Running Rich
Thread Starter
Senior Member
Joined: Dec 2000
Posts: 914
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From: Hampton Roads. VA
Running Rich
I have a 91 RS with a 305 TBI. It's been running rich ever since I bought it. I've changed the O2 sensor, and checked the MAP sensor to no avail. Any input would be appreciated.
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91 Camaro RS, 305 TBI
No mods yet...Hopefully:
Convert to dual-cat with headers and Borla catback exhaust.
Edelbrock MPFI system.
RAM air hood & Z28 wing.
Z28 cam.
ABS system.
Positraction rearend with rear disc brakes.
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91 Camaro RS, 305 TBI
No mods yet...Hopefully:
Convert to dual-cat with headers and Borla catback exhaust.
Edelbrock MPFI system.
RAM air hood & Z28 wing.
Z28 cam.
ABS system.
Positraction rearend with rear disc brakes.
Moderator
Joined: Jan 2000
Posts: 19,685
Likes: 318
LBC,
Welcome aboard! You might well be the LAST new member of the year. Gotta start sometime, and tomorrow you'll be a seasoned veteran.
You're fortunate that you have no mods, making the problem a little easier to solve. How are you determining that you have a rich condition? Scanner monitoring of the O2? Sniffer? F/A meter? Field Service Mode test? Have you scanned for error codes? (Would be a good idea.)
I'm guessing you've changed the air filter but had to mention it just in case. Since yuo have a TBI, you should be able to physically examine the spray pattern of the injectors while the throttle is "blipped" open. The pattern should be a regular cone shape of fuel with no dribbles or drops.
Even though your TPS is not designed to be adjustable, there is an acceptable range of voltages at the idle position. If someone had attempted to raise the idle speed by way of the throttle stop screw, your idle TPS reading could be on the high end of acceptable. Reset the minimum air position of the throttle plates and reinitialize the ECM if you suspect tampering with the throttle stop screw. If the TPS is still out of range, replace it or make it adjustable.
Make sure the IAC is clean and the passages are unobstructed by the injector wiring harness. Make sure the ignition timing is correct. Check for leaks in the MAP system.
Check the MAT and CTS sensors to be sure they are reporting correctly. One or both could be within the acceptable range to prevent an error code, but so far off that the fuel calculations are skewed to the rich end. Even if they are
Fuel pressure should be checked if you still have problems. Pressure at the injector body should be 15-18PSIG at idle.
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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0
Welcome aboard! You might well be the LAST new member of the year. Gotta start sometime, and tomorrow you'll be a seasoned veteran.
You're fortunate that you have no mods, making the problem a little easier to solve. How are you determining that you have a rich condition? Scanner monitoring of the O2? Sniffer? F/A meter? Field Service Mode test? Have you scanned for error codes? (Would be a good idea.)
I'm guessing you've changed the air filter but had to mention it just in case. Since yuo have a TBI, you should be able to physically examine the spray pattern of the injectors while the throttle is "blipped" open. The pattern should be a regular cone shape of fuel with no dribbles or drops.
Even though your TPS is not designed to be adjustable, there is an acceptable range of voltages at the idle position. If someone had attempted to raise the idle speed by way of the throttle stop screw, your idle TPS reading could be on the high end of acceptable. Reset the minimum air position of the throttle plates and reinitialize the ECM if you suspect tampering with the throttle stop screw. If the TPS is still out of range, replace it or make it adjustable.
Make sure the IAC is clean and the passages are unobstructed by the injector wiring harness. Make sure the ignition timing is correct. Check for leaks in the MAP system.
Check the MAT and CTS sensors to be sure they are reporting correctly. One or both could be within the acceptable range to prevent an error code, but so far off that the fuel calculations are skewed to the rich end. Even if they are
Fuel pressure should be checked if you still have problems. Pressure at the injector body should be 15-18PSIG at idle.
------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0
Thread Starter
Senior Member
Joined: Dec 2000
Posts: 914
Likes: 0
From: Hampton Roads. VA
I can smell it in the exhaust. What do you mean by blipped open? Every damn camaro/firebird I've ever got behind on the road was running rich. Do you know if GM ever posted a bulletin about it? I've put injector cleaner in it but haven't bothered checking the spray pattern. I will tommarow.
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