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Vortec 4300. MAP AND TPS codes, but sensors test good

Old 07-26-2015, 03:48 PM
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Default Vortec 4300. MAP AND TPS codes, but sensors test good

GM with CMFI. Has OBD I codes for MAP and TPS. Had a bad fuel pressure regulator (leaky), but I replaced it. Still has a very surging idle and a very rich idle. The MAP and TPS test working, and their respective wiring test out good too. Any ideas?
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Old 07-28-2015, 02:42 PM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

PCM
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Old 08-15-2015, 01:22 PM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

Are you sure enough that I should just go buy one. I did eventually grab a can of carb cleaner and did not find any vac leak.
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Old 08-15-2015, 02:48 PM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

Is there an EGR valve on the engine?
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Old 08-15-2015, 04:37 PM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

Yep. I don't know if it tells you anything, but if I leave it to idle for a while it will smooth out, and if you hit the throttle it will surge up and down for a little while. Also seems to idle a little high.
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Old 08-26-2015, 02:23 PM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

I didn't test all the wiring on the egr valve, but the plunger it in moved freely and it wasn't overly carboned up or anything like that. If it helps, when it does stall out the only way to start it is to floor it while you crank.
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Old 08-30-2015, 09:45 AM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

Any progress? What exactly are the codes and what is the year/make? Vortec's were mostly OBD2. With the cross over year that you have the 2 plug and 1 diag. My '94 SSEi was like that- what a PITA.
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Old 08-30-2015, 09:51 AM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

This one is OBD 1, 1994 Olds Bravada. I forget the exact codes, but OBD 1 is simple enough that there is only one code for each of those sensors, so it was just the two codes that equate to those sensors.
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Old 08-30-2015, 12:49 PM
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

Fine. Can't help if you don't.
Maybe my name might get the impression I like '80s GM cars and might of been the go to guy when I was down there. I still know how to work the Morris code. Pull in to a Advance or Autozone and see the blank look you'll get. Yes being a 94 you would have a 1.
There are at least 2 codes each they could be. Being I'm not standing over the car we would have to play 20+ questions getting into the possible issues- but never mind.

If you got to floor it to start it you may want to look into this-

CLEAR FLOOD MODE
If for some reason the engine should become flooded, provisions have been built into the computer to help clear this out. If during cranking of the engine you depress the throttle more than 80%, the ECM will enter what is called “clear flood mode”. In this mode the ECM commands a delivered Air/Fuel ratio to very lean (usually 20:1). The ECM will stay in clear flood mode as long as the throttle is 80% or higher and the RPMs are less than about 600. As soon as throttle position falls below the 80% threshold or RPMs go above 600, the ECM disables clear flood mode and calculates fuel delivery based on coolant temperature and other factors it normally uses.

Last edited by Rosco The Iroc; 08-30-2015 at 12:53 PM.
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Old 08-30-2015, 01:11 PM
  #10  
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Default Re: Vortec 4300. MAP AND TPS codes, but sensors test good

You're right, looked again, there are two possible. 21 and 34 are what I had.
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