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Ranger running rough...LOST!!!


RangerGirlwi

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Alright guys I got a Ford ranger being a stubborn jerk right now. Noticed it starting to run rough at a cold start. Only lasts for about 30 seconds, but still drives me insane. I replaced Fuel filter, cleaned MAF, and put some fuel injector cleaner in it. When you disconnect the spark plug wire from the coil pack and set it off to the side for cylinder 6 sparks shoot out of the coil pack. Not sure where it's finding a ground or why just trying to figure out where my roughness could be coming from when cold. When I change my heat settings from the floor to blowing right on me the fuel pump kicks in a lot. For some reason my truck thinks I need more gas. Not sure why or what is causing my problem, but I need answers. I did take it to a mechanic and p0171 and p0174 did pop up. When I did the work I did both codes did clear without coming back on yet. I'm not sure if the problem I'm having hasn't tripped the code yet, or if I'm having a different issue. When I first bought the truck it was having issues staying running. I'd have to start it 3 to 4 times before it would actually stay going, but there was still that chance of it dying at a stop. It actually ended up dying the day i bought it after sitting for a few minutes while I went to the bathroom. The dealers mechanic did something with either the MAF or the Idle Air Control Valve. I have recently looked for any cracked air lines, but didn't seem to find anything.

So to put it short any of you have any ideas what my malfunction could be? I love my little ranger, but I'm getting to the point of selling it if I can't fix my problem.
 


Spott

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We're going to need to know what engine your truck has, before we can offer specific advice.
 

RonD

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Yes, what engine?

I assume a V6 since you got Bank 1 and 2 lean codes

The Fuel pump should come on when you turn on the key, then go off after 2 seconds, listen for this happening.
And then turn key off and then on again, listen for fuel pump, 2 seconds then off.
Repeat 3 times, this will build up fuel pressure.

There is no fuel pressure sensor, the fuel pump should be on all the time when engine RPMs are above 500, it doesn't cycle off and on when engine is running, the fact it only runs for 2 seconds with engine off is a safety feature, in case of a broken fuel line(Accident) engine would stall and fuel pump would not continue to pump gas out of the broken line.

Changing heating vents shouldn't effect fuel pump.

Fuel pump is controlled by the computer via the Fuel Pump Relay, it is in the Power Box in the engine compartment.
With relay pulled out and key off there should be one 12volt socket active, with key on there should be two 12v sockets, if the key on 12v is only 8volts then you have a corroded connector most likely and relay is not being held closed
 
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RangerGirlwi

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It's got the 4.0, but originally should have the 3.0 which I know really shouldn't matter. I'm not really believing the dealer when he said the original owner took it to a ford dealership to have the motor swap. I could be wrong though, but there are just to many signs showing this wasn't the case.
 

Andy D

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This is a wild &$$ guess. It is something in the cold start system. The brain reads the resistance of the coolant temp sensor. Yours maybe on the way out or there may be a dirty connection. . I dont usually recommend swapping out a part without testing it , but CTSs are cheap. The test with rising temps and specific ohm values is a PITA to perform accurately
 

RangerGirlwi

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This is a wild &$$ guess. It is something in the cold start system. The brain reads the resistance of the coolant temp sensor. Yours maybe on the way out or there may be a dirty connection. . I dont usually recommend swapping out a part without testing it , but CTSs are cheap. The test with rising temps and specific ohm values is a PITA to perform accurately

I am almost willing to bet that this is not my issue. Considering it really isn't acting remotely close to it being the CTS. Thanks for trying to take a guess though.
 

knucksfirst

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How does the EGR valve look? Ive had 4 rangers and every single one of them needed the EGR replaced when I bought them.
 

RonD

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Yes that 3.0l to 4.0l "dealer swap" reads like a tall tale to me as well, lol.
8th digit in the VIN will tell you what it "came with"
U = 3.0l Gas Only
V = 3.0l Flex Fuel
X = 4.0l OHV

4.0l SOHC wasn't offered until 2001 models

I guess the best thing would be to look at how a normal cold start should go.
Key on, fuel pump runs for 2 seconds
Start up, computer opens IAC valve all the way and RPMs should go up to 1,500+ then drop to cold idle level of about 1,000rpms, on very cold days it might be 1,200, but usually no lower than 1,000
Computer is also running "choke mode", so besides the higher idle it will be running rich air/fuel mix and advanced spark timing, this is based on one sensor(see ECT below).
Over the next 5 mins engine RPMs should steadily drop to warm engine idle of 700-750(manual), 800-850(automatic)

O2 sensors are not used until engine warms up, computer is running air/fuel mix from pre-set tables based on info from MAF, TPS, and IAT(intake air temp) .
O2 sensor won't work until they reach 650degF, they are heated but still require hot exhaust for a few minutes to get above that temp.

Computer bases cold/warm on one sensor, the ECT(engine coolant temp) sensor, this is a TWO wire SENSOR that looks similar to the ONE wire temp SENDER used for the dash board gauge.
The ECT sensors rarely fail, not never but rarely, wiring can get corroded though, always good to check connectors.
Computer sends ETC sensor 5volts, if it gets back 3+ volts engine is cold, under 1volt engine is warm, so a corroded wire will lower the voltage making computer think the engine is warmer than it is, so cold engine would struggle with the leaner air/fuel mix.


Simple test for vacuum leak is, with engine warmed up, unplug IAC valve, idle should drop to around 500rpm or engine may even stall, either is fine, it means all the air is coming in via IAC valve or throttle plate.
If idle stays up then start unplugging vacuum lines from intake manifold and put your finger over the hole, when idle drops you found the line with the leak.
 
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