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9th injector shut off

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tom_85_vet

Guest
I have posted this problem before and still can not resolve. What I have learned and please correct me if I am wrong. My car runs with a slightly high idle on a cold start-up (9th injector on and running rich). Once the car warms up (160 degrees) the 9th injector turns off and idle starts cycling up and down (55-65-70) before finally setting to 55. I have clean all intake parts including IAC. At this time I have tried all the cheep repairs and I am thinking it may be an ECM issue.

I believe that the ECM is processing all the information from the sensors and there is a circuit that handles setting the idle which may be out of spec. I hate to buy an ECM and find that the problem was a cheep fix that I have over looked

What I have in my car:
Adjustable FP, high volt dist, accel FI (stock #), KN air filter, 160 thermostat, high performance chip, after market IAC.

The only other crazy thing is the problem seems to be more significant when that car has not been driven for couple of days. Almost like it needs to be exercised.

BTW, I will have my car at Carlie PA for the Corvette show and hope to see any forum members!!!!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Tom...this is an 85

Do you have a 9th injector?

Think ya better count em.....

Dont think the "feature" hit till 88.

Vig!
 
L

LarryK 87

Guest
Is that the same as the cold start injector? The 87 has one if it is, but they only activate when engine temp is below a given threshold ( well below 160 ), then only activates for a brief time.
 
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Shadowing1985v

Guest
i can help on this a little i guess

yeah i own a 85 it has a cold start injector/valve
what ever u want to call it

you sure its your cold start valve giving you high idle

your car is suppose to start with high idle at start up for a few seconds then it will go down


there are like 20 diffearnt things that cuases high idle


If your ecm detects lack of juice, air or gas

it will set its self higher in idle
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Ok the real deal

The 9th injector is controlled by the following.


The CRANK line provides power to a cold start switch ( Located on the front of the intake manifold with a purple & Tan wire)

There are a few sensors up there make sure you have the correct one.

This switch open's & closes based on engine temp & current flow.

So when the car is COLD the injector stays OPEN for 8 seconds @ -4 F

As the car is warmer ( So Cal 60-100 degrees ambient ) the duration is shorter.

This supplies a prime spray to help richen the mix for start.

The COLD START VALVE/SENSOR is NO WAY controlled by the ECM


..... real world

Your injectors are leaking anyway... so if you trigger the 9th youve flooded the engine (Typically).

I unplugged mine last week and she starts better.... and I do not get the WAFT of Chevron unburnt supreem anymore.


FYI

Vig!
 
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Shadowing1985v

Guest
so since its flooding the engine

wouldn't that cause lower idle

or rough idle

not really high idle
 
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Shadowing1985v

Guest
wait a sec,, sorry about all the post

if the car floods

does the ecm pick up a signal from the o2 sensor

and the ecm probalby gives more spark

which puts it a a higher idle,, so maybe it does cause higher idle,,

but u said the idle comes down after a while

right?
 
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tom_85_vet

Guest
Ok, it is the cold start value. I will try disconnecting the value for the next start-up and see what happens. I did replace all the injectors, which did make a big difference for the cold start (old dirty/leaky injectors). I also tried resetting the computer with the car at operating temp and in gear, that seemed to help a little. Any more suggestions???
 

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