back to normal.

Good luck
Sean

buzzinhalfdozen · 07-02-2012, 02:13 PM

I would agree with the fuel pump theory, he should see EGT's or O2 readings spiking if this is the case. Though EGT's are slow to resond you should see a corresponding increase (perhaps delayed a bit) when your issue arises. If using O2's (which are for the most part MUCH faster) you should see it go almost dead lean during the misfire event, as the AFR needs to depart from normal quite a bit to induce a misfire. The part I can't get over is he states that the tach and datalogger RPM "jump around" normally this does not happen with a fuel induced misfire the RPM's simply flatten out. Joe

randy wilson · 07-02-2012, 04:57 PM

Brand new pump, used one weekend at KCIR, before and never missed. Not saying this is not it, but doubtful. Did not have exhaust temperatures hooked up, just enstalled for the first time, but plugs looked real lean. Switched from C14 to C25, And jetted up 4 sizes, was that close?

Mike Taylor 3601 · 07-02-2012, 06:56 PM

Most likely tach jumping is ign.related miss.
Mike Taylor3601

Ed Wright · 07-02-2012, 07:12 PM

Mine was missing intermittently in each gear at Joliet this past weekend. Felt like a leaky plug wire or plug. My plug wires are over due. Shouldn't run them more than 2 seasons. I usually put new plug wires on mine every winter. Gotten lax about it, and think it bit me. Bottom of the gears makes me think of plug wires if it has had the plugs changed.

randy wilson · 07-03-2012, 11:45 AM

I agree Mike, ignition. But that only narrows it down so much. But thanks guys, will run the tester on it, and tell you what we come up with.

07-02-2012, 10:19 AM	#21
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: another egine miss Thanks Ralph, didn't think of that. Was a little lean. __________________ don,t have one

07-02-2012, 11:32 AM	#22
Michael Compton Member Join Date: Dec 2003 Location: Neosho, MO Posts: 215 Likes: 0 Liked 59 Times in 13 Posts	Re: another engine miss When I had a miss, mine was at the top of high gear and you could hear the miss and see it on the racepak graph. It was crazy. Turns out we had a regulator and fuel pump going south. When under extreme load, the regulator and pump were causing flucuations in the fuel and making the motor miss because of no fuel. Might be something to check out.

07-02-2012, 12:09 PM	#23
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: another egine miss Thank you! Will do. The fuel pressure on the graph never flucuated though. __________________ don,t have one

07-02-2012, 01:20 PM	#24
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,410 Likes: 507 Liked 329 Times in 177 Posts	Re: another egine miss just remember that there is a difference between volume and pressure!!!! FED387

07-02-2012, 01:57 PM	#25
Sean Marconette Senior Member Join Date: Mar 2006 Posts: 977 Likes: 787 Liked 274 Times in 76 Posts	Re: another egine miss FED 87 hit the nail on the head! I had the same thing happen this year at Great Bend. Data logger showed no fluctuation in fuel pressure, I pulled the fuel filter to see if that would make a difference. None. My engine builder suggested it was probably the pump. I replaced the pump, and checked calibration of fuel pressure sensor, it was within .5 PSI of a calibrated instrument. Next time out my car was back to normal. Good luck Sean __________________ Sean Marconette 84 Mustang 5060 SS/N

07-02-2012, 02:13 PM	#26
buzzinhalfdozen Senior Member Join Date: Sep 2006 Location: Bellevue Ohio Posts: 984 Likes: 0 Liked 11 Times in 8 Posts	Re: another egine miss I would agree with the fuel pump theory, he should see EGT's or O2 readings spiking if this is the case. Though EGT's are slow to resond you should see a corresponding increase (perhaps delayed a bit) when your issue arises. If using O2's (which are for the most part MUCH faster) you should see it go almost dead lean during the misfire event, as the AFR needs to depart from normal quite a bit to induce a misfire. The part I can't get over is he states that the tach and datalogger RPM "jump around" normally this does not happen with a fuel induced misfire the RPM's simply flatten out. Joe __________________ Joe Buchanan SS/BX 3117 Last edited by buzzinhalfdozen; 07-02-2012 at 03:26 PM.

07-02-2012, 04:57 PM	#27
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: another egine miss Brand new pump, used one weekend at KCIR, before and never missed. Not saying this is not it, but doubtful. Did not have exhaust temperatures hooked up, just enstalled for the first time, but plugs looked real lean. Switched from C14 to C25, And jetted up 4 sizes, was that close? __________________ don,t have one

07-02-2012, 06:56 PM	#28
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,362 Likes: 337 Liked 279 Times in 96 Posts	Re: another egine miss Most likely tach jumping is ign.related miss. Mike Taylor3601

07-02-2012, 07:12 PM	#29
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: another egine miss Mine was missing intermittently in each gear at Joliet this past weekend. Felt like a leaky plug wire or plug. My plug wires are over due. Shouldn't run them more than 2 seasons. I usually put new plug wires on mine every winter. Gotten lax about it, and think it bit me. Bottom of the gears makes me think of plug wires if it has had the plugs changed. __________________ Ed Wright 4156 SS/JA

07-03-2012, 11:45 AM	#30
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: another egine miss I agree Mike, ignition. But that only narrows it down so much. But thanks guys, will run the tester on it, and tell you what we come up with. __________________ don,t have one