So confused
#1
So confused
Got a 95 z28 withe the lt4 hot cam kit.repaced all ignition parts as well as fuel.when the engine was rebuilt. I had a check engine lite on with a code 48 maf circuit failure.found a broken wire at the connector fixed checked for 4_6 v ref and 12 b+ all was good.cleared the code drove awhile the lite never comes back on but yet the car still bucks at normal driving speeds.fuel pressure also checks good .I'm losing my mind with this car
#2
Re: So confused
Got a 95 z28 withe the lt4 hot cam kit.repaced all ignition parts as well as fuel.when the engine was rebuilt. I had a check engine lite on with a code 48 maf circuit failure.found a broken wire at the connector fixed checked for 4_6 v ref and 12 b+ all was good.cleared the code drove awhile the lite never comes back on but yet the car still bucks at normal driving speeds.fuel pressure also checks good .I'm losing my mind with this car
#3
Re: So confused
Is this basically a continuation of the same problem ("bucking") in this thread?
https://www.camaroz28.com/forums/lt1...ucking-878304/
https://www.camaroz28.com/forums/lt1...ucking-878304/
#6
#8
Re: So confused
What about the tune? Did you ask Sinister Performance about the problem? Sounds like cam surge, which shouldn't happen with an LT4 HOT cam.
Next step would be a data log of the PCM, while operating it with the problem happening. Try Scan9495.
https://www.camaroz28.com/forums/com...95-lt1-874306/
Next step would be a data log of the PCM, while operating it with the problem happening. Try Scan9495.
https://www.camaroz28.com/forums/com...95-lt1-874306/
#10
Re: So confused
I also dbl checked my fuel press and have weird readings..koeo it has 37. Koer goes to ,40. Add pressure to the regulator no change in psi.. all the numbers seem low to me not sure if my new pump is junk or the reg
#11
Re: So confused
Idle you want 43.5 PSI with the vacuum line off the regulator. GM accepts anything in the range of 41-47 PSI as within spec. Reattach the vacuum line to the regulator, and pressure should drop proportional to intake manifold vacuum. With the HOT cam would probably drop about 6 PSI. Example: (no vacuum at the rail 43.5 PSI) - (6 PSI vacuum) = 37.5 PSI at the rail.
When the pump primes without the engine running, and shuts off, should be at least 40 PSI. When the pump shuts off, how fast does the pressure drop?
How did you "add pressure" to the regulator? Do you have an adjustable fuel pressure regulator? If so, what brand is it?
There are codes that don't turn on the SES light, although most of them prevent the engine from running. But you don't do a data log just to pull codes. You do it to see how all the sensors are working, and what parameters the PCM is using to run the engine.
When the pump primes without the engine running, and shuts off, should be at least 40 PSI. When the pump shuts off, how fast does the pressure drop?
How did you "add pressure" to the regulator? Do you have an adjustable fuel pressure regulator? If so, what brand is it?
There are codes that don't turn on the SES light, although most of them prevent the engine from running. But you don't do a data log just to pull codes. You do it to see how all the sensors are working, and what parameters the PCM is using to run the engine.
#13
Re: So confused
How did you "add" 15 lbs of vacuum to the regulator? 14.7 psi vacuum is a full vacuum and not possible with a typical vacuum pump. Or did you apply 14"Hg? In any case applying vacuum to the regulator should reduce the pressure.
The method I gave for measuring the pressure, both with and without the vacuum line connected is 100% correct.
The method I gave for measuring the pressure, both with and without the vacuum line connected is 100% correct.
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danielbmx
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08-27-2002 11:11 PM