Hard starting, high idle and black smoke

Tiny
JEFF_MACON
  • MEMBER
  • 1995 FORD BRONCO
  • 5.8L
  • V8
  • 4WD
  • AUTOMATIC
  • 70,000 MILES
My truck is a weekend driver, I start it every three or four days, it is basically a toy! The first thing I noticed was the fuel pump had a high pitched whine, more than it ever had, it did not stop pumping after a few seconds, and it cranked over without starting. Because of the high pitch sound from the fuel pump and it's continuous running I believed the fuel pump was bad.
I replaced the fuel pump but that did not fix it, it will start with a shot of starting fluid. After I get it started it will go through it is warm up stage and idle fine for a few seconds to a minute. Then for some unknown reason the idle will go up to around 1600-1800 rpm's and black smoke will come from the exhaust. It will stay like that for however long then it will go back to idling perfect to an undetermined amount of time until it starts all over again, heightened idle and black smoke, then back to fine idle and no smoke. Maybe, I shut it off if I am unable to get it to idle right. Also, during this time of high idle and black smoke the engine compartment feels hotter, do not know why but it does.
I have no "check engine" light until it starts the high idle/black smoke, when it idles right the check engine light turns off. I have no error codes in the current or extended memory and my system is the EEC-IV, not OBD.
I have replaced fuel pump, IAC motor, MAP sensor, fuel pressure regulator, fuel filter, cleaned fuel injectors/throttle body/plenum and installed new gaskets from plenum up. The EGR and smog system was removed long ago by the previous owner. I have had my truck since 2002 and have never had a problem I could not diagnose, until now! Please help me get my truck running right again!
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Monday, May 1st, 2017 AT 9:34 AM

6 Replies

Tiny
HMAC300
  • EXPERT
Instead of changing parts scan for codes and then check fuel pressure it may be a bad regulator or blocked return line. start there. See link for fuel pressure.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Monday, May 1st, 2017 AT 9:51 AM
Tiny
JEFF_MACON
  • MEMBER
I installed one other fuel pump before but took it out because it was not the right one and did not supply enough pressure, the current pump provides enough pressure. While the fuel tank was down we cleaned it out, pump fuel through the line to remove any debris, then the fuel pump, filter, and pressure regulator were installed. I think the original fuel pump might not have been the problem. The only codes I have had are EGR and O2 sensor related and been there for thirteen years. This issue has just started
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Monday, May 1st, 2017 AT 10:00 AM
Tiny
JEFF_MACON
  • MEMBER
If I reach half throttle during the high idle/black smoke, it sputters and backfires from the tail pipe and if I have the intake tube off there is a loud vacuum noise from the throttle body, the loud vacuum noise is only present during the high idle. I am going to try the self-test while the high idle is present.
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+1
Monday, May 1st, 2017 AT 10:14 AM
Tiny
HMAC300
  • EXPERT
If you are hearing a loud vacuum noise you have a vacuum leak. With the egr system not connected it's very possible that it has burnt a hole in intake from being disconnected which is quite common when this is done especially with the age of truck. There should not be any large or any vacuum leaks. If all that stuff in fuel system was replaced what is fuel pressure with key on only? Was the regulator on fuel rail replaced? Is the duct work leading to throttle body ok with no holes/cracks
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Monday, May 1st, 2017 AT 12:05 PM
Tiny
JEFF_MACON
  • MEMBER
I can't remember what the fuel pressure was, my brother checked it and it will spew alot of fuel if you open the bleeder valve. The specs on this fuel pump are
Electric Or Mechanical: Electric
Gasket Or Seal Included: Y
GPH (Free Flow) Rating: 50 gph
Grade: Standard Replacement
Ground: NEG.
Inlet Quantity: 1
Inlet Type: Strainer
Internal Or External: In Tank
Maximum Flow Rating: 50 gph
Maximum Pressure: 110 PSI
Minimum Flow Rate: 50
Minimum PSI: 100
Outlet Outside Diameter: 5/16
Outlet Quantity: 1
Outlet Type: Female Thread
PSI Shut Off: 100-110
Pump Only Or Module: Module
Sender Included: No
Voltage: 12 VDC
I've sprayed carb cleaner around the joints of the throttle body, plenum, intake manifold and every vacuum connection. All vacuum lines are new but we're inspected anyway. I just removed the spark plugs to inspect them and they're covered in black soot. I'm starting to think it's either the distributor or ECM.
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Monday, May 1st, 2017 AT 3:01 PM
Tiny
HMAC300
  • EXPERT
Well until you scan for codes and get back with them as well as fuel pressure I can't really say much but I think you have a bad vacuum leak among other things. You need to know pressure readings that includes letting it sit after taking them to see if they drop.
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Monday, May 1st, 2017 AT 3:17 PM

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