86 ford ltd lurches or has a miss at low speed

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  #1  
Old 09-18-05, 03:18 PM
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86 ford ltd lurches or has a miss at low speed

Just picked up a 86 5.0L LTD for a winter car and have some time to kill I guess.At low speeds around 25mph it wants to lurch or miss a little, feels like its getting tugged on or something to that effect.Once I goose the throttle it seems to go away for awhile.Hot or cold engine temp.Ran a scan,no codes.Fairly new plugs and wires.Replaced valve cover gaskets today and plenum gasket hopeing that may have been bad in the needed prosess anyway.Didnt help.Im not real familiar with this car yet but when you first start it the engine revs way up, down a little and partially way up and down and then to normal idle.Under no load it idles fine always.Ran all tests with my OTC scanner and nothing.All vacuum lines look connected and good.Higher speeds seem fine and throttle body plate bore is carbon free.The o2 sensors are up by the manifolds and does have a bad muffler if that would make a diff.Normally I wouldnt care but this is really a 1 owner old lay car and its in excellent shape.Thanks for any help .
 
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  #2  
Old 09-19-05, 06:15 PM
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Check the voltage on the Throttle Position Sensor by piercing the wires and hooking up a Volt Meter
Should be steady at around...0.95v

I'd check the Fuel Pressure too
There's a schrader valave on one of the rails, a FP gauge hooks up pretty easy

You might want to rig up a long hose Fuel Pressure gauge and duct tape it to the window and drive around a bit

I'd clean the injectors if you have the kit to hook up the can of cleaner to the fuel rail

The "Wandering Idle" of the '86 SEFI is pretty common
It may be normal, or rather acceptable, or it may be an indication of problem and can be fixed
 
  #3  
Old 09-25-05, 03:30 PM
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Well I finally had a chance to drive at highway speeds and the engine light came on then off then flickered,came on solid and then off.
Re-connected otc scanner and came up with this.
No on demand codes found.
code 34 found under key off,engine off in memory on the car computer.
All of my so called repair manuals do not show this type of EGR system that I have.Its mounted on the throttle body plate with a vacuum line to a sensor or switch on the fender,and a solenoid mounted on back of EGR with 3 wires.
I applied vacuum to the valve and it holds.Problem for me is that code 34 shows as 4 possible items : EGR valve opening not detected-or -EVP voltage above closed limit (SONIC) -or- EPI sensor voltage out of range (PFE) -or - exhaust pressure high/EPI circuit voltage high (PFE).
starting to get away from me!too many acronyms.Is there at least a way to check the EGR.
This has the EEC-IV-SFI and I did replace TP sensor a couple days ago before this.
Thanks again to anyone.
 
  #4  
Old 10-04-05, 05:27 PM
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update

Well I did change the throttle pos. sensor, didnt help even though I did get a jumping needle effect on an ohm meter while testing it.OTC scanner did show a code 34 in a keep alive code.Checked EGR position sensor, it was kind of hard to test with a digital multi meter but seemed to have its spots of uneven readouts so I replaced.That didnt help.I cleared codes by the scan tool and did a customer keep alive code
retested.Still shows a code 34 under keep alive and on demand.The strange thing is this thing can run fine and out of nowhere it will start to tug at low speeds.I noticed at one point when stopped at a light it snapped out of it or if it acts up while driving it seems that if I snap the accelorator for a sec. it will also help but not certain if this helps all the time since Im not the main driver.I do know that the dist. has been changed so someone might very well have been chaseing this before.One other scenario of this is if I drive until its warmed up and I shut it off for around 30 min or so while shopping, I restart an within 5 min it could start acting up again even though untill that point it ran fine.
Thanks again for input.
 
  #5  
Old 10-04-05, 07:47 PM
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More Acronyms

34 means different things in different modes
If I am understanding you correctly, it is 34 in the Continous Memory mode
This usually has to do with the PFE or Pressure Feedback EGR sensor, or it's signal circut (check for blocked sensor tube)
Or the EVP or EGR Valve Position sensor (check the EVP resistance)
 
  #6  
Old 10-05-05, 12:45 PM
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this has the sonic style EGR assy.I have put a new EVP sensor on last week and yes the code 34 shows up after I did the KOEO and checked for hard set codes in cars memory.All it has are the 3 wires to the EVP.I have also noticed today(keep forgetting to bring home my vacuum pump) that when I apply suction by mouth to the vacuum inlet hose to the EGR, I gradually try to open valve and it will open and hold but at first it pops open instead of a gradual opening.Not sure as to what vacuum reading it should start to open plus it has a slight carbon ring on the stem where it seats .Could this actually bind at initial opening and be the cause ?
Thanks
 
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