Idle surge after successful tuneup

93GTDIN · 08-19-2002, 11:03 PM

Well I did the 1000 mile tune up last saturday. We retightened the head bolts, the intake bolts, the header bolts, and adjusted the valvetrain, as well as changed both 02 sensors. The car runs much smoother now, and has better power down low. The only problem is the idle. It surges horribly. Out of gear, it will idle for about 10 seconds before it starts surging from 500- 1500 rpms sporadically. It will eventually die. Putting it in gear it will do the same to a lesser degree. It did not do this before the tuneup. I do however remember a problem resembling this right when i got the motor running 2 months ago. It went away. What could cause an idle surge like this? Any common things I should be checking. The car throws the codes:

EGR valve malfunctioning
Ignition profile eratic

Another thing i should probably mention is something odd about my cylinder #1. Compression is right on, but that particular intake runner is black from what looks like exhaust, but i'm not sure. Also, while 7 of my crappy flowtech header tubes are a gross white/back/rust, the #1 header is a flat gray. The spark plug is also blacker than the other ones. One thing I did notice is that the #1 wire has a resitance about half that of the other wires. Any and all help is welcome, thanks!

PKRWUD · 08-19-2002, 11:09 PM

Is the EGR still hooked up?

93GTDIN · 08-19-2002, 11:14 PM

yes it is. Not sure whether or not it is working. Oh yeah i forgot the mileage. Before tuneup - 13. After tuneup.... about the same. figured it would get better.

PKRWUD · 08-19-2002, 11:16 PM

Attach a hand vacuum pump to the EGR, and with the engine idling, slowly apply vacuum, until you get to 10". What happens? Does the gauge hold steady at 10"? Does the engine stumble or stall?

93GTDIN · 08-19-2002, 11:26 PM

I dont have a vacuum pump, i'll have to borrow one tomorrow. The car vacuum gauge I have shows about 16" at idle, which, of course, fluctuates w/ the idle.

08-19-2002, 11:09 PM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Is the EGR still hooked up? __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

08-19-2002, 11:14 PM	#3
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	yes it is. Not sure whether or not it is working. Oh yeah i forgot the mileage. Before tuneup - 13. After tuneup.... about the same. figured it would get better. __________________ 96 Cobra - a bit too stock. 14.0 @ 101

08-19-2002, 11:16 PM	#4
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Attach a hand vacuum pump to the EGR, and with the engine idling, slowly apply vacuum, until you get to 10". What happens? Does the gauge hold steady at 10"? Does the engine stumble or stall? __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

08-19-2002, 11:26 PM	#5
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	I dont have a vacuum pump, i'll have to borrow one tomorrow. The car vacuum gauge I have shows about 16" at idle, which, of course, fluctuates w/ the idle. __________________ 96 Cobra - a bit too stock. 14.0 @ 101

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08-19-2002, 11:03 PM	#1
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	Idle surge after successful tuneup Well I did the 1000 mile tune up last saturday. We retightened the head bolts, the intake bolts, the header bolts, and adjusted the valvetrain, as well as changed both 02 sensors. The car runs much smoother now, and has better power down low. The only problem is the idle. It surges horribly. Out of gear, it will idle for about 10 seconds before it starts surging from 500- 1500 rpms sporadically. It will eventually die. Putting it in gear it will do the same to a lesser degree. It did not do this before the tuneup. I do however remember a problem resembling this right when i got the motor running 2 months ago. It went away. What could cause an idle surge like this? Any common things I should be checking. The car throws the codes: EGR valve malfunctioning Ignition profile eratic Another thing i should probably mention is something odd about my cylinder #1. Compression is right on, but that particular intake runner is black from what looks like exhaust, but i'm not sure. Also, while 7 of my crappy flowtech header tubes are a gross white/back/rust, the #1 header is a flat gray. The spark plug is also blacker than the other ones. One thing I did notice is that the #1 wire has a resitance about half that of the other wires. Any and all help is welcome, thanks! __________________ 96 Cobra - a bit too stock. 14.0 @ 101