Failed Emissions Pressure Test/wont Idle
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
Failed Emissions Pressure Test/wont Idle
Ok I may need to call my therapist! I cant drive my C-4! It failed the pressure test...they said I have slight leak somewhere in the fuel vapor system. To be exact they said it holds then bleeds off very slowly. Any ideas on what might be a common fix for this problem?
Secondly...after going the emissions the vette was idling at 400as opposed to the usual 600-700...then once i got it home after turning the car off it didnt want to idle at all! If depress accelerator car stays on and sounds as strong as it usually does, but once I let go it dies! I have started checking vaccuums but nothing yet......
Please help me! I need my vette! Im lost without it!
Secondly...after going the emissions the vette was idling at 400as opposed to the usual 600-700...then once i got it home after turning the car off it didnt want to idle at all! If depress accelerator car stays on and sounds as strong as it usually does, but once I let go it dies! I have started checking vaccuums but nothing yet......
Please help me! I need my vette! Im lost without it!
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
No i havent changed the fuel cap...but I do know they do separate test on the fuel cap...to pressure test they screw their own cap with a pressure line attached and then pump 2 lbs of pressure into the tank...then they crimp the fuel return line up front by the canister....
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
Phoenix-Arizona
Im here in PHOENIX-ARIZONA
Jeesh...I agree that I thought the test was somewhat ridiculous
!
My car is passing the actual emissions tests with flying colors....just didnt pass that blasted pressure test...which qualifies as an equipment failure!
Jeesh...I agree that I thought the test was somewhat ridiculous
! My car is passing the actual emissions tests with flying colors....just didnt pass that blasted pressure test...which qualifies as an equipment failure!
Racer
Joined: Feb 2001
Posts: 276
Likes: 0
From: Springboro OH
Originally Posted by 1988 BlknBlk
Anyone?
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Intermediate
Joined: Sep 2004
Posts: 48
Likes: 0
From: Glendale AZ
My 87 failed the pressure test once also, just in front of the drivers side rear tire is a small piece of hose connecting two metal tubes that are part of the vent system. this hose was where my problem was. I also found the hoses going to the vapor cannister were in poor shape. check them close to.
Pro
Joined: Jun 2004
Posts: 646
Likes: 0
From: Santee Ca
Originally Posted by Perfusion
What the hell state is THIS!?!?! I thought CA was the worst-of-the-worst, and we don't even have to do that test!
It is coming though. Within the next year or two. It's about a $3000 upgrade to the smog system. And they also have a camera port that they might start videoing the tests as they are being done. The techs that maintain the machines just got done putting an anti-tamper system in the units so that if any unauthorized people open up the machine it disables it and reports back to the DMV and needs to be reset by the tech. Seams smog technicians figured out a way to open up the back of the machine and get just about any car to pass.
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
Thanks!
Originally Posted by mikesb
My 87 failed the pressure test once also, just in front of the drivers side rear tire is a small piece of hose connecting two metal tubes that are part of the vent system. this hose was where my problem was. I also found the hoses going to the vapor cannister were in poor shape. check them close to.
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
Any ideas on the idle?
I have checked the connectors on all the sensors (MAF-EGR-IAC) They all look good...I checked for fuel pressure at the fuel rail-fuel was there! I have checked every vacuum that I could see. Im at a loss here...
Thanks for all the help guys. You have been a big help already!
Thanks for all the help guys. You have been a big help already!
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
I feel like Im not the brightest at times!
Well I tested the IAC..ohms were at a steady 55...TPS checked out also.....So there I was, very frustrated, I decided well all else has failed. Why not see if a small adjustment of that idle screw will make a difference? A litttle over if not a half of turn made all the difference! Car is running just like it did a week ago! What do you guys think...is that normal? Is it normal that a small adjustment of that nature could be necessary? I read in my manual that it's factory set, but it solved my problem...
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
Thank You Steel Breeze & Cfi-efi!
Both of these gentleman took time out of their busy days to help me in getting some solid answers to the idle issue. They are why forums like these are in existence, to help and share with others.
Thanks a bunch guys! I will use the information right away!
Thanks a bunch guys! I will use the information right away!
Burning Brakes
Joined: Jun 2002
Posts: 1,001
Likes: 1
From: sd
Originally Posted by 1988 BlknBlk
Well I tested the IAC..ohms were at a steady 55...TPS checked out also.....So there I was, very frustrated, I decided well all else has failed. Why not see if a small adjustment of that idle screw will make a difference? A litttle over if not a half of turn made all the difference! Car is running just like it did a week ago! What do you guys think...is that normal? Is it normal that a small adjustment of that nature could be necessary? I read in my manual that it's factory set, but it solved my problem...
Your idle is controlled by the ECM. That screw you adjusted allows air through the TB blades to control your idle with the help of the IAC. By adjusting that screw you have thrown it out of adjustment and both the IAC and the TPS will need to be adjusted now. Get your trusty paper clip out and a volt meter to assist in the adjustments. The tech tips section has a few articles on how to do this if you don't have a FSM. Good luck!
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
I agree, after turning the minimal idle screw, you will have to recheck the TPS again. I did a little search and have some info on this.
From the Tech tips:
https://www.corvetteforum.com/techti...D=55&TopicID=2
From Vader86 webpage:
http://temp.corvetteforum.net/c4/vader86/tpsiac.html
From the Tech tips:
https://www.corvetteforum.com/techti...D=55&TopicID=2
From Vader86 webpage:
http://temp.corvetteforum.net/c4/vader86/tpsiac.html
Thread Starter
Heel & Toe
Joined: Jun 2006
Posts: 22
Likes: 0
From: Phoenix Arizona
Thanks!
Originally Posted by goldeneye_vet
Your idle is controlled by the ECM. That screw you adjusted allows air through the TB blades to control your idle with the help of the IAC. By adjusting that screw you have thrown it out of adjustment and both the IAC and the TPS will need to be adjusted now. Get your trusty paper clip out and a volt meter to assist in the adjustments. The tech tips section has a few articles on how to do this if you don't have a FSM. Good luck!
I will be replacing the IAC tonight and giving the TB a thorough cleaning! How does one adjust the TPS?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
The TPS is adjusted by unscrewing the 2 torx bolts and adjusting the sensor up or down to get you at about .54v stock. This should be done after you adjust the minimal idle due to changing the throttle plate position and will throw the TPS voltage off. With the new IAC you should get a new gasket and the pintle tip should already be 1 1/8" from the IAC flange but check and make sure before install. If not push or pull with a wiggle until there.