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Corvette Fuel Injection & Electronic Engine Control: 1982 through 2001
Corvette Fuel Injection & Electronic Engine Control: 1982 through 2001



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10/9/11 7:35pm - Original Message: 'Rough idle on 82 CFI'
Shawnee2
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Cherryville, NC - USA

Vette(s):
82 Collector

Joined: 1/10/2011
Posts: 78
I seem to have a rough idle, inconsist RPM's and seems to run rough went crusiing.  It also does not seem to have a fast idle either.   Acceleration seems to be fine.   Here is what I have done so far.
 
TB's have been rebushed and balanced.  Fuel filter changed.  Has a new sender and sock with a 82 pump.  Fuel pressure adjusted to a little over 11 psi.  Recently tuned up with new plugs, wires, rotor button and new distrib cap.  New manifold lid gasket and running around 15 inches of vacuum.
 
Any thoughts?  Would increasing the fuel pressure with a new 85 pump help?
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10/9/11 7:53pm - Reply: 'Re: Rough idle on 82 CFI'
corvette440hp Lifetime Member
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DCS might provide some info here is a link:

http://crossfireinjection.net/how_to.htm



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10/9/11 7:56pm - Reply: 'Re: Rough idle on 82 CFI'
corvette440hp Lifetime Member
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Cressfire1982 (Chip) can really help also provide quite a bit of information on this.


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10/9/11 9:38pm - Reply: 'Re: Rough idle on 82 CFI'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19457
Coolant temp sensor out of whack could cause this. Do you have any way to pull the codes? If there are any, it would help, but there may not be any set.
Fuel pressure spec is 10psi, so you're looking good there.
Is this a hard miss at idle, or is the idle just a little shaky?




|UPDATED|10/9/2011 7:38:42 PM (AZT)|/UPDATED|


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Joel Adams
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10/9/11 10:08pm - Reply: 'Re: Rough idle on 82 CFI'
Shawnee2
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Cherryville, NC - USA

Vette(s):
82 Collector

Joined: 1/10/2011
Posts: 78
No check engine light on.  Can pull the codes with WinAldl later this week.  Did not have anything the last time I looked.  Hard to explain the idle.  Best I can discribe is sort on like an erratic missfire or surging.  At cruising speed, feathering the throttle the car seems to flutter a little.  Harder throttle everything seems to be ok.  Good acceleration.  Hope that makes sense.
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10/10/11 7:12am - Reply: 'Re: Rough idle on 82 CFI'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19457
That description now has me leaning toward an EGR issue.....
The valve may have some doo-doo stuck under it keeping it from closing fully, or there may be a problem with the control of the valve, such as vacuum, or the solenoid...


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10/10/11 7:35am - Reply: 'Re: Rough idle on 82 CFI'
crossfire1982
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Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094
You have already done many of the standard fixes for this problem.  As for the fuel pressure you are already set at the top end of the factory spec for fuel pressure and in theory should be sufficient.  A buddy of mine had very similar problems as what you are describing.  We installed an 85 pump and slowly began to raise the fuel pressure.  When we hit 14 psi the idle smoothed instantly and his hesitation disappeared. I'm running about 14.5 psi on my crossfire.  This may not be the solution for your problem but its something Id consider.  Another part of the equation is the MAP sensor which feeds info to the computer.  check the hose to the map to make sure its not cracked and leaking and also disconnect the electrical to the map sensor and reattach to make sure its making good connection.  You may also want to clean pintle or point of  the idle air control (IAC) mechanism using throttle body cleaner.  Try not to get any cleaner back up in the electrical part of the IAC and make sure the fiber washer is in place between the throttle body and the IAC.  The crossfire injection forum has instructions in their technical section on testing the IAC motors to make sure they are operating properly.  I hope some of this helps.

You will have to paste this address into your browser, I cant get it to post as a link
http://www.crossfire.homeip.net/index.php?showtopic=662


Just saw Joel's post about the EGR, that is certainly a possibility as well.


|UPDATED|10/10/2011 5:35:01 AM (AZT)|/UPDATED|


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10/10/11 11:20am - Reply: 'Re: Rough idle on 82 CFI'
kwoody
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Tucson, AZ - USA

Vette(s):
1982 Black/Tan Leather Build Code C09E Bronze TTop CrossFire Fuel Injection L83 85 Fuel Pump Auto Axle 2.72 Firestone Firehawk Indy500

Joined: 7/11/2010
Posts: 415
Hello, 

     It does sound like you have done most of the standard stuff.  I really notice an improvement after
cleaning the IAC motors, connectors and passageways.  Stay on-top of any vacuum leaks.  I found my
cruise control vacuum path bad and blocking it off significantly improved the idle and gas mileage.  I also
recently set the timing to 6* BTDC from around 12* and started running 87 octane gas. The engine does
run just a tad hotter but, she still gets up and goes when I step or her tail. 

Almost forgot.  I did change the EGR valve and found that a "block off" gasket had been installed by a previous owner.  I was having
lots of other problems at that time so,  I could not tell what the improvement was for that by itself.  If it is old and you can't pull the
diaphragm up from the bottom it needs to be replaced.

 

Good Luck.  Let us know how it works out.

All the best from Tucson.

Keith 


|UPDATED|10/10/2011 9:20:51 AM (AZT)|/UPDATED|


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10/10/11 7:24pm - Reply: 'Re: Rough idle on 82 CFI'
Shawnee2
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Cherryville, NC - USA

Vette(s):
82 Collector

Joined: 1/10/2011
Posts: 78
Thanks for the advice everyone.  The IAC's and ports were cleaned when I did the TB rebushing so I think they are good but never hurts to check them again.  I will check them out per the shop manual to see if they are working correctly.
 
I did not think about the EGR.  I will check it per the shop manual instructions.  I know the gasket is good as I replaced it when I changed the lid gasket.
 
The hose to the MAP sensor is good as I just replaced it this past weekend.  Have not cleaned the connection so I will do that as well.  I think I read somewhere that if you pull the hose off while the engine is running the RPM's should increase.  I do not think mine is doing this.  I will use the S-M and check the operation.
 
I can plug off the vacuum system and see if that helps anything.  Any ideas as to what vacuum I should be see when everything is connected?  Timing is set at 8 degrees right now.  Should I change this?  Sounds like I am going to be busy this weekend!
 
Chip - what is the part number for the AC Delco pump you have used?  I have run across a couple of part numbers that fit the 85 model.


|UPDATED|10/10/2011 5:24:08 PM (AZT)|/UPDATED|
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10/15/11 9:34pm - Reply: 'Re: Rough idle on 82 CFI'
Shawnee2
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Cherryville, NC - USA

Vette(s):
82 Collector

Joined: 1/10/2011
Posts: 78
EGR and MAP sensor are working correctly according to the shop manual.  IAC also appear to be working correctly and clean.  I do have a vacuum leak on the cruise and headlight side.  I have plugged these off for now at the manifold ports.  Does not seem to help the idle any.  I did notice that as the idle goes down there is a ticking sound from the injectors and it appears to add a little more fuel.
 
Rechecked the fuel pressure and only running around 10.5 psi now.  Fuel pump came in today and will try to install tomorrow and get the pressure more up in the 14 psi range.
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10/16/11 8:07am - Reply: 'Re: Rough idle on 82 CFI'
crossfire1982
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Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094
Jeff,  Sorry I didnt reply to your request about the fuel pump number.  I didnt see the post until you posted today (Sunday) and it appears you have already ordered a pump. Just didnt want you to think I was ignoring your request.  The pump I used  was  AC Delco # EP241  GM # 25116163.  I hope the pump helps.

|UPDATED|10/16/2011 6:07:01 AM (AZT)|/UPDATED|


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10/23/11 8:39am - Reply: 'Re: Rough idle on 82 CFI'
Shawnee2
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Cherryville, NC - USA

Vette(s):
82 Collector

Joined: 1/10/2011
Posts: 78
Fuel pump definitely helped.  Car is running much smoother and does not stubble during normal driving.  Does not seem to flutter during cruising either.
 
Only thing I am not sure about is that each time I start the car the pressure seems to be different.  It can be anywhere from 14 to 18 psi.  Not sure if this is normal or whether I have another issue.  Pressure also fluctuates about half a pound at idle but does not seem to affect the idle.
 
I am much happier now, just need to fix a few vacuum leaks in the headlight system (system was diconnected during test run) and then onto the next issue.
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10/23/11 10:27am - Reply: 'Re: Rough idle on 82 CFI'
crossfire1982
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Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion

Joined: 8/22/2006
Posts: 1094
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10/24/11 1:28am - Reply: 'Re: Rough idle on 82 CFI'
tb2k82ce Lifetime Member
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Lemon Grove, CA - USA

Vette(s):
1982 C3 Collectors Edition 44000 miles, sat in the sun most of it's life, My wife purchased it for me for fathers day in 2007 from her girl friend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.

Joined: 10/17/2007
Posts: 2007
I have never heard of that type of fuel pressure fluctuations before.  For that to occur would require that the regulator are malfunctioning I would think. I put in a 85 fuel pump and have adjusted the pressure all the way from mid 14 down to where I run it now about 11.  Car runs fine but my gas mileage is about 10 mpg.  Which is way off for a crossfire. But this is your post not one on mileage. 

Like I said I have adjusted fuel pressure in about three places and it is rock solid no fluctuations at each of them.  Before I put in the new fuel pump I had bad mileage and the car starved for fuel when I jumped on it.   I rebuild the fuel regulator the left one on the rear TB controls the fuel pressure on the system. 




|UPDATED|10/23/2011 11:28:37 PM (AZT)|/UPDATED|


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