Re: 1991 dodge ram 5.9 gas computer issue??
[Re: donsace]
#1360757
12/29/12 10:14 PM
12/29/12 10:14 PM
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Joined: Oct 2003
Posts: 2,537 PORT ALBERNI , BC., CANADA
superwrench
master
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master
Joined: Oct 2003
Posts: 2,537
PORT ALBERNI , BC., CANADA
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Does your truck have an EGR valve on the intake? If so, try disconnecting the vacuum supply and see how it runs. Then try to give the EGR valve shaft a good flick with a screwdriver to help it seat. Also you could just remove it and check to see if the valve is seating. I'd be very skeptical that it is anything to do with the computor....like has been mentioned it's more likely to be a sensor/injector/egr problem. I've seen ton's of trucks come in with stuck EGR's or bad EGR transducers (the black vacuum pot on the EGR). Please let us know what you do find.
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Re: 1991 dodge ram 5.9 gas computer issue??
[Re: superwrench]
#1360758
12/30/12 12:15 AM
12/30/12 12:15 AM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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You say you unplug the ECU and it still runs the same. What are you refering to as the ECU ? It sounds like a bad coolant temp sensor as I have seen that a few times. The coolant temp sensor is like the choke on a carb for a cold injected eng and it can cause to much fuel to be dumped by the wrong reading and not set a code. As long as its in the operating parameters it wont set a code on yours. When you start it cold it will be in open loop for a few minutes on your 91 and it will ignore the O2 until the oxygen senser heats up in a few minutes. The coolant sensor has most control over the fuel mixture on a very cold eng along with the MAP and RPM signal. Ron
Last edited by 383man; 12/30/12 12:16 AM.
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Re: 1991 dodge ram 5.9 gas computer issue??
[Re: Supercuda]
#1360760
12/30/12 09:22 PM
12/30/12 09:22 PM
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Joined: Oct 2003
Posts: 2,537 PORT ALBERNI , BC., CANADA
superwrench
master
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master
Joined: Oct 2003
Posts: 2,537
PORT ALBERNI , BC., CANADA
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Upon re-reading this post, I'd think it may be advantageous to have the system scanned.....or at least cycle the key for a trouble code. It's probably going to come up with a code 51 or 52 anyways ...O2 going rich or lean...but that could be the result of whatever's causing the system to puke black smoke....not the O2 itself. 383Man could be right....the temp sensor is important....otherwise there is something else telling the system it needs fuel...i.e. a lower than normal vacuum signal. That's why I suggested the EGR.A stuck thermostat will only cause the truck to get crappy mileage...not cause smoke. A scanner will show a poor vacuum reading from the MAP. I'd be checking it for sure. Oh...and an OBD scanner won't do....you'll have to find someone with the proper 6 way plug-in cable for the older Mopars or go to the dealer and they'll use the DRB scanner.
Last edited by superwrench; 12/30/12 09:57 PM.
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Re: 1991 dodge ram 5.9 gas computer issue??
[Re: superwrench]
#1360761
12/30/12 10:45 PM
12/30/12 10:45 PM
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Joined: Jan 2003
Posts: 4,576 Sarcoxie, MO, USA
MoPar Jamie
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master
Joined: Jan 2003
Posts: 4,576
Sarcoxie, MO, USA
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I had a computer die in an '89 D-100 and it caused the injectors to stick open. Ran so rich I couldnt get it to run at idle and black smoke bad out the tailpipe driving.
- MoPar Jamie
1972 Fury III 4dr 1986 D-150 LWB Royal SE
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