Running Bad after Warm Up!
Running Bad after Warm Up! My car is running rough after it warms up. It starts out running great, then after about fifteen minutes I start noticing a slight surge when coming to a stop. Not long after the first surge, it will develop what seems to be an ignition miss at idle. At first it is very slight and will go away as soon as I touch the gas. The warmer it gets the higher the rpm's have to go for it to go away. It continues to get worse until it literally jerks me back in the seat when it stops missing. If I drive far enough it starts missing so bad that I can't pick up speed in fourth with the converter locked. If I park it for a few hours it runs fine for a few minutes, then starst the same cycle over again. It is not setting off the SES light.
The car is a 94 A-4. I just installed pacesetter longtubes, ory, and a 3000 stall converter. I also deleted the air and egr. The plugs are new. The wires are fairly new and routed safely around the headers and pulleys. I have double checked this. It is also running through a 12'' Dynomax race Bullet muffler, dumped before the axle.
Any suggestions will be appreciated!
The car is a 94 A-4. I just installed pacesetter longtubes, ory, and a 3000 stall converter. I also deleted the air and egr. The plugs are new. The wires are fairly new and routed safely around the headers and pulleys. I have double checked this. It is also running through a 12'' Dynomax race Bullet muffler, dumped before the axle.
Any suggestions will be appreciated!
Lt1junkie, I've never touched the opti. I just bought the car late last summer, so I don't know if it's ever been changed.
Here is a little more info. I drive thirteen miles to and from work. It is just starting to act up in the last mile or so, in each direction. If I go beyond that it just gets worse. If I stop, even for ten minutes, it will run normal when I start out. If I let it set for an hour, I'm good to go for thirteen miles. Still no SES light and it runs great at WOT, even when it is acting up at lower engine speeds.
It feels like an ignition problem, but if it were mis-firing shouldn't that cause the converter to unlock when it is happening?
If it were a fuel pressure problem would that set an SES light?
Could the higher underhood temps with the headers somehow cause the fuel to overheat?
Again, any suggestions are appreciated. I know it's difficult to diagnose drivability issues over the internet. If I can't figure it out, I'll be spending my drag radial money to have a shop diagnose it for me, or I could just limit my travels to under thirteen miles.
Here is a little more info. I drive thirteen miles to and from work. It is just starting to act up in the last mile or so, in each direction. If I go beyond that it just gets worse. If I stop, even for ten minutes, it will run normal when I start out. If I let it set for an hour, I'm good to go for thirteen miles. Still no SES light and it runs great at WOT, even when it is acting up at lower engine speeds.
It feels like an ignition problem, but if it were mis-firing shouldn't that cause the converter to unlock when it is happening?
If it were a fuel pressure problem would that set an SES light?
Could the higher underhood temps with the headers somehow cause the fuel to overheat?
Again, any suggestions are appreciated. I know it's difficult to diagnose drivability issues over the internet. If I can't figure it out, I'll be spending my drag radial money to have a shop diagnose it for me, or I could just limit my travels to under thirteen miles.
I'd look at the O2's while on a scanner. If it's running ok while it's cold, then sounds like you have given it enough time to warm up and then go into closed loop. At WOT, I believe O2's are bypassed anyway.
On The Tree
Joined: Feb 2007
Posts: 120
Likes: 0
From: oregon
Opti...my corvette did very similar thing...ran good at WOT - very poorly at low rpm and idle. Started out slow - progresively got worse over about 2 weeks maybe. Mine was throwing a knock sensor code though. I changed them (2 on the vettes) - but of course it did nothing to help. Finally dove into the opti...that was it. No gaurantee..could be something else - but your symptoms are very similar to what mine was doing from what I remember (this was a couple years ago....so take it for it's worth).
dhdenny, I might have to bite the bullet and get a laptop, cable, and scanning software or pay someone to scan it. I guess it's the price you pay when playing with a computer controlled vehicle.
It should be well into closed loop by the time it starts acting up. A thirteen mile drive around here takes between 40 and 60 minutes. I unplugged the egr vacum solenoid so it would set off the SES light and stay in open loop. The only change that I noticed was that both fans ran all the time.
It should be well into closed loop by the time it starts acting up. A thirteen mile drive around here takes between 40 and 60 minutes. I unplugged the egr vacum solenoid so it would set off the SES light and stay in open loop. The only change that I noticed was that both fans ran all the time.
Originally Posted by Razor_Blade
dhdenny, I might have to bite the bullet and get a laptop, cable, and scanning software or pay someone to scan it. I guess it's the price you pay when playing with a computer controlled vehicle.
It should be well into closed loop by the time it starts acting up. A thirteen mile drive around here takes between 40 and 60 minutes. I unplugged the egr vacum solenoid so it would set off the SES light and stay in open loop. The only change that I noticed was that both fans ran all the time.
It should be well into closed loop by the time it starts acting up. A thirteen mile drive around here takes between 40 and 60 minutes. I unplugged the egr vacum solenoid so it would set off the SES light and stay in open loop. The only change that I noticed was that both fans ran all the time.
Trending Topics
Originally Posted by KTM
Opti...my corvette did very similar thing...ran good at WOT - very poorly at low rpm and idle. Started out slow - progresively got worse over about 2 weeks maybe. Mine was throwing a knock sensor code though. I changed them (2 on the vettes) - but of course it did nothing to help. Finally dove into the opti...that was it. No gaurantee..could be something else - but your symptoms are very similar to what mine was doing from what I remember (this was a couple years ago....so take it for it's worth).
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo On The Tree
Joined: Feb 2007
Posts: 120
Likes: 0
From: oregon
You're definately right....95% of the time - what ever you touched last is what is screwed up and giving you problems. Other than a wire issue related to being burnt from headers - or a broken plug from installing...I don's see anything that you have recently done to cause this type of reaction.
I pretty much did all the same stuff to my car and have no problems (emissions delete - headers, off road y)
I pretty much did all the same stuff to my car and have no problems (emissions delete - headers, off road y)
Originally Posted by KTM
Opti...my corvette did very similar thing...ran good at WOT - very poorly at low rpm and idle. Started out slow - progresively got worse over about 2 weeks maybe. Mine was throwing a knock sensor code though. I changed them (2 on the vettes) - but of course it did nothing to help. Finally dove into the opti...that was it. No gaurantee..could be something else - but your symptoms are very similar to what mine was doing from what I remember (this was a couple years ago....so take it for it's worth).
when my opti started to go out i replaced it right away. the only thing it was doing was a slight miss at around 4800. pulled my hair out thinking it was the wires/plugs never acted up in any other rpm. only wot around 4800. Also i wasnt even using the cap and rotor so it was the optical sensor assembly in the opti that was bad
Originally Posted by i420tom
when my opti started to go out i replaced it right away. the only thing it was doing was a slight miss at around 4800. pulled my hair out thinking it was the wires/plugs never acted up in any other rpm. only wot around 4800. Also i wasnt even using the cap and rotor so it was the optical sensor assembly in the opti that was bad
Staging Lane
Joined: Apr 2005
Posts: 79
Likes: 0
From: Loudonville, Ohio
I had the same problem on my 96...and all it was was that i put those O2 eliminator things on...and it ran like crap down low...would surge and miss when lugging the motor...i took those off and its never done it before...
I just spoke to a local Tuner who is also a sponsor here. I set up an appointment for him to look at the car. Based on the my description, he suggested changing the O2 sensors before bringing it in. They look to be pretty old, mabey even original to the car, so I'm going to give it a shot.
Starting tomorrow, I will be out of town for a week. When I get this resolved, I will post up whatever the problem was. Thanks to all, who threw out some suggestions!
Starting tomorrow, I will be out of town for a week. When I get this resolved, I will post up whatever the problem was. Thanks to all, who threw out some suggestions!
If it runs good at wot and while cold, I'd be 90% sure its O2s as those are the only times when the O2 reading is not used by the computer. I really doubt its the opti if you don't have problems at high rpm, that's usually where problems with the opti will first become apparent.
You can do an easy test though that will let you know whether it is an O2 problem (so you don't replace them if it isn't). Just unplug one of the O2 sensors and drive it that way for a while. If the computer doesn't get a reading from both sensors it will not enter closed loop. If the problem goes away under this condition then you know it is the O2s. If it behaves the same way then it's likely something else.
You can do an easy test though that will let you know whether it is an O2 problem (so you don't replace them if it isn't). Just unplug one of the O2 sensors and drive it that way for a while. If the computer doesn't get a reading from both sensors it will not enter closed loop. If the problem goes away under this condition then you know it is the O2s. If it behaves the same way then it's likely something else.
Quick question. I was looking up the O2 sensors on the web and noticed references to the Left and Right sides, but the part number was the same. Are the sensors specific to a particular side of the engine?
