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Truck will not pass smog.
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skydogdonn
New User
May 5, 2011, 4:29 PM
Post #1 of 8
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Truck will not pass smog.
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idle HC 642 (max 100) CO 4.99 (max 1.10) 2500 rpms HC 35 (max 180) CO .05 (max 1.1)
1993 Chevrolet C1500 Suburban Base 8Cyl5.7L - Engine
OBD1 code is 35 -idle air control sensor circuit fault..which jives with all info I have.. where do I begin? any takers?
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zmame
Veteran
/ Moderator
May 5, 2011, 4:40 PM
Post #2 of 8
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Re: Truck will not pass smog.
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Sounds like could be high fuel pressure maybe fuel regulator inop. I don't have the specs for that perticular vechical for fuel pressure. Possible missfire at idle. That would be my guess.
keep in mind I know very little on TBI engines not sure how they regulate fuel pressure..
(This post was edited by zmame on May 5, 2011, 4:41 PM)
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Mr.scotty
Enthusiast
May 5, 2011, 5:33 PM
Post #3 of 8
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Re: Truck will not pass smog.
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Pressure should be around 10-14 i read.
Fuel regulators run off of vacuum.
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Your only as good as your tools!
(This post was edited by Mr.scotty on May 5, 2011, 5:55 PM)
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zmame
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May 5, 2011, 5:41 PM
Post #4 of 8
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Re: Truck will not pass smog.
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Are you sure i thought TBI engine run lower pressures. I though it was only actually 13psi at the injector(s) it's self. I belive the fuel regulator is in the TB it's self (not %100 sure). Line pressure might be 68, but I think it's only 13psi at the actual injector if I remember trade school.. but that was a while ago.
Not sure how you go about testing it hopfully somone here will have some insight on that.
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Mr.scotty
Enthusiast
May 5, 2011, 5:56 PM
Post #5 of 8
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Re: Truck will not pass smog.
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Sorry, For some reason i looked up a 98..
For this year i read 10-14psi.
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Your only as good as your tools!
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Hammer Time
Ultimate Carjunky
/ Moderator
May 5, 2011, 6:01 PM
Post #6 of 8
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Re: Truck will not pass smog.
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[quote[Sorry, For some reason i looked up a 98..
For this year i read 10-14psi.
SURE, just dig your hole deeper....
The 98 spec is 55 to 66PSI
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Mr.scotty
Enthusiast
May 5, 2011, 6:01 PM
Post #7 of 8
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Re: Truck will not pass smog.
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This is what i found:
- Turn engine OFF to relieve system pressure.
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- Disconnect negative battery terminal to avoid possible fuel discharge if an accidental attempt is made to start the engine.
- Loosen fuel filler cap to relieve tank vapor pressure.
- The constant bleed feature relieves fuel pump system pressure when the engine is turned "OFF".
- Uncouple fuel supply flexible hose in engine compartment. Install fuel pressure gauge between steel line and flexible hose.
- Tighten gauge in line to insure no leaks occur during testing.
- Connect negative battery terminal and START engine and observe fuel pressure reading. It should be 62-90 kPa (9-13 psi). If not, refer to DIAGNOSTIC CHARTS/FUEL SYSTEM PRESSURE TEST (CHART A-6).
- Turn engine OFF to relieve system pressure.
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- Disconnect negative battery terminal to avoid possible fuel discharge if an accidental attempt is made to start the engine.
- Loosen fuel filler cap to relieve tank vapor pressure.
- Remove fuel pressure gauge.
- Install new O-ring on fuel feed line. Reinstall fuel line.
- Connect negative battery terminal and START engine and check for fuel leaks.
- Install air cleaner assembly.
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Your only as good as your tools!
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Mr.scotty
Enthusiast
May 6, 2011, 2:47 PM
Post #8 of 8
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Re: Truck will not pass smog.
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I said to Zmame that I looked up a 98 spec by mistake.
I posted 10-14psi for the 93 5.7 the guy has posted.
Should have made that a little more clear, sorry.
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Your only as good as your tools!
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