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86 Bronco II Starting Issues


The Slider

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I have noticed lately that my 2.9l is getting hard to start. When I first start it in the mornings it starts pretty much right away ( 3 sec crank) when I turn it off 2-3 mins later and I goto start it again, I crank sometimes 3-4 seconds at a time maybe around 5-6 times before it will start. It lacks some power going up hills ( NO SMOKING) so I changed the BOTH fuel pumps and IAC now every once in a while I get a whiff of gas. My EEC-IV gives me a clear bill of health ( NO CODES)... At idle about 90% of the time its SMOOTH! 10% of the time the idle might be a little erratic. I have been fighting this issue for some time. with NO codes, I'm kind of stuck...

Thanks!
Chaz
 


RonD

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Turning it off after only running 2 or 3 minutes might be causing the ECT sensor to warm to fast, when you turn off the engine the water pump stops and ECT will get heat soaked from standing warm coolant, so when you go to restart it computer is no longer in Choke Mode, it thinks engine is warmer than it is.
So mix is too lean and takes longer to start.

Fuel Pressure Regulator has a vacuum hose attached, pull it off and check it for gasoline, shouldn't be any in there and no smell of gasoline.
If FPR has a small leak in diaphragm it could cause gas smell and air/fuel mix imbalance via vacuum hose.


After engine is fully warmed up and idling, unplug the 2 wires on IAC Valve
IAC Valve will close all the way and RPMs should drop to 500 or engine may even stall, either is good it means no vacuum leaks.
If idle stays high then you do have a vacuum leak.

OR......someone has messed with the anti-diesel screw on the throttle linkage thinking it was an "idle screw", fuel injection can't use an idle screw, no Jets, which is why there is an IAC Valve.
If idle stays high after unplugging IAC Valve turn the anti-diesel screw counter clockwise to see if idle starts to drop, if it does keep turning to get to 500rpm, below 600 for sure.
If idle doesn't change then turn it back to where it was, and look for the vacuum leak
 
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rusty ol ranger

rusty ol ranger

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Ill about bet on a failed FPR.
 

The Slider

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Good Call!!!! FPR is leaking through the Vac. hose.. Would that also cause the RPM's to rev high when I first start it???
 

RonD

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Yes, could be

But gas engines REV higher by adding more air, adding more fuel floods out the engine

IAC Valve should be open all the way for starting, so any fuel injected engine should REV when started, then RPMs drop down to "target idle" based on engine temp, as computer closes IAC valve
If there were some extra fuel in the engine, i.e. the vacuum line, then REV would last longer and be higher than 1,500 or so expected
 
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The Slider

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When I first start it, the RPM's goto around 2000 - 2500 RPM and will sit there for about 3-5 mins before is starts to drop to normal. I turn on the AC to try to help bring down the RPM's..
 
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RonD

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Yes, something is wrong there

Open hood
Start cold engine
If RPMs are above 1,100 unplug IAC valve and see if they drop and engine stalls, it should stall if cold.
If so computer is holding open IAC Valve for some reason

But thats after fixing FPR leak, which could get that REV down to "normal" 1,500 for a few seconds then drop to 1,100 cold idle
 

The Slider

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1972
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Yes, Pulling the IAC cold kills the engine...

NAPA is getting me a new FPR Tuesday morning... WOO HOO!!! I hope that solves the problem.

Thanks!
 
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