Very rough idle
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Joined: Apr 2003
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Very rough idle
'92 Ford 150 5.0 liter, dual tank 100K miles
This is long winded please be patient...
Background:
I am an amateur at this stuff, but too cheap to take it to the shop. This is my son's truck. He calls me from the high school parking lot and says the truck won't start. I go to check and the engine will turn over but not start. First thought is bad gas. So I tried both tanks and put some STP gas treatment in the front tank (I know STP is probably crap).
Went bought a Haynes book.
Pull codes KOEO. Code 542 Fule Pump circuit open. PCM to GND.
Troubleshooting route 1: Go gas?
Checked that both fuel pumps spin up. Next I changed the fuel filter (pain in the A**) after figuring out that I needed a special tool. Also depressed the schrader valve to see if there was any pressure. Haven't got a fuel pressure valve on it yet.
Troubleshooting route 2: Get air?
Checked air filter. Clean.
This is long winded please be patient...
Background:
I am an amateur at this stuff, but too cheap to take it to the shop. This is my son's truck. He calls me from the high school parking lot and says the truck won't start. I go to check and the engine will turn over but not start. First thought is bad gas. So I tried both tanks and put some STP gas treatment in the front tank (I know STP is probably crap).
Went bought a Haynes book.
Pull codes KOEO. Code 542 Fule Pump circuit open. PCM to GND.
Troubleshooting route 1: Go gas?
Checked that both fuel pumps spin up. Next I changed the fuel filter (pain in the A**) after figuring out that I needed a special tool. Also depressed the schrader valve to see if there was any pressure. Haven't got a fuel pressure valve on it yet.
Troubleshooting route 2: Get air?
Checked air filter. Clean.
Last edited by craigdallen; Apr 28, 2003 at 11:52 PM.
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Very rough idle
Troubleshooting route 3: Got Spark?
Check plug wires. Go bad corrosion on coil to plug wire. Buy new plug wires and coil. Check with spark tester. Good spark.
Next check plugs. They are fuel fouled. Black shinny and smells like gas. Change plugs (Motorcraft plugs).
Truck now starts, but idle rough and exhaust is black. Figure I might have a bad fuel presure valve resulting is high fuel pressure. Still need to buy a pressure gauge.
Checked battery and cables. Battery is shot. Replaced it. Negative battery cable doesn't look good. Replace it.
Pull KOEO codes again. 542 is gone (due to battery disconnect). Now have 327 EGR circuit low voltage.
Get new EGR Valve Position sensor. Start engine, but still idling very rough. Black smoke gone. Code 327 gone.
Check EGR valve with hand vacuum pump while idling. Pull vacuum on valve and idle goes from bad to worse and dies. Book says this shows that the valve is working. Also vacuum will stay and not bleed off on valve. Probably good valve.
What next? MAP sensor?, fuel pressure?, vacuum leak?
How do you check for vacuum leak?
thought? comments?
Check plug wires. Go bad corrosion on coil to plug wire. Buy new plug wires and coil. Check with spark tester. Good spark.
Next check plugs. They are fuel fouled. Black shinny and smells like gas. Change plugs (Motorcraft plugs).
Truck now starts, but idle rough and exhaust is black. Figure I might have a bad fuel presure valve resulting is high fuel pressure. Still need to buy a pressure gauge.
Checked battery and cables. Battery is shot. Replaced it. Negative battery cable doesn't look good. Replace it.
Pull KOEO codes again. 542 is gone (due to battery disconnect). Now have 327 EGR circuit low voltage.
Get new EGR Valve Position sensor. Start engine, but still idling very rough. Black smoke gone. Code 327 gone.
Check EGR valve with hand vacuum pump while idling. Pull vacuum on valve and idle goes from bad to worse and dies. Book says this shows that the valve is working. Also vacuum will stay and not bleed off on valve. Probably good valve.
What next? MAP sensor?, fuel pressure?, vacuum leak?
How do you check for vacuum leak?
thought? comments?
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Very rough idle
Originally posted by craigdallen
What next? ... How do you check for vacuum leak?
What next? ... How do you check for vacuum leak?
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Very rough idle
Continued..
Started checking for vacuum leaks. Used a hand pump and pulled a vacuum through each hose from the manifold connections.
Small leak in hose going to A/C. Fuel Pressure Valve line good. Major leak in line that goes to EVR (EGR Valve Regulator).
Removed EVR and pulled vacuum on lower connector (vacuum input). Major leak. My understanding is that this should hold.
This is a special order or dealer part..
Plugged hose going to EVR. Still idling very low and rough.
Removed MAP sensor and had auto parts store check. Check good.
Next, get in new EVR and check again.
Still need to get Fuel pressure gauge.
I've read that the Fuel pressure regulator is a PITA to change out. It is upside down and in the very back. I think you need to make your own special Allen wrench..
thoughts??
Started checking for vacuum leaks. Used a hand pump and pulled a vacuum through each hose from the manifold connections.
Small leak in hose going to A/C. Fuel Pressure Valve line good. Major leak in line that goes to EVR (EGR Valve Regulator).
Removed EVR and pulled vacuum on lower connector (vacuum input). Major leak. My understanding is that this should hold.
This is a special order or dealer part..
Plugged hose going to EVR. Still idling very low and rough.
Removed MAP sensor and had auto parts store check. Check good.
Next, get in new EVR and check again.
Still need to get Fuel pressure gauge.
I've read that the Fuel pressure regulator is a PITA to change out. It is upside down and in the very back. I think you need to make your own special Allen wrench..
thoughts??
Senior User
Joined: Jan 2003
Posts: 383
Likes: 1
From: Newport News USA
Very rough idle
It will make the job a lot easier replacing the FPR if you first move the coil bracket holding the TAD,TAB, and EGR solenoid from it's perch. With that outta the way, life is a hell of a lot easier, and my arms didn't hurt as much from stretching back there. I'm 6'2" with long arms and I was still leaning completely over the truck. I can't imagine how painful it is for someone shorter than myself.
Luke
Luke
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
Very rough idle
It might be easier if you pull the fuel rail off the injectors so you can work with it...
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Thread Starter
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New User
Joined: Apr 2003
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Very rough idle
Do you think it could be the idle air control (IAC)?
How about a blown gasket in the throttle body?
Several posts talk about cleaning the throttle body cavity. How difficult is this?
Thanks,
Craig
How about a blown gasket in the throttle body?
Several posts talk about cleaning the throttle body cavity. How difficult is this?
Thanks,
Craig
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Thread Starter
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Very rough idle
Pulled the IAC valve. Very black inside with carbon buildup.
Also looked in the intake manifold, also very black with carbon.
What amount of carbon buildup is OK?
Cleaned the IAC with carb cleaner and replaced.
Problem is now I have a no start condition. Pulled the plugs and they are fuel fouled again (brand new plugs)
Also looked in the intake manifold, also very black with carbon.
What amount of carbon buildup is OK?
Cleaned the IAC with carb cleaner and replaced.
Problem is now I have a no start condition. Pulled the plugs and they are fuel fouled again (brand new plugs)
New User
Joined: May 2003
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Very rough idle
Hey,
I just had the same problem with my truck, we thought it was all of that stuff too. Ive got a 1989 Ford F-150 with a 5.0, come to find out on these years there was a recall on the ignition module. I replaced mine and everything is working great again. This should be on the bottom of the distributer under the cap. Take this part off and take it too a parts store and have it tested.
I may be 16 but I just fixed my truck and it just turned 212000 miles and im the third owner.
Thanx
Let me know if it helps
toolman086(No Email Addresses In Posts!)
I just had the same problem with my truck, we thought it was all of that stuff too. Ive got a 1989 Ford F-150 with a 5.0, come to find out on these years there was a recall on the ignition module. I replaced mine and everything is working great again. This should be on the bottom of the distributer under the cap. Take this part off and take it too a parts store and have it tested.
I may be 16 but I just fixed my truck and it just turned 212000 miles and im the third owner.
Thanx
Let me know if it helps
toolman086(No Email Addresses In Posts!)
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New User
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Very rough idle
Fixed it !!!
Fuel pressure regulator
Fuel pressure was at 80psi !!
after repair running at 40 psi.
The thing sure was hard to replace.
Also changed out the IAC (throttle bypass) in the process and new plugs.
Runs great now.
Next problem, won't pass emmisions test. HC too high..
I had it tested next day after repair. Computer had been reset the night before.
Suggestions ??
Fuel pressure regulator
Fuel pressure was at 80psi !!
after repair running at 40 psi.
The thing sure was hard to replace.
Also changed out the IAC (throttle bypass) in the process and new plugs.
Runs great now.
Next problem, won't pass emmisions test. HC too high..
I had it tested next day after repair. Computer had been reset the night before.
Suggestions ??
Posting Guru
Joined: Jul 2002
Posts: 2,205
Likes: 1
From: Vancouver WA
Very rough idle
How long had the truck run after resetting the computer before it was taken to the emission test. Maybe the computer hadn't had long enough to re-learn everything.
Here are 2 sites that have good info about emission readings.
Planet Equipment
Interro
Here are 2 sites that have good info about emission readings.
Planet Equipment
Interro
Thread Starter
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New User
Joined: Apr 2003
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Very rough idle
Filled up with a tank of premium gas and added a bottle of Slick 50 fuel system cleaner. Ran the truck for awhile. Took it back to the testing center while the engine was nice and warm.
Passed!!
Passed!!
Posting Guru
Joined: May 2003
Posts: 1,388
Likes: 0
From: Live Oak, FL
Very rough idle
You say you are an amateur at this? Sounds like pretty good troubleshooting to me. If you had just bought the fuel pressure gauge a little sooner .........
Well anyway, you are invited to move next door to me anytime you want. Matter of fact, why don't all you guys just move to Live Oak, FL.
Well anyway, you are invited to move next door to me anytime you want. Matter of fact, why don't all you guys just move to Live Oak, FL.
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