Rough running engine the result of a custom exhaust?

Bohanan · 05-08-2001, 06:50 PM

I need some help from all the experts out there. I've got a '99 RS that is basically stock except for the Amsoil filter in the stock air box, second air box gasket, and a custom 2.25" cat-back exhaust with a Flowmaster Deltaflow 50 series muffler (p/n 942451). The car has 37,000 miles, but the exhaust has only been on for a few weeks.

I've started noticing a funky problem a couple of weekends ago. I drove from Houston to College Station (about 2 hours) and had the cruise set at 70-80 at various stretches. The problem also occured again this weekend, and today it was more pronounced.

The engine seems to run rough or hesitate. It almost acted like it wanted to come out of cruise. I turned cruise off and held the speed steady at various speeds for several minutes at a time. 65, 70, 75, 80, it didn't seem to matter. The car would be fine then act up. I don't want to call it a hiccup because the car doesn't backfire. It's also not thrown a check engine light yet. I've watched the rpms while this happens and don't notice a major fluctuation.

Has anyone had a problem like this after installing a 2.25" cat-back system? I'm thinking of taking the car into the dealer and see what they can find. Do you think the muffler could be having an adverse affect on the back pressure to cause this? I didn't have this problem back when I had the Rallispec 2.25" system with the dual tip muffler, so this is kind of a surprise.

Any ideas, or suggestions would be appreciated. Thanks.

Adam

[This message has been edited by Bohanan (edited May 08, 2001).]

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kaos200 · 05-08-2001, 07:16 PM

how far back is the custom exhaust?
does it affect o2 sensor placement?

Skylab · 05-08-2001, 07:45 PM

Your car has a bad 02 sensor. I got mine replaced (on a minivan) and it cured the problem.

My van had the same problem your describing...the car wouldn't cruise reliably at any speed above 55 mph. Half throttle it would start to stutter and hiccup and exhaust would pop. WOT there was no problem though.

Anyways, got the O2 sensore replaced and problem solved for $165.

Skylab™

*hope that helps*

Bohanan @ work · 05-09-2001, 06:06 AM

kaos, it's a cat-back. The new pipe was welded to the original flange. It doesn't affect the O2 sensor placement.

Thanks Skylab. I went ahead and dropped the car off at the dealer. Hopefully they'll come back and say it's something simple like that. But, the problem is also showing at full throttle too.

Adam

skeletor25rs · 05-09-2001, 06:33 AM

Thats what mine was doing when the coil-pack went bad. One of my plugs was arching to the engine block. It got worse and worse, until on the way to West Houston it would only go about 50mph.

Bohanan @ work · 05-09-2001, 09:50 AM

Just received word from the dealer. The coil pack went out and managed to fry the number 2 spark plug wire. He said they could see the sparks arcing across the wire while it was running.

Hopefully I should have the car back today.

Thanks for all the input. I had a list going of everyone's ideas. I appreciate it.

Adam

05-09-2001, 11:19 AM

Bohannan, Ever seen me on the road in College Station, or on the way there from houston??? I'm there almost every weekend visiting my girlfriend. I drive a silver '00 RS with Apex N1. What were you doing in College Station anyway? That place is the pits.

NateDogg · 05-09-2001, 08:20 PM

quick question.....what did you do with your rallispec exhaust, if you still have it im willing to buy it

Bohanan @ work · 05-10-2001, 12:24 AM

Hey Ko Ko! I may have. I was up there for an autocross out at the Riverside Annex. I don't get up there much, except for the occasional race.

I do go out to Conroe quite a few times a month. Of course, I live in Spring, so it's not like a major drive any way.

I'll keep my eyes open for you. I have a white '99 with Speedline wheels. Later!

Adam

Bohanan @ work · 05-10-2001, 05:22 AM

Sorry, but I've since sold it to Aubrey (skeletor25rs). The resonance inside the car got so bad on extended road trips that I had to get rid of it. It was pretty sweet looking though. Polished S.S. resonator and dual tip muffler, S.S. piping, excellent workmanship. I believe it was the first dual tip they put together.

Adam

05-08-2001, 06:50 PM	#1
Bohanan Scooby Specialist Member#: 722 Join Date: Jan 2000 Chapter/Region: TXIC Location: Spring, TX Vehicle: I'M DEBT FREE!! 04 WRX Wagon/01 Odyssey	Rough running engine the result of a custom exhaust? I need some help from all the experts out there. I've got a '99 RS that is basically stock except for the Amsoil filter in the stock air box, second air box gasket, and a custom 2.25" cat-back exhaust with a Flowmaster Deltaflow 50 series muffler (p/n 942451). The car has 37,000 miles, but the exhaust has only been on for a few weeks. I've started noticing a funky problem a couple of weekends ago. I drove from Houston to College Station (about 2 hours) and had the cruise set at 70-80 at various stretches. The problem also occured again this weekend, and today it was more pronounced. The engine seems to run rough or hesitate. It almost acted like it wanted to come out of cruise. I turned cruise off and held the speed steady at various speeds for several minutes at a time. 65, 70, 75, 80, it didn't seem to matter. The car would be fine then act up. I don't want to call it a hiccup because the car doesn't backfire. It's also not thrown a check engine light yet. I've watched the rpms while this happens and don't notice a major fluctuation. Has anyone had a problem like this after installing a 2.25" cat-back system? I'm thinking of taking the car into the dealer and see what they can find. Do you think the muffler could be having an adverse affect on the back pressure to cause this? I didn't have this problem back when I had the Rallispec 2.25" system with the dual tip muffler, so this is kind of a surprise. Any ideas, or suggestions would be appreciated. Thanks. Adam [This message has been edited by Bohanan (edited May 08, 2001).] * Registered users of the site do not see these ads.

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05-08-2001, 07:16 PM	#2
kaos200 Scooby Guru Member#: 2692 Join Date: Oct 2000 Chapter/Region: SCIC Location: SoCal	how far back is the custom exhaust? does it affect o2 sensor placement?

05-08-2001, 07:45 PM	#3
Skylab Scooby Specialist Member#: 4263 Join Date: Feb 2001 Location: Cardiff-by-the-Sea, Ca	Your car has a bad 02 sensor. I got mine replaced (on a minivan) and it cured the problem. My van had the same problem your describing...the car wouldn't cruise reliably at any speed above 55 mph. Half throttle it would start to stutter and hiccup and exhaust would pop. WOT there was no problem though. Anyways, got the O2 sensore replaced and problem solved for $165. Skylab™ hope that helps

05-09-2001, 06:06 AM	#4
Bohanan @ work Scooby Specialist Member#: 836 Join Date: Feb 2000 Location: Houston, TX	kaos, it's a cat-back. The new pipe was welded to the original flange. It doesn't affect the O2 sensor placement. Thanks Skylab. I went ahead and dropped the car off at the dealer. Hopefully they'll come back and say it's something simple like that. But, the problem is also showing at full throttle too. Adam

05-09-2001, 06:33 AM	#5
skeletor25rs Scooby Guru Member#: 1844 Join Date: Jul 2000 Chapter/Region: TXIC Location: Edna, TX Vehicle: 1970 Scout Gold, Tan, Rust, Primer	Thats what mine was doing when the coil-pack went bad. One of my plugs was arching to the engine block. It got worse and worse, until on the way to West Houston it would only go about 50mph.

05-09-2001, 09:50 AM	#6
Bohanan @ work Scooby Specialist Member#: 836 Join Date: Feb 2000 Location: Houston, TX	Just received word from the dealer. The coil pack went out and managed to fry the number 2 spark plug wire. He said they could see the sparks arcing across the wire while it was running. Hopefully I should have the car back today. Thanks for all the input. I had a list going of everyone's ideas. I appreciate it. Adam

05-09-2001, 11:19 AM	#7
KoKo Guest Member#:	Bohannan, Ever seen me on the road in College Station, or on the way there from houston??? I'm there almost every weekend visiting my girlfriend. I drive a silver '00 RS with Apex N1. What were you doing in College Station anyway? That place is the pits.

05-09-2001, 08:20 PM	#8
NateDogg Scooby Specialist Member#: 6467 Join Date: May 2001 Location: philadelphia, pa, usa Vehicle: 1999 Impreza 2.5 RS silver	quick question.....what did you do with your rallispec exhaust, if you still have it im willing to buy it

05-10-2001, 12:24 AM	#9
Bohanan @ work Scooby Specialist Member#: 836 Join Date: Feb 2000 Location: Houston, TX	Hey Ko Ko! I may have. I was up there for an autocross out at the Riverside Annex. I don't get up there much, except for the occasional race. I do go out to Conroe quite a few times a month. Of course, I live in Spring, so it's not like a major drive any way. I'll keep my eyes open for you. I have a white '99 with Speedline wheels. Later! Adam

05-10-2001, 05:22 AM	#10
Bohanan @ work Scooby Specialist Member#: 836 Join Date: Feb 2000 Location: Houston, TX	Sorry, but I've since sold it to Aubrey (skeletor25rs). The resonance inside the car got so bad on extended road trips that I had to get rid of it. It was pretty sweet looking though. Polished S.S. resonator and dual tip muffler, S.S. piping, excellent workmanship. I believe it was the first dual tip they put together. Adam