Changed plugs - Low idle:Dies at stops
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Joined: Feb 2019
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A few years later... I have the exact same issue. I'm posting this in hopes that RiverRacerX or someone else with similar experience can point me in the right direction. I changed out my plugs today at 127631mi with motorcraft 546. I have a 2004 f150 4x4 5.4l 24v. The engine sort of surges or hunts while trying to idle where it will drop very low, about 300RPM and then rev up to about 900RPM and then back down, repeat until eventually, it dies. If I am attentive, I can give it some gas and keep it running. It will also surge if I hold a little throttle, say 1200RPM. During the plug change I broke the vacuum nipple off of the vapor canister purge valve so I plugged the vacuum line and started it up. It started easily and ran fine for a moment then began the surging idle dance. I thought it was due to the broken purge valve so I replaced that but it didn't make any difference. Interestingly, after I installed the new vapor canister purge valve, it started and ran smoothly for about 15 seconds then it resumed the surging. I haven't driven it around town yet. I did disconnect the computer/battery during the plug change but not after the new purge valve.
The truck was running well before the spark plug change but fuel mileage was around 12. I just bought the truck and have been covering maintenance that I think hasn't been done. The spark plugs I pulled out were autolite brand and the electrodes were visibly worn/eroded. Also, I tried disconnecting the cam phasers per a youtube vid but it didn't have any noticeable effect. Interestingly I didn't get a CEL when the cam phasers were disconnected. Any advice is welcome.
Thanks,
Truckma
The truck was running well before the spark plug change but fuel mileage was around 12. I just bought the truck and have been covering maintenance that I think hasn't been done. The spark plugs I pulled out were autolite brand and the electrodes were visibly worn/eroded. Also, I tried disconnecting the cam phasers per a youtube vid but it didn't have any noticeable effect. Interestingly I didn't get a CEL when the cam phasers were disconnected. Any advice is welcome.
Thanks,
Truckma
Last edited by Truckma; Feb 10, 2019 at 09:12 PM.
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Joined: Feb 2019
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For whoever finds this post next:
My issue turned out to be defective spark plugs. They were Motorcraft 546 that I purchased on Amazon. I paid only like $57ish for the set of eight but in the end, it wasn't a deal at all. I was able to see which cylinders were misfiring on a friend's snap-on computer and exchanged spark plugs and coil packs between the cylinders that were firing properly and by process of elimination determined the spark plugs were the culprit. I ended up replacing 7 of the 8 plugs with new ones. HOWEVER... I still had a low idle and occasional stalling but only when in low RPM, high demand situations like parking. Cleaned throttle body has eliminated the stalling but the engine still will idle down as low as 500RPM which isn't optimal. Anyway, I wanted to share my discovery for those that come after. Seems like there are a ton of forums for these trucks and I didn't get one reply here... maybe because I resurrected such an old thread or maybe this forum dying or just not very popular, IDK. Anyway, best of luck to those that come next.
T
My issue turned out to be defective spark plugs. They were Motorcraft 546 that I purchased on Amazon. I paid only like $57ish for the set of eight but in the end, it wasn't a deal at all. I was able to see which cylinders were misfiring on a friend's snap-on computer and exchanged spark plugs and coil packs between the cylinders that were firing properly and by process of elimination determined the spark plugs were the culprit. I ended up replacing 7 of the 8 plugs with new ones. HOWEVER... I still had a low idle and occasional stalling but only when in low RPM, high demand situations like parking. Cleaned throttle body has eliminated the stalling but the engine still will idle down as low as 500RPM which isn't optimal. Anyway, I wanted to share my discovery for those that come after. Seems like there are a ton of forums for these trucks and I didn't get one reply here... maybe because I resurrected such an old thread or maybe this forum dying or just not very popular, IDK. Anyway, best of luck to those that come next.
T
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For whoever finds this post next:
My issue turned out to be defective spark plugs. They were Motorcraft 546 that I purchased on Amazon. I paid only like $57ish for the set of eight but in the end, it wasn't a deal at all. I was able to see which cylinders were misfiring on a friend's snap-on computer and exchanged spark plugs and coil packs between the cylinders that were firing properly and by process of elimination determined the spark plugs were the culprit. I ended up replacing 7 of the 8 plugs with new ones. HOWEVER... I still had a low idle and occasional stalling but only when in low RPM, high demand situations like parking. Cleaned throttle body has eliminated the stalling but the engine still will idle down as low as 500RPM which isn't optimal. Anyway, I wanted to share my discovery for those that come after. Seems like there are a ton of forums for these trucks and I didn't get one reply here... maybe because I resurrected such an old thread or maybe this forum dying or just not very popular, IDK. Anyway, best of luck to those that come next.
T
My issue turned out to be defective spark plugs. They were Motorcraft 546 that I purchased on Amazon. I paid only like $57ish for the set of eight but in the end, it wasn't a deal at all. I was able to see which cylinders were misfiring on a friend's snap-on computer and exchanged spark plugs and coil packs between the cylinders that were firing properly and by process of elimination determined the spark plugs were the culprit. I ended up replacing 7 of the 8 plugs with new ones. HOWEVER... I still had a low idle and occasional stalling but only when in low RPM, high demand situations like parking. Cleaned throttle body has eliminated the stalling but the engine still will idle down as low as 500RPM which isn't optimal. Anyway, I wanted to share my discovery for those that come after. Seems like there are a ton of forums for these trucks and I didn't get one reply here... maybe because I resurrected such an old thread or maybe this forum dying or just not very popular, IDK. Anyway, best of luck to those that come next.
T
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