High idle and no start after engine warms up... help!!
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2000 5.4L 4wd High idle and no start after engine warms up... help!!
Going to try this again. See if I can make it make sense.
Early January I replaced the intake manifold because the old one was leaking coolant into the spark plug wells. The truck ran fine prior to replacing the intake manifold, and that a mystery to me because the EGR valve was not working properly, it was open all the time. Plus the EGR tube was not connected to the exhaust manifold due to the nut being eroded. More on that below.
After replacing the intake manifold the truck ran fine for a couple of days. I took it to get gas and after filling up I went to start it and it acted like it was going to fire and then didn't. I got it started by putting the gas pedal all the way to the floor. It was at that point that the engine ran at a high idle 1600 rpms. On the way home I noticed my coolant temperature sensor was not working. This was after dark so I got it home and left it until the next day.
The next day I started going through the system. I started the truck and first checked the vacuum at the hose that connects to the EGR valve. I had 3 Hg vacuum there. However, there was no difference in the rpms with the vacuum hose removed. I pulled the EGR valve and blew air through it with my compressor nozzle. Air passed through so I knew it was bad. Ordered a new one along with a new EGR tube and installed them a couple of days later. Started the truck and still had high idle.
Over the next couple of days I found the two vacuum control valves near the battery were not working and when tested they were 20+ ohms over their rated resistance (66 on one and 63 on the other). I ended up to get a new IAC valve, both vacuum control valves near the battery, and a new TPS. (NOTE: Before and after replacing these items I had no codes.) After replacing those items I still had the same high idle issue. When I replaced the intake manifold I did not clean the throttle body, so I took it off and cleaned it thoroughly. After putting the throttle body back on and reconnecting everything I started the truck and the idle (cold engine) was at 1100. As the engine warmed the idle increased to just over 1400 rpms. I pulled the vacuum line from the EGR and, as before, there was no difference. I rechecked the vacuum at the EGR hose and had nothing. So I tested the EGR vacuum control solenoid. It did not "click" when I provided power, though it did spark at the pin when I provided power. Also, I could pass air through the active port. I ordered a new EGR vacuum control solenoid and installed it. There was no change.... cold idle was still 1100 rpms and climbed to 1400 rpms as the engine warmed up. I checked the vacuum again at the EGR vacuum hose and nothing. I pulled the vacuum hose connector off the EGR vacuum control solenoid and I had very strong vacuum at the bottom hose, but when I reconnected the vacuum to the solenoid I still had no vacuum to the EGR valve hose. I checked the plug for voltage and have 14.38 vdc at the plug. The vacuum hose from the EGR vacuum control solenoid is unobstructed and has no cracks ( it is the OEM hard plastic vacuum tube as are all the vacuum lines except the EVAP line. All the vacuum tubes are intact with no leakage at all. Though I will admit the EVAP line probably needs replacing, but I don't believe it is anything to do with the issue.) I still have no codes. All parts replaced parts are Motorcraft except for the EGR valve itself, but at this point that doesn't matter because I am not getting vacuum to the EGR valve from the EGR vacuum control solenoid. The engine will start up no problem when it is completely cooled off, though it still has the high idle issue. However, after I let it warm up it will not start at all. For whatever reason the brand new EGR vacuum control solenoid is not opening to provide vacuum to the EGR valve. DPFE tested within specs.
I have performed both Throttle Relearn procedures I found in another thread. Even drove the truck well over 40 miles hoping the ECU would sort out the trims. No effect.
In short, I am completely stumped!!! Any input would be greatly appreciated!!! A humble and heartfelt thanks in advance.
Early January I replaced the intake manifold because the old one was leaking coolant into the spark plug wells. The truck ran fine prior to replacing the intake manifold, and that a mystery to me because the EGR valve was not working properly, it was open all the time. Plus the EGR tube was not connected to the exhaust manifold due to the nut being eroded. More on that below.
After replacing the intake manifold the truck ran fine for a couple of days. I took it to get gas and after filling up I went to start it and it acted like it was going to fire and then didn't. I got it started by putting the gas pedal all the way to the floor. It was at that point that the engine ran at a high idle 1600 rpms. On the way home I noticed my coolant temperature sensor was not working. This was after dark so I got it home and left it until the next day.
The next day I started going through the system. I started the truck and first checked the vacuum at the hose that connects to the EGR valve. I had 3 Hg vacuum there. However, there was no difference in the rpms with the vacuum hose removed. I pulled the EGR valve and blew air through it with my compressor nozzle. Air passed through so I knew it was bad. Ordered a new one along with a new EGR tube and installed them a couple of days later. Started the truck and still had high idle.
Over the next couple of days I found the two vacuum control valves near the battery were not working and when tested they were 20+ ohms over their rated resistance (66 on one and 63 on the other). I ended up to get a new IAC valve, both vacuum control valves near the battery, and a new TPS. (NOTE: Before and after replacing these items I had no codes.) After replacing those items I still had the same high idle issue. When I replaced the intake manifold I did not clean the throttle body, so I took it off and cleaned it thoroughly. After putting the throttle body back on and reconnecting everything I started the truck and the idle (cold engine) was at 1100. As the engine warmed the idle increased to just over 1400 rpms. I pulled the vacuum line from the EGR and, as before, there was no difference. I rechecked the vacuum at the EGR hose and had nothing. So I tested the EGR vacuum control solenoid. It did not "click" when I provided power, though it did spark at the pin when I provided power. Also, I could pass air through the active port. I ordered a new EGR vacuum control solenoid and installed it. There was no change.... cold idle was still 1100 rpms and climbed to 1400 rpms as the engine warmed up. I checked the vacuum again at the EGR vacuum hose and nothing. I pulled the vacuum hose connector off the EGR vacuum control solenoid and I had very strong vacuum at the bottom hose, but when I reconnected the vacuum to the solenoid I still had no vacuum to the EGR valve hose. I checked the plug for voltage and have 14.38 vdc at the plug. The vacuum hose from the EGR vacuum control solenoid is unobstructed and has no cracks ( it is the OEM hard plastic vacuum tube as are all the vacuum lines except the EVAP line. All the vacuum tubes are intact with no leakage at all. Though I will admit the EVAP line probably needs replacing, but I don't believe it is anything to do with the issue.) I still have no codes. All parts replaced parts are Motorcraft except for the EGR valve itself, but at this point that doesn't matter because I am not getting vacuum to the EGR valve from the EGR vacuum control solenoid. The engine will start up no problem when it is completely cooled off, though it still has the high idle issue. However, after I let it warm up it will not start at all. For whatever reason the brand new EGR vacuum control solenoid is not opening to provide vacuum to the EGR valve. DPFE tested within specs.
I have performed both Throttle Relearn procedures I found in another thread. Even drove the truck well over 40 miles hoping the ECU would sort out the trims. No effect.
In short, I am completely stumped!!! Any input would be greatly appreciated!!! A humble and heartfelt thanks in advance.
Last edited by chucktone; Mar 12, 2026 at 06:53 PM. Reason: To put things in a proper timeline.
