c4 exhaust problems
Thread Starter
7th Gear
Joined: Sep 2016
Posts: 7
Likes: 0
c4 exhaust problems
i had thrush welded mufflers installed on my 1989 corvette, after they were put on the car have a very hard time starting and ran horrible. it would only start with my foot to the floor and died at red lights. i brought it home and cut the mufflers off, it runs better but sometimes have trouble starting and rpms drop low at idle. what could be causing this to happen and what mufflers have people put on were there c4s ran good? any help would be great first time on this forum. i also checked the throttle body when i parked it before i cut the mufflers and it was flooded with gas.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
Plus you stated that you cut the mufflers off and still have problems. So the mufflers are not the issue.
I would check if you have any DTC codes. That may point you to the problem.
I also would check for other things that may have been inadvertently changed during the exhaust work. Things like an O2 sensor that was damaged or wire cut/burned etc.
Good luck.
Team Owner
Joined: Feb 2006
Posts: 23,278
Likes: 117
From: San Antonio Texas
Were you able to drive it home from the muffler shop normally, or was the problem immediate after their work?
Did they disconnect the battery before doing welding on the car? If not, it's possible they grounded to the frame while they welded to the exhaust and the current spiked through the wiring harness into the computer through through the O2 or another sensor. You'll have to check codes to see what sensor has a problem now.
Muffler shops should know proper grounding procedures for welding on computerized cars by now, but some people are still careless.
Did they disconnect the battery before doing welding on the car? If not, it's possible they grounded to the frame while they welded to the exhaust and the current spiked through the wiring harness into the computer through through the O2 or another sensor. You'll have to check codes to see what sensor has a problem now.
Muffler shops should know proper grounding procedures for welding on computerized cars by now, but some people are still careless.
Thread Starter
7th Gear
Joined: Sep 2016
Posts: 7
Likes: 0
i had all injectors replaced about 2 months ago and it ran great until i brought it to the muffler shop. i dont think they took the battery off, its not showing check engine light or anything. i ran horrible on the way back from the shop. at red lights i had to put it in neutral and keep my foot on the gas just to keep it running. how do i tell if my fpr is bad? it also smokes bad white smoke when i first start it and drive it but then goes away
Team Owner
Joined: Feb 2006
Posts: 23,278
Likes: 117
From: San Antonio Texas
You can check the fuel pressure regulator by pulling off the vacuum like and check there for raw fuel or really strong smell. You can turn the engine on (if it will stay running) and then remove the vacuum line. There should be a big difference in how the car idles. Either normally with the vacuum on or rough with the line unplugged. If the Diaphragm in the FPR has a leak, gas will get out of the fuel rail through the FPR.
I had a sticking injector that made my car run exactly like you described, and they were also newer injectors, but had more miles on them. Just because they are new doesn't mean they won't fail. If electronics last for the first few hrs. they are usually OK, but early on is when weak new ones often fall out of line.
I had a sticking injector that made my car run exactly like you described, and they were also newer injectors, but had more miles on them. Just because they are new doesn't mean they won't fail. If electronics last for the first few hrs. they are usually OK, but early on is when weak new ones often fall out of line.
