Crappy idle on startup

[matt351]

Hey guys, I'm pretty much stumped with this thing... it barely stays running on startup. So far I've done plugs, wires, fuel pressure regulator and crankshaft position sensor. It still seems to run like garbage. The only codes I get are for a random misfire. Any guidance here guys?

 

[intelisevil]

When you say "random misfire", I'm assuming you're seeing PO101 - PO106 codes?

I was having a rough idle on my '00 4.0 SOHC. Once I got it over about 1500 RPM it would smooth out but was still low on power.

I was chasing PO303 & PO304 codes for a while and finally found out how to test my coil pack. The part of the coil pack that fired cylinders 3 & 4 was bad.

Replaced the coil pack, idle smoothed out, power was back up (running on all 6 cylinders!) and MPGs went back to normal.

Look at post #2 in the following thread:

http://www.fordrangerforum.com/4-0-s...coil-pack.html

Good Luck,

 

[wcjeep]

I did everything the OP did. Then the coil pack. Each step helped. I also verified the fuel pressure. Finally changed the intake gasket set. I used the Fel Pro from Oreilly's for $26 +/-. The intake gaskets appear to shrink from age. They allow unlimited non metered air into the engine. After the engine warmed up the gaskets appear to have expanded for near normal engine operation.

My engine is now 99% operational. Don't feel like spending big money or time to get the extra 1%. Be sure to double check the torque value for the plastic intake bolts. My book (Chilton or Haynes) was incorrect. I have both. I don't recall which book was wrong. I don't have to work outside in the weather. This repair takes a little time. Nothing difficult.

 

[Flash]

Clean or replace your idle control valve and check for vacuum leaks first, then look at things like coil pack and injectors.

 

[matt351]

I went ahead and replaced the o-ring seals for the upper and lower intake manifolds. It started up and seems to run fine so far. I won't truly know until the truck sits overnight. I'll fill you all in tomorrow morning on the results. Thanks guys for all of the input!

 

[matt351]

Well the o-rings definitely fixed the issue! Thank you guys for all of the help!

 

[Y2K Explorer]

I'm having the same issue but have not connected my scanner to see what code its throwing....
>
-On Cold Cold Mornings-
I actually have to keep my foot on the gas to keep it at or above 1500 rpm or the engine dies.... then after roughly few minutes it will idle on its own but rough.
Then when the truck has been in motion for a few miles, all is normal, except for the CEL

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Being so cold I haven't gotten a chance to start replacing parts but I'm ordering everything.
More oil filters, fuel-filter, spark plugs & wires, DIS coil pack, valve-cover gaskets, brake rotors & pads, new shocks [front & rear], and bulbs.....

Do you have a part number for the intake manifold gaskets? Probably just going to order them off amazon if I could get a "laundry" list...

 

[Flash]

Do you have a part number for the intake manifold gaskets? Probably just going to order them off amazon if I could get a "laundry" list...

Try cleaning the Idle Control Valve first and checking for other vacuum leaks.

 

[Y2K Explorer]

It's been quite awhile-

Instead I bought parts:

New Idle Control Valve
BOTH Fel-Pro Upper & Lower Plastic-Manifold Gaskets
New rear PCV valve/hose/tubing assembly
New Motorcraft Platinum Spark Plugs
Both K & N fuel filter and Motorcraft fuel filter
Autozone-special DIS coil assembly
Taylor-Wires 8.2mm wires
Motorcraft Thermostat Housing assembly [$$$]
New water-pump w/ upgrade Fel-Pro gasket
New Idler/tensioner/serpentine belt
New upper & lower Radiator/heater hoses
BOTH new OEM/Ford valve cover gaskets
Obviously all new preston radiator fluid

So come to find out, who ever worked on this truck previously: they lost two of the rear wood-screw for the upper manifold section. Thankfully I had an acquaintance that had an explorer he was parting-out & gave me all the "impossible-to-find" upper manifold wood-screws.

So it starts up sorta normal during the summer & cool mornings....
But now that its cold, again, its a hit or miss- get a somewhat rough start or the choking feel where the engine dies...
So a couple of gentle taps on the accelerator [like its choking or needing fuel] or a slight "hold" to maintain an idle speed of 1100/1200 rpm < as if it doesn't want to wake-up.
It happens randomly either 15 or 45 seconds & even a minute of the pedal "maneuver"....

...........................................................................................................................................

Yes, I checked all those annoying hoses around the plastic-manifold & even use carb-cleaner to clean off all the oil residue in both sections of the plastic manifold.

Guess I have to live with it 'cause once it's "warm", now it runs like a champ