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Automotive Science or Voodoo?

117 messages,  Last post on Nov 19, 2012 at 8:45 AM

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Messages Page 13 of 13

#113 of 117 Re: Automotive Science or Voodoo? [dmcvickar] by Mr_Shiftright HOST

Oct 11, 2006 (8:17 am)

Replying to: dmcvickar (Oct 06, 2006 4:37 pm)
This seems counter-intuitive, since a light carbonization of the fuel chamber would increase compression and hence power. I don't see the relationship of carbon to a "complete burn" one way or the other.
 
I could see where a fuel injector CLEANER would give a better spray pattern but this has nothing to do with the combustion chamber.
 
If the claim is that the additive changes the chemical composition of gasoline itself, I'd like to see the science behind that claim and what molecular changes have occurred.

#114 of 117 Cavalier Diagnostics by smonday

Jan 19, 2011 (6:14 am)

Hello, I am having idle problems with my 1998 Chevy Cavalier Z24. The car runs great when I first start the vehicle but after it warms up it will start running poorly. It is most noticable after it warms up and then I shut it down for a few minutes (like running into the store), after I re-start the car it accelerates terrible. Idles fine but won't accelerate.
I borrowed a Actron Autoscanner from a buddy of mine and ran diagnostics on the vehicle, this is what I got:
 
Trouble codes, ignition on, engine off:
 
P0141
P0171
P0420
P0442
P0502
P0137
 
Diagnostic codes, Engine running:
 
ABSLT TPS(%) 0.0
RPM 920
CALC LOAD(%) 19.2
MAP ("HG) 8.9
IAT (F) 63
IGN ADV(DEG) 17 TO 26
LT FTRM1(%) 21.9
ST FTRM1(%) -9.4 TO -14.8
FUEL SYS1 CLSD
FUEL SYS2 N/A
O2S11(V) .195/.760
ST FTRM11(%) -10.9 TO -14.1
O2S12(V) .000 TO .005
OBD2 STAT
 
From what I've been able to read into this is that my map sensor isn't working correctly and my downstream O2 sensor is faulty. I'm clueless regarding the other information. Are they normal or not?
 
Thanks in advance!

#116 of 117 Re: Cavalier Diagnostics [smonday] by srs_49

Nov 19, 2012 (6:48 am)

Replying to: smonday (Jan 19, 2011 6:14 am)
I don't think the P0171 code means that the downstream O2 sensor is bad. Just that it's detecting an excess of oxygen on the exhaust flow. Which could be caused by a bad MAF sensor.
 
All the rest of the codes could be a result of the excess oxygen in the exhaust.

#117 of 117 Re: Cavalier Diagnostics [srs_49] by Mr_Shiftright HOST

Nov 19, 2012 (8:45 am)

Replying to: srs_49 (Nov 19, 2012 6:48 am)
yep P0171 is tricky. Many a good 02 sensor has been replaced because of that code.
 
MAF sensor is a good guess; also coolant temp. sensor can throw this code; perhaps even a vacuum or exhaust leak.

Messages Page 13 of 13

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