Idles Rough & Gets TOO low also Engine not starting

[Mr.Ford]

I have had this problem for a year now and it is becoming serious it caused me to lose my job because i was late. Perfect Timing

Here are my problems

1) When in reverse or drive(not moving), engine idles at 500-600rpm very unstably, sometimes it stalls out.

2) When engine is hot and has been turned on/off,on/off,on/off. It doesnt want to start. It will attempt to start but it will sputter and act as if theres no gas.(Also i noticed the fuel pump wont prime for some reason when this does happen).

3) I noticed when the idle gets low to 500-600rpm the battery meter goes to low or middle normal. This is annoying because all lights dim and the a/c doesnt kick out as strong.

4)I thought about pressure in the fuel pump and maybe it cant hold pressure. So one day it wouldnt start so i toke the gas cap of and put it back on. The fuel pump primed and the engine started but this did not solve the low idle problem and i dont think it solve the fuel pump problem either.

In the summer is when i had the problem. I cleaned the fuel injector with Gumout and it ran fine for a month. After that its never ran good since.

So far what ive done to fix the problem is

1)Replaced the fuel filter - No Change
2)Fuel Injector Cleaner - No Change
3)Cleaned IAC - No Change
4)Replaced EGR Valve Pressure Sensor - No Change

I also got some codes ran, the check engine light WAS NOT on. Im an engineering student and i know you can get codes ran even if your check engine light isnt on.

1) EGR(EVP) - Circuit Below Minimum Voltage Requirement-Sonic(PFE)

Its beginning to get expensive and im running out of solutions. I was told it could possibly be the fuel pump if it is I want to make sure because a fuel pump is not cheap or that easy to get to. Please i need help!!!

 

[dogfriend]

You may need to replace the IAC. The IAC should be able to maintain the idle speed at 750 - 830 rpm when the engine is warm and the trans is in P or N.

If the IAC valve is sticking, it may not let enough air past the throttle plate to maintain the idle. This may be worse when the engine is warm or during warm weather (related to the expansion between internal parts of the IAC).

 

[Willard]

If the fuel pump isn't priming all the time - you should replace the fuel pump relay as well.

 

[Mr.Ford]

You may need to replace the IAC. The IAC should be able to maintain the idle speed at 750 - 830 rpm when the engine is warm and the trans is in P or N.

If the IAC valve is sticking, it may not let enough air past the throttle plate to maintain the idle. This may be worse when the engine is warm or during warm weather (related to the expansion between internal parts of the IAC).

I am going to replace the iac this sat(2/29) and i am wondering is there anything that could cause the iac to malfunction. Sense the iac is controlled by air is there anything that could cause not enough air to flow if the there is some type of hose then what hose is it.

 

[dogfriend]

I am going to replace the iac this sat(2/29) and i am wondering is there anything that could cause the iac to malfunction. Sense the iac is controlled by air is there anything that could cause not enough air to flow if the there is some type of hose then what hose is it.

The IAC (idle air control) isn't controlled by air - it controls the amount of air that bypasses the closed throttle plate in the throttle body. If you remove it, you will see that it has two air ports (one in and one out) with a valve in between them. The PCM (computer) controls the IAC by sending an electrical signal using PWM (pulse width modulation) to open or close the valve.

The IAC used to be called the ISC-BPA (Idle Speed Control - Bypass Air) on older Fords, the newer terminology is IAC.

Other than the valve itself sticking, you should check that the ports on the throttle body (where it bolts on) are clear and that the electrical connections and wiring are not damaged.

 

[aldive]

Did you check the fuel pressure?

 

[Mr.Ford]

Did you check the fuel pressure?

idk exactly how but hopefully i can find a mechanic who can do it for me

 

[Mr.Ford]

The IAC (idle air control) isn't controlled by air - it controls the amount of air that bypasses the closed throttle plate in the throttle body. If you remove it, you will see that it has two air ports (one in and one out) with a valve in between them. The PCM (computer) controls the IAC by sending an electrical signal using PWM (pulse width modulation) to open or close the valve.

The IAC used to be called the ISC-BPA (Idle Speed Control - Bypass Air) on older Fords, the newer terminology is IAC.

Other than the valve itself sticking, you should check that the ports on the throttle body (where it bolts on) are clear and that the electrical connections and wiring are not damaged.

ports and holes all clear iac clean and clear. time to replace it!

 

[Firestorm]

Before you go tossing money out for a new IAC you should connect a multimeter to see if it is actually bad.

Start with KOEO, probe the harness. Should be 10.5-12.5 volts. This shows whether the IAC valve is receiving the signal from the PCM.

If it is has the proper voltage; measure the resistance across the terminals on the IAC valve. There should be 6.0-13.0 ohms. If the resistance is incorrect, replace the IAC.

Measure the resistance from either terminal to the IAC body. There should be 10,000 ohms or greater. If less, the internal circuitry is grounding against the case.

Also, as suggested by Al, you definitely need to get a fuel pressure gauge on it, this would be alot more helpful in your diagnosis. After cleaning the IAC did you disconnect the negative battery cable?

 

[Mr.Ford]

i've changed the iac engine still idle at 600rpms in drive. That is to low for me is there a way to turn the idle speed up.

 

[dogfriend]

What is the idle speed when it is in P with all electrical loads off (A/C, headlights, etc)? With a warm engine, it should idle at 750 to 830 rpm in P.

 

[Mr.Ford]

What is the idle speed when it is in P with all electrical loads off (A/C, headlights, etc)? With a warm engine, it should idle at 750 to 830 rpm in P.

the idle is at 750 exactly.

 

[dogfriend]

It is barely in spec at 750.

There is not a way to adjust idle speed. The PCM is supposed to do that using the IAC.

I would also agree with testing the fuel pressure based on your other observations.

How many miles are on this truck? Have you ever checked the compression?
When did you last replace the spark plugs and ignition wires?

 

[Mr.Ford]

It is barely in spec at 750.

There is not a way to adjust idle speed. The PCM is supposed to do that using the IAC.

I would also agree with testing the fuel pressure based on your other observations.

How many miles are on this truck? Have you ever checked the compression?
When did you last replace the spark plugs and ignition wires?

It idles at 750 in park but at 600 in R,D. My truck has 198,000 miles. when u say check the compression...what do u exactly mean? i havent replaced the spark plugs/wires yet but i do know how and i do plan to do that. Also i was wondering what could i buy and how do i measure the fuel pressure.

 

[Firestorm]

Also i was wondering what could i buy and how do i measure the fuel pressure.

You can buy a fuel pressure tester at Auto Zone. I got mine for $40, something like that.

A compression test shows how much compression there is inside of the combustion chamber.

 

[Mr.Ford]

You can buy a fuel pressure tester at Auto Zone. I got mine for $40, something like that.

A compression test shows how much compression there is inside of the combustion chamber.

I also noticed that when i dont have anything on. My battery meter is at high normal. then when i want to turn my heat and lights on it goes to low normal and the lights dim im wondering is it the battery or the alternator.

 

[dogfriend]

A compression test will tell you how well each cylinder is holding compression. An alternate test that does the same thing is called a cylinder leakdown test. The object of running either test is to tell how well the rings and valves are sealing and how well balanced the compression is compared to the other cylinders. If one or two cylinders have low compression, it can cause the engine to idle rough and uneven. If all of the cylinders have low compression, you will have less power and it may be hard to start. 198K is enough miles that you could have some mechanical issues with the engine.

To measure fuel pressure, you will need a fuel pressure gauge. There is a fitting on the fuel rail that the gauge connects to (it has a Schrader fitting, like a tire valve stem). You would typically check pressure KOEO (key on, engine off) and KOER (key on, engine running). There is also a spec for pressure after the key is off, it must maintain a pressure for a certain amount of time.

If you haven't replaced the plugs and wires for awhile, you should look at that also.

 

[Mr.Ford]

So far so good i have programed it to the comp. and now the idle is normal it is stable at 600rpms. But i went to the gas station and i didnt here the fuel pump prime and it wouldnt start it toke to more times for it to start but other then that it idles fine. I can turn all my accessories on lights, heat, defrost, and radio without the idle stalling out at 500rpms. But i do notice the battery meter drop to mid-normal but it definetly doesnt drop as low as it used to.

 

[aldive]

I also noticed that when i dont have anything on. My battery meter is at high normal. then when i want to turn my heat and lights on it goes to low normal and the lights dim im wondering is it the battery or the alternator.

Test the alternator and battery with a voltmeter.

 

[BIGHVM]

fault

I have had this problem for a year now and it is becoming serious it caused me to lose my job because i was late. Perfect Timing

Here are my problems

1) When in reverse or drive(not moving), engine idles at 500-600rpm very unstably, sometimes it stalls out.

2) When engine is hot and has been turned on/off,on/off,on/off. It doesnt want to start. It will attempt to start but it will sputter and act as if theres no gas.(Also i noticed the fuel pump wont prime for some reason when this does happen).

3) I noticed when the idle gets low to 500-600rpm the battery meter goes to low or middle normal. This is annoying because all lights dim and the a/c doesnt kick out as strong.

4)I thought about pressure in the fuel pump and maybe it cant hold pressure. So one day it wouldnt start so i toke the gas cap of and put it back on. The fuel pump primed and the engine started but this did not solve the low idle problem and i dont think it solve the fuel pump problem either.

In the summer is when i had the problem. I cleaned the fuel injector with Gumout and it ran fine for a month. After that its never ran good since.

So far what ive done to fix the problem is

1)Replaced the fuel filter - No Change
2)Fuel Injector Cleaner - No Change
3)Cleaned IAC - No Change
4)Replaced EGR Valve Pressure Sensor - No Change

I also got some codes ran, the check engine light WAS NOT on. Im an engineering student and i know you can get codes ran even if your check engine light isnt on.

1) EGR(EVP) - Circuit Below Minimum Voltage Requirement-Sonic(PFE)

Its beginning to get expensive and im running out of solutions. I was told it could possibly be the fuel pump if it is I want to make sure because a fuel pump is not cheap or that easy to get to. Please i need help!!!

First replace the inlet manifold seals- I believe this is the cause- too much air causing weak mixture and poor running. This would be the cheapest fix mate...............a good place to start!