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2.9 hard start when warm


steveoelo

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Still haven't found a good answer but every time I try to start the truck when it's warm it takes several cranks before it goes. If I hit the gas then it starts a bit easier. In the morning when I start it it goes first time and runs perfect. I just replaced the fuel pump and filter. Ideas?
 


wildbill23c

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Having about the same issue with my 88 Bronco 2, haven't changed the fuel pump, but it runs and drives fine other than trying to get it started after its been running a while. Sometimes a bit of throttle when starting works, sometimes it doesn't make a difference, and usually it takes several tries to get it started. Wondering if there's something going on like vapor lock.
 

RonD

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The gas pedal on a fuel injected engine doesn't give engine more gas when you push it down, there is no accelerator pump like a carb had.
It gives the engine more air, so we should change the name to the "air" pedal, lol, OK so not going to happen.

Fuel injected engines have the IAC(idle air control) Valve, when you turn on the key the computer will open the IAC Valve all the way, cold or warm, this is why if you don't touch the "gas" pedal when starting the engine RPMs will usually go above 1,500 then drop back down to cold or warm idle levels, IAC Valve open all the way causes that higher RPM then computer closes it to set target idle.

You can remove the 2 bolts and take the IAC valve off the upper intake, then leaving it's wires connected turn on the key, it should open all the way, then unplug the wires, or turn off the key and it should close all the way.
Repeat that a few times to make sure it is not sticking, clean it if you need to.
This will tell you if IAC Valve is working.

Needing more air to start, opening throttle, when warm could be a couple of things besides IAC Valve not opening all the way.
Fuel leaking in to intake when engine is off, causing a flooded condition, so more air is needed.
Easy to check for that, with engine still warm remove intake's air tube, open throttle and smell for gasoline, there would be no fuel left in the intake with fuel injection, when you turn off the key fuel injectors stop instantly and as engine RPMs drop to 0 any residual fuel or fuel smell would be pumped out of the intake and into the exhaust.

Weak spark, the computer will usually give the engine a good shot of fuel for starting which is why IAC Valve is open all the way, if spark is weak then the Rich mix can prevent ignition of the mixture, opening throttle Leans out the mix so weaker spark can ignite it.
Could be from warm TFI module or weak Coil when warm, both can become temp sensitive.
And the wiring for these as well, warm wires have higher resistance, that's normal and expected, but if a connection is dirty then resistance can lower voltage to a point where it causes a problem.


Vapor lock with fuel injection can happen just isn't as likely with the higher pressure in the fuel lines.
You can test for this at the fuel rail, but be careful, with engine warm/hot, and off, have a towel handy and press center pin on schrader valve on fuel rail, 25-30psi pressure in there so be careful it doesn't get to exhaust manifolds.
If you are getting liquid fuel then no vapor lock.
I would wait a few minutes after shutting off engine and leave hood closed.
Let the fuel in the rail absorb as much heat as possible, then test it.

The vapor lock would have to be in the fuel rail or the engine would start and then die if it was in the fuel line
 
Last edited:

wildbill23c

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With my issue I'm thinking I've got a bad TFI, occasionally it starts when hot just fine, however yesterday and today I have a no start at all, but that's also caused by my current starter problem, I believe the starter needs replaced or rebuilt at least since it only engages for a couple seconds at the most and doesn't crank the engine long enough to start. Going to put a new starter in this weekend to correct the starter issue so I can get it to the shop to have the transmission diagnosed and see what's going on with it, and have everything major fixed.
 

steveoelo

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Update: I put a new distributor in with an other TFI module (truck had 60000 miles, mostly idle time) and no dice. Checked the timing and it was out 8 degrees so I set it back to 10 degrees. Setting the timing again seemed to make starting hot or cold about the same. Before when cold it would start as soon as you would touch the key to start but now after the timing adjustment it seems to take a second or two. Ideas?
 

lil_Blue_Ford

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Just a thought.... when was the last time the fuel filter was replaced?


Sent from my kite using a trebuchet
 

wildbill23c

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19K, 19D, 92Y, 88M, 91F....OIF-III (2004-2005)
My issue turned out to be related to a bad fuel pressure regulator.
 

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