Need help after new Exhaust install...
Thread Starter
Heel & Toe
Joined: Feb 2006
Posts: 21
Likes: 0
From: Berlin New Jersey
Need help after new Exhaust install...
I recently had a new Corsa Cat-back exhaust system and SW Longtube headers installed on my 91 vette, and I love the way it sounds. However about a week after I had them put on, I started to notice a weird sound, almost like a bubbling-popping sound, if that makes any sense. It happens when I get above 30 mph and 2600 RPMs. There is also a noticeable loss in power when this happens.
My question is: What is causing this to happen? Could it be that the pipes are not clamped tight enough? If not, should I get them welded? Or do I just need a good tuning? Thanks in advance.
My question is: What is causing this to happen? Could it be that the pipes are not clamped tight enough? If not, should I get them welded? Or do I just need a good tuning? Thanks in advance.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Are they sealing good against the head?
Where is the O2 sensor and is it a heated unit?
What is the fuel pressure doing when this happens?
Have you checked all the plug leads to make sure none have burned through on the headers?
I dont think welding them will help the situation if youre talking about welding them to the rest of the exhaust, i cant see how it would anyway. If youre losing power when it happens then id have to think there is a fuel or spark problem of some kind.
Where is the O2 sensor and is it a heated unit?
What is the fuel pressure doing when this happens?
Have you checked all the plug leads to make sure none have burned through on the headers?
I dont think welding them will help the situation if youre talking about welding them to the rest of the exhaust, i cant see how it would anyway. If youre losing power when it happens then id have to think there is a fuel or spark problem of some kind.
Race Director
Joined: Feb 2003
Posts: 11,672
Likes: 20
From: Lake Wylie SC
I'd also check the compression of each cylinder, maybe a valve is in need of attention. But that's the worst case. I agree it must be in the fuel management or ignition. It didn't do this before the exhaust change, right?
Thread Starter
Heel & Toe
Joined: Feb 2006
Posts: 21
Likes: 0
From: Berlin New Jersey
I've had the seals checked around the head and they are good.
Not too sure about the O2 sensor, and I'm not home right now, so I can't check that until the weekend.
Fuel Pressure is the same as it's always been.
I'll have to check the plug leads, but I don't remember them being too close to the headers.
The problem just started about a week after the install. When I was talking to my friend who is a mechanic, he suggested that I should upgrade my igniton coil to an MSD ignition coil. Do you guys think this could solve the problem?
Not too sure about the O2 sensor, and I'm not home right now, so I can't check that until the weekend.
Fuel Pressure is the same as it's always been.
I'll have to check the plug leads, but I don't remember them being too close to the headers.
The problem just started about a week after the install. When I was talking to my friend who is a mechanic, he suggested that I should upgrade my igniton coil to an MSD ignition coil. Do you guys think this could solve the problem?
Last edited by InsiGnia; Nov 20, 2006 at 10:33 PM.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
No i wouldnt think that will fix it unless the coil you have now is no good.
One thing you could try is disconnect the battery for about 15-20 minutes so the ECM loses its memory, i cant see that doing much but it is worth a try to see if it helps.
Check the TPS and make sure its set right, working right, and not loose.
Also does it do this when it is stone cold and at first start up or does it only do it after the engine warms up? (Cold is in open loop, warmed up should be in closed loop)
Fuel pressure being the same as its always been doesnt say alot, did you test it while driving? What pressure is it when this issue occurs?
How long since you replaced the fuel filter?
If you take off from a standing start and put your foot right down (WOT), revving right out in first (or trying to) what does it do then??
One thing you could try is disconnect the battery for about 15-20 minutes so the ECM loses its memory, i cant see that doing much but it is worth a try to see if it helps.
Check the TPS and make sure its set right, working right, and not loose.
Also does it do this when it is stone cold and at first start up or does it only do it after the engine warms up? (Cold is in open loop, warmed up should be in closed loop)
Fuel pressure being the same as its always been doesnt say alot, did you test it while driving? What pressure is it when this issue occurs?
How long since you replaced the fuel filter?
If you take off from a standing start and put your foot right down (WOT), revving right out in first (or trying to) what does it do then??
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Le Mans Master
Joined: Aug 2002
Posts: 6,080
Likes: 3
From: Clearwater FL
St. Jude Donor '06
Some good advice above. I have the same setup on my car with the RT cats and there is definately some burble when letting off the gas and some noticable backfire in open loop. But not when accelerating and definately no power loss... Could you have a plug wire not fully secured. How old are they? I had to replace mine not long after the headers from tugging and pulling on them, I noticed quite a light show at night around a couple wires, so I replaced them.
Last edited by C4DC; Nov 20, 2006 at 11:17 PM.
Thread Starter
Heel & Toe
Joined: Feb 2006
Posts: 21
Likes: 0
From: Berlin New Jersey
It does it whether I just started the car 15 seconds ago, or if I have been driving for an hour. I'm not too sure when the fuel filter was changed last, but I have not changed it since I got it last January. If I go WOT right from a standing start, it responds quick and acts fine, but when I just accelerate normally is when the noise occurs.
The plug wires and plugs are all pretty new, maybe about 2 months old now.
I won't be able to do any real testing on the car until the weekend, because I'm working out of state until Thursday.
The plug wires and plugs are all pretty new, maybe about 2 months old now.
I won't be able to do any real testing on the car until the weekend, because I'm working out of state until Thursday.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Ok, now that there is more info we can rule a couple things out, in Open loop mode it will be ignoring the O2 sensor, if it will go hard from standing start at WOT your fuel pressure should be ok.
Pull out the plugs and see what they look like,
Check and correctly adjust the TPS
Check the brake booster to make sure its not leaking vacuum
Check the MAP sensor
Check the fuel pressure regulator
Check for vacuum leaks
Also give the battery disconnect a try, take off the negative terminal for about 15-20 minutes then re-attach. Then start it up, take it for a run and see if it does the same thing.
The theory behind this is the BLM data may be the cause of this issue, and if you disconnect the battery long enough it will reset.
IF this does make a noticable change to the way it runs, it probably needs a new tune, or you need to look into the location of the O2 sensor and make sure its feeding accurate data.
Pull out the plugs and see what they look like,
Check and correctly adjust the TPS
Check the brake booster to make sure its not leaking vacuum
Check the MAP sensor
Check the fuel pressure regulator
Check for vacuum leaks
Also give the battery disconnect a try, take off the negative terminal for about 15-20 minutes then re-attach. Then start it up, take it for a run and see if it does the same thing.
The theory behind this is the BLM data may be the cause of this issue, and if you disconnect the battery long enough it will reset.
IF this does make a noticable change to the way it runs, it probably needs a new tune, or you need to look into the location of the O2 sensor and make sure its feeding accurate data.