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Running Rich?

V

Vrotate

Guest
My 87 seems to be running rich to me... I was wondering the quickest way to test this. What should the fuel pressure be?

Thanks for the help

Vrotate
 

vigman

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

Idle AVG

+/- 5 psi


Vig!
 

WhalePirot

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Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
Aftermarket performance items, especially camshafts, can enrichen the mixture, if the vacuum ends up low. The computer thinks the throttle is open wider, dumping more fuel into the mixture. The computer has limited authority to 'learn' and adjust, based upon exhaust gases (oxy sensor). The older the computer; the less capable. Speed density systems are less 'forgiving' than MAF systems. My SD ('90) ECM allows +/- 128 bits, as 255 is the range and zero is no adjustment.

The best remedy, once you pass a point of modification, is to have a custom chip done, on YOUR car, in person! This is best done on a variable load dyno, which is VERY hard to find, along with the proper technician to do it. Some mechanics can pull the computer's adjustments, and tell if it is up against a wall, trying to lean out or enrichen a mixture.

I have 'called in' my engine specs; used various 'custom' chips, and the car ran poorly until MY chip was dialed in for MY engine. Now it runs at zero adjustment, as the fuel tables are dead on. It idles nicely, not too rich for the first time, and outputs the maximum power the engine can produce, while running at 14.7:1; the mixture the ECM works for.

Dick Guldstrand told me, long ago that these cars run rich at idle; are optimized for highway. That puzzles me, with the chip's fuel map, but I relay his words. He may have been referring to the Crossfire's 'puddling' problem.

:w
 
V

Vrotate

Guest
The only mods I've made are a 160 stat and a hypertech power chip. But it "smelled" rich before the chip...
 

WhalePirot

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Joined
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Messages
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Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
Hell, I understand V speeds.

It seems your minor mods should not be the cause. While not familiar with the intircacies of that chip, I hear that most performance chip only alter the WOT tables.

The basics still apply to a computer controlled engine. The ignition side is easily checked; the fuel side is computer controlled and most often is a bad sensor, unless some of the below is the issue.

To verify your facial sniffer, I'd check the tailpipe for excess soot and the plugs for any fouling. Is a lot of black soot sticking to your finger? I'd expect some, if the car was just started and had been idling, but it should have little, if just back from a highway drive. Is there sooty crap all over the rear fascia?

A vacuum gauge can tell a lot to those who know how to read it. Mine came with pretty fair verbiage, describing what variable and low vacuum might indicate.

Also, compute, with pencil and paper, the fuel economy; I just don't fully trust the ECM on this one. Talk here, with consideration given for how you drive, should tell you if yours is low.

I wonder if your 160 stat allows the car to run so cold that the ECM thinks it's not warmed up. Your Hypertech papers or a call to them might tell you when the mixture is enrichened.

The basics, especially the plugs will tell volumes. Your AIR system or the cat may not be functioning properly, either, but simple checks can start you on the right path.

:w
 
L

LarryBible

Guest
By connecting a voltmeter to the oxygen sensor output, you will be able to tell if it is cruising rich or lean. You will need to connect to the wire from the oxygen sensor and get that into the passenger compartment. Use a DVM connected to that wire and to ground.

As a previous poster pointed out, the chip alters the data used in open loop (WOT) operation. You will need to monitor you O2 sensor at cruise while the system is in closed loop operation.

Ideal stoichiometric ratio is indicated by an O2 sensor voltage of about 250 to 650 millivolts. This means that the meter will read .250 to .650. If the reading exceeds about .800 you are running rich. This is not a linear scale, so it'sdifficult to describe here, but ideal ratio is 14.7. 14:1 will be about.850, 13:1 will be about .925 and12:1 will be almost one volt.

If you know someone with scanning software such as Diacom or EASE Diagnostics, you can connect a laptop to the ALDL under the dash and read the O2 Sensor reading directly on the real time value page.

Good luck,
 

BigRed

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Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
Is it doing it all the time or more on initial startup? (If not o2 sensors Im think Cold start injector same as mine)
 
V

Vrotate

Guest
cold start injector? How do I check it?
 
Joined
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Tallahassee, FL
Corvette
none right now :(
does it smell rich, or do you smell gas?? they are two separate issues... you could have an emissions problem with the charcoal canister... My '87 used to smell like gas because of the emissions problem.
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
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Location
SoCA
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1984 White Z-51/ZF6-40/Shinoda body
You can 'throw parts' at it, or use procedures, as Larry stated, to isolate the problem. Use a logical, ordered troubleshooting procedure to find the fault.

You have no fault codes stored?

:w
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
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Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Cold start...JOKE!

So here is my take on Cold start.... WHO NEEDS IT!

I disconnected mine.... just pull the injector wiring off the cold start.

Before I did this.. the car would crank FOREVER before it would light.. and once it did PHEW... unleaded stinko!

I have remote start on mine.. and as I walked up to the car I would get blasted....
It was SOOOO bad I stopped using that feature.



Now( after disconnection ) just a little bit O stink.. when I'm right up to the tail of the car.


PLUS... 3 cranks.. VROOM she lights!

Now that being said...... as the O2 sensor gets OLD the, voltage generated for a paticular mix/burn changes... and it always goes the WRONG WAY... leaning rich.... I got a NEW O2 sensor from GM and it works great..... car has just the right amount of bounce between rich/lean on the scanner... and the plugs prove it...

But the car @ idle does run a tad rich......

In mine...I believe my injectors are leaking just a bit.


Vig!
 

vigman

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

Pass side by waterpump area.... mounted on front...of intake..2 pin connector

LARGE size... I'll have to check a previous post for wire colors .... since I'm at work ( goofing off ) and do not have my shop manuals on hand.


Vig!
 

BigRed

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May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
Vig will the computer scream because its unplugged? Are there any other symptoms that result from your mod? If not Im going to do it like TOMMORROW. I get STINKO supreme off start up!

But your thread says Im a 85 Vette and I don't have one?? But I get the same symptom you got.

(Its another Shadow thread) I'll trust you better thanks LOL.
 

vigman

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

Is not controlled by the computer,so no screaming EH!


Vig!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Oh yes I was in error

The 85-88 have it.



Vig!
 

BigRed

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Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
EH!

Vig I'll give you one thing, your relentless EH!

Thanks for the assistance bud I hated that smell off start its kind of embarrasing.
 
L

LarryBible

Guest
vigman,

How much will the O2 sensor change with age? I use O2 sensors for a mixture meter by welding a fitting in the exhaust pipe and running a wire to a test prod connector under the dash. I then use a DVM to check mixture. I did this and jetted the carb with a brand new sensor, but if I need to use this again later, how much could it shift?

This is on my old pickup that I did this and it worked great.

Thanks for your feedback,
 

vigman

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

Well EH No problem EH Glad to be of help EH
Good day EH!

So stink gone EH?



Vig!
 

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