Sensor Blues
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Sensor Blues
Hello everyone. I was outta the ford truck business for awhile but im back now. Got an 88 f-150 that i bought a couple weeks ago that sat for about a year. Im having trouble geting it to idle right. seems to be getting way to much gas. I was talking to a guy about it and he pointed me to the EGR. I changed it out, and it idled good. For awhile. the first time i started it it worked well, idled good. After the truck warmed up good, it stopped idling down. would idle at about 2400 rmp's. i shut it off, and then started it about 20 minutes later. back to sqare one. wont idle for anything. so the question is, bad EGR? i did put a used one in it. and what about the EGR contro; colinoid? where exectly on the truck is this located and would that cause it to idle poorly like this? sorry for being long winded. hope i explained well enought.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Might be the IAC or might be a vacuum leak. But first start by checking it for codes, running the self test.
and what about the EGR contro; colinoid?
EVR – EGR Vacuum Regulator, allows engine vac to open valve as directed by computer.
EVP – EGR Valve Position sensor, allows computer to monitor egr valves position.
Yes a partially hung open egr valve can cause a rough idle, all the way open would/should stall the motor out. Start with the computer, see what it knows about any problems before replacing any more parts.
How to run a self test> Ford Fuel Injection » How To Run a Self-Test
Link is from here, plenty more helpful info Ford Fuel Injection
See what that gets ya then come back with results and or if you have more questions.
and what about the EGR contro; colinoid?
EVR – EGR Vacuum Regulator, allows engine vac to open valve as directed by computer.
EVP – EGR Valve Position sensor, allows computer to monitor egr valves position.
Yes a partially hung open egr valve can cause a rough idle, all the way open would/should stall the motor out. Start with the computer, see what it knows about any problems before replacing any more parts.
How to run a self test> Ford Fuel Injection » How To Run a Self-Test
Link is from here, plenty more helpful info Ford Fuel Injection
See what that gets ya then come back with results and or if you have more questions.
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Ran the self test, here goes.
In KOEO i got code 23: Closed throttle TPS voltage higher or lower than expected.
In the CM category i got:
18: IDM circuit failure or SPOUT circuit grounded.
34: PFE or EVP circuit has intermittently failed above the closed limit of 0.67 volts.
53: TPS circuit has intermittently failed above maximum 4.5 volts.
63: TPS circuit has intermittently failed below minimum 0.6 volts.
96: Fuel pump secondary circuit failure. The EEC did not sense battery voltage on the Fuel Pump Monitor circuit.
I may also note that i had no vacuum at the EGR at an idle or when revving.
So. Any ideas?
In KOEO i got code 23: Closed throttle TPS voltage higher or lower than expected.
In the CM category i got:
18: IDM circuit failure or SPOUT circuit grounded.
34: PFE or EVP circuit has intermittently failed above the closed limit of 0.67 volts.
53: TPS circuit has intermittently failed above maximum 4.5 volts.
63: TPS circuit has intermittently failed below minimum 0.6 volts.
96: Fuel pump secondary circuit failure. The EEC did not sense battery voltage on the Fuel Pump Monitor circuit.
I may also note that i had no vacuum at the EGR at an idle or when revving.
So. Any ideas?
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
You didn't state what motor it has.
Your codes tend to suggest a ground problem.
As for your KOEO 23 you can test the TPS but again might all be result of a bad ground at some point causing it to fluctuate/fail.
Turn ignition on, engine off, probe ground and signal wire on backside of electrical connector. Sensor should read .50 to 1.0 volts at idle, 4.0 to 5.0 volts rotated full open.
Reference voltage should be approx 5.0 volts.
Disconnect harness connector, check resistance of the potentiometer within TPS from ground and tps signal wires.
Throttle valve fully closed the tps should read between 3.0 and 4.0K ohms.
Open the throttle slowly while watching meter reading, full open 350 ohms and should exhibit a smooth change in resistance as it travels from fully closed to fully open.
Make sure the bat grounds, both connections are clean and tight, should be a smaller gauge "black - light green" wire connected with the large ground cable at the battery.
Your codes tend to suggest a ground problem.
As for your KOEO 23 you can test the TPS but again might all be result of a bad ground at some point causing it to fluctuate/fail.
Turn ignition on, engine off, probe ground and signal wire on backside of electrical connector. Sensor should read .50 to 1.0 volts at idle, 4.0 to 5.0 volts rotated full open.
Reference voltage should be approx 5.0 volts.
Disconnect harness connector, check resistance of the potentiometer within TPS from ground and tps signal wires.
Throttle valve fully closed the tps should read between 3.0 and 4.0K ohms.
Open the throttle slowly while watching meter reading, full open 350 ohms and should exhibit a smooth change in resistance as it travels from fully closed to fully open.
Make sure the bat grounds, both connections are clean and tight, should be a smaller gauge "black - light green" wire connected with the large ground cable at the battery.
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So i did some testing. Couldn't make much sense of the numbers but i thought by the looks of it that i needed a new TPS, so i replaced it and it idles now. But sadly thats the least of my worries now. Truck has a real bad miss and i tracked it down to the number one hole, tested the compression and walla. 60 pounds. But thats a new thread.
Thanks for the help!
Thanks for the help!
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rdgerunrpa
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