High RPM miss

TimboStang · May 9th, 2009, 11:09 AM

Took the car to the track last night and I developed a miss at around 5k. Where would be the first place to start diagnosing. I don't have any way of datalogging. I guess I need to pull the plugs first and check them out. Kind of felt like it could have been blowing the spark out. Any suggestions?

ROUSH STAGE II · May 9th, 2009, 12:25 PM

What's your plug gap set at right now? The only time I've had an upper rpm miss with mine is when I blew the air intake coupling off slightly and it created a gap at the throttle body.

Anthony05GT · May 9th, 2009, 03:18 PM

I'd check for the obvious and a new set of HTO plugs gapped at .030

TimboStang · May 9th, 2009, 03:42 PM

When I get a chance I'll go over all my connections and pull the plugs. I guess it could be a coil pack getting weak.

JakeM · May 9th, 2009, 03:46 PM

Originally Posted by TimboStang

When I get a chance I'll go over all my connections and pull the plugs. I guess it could be a coil pack getting weak.

I very much doubt that. I would check your plugs, including the gap. Then I would check your connections after you replace the plugs. Then go run it hard and see if you still have a miss. If you do, you have the ability to datalog right? Datalog and see where the problems is. Whether its fuel or spark.

Anthony05GT · May 9th, 2009, 08:01 PM

I know I've had Motorcraft HTO's give me problems (seen on the dyno too) with just a few thousand miles on them. The simple rule of thumb is if you are running forced induction change the plugs at every 10k miles and gap them down to about .030

05roush0090 · May 9th, 2009, 08:11 PM

Plugs are exactly where I would start.

TimboStang · May 10th, 2009, 10:58 AM

Used my Predator to watch some fuel parameters this morning and the fuel pressure is dipping at 4800-5200 rpm. Should it be showing a steady 38 or should it rise with boost pressure? It rises up to 48 and then when it gets around 4800 it will drop to as low as 33psi and then start to rise back up after 5200. Maybe it's time for a fuel filter.

TimboStang · May 10th, 2009, 10:59 AM

What voltage does the factory computer and maf run on? At one point this morning it saw 4.5v

Anthony05GT · May 10th, 2009, 11:25 AM

One thing's for sure, when you are running boost change the filter every 10k miles.

TimboStang · May 10th, 2009, 12:48 PM

Here is the spark plug gaps. 3@.035 3@.034 1@.038 1@.040.

Is that enough gap to cause spark blow out at 11psi?

JakeM · May 10th, 2009, 01:04 PM

I'd slam them all down to .030 or .032. Also, changing your fuel filter will probably be a good idea. Max volts on the MAF is 5v's I think.

TimboStang · May 10th, 2009, 02:37 PM

Changed fuel filter. Gapped plugs to .031. Now time to go test her out.

I probably need to get one of those slot style ba5000 meters so I don't run out of maf down the road.

JakeM · May 10th, 2009, 02:59 PM

Its a good idea if you plan on going big boost someday. If not you could always got a Diablo MAFia MAF range extender.

TimboStang · May 11th, 2009, 01:28 AM

I've got a mafia on it now. Took it to the track tonight and the miss is gone.

ROUSH STAGE II · May 11th, 2009, 01:43 AM

Originally Posted by TimboStang

Changed fuel filter. Gapped plugs to .031. Now time to go test her out.

I probably need to get one of those slot style ba5000 meters so I don't run out of maf down the road.

Just so you know... I'm using a 2400 maf without a mafia without any issues.

flattusmaximus78 · May 11th, 2009, 01:08 PM

Whats your Combo? 97 in the 8th is about 122 or 123 in the quarter.

JakeM · May 11th, 2009, 01:20 PM

Originally Posted by TimboStang

I've got a mafia on it now. Took it to the track tonight and the miss is gone.

Awesome! So, did you try it with just the plugs? Or was it indeed the MAF running out of range?

TimboStang · May 11th, 2009, 02:49 PM

Originally Posted by Towelly

Awesome! So, did you try it with just the plugs? Or was it indeed the MAF running out of range?

I phrased that wrong. I already had a mafia on it. The only things I changed were the gap and the fuel filter. I should have done these two individually and tested each one just for knowlege sake. I don't know which actually fixed the problem. I poured the fuel filter out today and the fuel that came out the inlet side was nasty nasty. Looked like Galveston beach water.

TimboStang · May 11th, 2009, 02:58 PM

Originally Posted by flattusmaximus78

Whats your Combo? 97 in the 8th is about 122 or 123 in the quarter.

Stock 05 mustang GT with a turbonetics single 60mm turbo. I ran friday at the 1/4 track and only trapped 113. That is why I started this thread. Ran at the 1/8th track last night and was trapping 93. We had some really muggy air last night. I'm hoping that is why the mph came down so much. We are at around 95ft. elevation, but with the DA last night it was like 1867ft.

Hopefully that warrants dropping 3-4mph, otherwise that would show that I lost some power by gapping my plugs down. What do yall think?

Oh, and on a side note, I manged to pull off a 1.80 60' on Nitto555 street tires with less than half tread on them. 7.80 @ 93. The two step really helps on launch control.

May 9th, 2009, 11:09 AM	#1
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	High RPM miss Took the car to the track last night and I developed a miss at around 5k. Where would be the first place to start diagnosing. I don't have any way of datalogging. I guess I need to pull the plugs first and check them out. Kind of felt like it could have been blowing the spark out. Any suggestions? __________________ Turbonetics single 60mm

May 9th, 2009, 12:25 PM	#2
ROUSH STAGE II Hardcore Enthusiast 2005 Turbonetics Baby!!! Join Date: Jul 2007 Location: Mauriceville, Texas Posts: 2,218 iTrader: 0 reviews	What's your plug gap set at right now? The only time I've had an upper rpm miss with mine is when I blew the air intake coupling off slightly and it created a gap at the throttle body. __________________ Turbonetics baby!!! 11.23@122 mph...

May 9th, 2009, 03:18 PM	#3
Anthony05GT Hardcore Enthusiast Join Date: Feb 2009 Posts: 1,461 iTrader: 1 reviews	I'd check for the obvious and a new set of HTO plugs gapped at .030 __________________ JDM 302 Stroker, Whipple 10 rib 12 psi, L&M, JBA, J&M, LFP, Corsa, BBR Stage II cams, Manley, MGW, McLeod RST, Metco, Steeda, Autometer, CDC, Street Scene, SOS, Tuned at JPC Racing by Kevin MacDonald

May 9th, 2009, 03:42 PM	#4
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	When I get a chance I'll go over all my connections and pull the plugs. I guess it could be a coil pack getting weak. __________________ Turbonetics single 60mm

May 9th, 2009, 08:01 PM	#6
Anthony05GT Hardcore Enthusiast Join Date: Feb 2009 Posts: 1,461 iTrader: 1 reviews	I know I've had Motorcraft HTO's give me problems (seen on the dyno too) with just a few thousand miles on them. The simple rule of thumb is if you are running forced induction change the plugs at every 10k miles and gap them down to about .030 __________________ JDM 302 Stroker, Whipple 10 rib 12 psi, L&M, JBA, J&M, LFP, Corsa, BBR Stage II cams, Manley, MGW, McLeod RST, Metco, Steeda, Autometer, CDC, Street Scene, SOS, Tuned at JPC Racing by Kevin MacDonald

May 9th, 2009, 08:11 PM	#7
05roush0090 Enthusiast 2005 Mustang GT Roush Join Date: Mar 2008 Location: Indiana Posts: 728 iTrader: 0 reviews	Plugs are exactly where I would start. __________________ Paxton/Vortech crew member # 2 Vortech V3 si, A/A cooler, 3.48" pulley, 39lbers, KB BAP, Billet delete plates, Stage 2 thumprs, phaser limiters, Mac Lts, Offroad x, Roush short throw, Brisk plugs, Brenspeed 93 tune, relocated IAT.

May 10th, 2009, 10:58 AM	#8
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	Used my Predator to watch some fuel parameters this morning and the fuel pressure is dipping at 4800-5200 rpm. Should it be showing a steady 38 or should it rise with boost pressure? It rises up to 48 and then when it gets around 4800 it will drop to as low as 33psi and then start to rise back up after 5200. Maybe it's time for a fuel filter. __________________ Turbonetics single 60mm

May 10th, 2009, 10:59 AM	#9
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	What voltage does the factory computer and maf run on? At one point this morning it saw 4.5v __________________ Turbonetics single 60mm

May 10th, 2009, 11:25 AM	#10
Anthony05GT Hardcore Enthusiast Join Date: Feb 2009 Posts: 1,461 iTrader: 1 reviews	One thing's for sure, when you are running boost change the filter every 10k miles. __________________ JDM 302 Stroker, Whipple 10 rib 12 psi, L&M, JBA, J&M, LFP, Corsa, BBR Stage II cams, Manley, MGW, McLeod RST, Metco, Steeda, Autometer, CDC, Street Scene, SOS, Tuned at JPC Racing by Kevin MacDonald

May 10th, 2009, 12:48 PM	#11
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	Here is the spark plug gaps. 3@.035 3@.034 1@.038 1@.040. Is that enough gap to cause spark blow out at 11psi? __________________ Turbonetics single 60mm

May 10th, 2009, 02:37 PM	#13
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	Changed fuel filter. Gapped plugs to .031. Now time to go test her out. I probably need to get one of those slot style ba5000 meters so I don't run out of maf down the road. __________________ Turbonetics single 60mm

May 11th, 2009, 01:28 AM	#15
TimboStang Regular 2005 Mustang GT 11.88 @ 118 Join Date: Jul 2008 Location: Conroe TX Posts: 395 iTrader: 0 reviews	I've got a mafia on it now. Took it to the track tonight and the miss is gone. __________________ Turbonetics single 60mm

May 11th, 2009, 01:08 PM	#17
flattusmaximus78 I Post Entirely Way Too Much 1993 5.ohhhh 12.97 @140mph Join Date: Apr 2006 Location: Gatorland Posts: 6,077 iTrader: 3 reviews	Whats your Combo? 97 in the 8th is about 122 or 123 in the quarter. __________________ 02 Pewter z28, hoosiers/lid/exhaust/spray...125mph 1993 gt Sold, already missed --Moates Quarter horse $225-- --Cobra intake $150-- --tremec 3550 bell and shifter $1100--

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