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does anyone have any information or tsb's on the cross fire engine. mine goes full rich when cold. i have replaced the coolant temp. sensor in the front of the engine. no help. no codes in the ecm at all. put an tech one on it everything is working o2 sensors , all sensors seam fine. any help or suggestions would be helpfull. thanks
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Why do you think it is running rich? Is it blowing black smoke from the pipes?
Over rich at idle could be a leaking infector, damaged o-rings on the infector(s), a bad/skewed MAP sensor signal, fuel pressure too high, TPS, ...lots of stuff could cause it.
The ECM ignores any signal from the O2 sensor(s) until they are at operating temp(closed loop), so even a bad signal from the O2 shouldn't effect a cold start rich condition. You would need to monitor all of the pertinent sensor at a cold start to see if one or more are out of whack...once the engine is warmed up, those reading may not be of any help.
I would start with a fuel pressure reading, then check the infectors for leakage, and go from there.
Over rich at idle could be a leaking infector, damaged o-rings on the infector(s), a bad/skewed MAP sensor signal, fuel pressure too high, TPS, ...lots of stuff could cause it.
The ECM ignores any signal from the O2 sensor(s) until they are at operating temp(closed loop), so even a bad signal from the O2 shouldn't effect a cold start rich condition. You would need to monitor all of the pertinent sensor at a cold start to see if one or more are out of whack...once the engine is warmed up, those reading may not be of any help.
I would start with a fuel pressure reading, then check the infectors for leakage, and go from there.
Joel Adams
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Adam, yes black smoke comes out the pipes. also the motor runs rough. pulled a plug to look it was fouled out. thanks for your suggestions ill look at the injectors and run a fuel pressure test. i bought 2 new injectors on e-bay still in the gm box. correct part numbers for it. front and rear. let me ask this would the fuel pressure diaphragms cause this? i haven't replace them as of yet. nor rebuilt my throttle bodies. if i could resolve this the motor would run great. opps i'll check out the tps to make sure its in range. the map is brand new from gm they only made one kind for that year. i'll get back with you and let you know what i find. thanks
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22742
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Only the rear throttle body has the fuel pressure regulator. The front TB has a "compensator" that evens out the pressure between the two, iirc. A fuel pressure test would tell you if the regulator is bad...if the pressure is too high, and your infectors are so-so, then they can certainly leak too much fuel past them while running. Strange that it only does it when it's cold, tho....normally, you will have a richer fuel mixture when cold anyway. A bad regulator would be bad all the time. My best bet is on the infectors, or some other sensor that is out of whack.
And, just in case you didn't know, the front and rear infectors are different, so make sure you replace them in the correct location. Compare the part numbers with the new ones.
And, just in case you didn't know, the front and rear infectors are different, so make sure you replace them in the correct location. Compare the part numbers with the new ones.
Joel Adams
C3VR Lifetime Member #56
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(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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Check your IAC valves for proper operation....you can see them moving in the kidney shaped holes on top. Maybe one or both are sticking/failing.
I'd also check for "min-air" and the balance of the TB's.
I'd also check for "min-air" and the balance of the TB's.
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in Forum: C4 Engines, Driveline and Handling
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