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Truck dies when stopped for too long


Ogonz9494

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92 l4 ranger. I drove it the other morning and when I stopped at whataburger to get some food at the drive through it started idleing bad. Since then the truck is super hard to start I have to keep pressing the gas and once the truck is running it's fine but when I'm in neutral at a stop it starts idling bad and if I'm sitting still for too long, when I take off it' doesn't want to and keep jumping forward. I recently clean the throttle body and maf and put new air filter. The only thing I see going on is my fuel pump failing. Anyone's input or advice would be helpful.
 


RonD

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Wouldn't be fuel pump, you notice that at highway speed when fuel demand is high.

Reads like IAC(idle air control) valve isn't working like it should, or you have a vacuum leak.

When you start engine cold idle should go up to 1,100 or higher RPMs and stay there, that's the IAC valve opening to let in more air.
Then as engine warms up idle will go down, IAC valve closing bit by bit over next 5 to 10 minutes.

Once engine is warmed up and idling, unplug the wires on the IAC Valve, idle should drop to 500 or engine may stall, either is good it means no vacuum leak, idle 700 or higher means vacuum leak.

The computer controls the IAC Valve

On a fuel injected engine there is no "gas" pedal, like on a carb engine, when you press down on that pedal now you are letting in more air, not adding gas, so it is an "air" pedal, lol.
Any way your description of having to press down on the "gas" pedal when starting could mean IAC Valve is not opening all the way for starting.
When you turn on the key the computer opens IAC Valve all the way to get in enough air to start engine, if that doesn't happen then using the gas pedal would do the same thing.

You can remove the IAC Valve and turn on the key, you should see it open all the way, then unplug it's wires and it should close all the way, repeat a few times to make sure it isn't sticking.


Long shot is electrical system, do the head lights dim at idle?
If so then alternator could be failing and drawing voltage down at idle, which reduces spark voltage so misfires and stalling when idling, but you should begin to notice slow starter motor cranking after a few days of that.
 
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Ogonz9494

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Thanks man!! Will look into all of this tomorrow and will get back to you. I will say that on the highway in 4th going about 65, if I keep pushing to go faster by pressing the peddle the truck starts to slow down so I have to down shift to third to get some power and then back to 4th. Ether way I've found the pump for cheap so I will replace it anyways. Thanks again.
 

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What do the plug tips look like? In general, how old are the ignition parts? Stop throwing parts at it. 24 yr old Fords are prone to anything and everything. With an older car, the mantra is to do the cheap easy stuff first. The more stuff you replace , the greater the chance that something will break. I'm not an I 4 guy. But if it has a distributor cap and rotor, I would remove it and check the contacts. I scrape the carbon off the contacts with a jack knife. Always get a cap with brass contacts, not aluminum. and just as important, wipe the crud off the inside of the cap. Carbon tracking can do what you're describing too. I use alcohol or acetone. :D
 

Pauls 4x4

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Ether way I've found the pump for cheap so I will replace it anyways. Thanks again.
NOOOO!!!:badidea:

Don't buy anything but OEM fuel pumps unless they stop making 'em, you're poor, or you're not stock. If you really think it's a pump rent the vato-zone pressure tester for free.

But you put in a cheap fuel pump, you'll just ADD fuel pump to the problem list.

Now, my 2 cents... is disconnect the MAF and see if it runs better. That seems to have poked the bear...

I'd check also check the common criminals like the TPS voltage, CTS voltage, etc. and do a solid run down on ignition.
 

Ogonz9494

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Cleaned the IAC this morning and put it back on and same problem. Didn't have time to keep working on it bc I had work so I will check if it even works first.

The plugs are two months old, has new ignition coils, new Ignition control module (old one tested bad) and new starter solenoid.

I'm about to go after it again and see what happens. +1 on the pressure tester, I will use that before I purchase a new pump. I should know better to get oem parts I'm a BMW enthusiast and on my 95 530i all I use and buy is oem or oem supplier so I will definitely take the advice on purchasing an oem pump if that ends up being he issue.

Wish me luck!!
 

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Well, that didn't work. Let's try something else!
Is it an automatic? Could be the torque converter failing. I had ano oldsmobile that did almost exactly what you describe. It would die at stops after trying to continue moving. Swapping tc's fixed it. Just a thought. Good luck!
 

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Put a can of SeaFoam in the gas tank, that will clean injector tips.

As injector tips get dirty, they drip instead of spray, so at idle(lower air flow) this can cause a problem.

The reason all gas engines need to be "choked" when cold is because liquid gasoline doesn't burn, only gas vapor burns.
The colder the temp the less gasoline vapor there will be, the "Choke Plate"(carburetor) caused more gasoline to be sucked into the engine so so there would be more vapor by default because there was more gasoline.

Fuel injection can't use a choke plate but computer does "spray" in more fuel on cold start for the same reason, but if it was dripping not spraying then less vapor is available.
 

Ogonz9494

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So I bought a new IAC valve and nothings changed... also disconnected the maf and still the same....
Don't want to keep buying parts and throwing them on as advices above, the truck does only have 120k miles though.
Will try the sea foam next as it's an easy thing to do.

Once again truck starts, has high idle then just turns off. I press on the gas peddle to keep the idles up and truck stays running until I let go and the it dies.
 

Ogonz9494

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It is a 5sp
 

Pauls 4x4

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If the pedal keeps it going than it's the extra air. You're probably too rich. Is it just not running now or still when warm? If it's to rich when hot and maf isn't helping (although I think air temp is separate on these) then coolant temp sensor needs a multimeter shoved in it. If the truck thinks it's colder than it is that would be to rich. Other is the 02 sensor. But definitely check the sensors not just throw them. Reference voltages don't get fixed by new parts
 

Ogonz9494

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Update: I rented out a fuel pressure tester and it read 0psi. So the problem was the fuel pump. I purchased a new one and just got done installing it and now it starts right up but it has a rough idle now.

Only other thing I replaced was the IAC valve. Anyone have any idea of what the cause of the rough idle is now??

Maf and throttle body were cleaned, new fuel pump and fuel filter, new air filter, new IAC valve.
 

Pauls 4x4

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Did you yank the bat? It might have to relearn a tad.
Also, when mixed wrong plugs foul.

Assuming its not that easy... I'd check the fuel pressure again. Fpr and other bits might be leaking. At a true 0 it wouldn't of ran at all, so I'm dubious of the pump being the full fix. I think it wasn't holding pressure and leaking down. Now with full pressure its probably pushing gas through a seal somewhere.

You've gotten most the rest of it.

It smell?
 

Ogonz9494

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Alright I forgot to get back on here and post the outcome.

Drove the truck one morning on the freeway and all of a sudden a lack of power happened, slowing the truck down. Made it home fine but then truck didn't want to start again after a let it sit. I came back to it after a while and got it to start by pressing the gas pedal but truck just didn't run smooth, I would be at a stop and got a real rough idle and would have to give it steady gas to keep her on. I would take at least 3 cranks to strart her up.

First thing I did was clean the maf, throttle body, IAC valve, and put a new air filter in. Nothing changed, so I decided to buy a new IAC valve and the truck still took 3 cranks to start and it wouldn't stay on at all.

From the beginning I thought it had something to do with the pump so I decided to rent out a pressure tester, plugged it all up and read 0psi so the pump was bad. I purchased a new one and installed it. At the beginning it started but ran real rough but truck finally stayed on on its own. I thought something was still wrong somewhere so I didn't drive it yet the first two days and then finally I drove it and wow what a difference!! The truck needed a new fuel pump for a while, I got a good amount of power I didn't have and the truck just runs right. I guess I just needed to drive it and let everything work together.

I still get a rough idle when the truck sits on for too long like at a light and you definitely smell it but other than that this little 92 i4 got its power back that it was lacking. Put a new o2 sensor in to see it that was it but still idles rough when sitting at a stop for too long.
 

Rangerbro2002

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I had this problem with my ranger a year ago, had a rough idle but drove fine after take off. Turned out the IAT sensor was dirty and my maf was dirty. I cleaned them, and i noticed improvement but ended up replacing the IAT cause it was cheap which really had the most affect for some reason... Got a fairly smooth idle after that. Did plugs and wires after that to find Previous owner really let them go... tips were pretty much gone... after all 3 of those its very smooth. Ive come to find idle problems can be multiple issues combined.
 

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