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Rough idle after new injectors

Dmod81

Member
Joined
Mar 28, 2005
Messages
15
Location
Minot AFB
I installed new injectors to fix a hard start when hot condition, which did get fixed. Now it idles really rough. It will hunt for a idle speed for about 20 seconds then settle at the idle speed that it was at before I replaced the injectors, but roughly. Also the new injectors are extremely loud. Any ideas?

Thanks


91 manual
 

Achilles

Well-known member
Joined
Oct 31, 2004
Messages
447
Location
Back in Sunny California!
Corvette
1982 CE, 03 MY Z06
What size injectors did you install? Is your motor stock? Did you drive the car to warm operating temps afterwards to reset the ecm.

I usually disconnect the battery before I make any modifications so that on restart the computer can relearn the changes and adjust accordingly. I don't know if that needs to be done with the latest ecm's that are available today, but someone told me that once so thats just what I have always done.
 

Dmod81

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Joined
Mar 28, 2005
Messages
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Minot AFB
I believe they are the same as stock, 22lb. I got the ford/bosch yellowtops. Engine is stock, and I did reset the ecm drive it to operating temp.
 

Achilles

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Oct 31, 2004
Messages
447
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Back in Sunny California!
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1982 CE, 03 MY Z06
Hmmm...Bosch yellow tops = 22#? I had a set of pink tops that were 22#. Maybe they changed their colors. :confused If they are 22#, you shouldn't have any problems unless one or more of them are leaking.
 

vetteboy86

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May 26, 2003
Messages
2,760
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IN
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1986 Black "Indy 500 Pace car replica"
Possible vacuum leak causing the IAC to search for a correct idle on start up? But that wouldn't make any sense as to why the idle finally does correct itself.
 

Dmod81

Member
Joined
Mar 28, 2005
Messages
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Location
Minot AFB
I looked closer at the fiveo motorsport website. It seems the yellow ones might be 19lb injectors that he is selling as a direct replacement for stock. The set he sells for the chevy tpi are yellow, but say 22lb, while all other yellow ones on the page say 19lb. I think I may have been ripped off.
 

vee93

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Nov 15, 2002
Messages
585
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Mississippi
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1993 Medium Quasar Blue Metallic Coupe
Maaaaybe not ripped off--maybe the vendor made a bad assumption so a mistake was made!!! I'd contact them with your info about the injectors and have them check.
 
F

fatboyreyn

Guest
injectors

I installed new injectors to fix a hard start when hot condition, which did get fixed. Now it idles really rough. It will hunt for a idle speed for about 20 seconds then settle at the idle speed that it was at before I replaced the injectors, but roughly. Also the new injectors are extremely loud. Any ideas?

Thanks


91 manual

How was the replacement job. How long. Any problems? Thinking about changing mine.
 

Dmod81

Member
Joined
Mar 28, 2005
Messages
15
Location
Minot AFB
This was the second time (now third after I put pink tops in) that I have taken the top end apart. The first time was for intake gaskets. So I have it pretty much down to about 4 hrs total. When I get down to the runners, I only take off the passenger side and that saves some time. Job isn't really too bad, except the gas everywhere... Make sure you have something to cap off the fuel lines ready before you start.
 

jam019

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Feb 10, 2006
Messages
30
Location
Texas
Corvette
90' Corvette
Hope you didnt buy them for Fiveomotorsport, if so good luck..
 
B

Black Bart

Guest
FORD injectors are rated at 39lbs fuel pressure and GM injectors are rated at 42lbs. so when you put a ford injector in a GM with 42 0r more lbs of fuel pressure the engine will run rich.
People buy the ford injectors because they sell for less and they don't understand that they need to calibrate the ECM for these to run properly.
This is a small difference and unless you have an air/fuel ratio gauge or pay close attention to your mileage you won't know that they are not providing the correct A/F ratio.
I don't think that is the problem with your idle but you need to know that these are NOT the correct injectors for your engine.
 

Achilles

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Joined
Oct 31, 2004
Messages
447
Location
Back in Sunny California!
Corvette
1982 CE, 03 MY Z06
Well that all depends on what Ford & GM injectors your refering too. Not all GM injectors are 42lbs. My '86 had 22# stock GM and my '95, I believe has 26# stock GM injectors. The automobile manufactures have different flow injectors for different models & years of cars. I think the injectors he's refering to (pink tops) are made by Bosch for Ford Motor Co. They also have the blue oval Ford logo on them.
 

Achilles

Well-known member
Joined
Oct 31, 2004
Messages
447
Location
Back in Sunny California!
Corvette
1982 CE, 03 MY Z06
My humble appologies. I read your post again and see you were refering to fuel pressures & not injector flow rates.

You are correct. My bad.
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
HI there,
And some Ford injectors have a different tip on the injector, so fuel atomization is different then with the GM Multec injectors, even if the pound/hour ratings are the same.
The atomization could be your entire problem.
They should also have 16.5 ohms resistance, if you are above or below, your ECM will suffer.
Allthebest, c4c5
 

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