1996 C1500 silverado 5.7l vortec engine. Running rich


Asked by simperfi84 Jan 16, 2020 at 10:58 AM about the Chevrolet Silverado 1500

Question type: Maintenance & Repair

I have a 96 chevy c1500. I have a new factory GM engine it seems to be
running rich. Exhaust has a strong fuel smell. All O2 sensors are new,
new cats, new MPFI system, with the exception of the EGR and MAF
sensors, all others are new (aftermarket). Here are my live data from
testerday at 66mph according to scan tool, RPMs 2052.  
STFT BK1 -0.8 to 0.8
LTFT BK 1 13.3
STFT BK 2  -0.8 TO -1.6
LTFT BK 2 14.8
MAF 5.28 LB/ MIN
TPS 10.3
ECT 194
STFT BK 1 -1.6 TO 0.8
LTFT BK1 4.7
STFT BK 2  -1.6 TO 08
LTFT BK 1 1.6

I do have a difference of about 5 MPH BETWEEN speedometer and
what scan tool shows. Speedo showed 71mph . I believe the ECT TEMP
should show between 200 to 205 degrees for normal operating temps
for the 5.7l .. Been told these engines like AC delco parts. I may go
ahead and replace ECT with OEM. Thoughts please. No codes by the

2 Answers


Thats not rich thats lean.. and since its lean under load check the maf sensor if its dirty or suspect a weak pump


Thanks Guru84BD1, I can never keep that straight in my head, thanks for setting me straight on that. Fuel pump is new and got 62+ pressure. MAF is original , So I will clean it and see how it does and go from there. Thanks again I have a direction now.

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