idle problems
10-16-2008, 01:20 AM
#1
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idle problems
Ok, I've got an 87 f150 with the 4.9 engine.
I'm having occasional problems with a rough idle, and sometimes the idle isn't rough, it will just stall when I put it in gear or if I just let it idle on it's own it will run ok, then for no apparent reason, just stall after a few seconds.
sometimes upon restart, it will run smoothly, sometimes it will be very rough for a short time, then go away.
Now other times, and probably more times than not I would say, it will run just fine with no rough idle or stalling issues.
I've changed the air filter, the plugs, the wires, put on a new IAC, and a new TPS.
after changing the IAC, it seemed to be ok and I thought I had it fixed, but after a few days of running good, the problems came back.
Same story after changing the Throttle position sensor. It ran noticeably better after putting a new one on, but now after a week or so the same problems are coming back.
I don't feel I can trust the truck to go any distance for fear of being stranded if it stalls and won't start back up at all one of these times.
What the heck should I look at next?
Let me add that when Im not having the idle problem, the engine runs strong and smooth. no signs of timing being off etc.
Any help would be appreciated. I'm a carpenter/contractor, not a mechanic ( I have a van I use mostly for everyday use).
I'm having occasional problems with a rough idle, and sometimes the idle isn't rough, it will just stall when I put it in gear or if I just let it idle on it's own it will run ok, then for no apparent reason, just stall after a few seconds.
sometimes upon restart, it will run smoothly, sometimes it will be very rough for a short time, then go away.
Now other times, and probably more times than not I would say, it will run just fine with no rough idle or stalling issues.
I've changed the air filter, the plugs, the wires, put on a new IAC, and a new TPS.
after changing the IAC, it seemed to be ok and I thought I had it fixed, but after a few days of running good, the problems came back.
Same story after changing the Throttle position sensor. It ran noticeably better after putting a new one on, but now after a week or so the same problems are coming back.
I don't feel I can trust the truck to go any distance for fear of being stranded if it stalls and won't start back up at all one of these times.
What the heck should I look at next?
Let me add that when Im not having the idle problem, the engine runs strong and smooth. no signs of timing being off etc.
Any help would be appreciated. I'm a carpenter/contractor, not a mechanic ( I have a van I use mostly for everyday use).
10-16-2008, 12:03 PM
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check the codes in your computer its the easiest way if you have a test light connect one side of the the test light to the sti port then connect the other to the positive side of the battery, then take another wire between like a 6 and 10 wire run it from the negative side of the battery to the sto port get all the wires ran then turn the key for the ignition to where the power comes on and the count the number of blinks in the test light you will have to get a haynes manual for the truck its more detailed and will explain easier for you to check the codes on your computer i would check the codes first this is the cheap easy way to do it yourself rather than pay a fortune to have someone else do it
10-17-2008, 07:14 AM
#4
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Listen to Sean, he is the resident expert on that vintage truck. Before his time and the OBD II stuff it was EEC stuff. Infant era for the computor and its testing. Your symptoms sound like an EGR problem. Theory, exhaust gas recycled into intake at above closed throttle operation. If the valve would stick the engine would be either be rough at idle or stall. Sometimes the sensor on top of it (EVP) would be out of specs and mislead the computor and cause the same.
10-17-2008, 08:13 PM
#6
Recheck your connections and be very certain they are making contact. You may not have them inserted deep enough. You need to be absolutely sure the computer won't go into diagnostic mode because if it won't, the computer is fried or you have a broken wire.
10-18-2008, 01:01 PM
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I went to the link above and tried to pull some codes.
This is what I came up with for KOEO codes (engine off)
22,15,13,35,13,3
I did it twice and came up with the same sequence both times.
the last code never had a second number with it...unless I misinterpreted the needle on my meter.
as far as continuous codes, there never were any codes displayed after a 6 to 9 second delay following the KOEO codes.
Any idea where to begin based upon that? I needed to get longer jumper wires to run my meter back to the cab to do the engine running test. I figured the other test gave me enough to get started.
then the napa store didnt have a manual to look up the codes and someone has checked out the manual I need from the library.
the closest i found was chilton for 83-90 ford ranger and bronco. I looked in there figuring computer codes were probably similar, but found a few things that didn't seem to line up (like no code 35 listed for a KOEO test), so I gave up on that too. That and the codes that did seem to make sense as far as symptoms were full of abbreviations that I didnt know what they meant. some of them I figured out, but some I coudlnt find. ( like "BP sensor" and "ECA problems")
the truck still has the same problems when I started it this morning.
Started easily with a turn of the key-didnt have to touch the gas pedal.
idle speed increased, then eventually, gradually eased back down. I sat and waited a minute and thought everything was ok....then put it in gear and it stalled immediately.
restarted ok and ran fine then.
after going to the library. same thing. stalled, restarted it..revved the engine a little this time...then was able to drive away with no problems.
at this point its just an annoyance (that Im sure is reducing the life of my starter with all the extra starts), but I don't want stranded somewhere someday. thanks for any help
This is what I came up with for KOEO codes (engine off)
22,15,13,35,13,3
I did it twice and came up with the same sequence both times.
the last code never had a second number with it...unless I misinterpreted the needle on my meter.
as far as continuous codes, there never were any codes displayed after a 6 to 9 second delay following the KOEO codes.
Any idea where to begin based upon that? I needed to get longer jumper wires to run my meter back to the cab to do the engine running test. I figured the other test gave me enough to get started.
then the napa store didnt have a manual to look up the codes and someone has checked out the manual I need from the library.
the closest i found was chilton for 83-90 ford ranger and bronco. I looked in there figuring computer codes were probably similar, but found a few things that didn't seem to line up (like no code 35 listed for a KOEO test), so I gave up on that too. That and the codes that did seem to make sense as far as symptoms were full of abbreviations that I didnt know what they meant. some of them I figured out, but some I coudlnt find. ( like "BP sensor" and "ECA problems")
the truck still has the same problems when I started it this morning.
Started easily with a turn of the key-didnt have to touch the gas pedal.
idle speed increased, then eventually, gradually eased back down. I sat and waited a minute and thought everything was ok....then put it in gear and it stalled immediately.
restarted ok and ran fine then.
after going to the library. same thing. stalled, restarted it..revved the engine a little this time...then was able to drive away with no problems.
at this point its just an annoyance (that Im sure is reducing the life of my starter with all the extra starts), but I don't want stranded somewhere someday. thanks for any help
Last edited by trptman; 10-18-2008 at 01:05 PM.
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10-18-2008, 01:35 PM
#8
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This doesn't make sense - 13 would be an engine running code, and there is no 3...
Are you sure that you didn't get 22 (MAP sensor)
A 1 (separator between code types)
And then 51 (ECT circuit open) and 33 (EGR movement not detected) - my truck displays the cm codes twice too.
This makes a little more sense to me, but without seeing the sequence and timing, it's hard to tell.
If my guess is closer, there would be a longer pause before and after the 1
The 22 for the MAP sensor could be a vacuum leak on that line - I'd check that first (as well as your other vacuum lines/fittings). I'd check that before spending $100 on a BP/MAP sensor.
The Engine Coolant Temperature sensor is fairly common, and you can check it with a voltmeter. If that's gone, they don't cost much (and are easy to swap).
The EGR code may be due to a vacuum leak as well. I'd recommend testing your way through the other two before diving into the EGR thing. It might be caused by the other codes, or you might find the simple fix along the way. See my thread titled EGR code 33 if you want to see where this one could take you...
Are you sure that you didn't get 22 (MAP sensor)
A 1 (separator between code types)
And then 51 (ECT circuit open) and 33 (EGR movement not detected) - my truck displays the cm codes twice too.
This makes a little more sense to me, but without seeing the sequence and timing, it's hard to tell.
If my guess is closer, there would be a longer pause before and after the 1
The 22 for the MAP sensor could be a vacuum leak on that line - I'd check that first (as well as your other vacuum lines/fittings). I'd check that before spending $100 on a BP/MAP sensor.
The Engine Coolant Temperature sensor is fairly common, and you can check it with a voltmeter. If that's gone, they don't cost much (and are easy to swap).
The EGR code may be due to a vacuum leak as well. I'd recommend testing your way through the other two before diving into the EGR thing. It might be caused by the other codes, or you might find the simple fix along the way. See my thread titled EGR code 33 if you want to see where this one could take you...
Last edited by aliens8mycow; 10-18-2008 at 01:39 PM.
10-18-2008, 09:25 PM
#9
Yes, seems like 22, 1, 51, 33, 51, 33. Recheck to make sure. ECT= engine coolant temperature sensor, check it or change it and check the wiring. This sensor is the one for the computer near the thermostat. Check for vacuum leaks to the MAP and EGR. With more than one vacuum operated sensor malfunctioning it looks to be vacuum problems. The plastic lines tend to get brittle and crack.
10-18-2008, 10:23 PM
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I'll look for vacuum leaks and get back to you. may just go ahead and change the coolant sensor also. because of the age of the truck and if its an inexpensive sensor, it makes sense to me to just change it and not have to worry about it.
thanks
thanks
