Rough Idle
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Pull the connector off the IAC. If the idle remains high, you have a vacuum leak or sticking throttle body or someone jacked with the throttle stop screw.
If the idle RPM drops or the engine stalls it's most likely something electronic. An out of specification sensor such as the ECT, MAP or ACT can do it. The output may not be far enough out to trigger a code. Could be a computer going bad too. Pull it out then inspect for signs of leaking capacitors. Very common problem with different symptoms from time to time.
If the idle RPM drops or the engine stalls it's most likely something electronic. An out of specification sensor such as the ECT, MAP or ACT can do it. The output may not be far enough out to trigger a code. Could be a computer going bad too. Pull it out then inspect for signs of leaking capacitors. Very common problem with different symptoms from time to time.
To back up a bit, when I replaced the valve cover gasket, I cleaned the TB and of course now I see the sticker saying don't clean it and don't jack with the TSS. So the TB is sure suspect and I can pull it and check for light around the Butterfly valves etc. Of course the TSS is misadjusted probably also. The TB is original.
I will WD 40 the suspect vacuum areas shortly. Before I WD it, is there anything else I can check with the above info? Thank you very much. I really love this truck and want it to be right. Sandymane
Fleet Owner
Joined: Oct 2005
Posts: 20,784
Likes: 1,751
From: Kentucky
The I6 intake manifold is known to warp and crack over the years. A few have found leaks by doing a smoke test. A few threads on here for how to do it. The vacuum reservoir on the passenger side fender is known to rust through on the bottom. The brake booster is another common failure.
Highly suggest to replace ALL of the vacuum hoses as preventative measure.
Simple test to eliminate all outside sources of vacuum leaks is to remove all the vacuum lines from the manifold tree. Run a single dedicated line to the MAP sensor. If the idle is still high it's a gasket, cracked manifold issue or something else on the engine. Bad throttle body, worn throttle body bore, leaking/stuck IAC, etc. You already know you need to move the TSS back to factory position.
Highly suggest to replace ALL of the vacuum hoses as preventative measure.
Simple test to eliminate all outside sources of vacuum leaks is to remove all the vacuum lines from the manifold tree. Run a single dedicated line to the MAP sensor. If the idle is still high it's a gasket, cracked manifold issue or something else on the engine. Bad throttle body, worn throttle body bore, leaking/stuck IAC, etc. You already know you need to move the TSS back to factory position.
Thread Starter
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
The I6 intake manifold is known to warp and crack over the years. A few have found leaks by doing a smoke test. A few threads on here for how to do it. The vacuum reservoir on the passenger side fender is known to rust through on the bottom. The brake booster is another common failure.
Highly suggest to replace ALL of the vacuum hoses as preventative measure.
Simple test to eliminate all outside sources of vacuum leaks is to remove all the vacuum lines from the manifold tree. Run a single dedicated line to the MAP sensor. If the idle is still high it's a gasket, cracked manifold issue or something else on the engine. Bad throttle body, worn throttle body bore, leaking/stuck IAC, etc. You already know you need to move the TSS back to factory position.
Highly suggest to replace ALL of the vacuum hoses as preventative measure.
Simple test to eliminate all outside sources of vacuum leaks is to remove all the vacuum lines from the manifold tree. Run a single dedicated line to the MAP sensor. If the idle is still high it's a gasket, cracked manifold issue or something else on the engine. Bad throttle body, worn throttle body bore, leaking/stuck IAC, etc. You already know you need to move the TSS back to factory position.
Lead Driver
Joined: Aug 2009
Posts: 7,557
Likes: 249
From: Laquey, MO
At this point, I would strip the entire intake manifold and both exhaust manifolds off, check for damage to the lower intake where it mounts to the head, scrape everything clean, and then put it all back together again with quality gaskets at every component. I found several of the mounting ears that mount to the head cracked and falling off. That's what it took to finally find my intake leak. Your mileage may vary...
Thread Starter
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
At this point, I would strip the entire intake manifold and both exhaust manifolds off, check for damage to the lower intake where it mounts to the head, scrape everything clean, and then put it all back together again with quality gaskets at every component. I found several of the mounting ears that mount to the head cracked and falling off. That's what it took to finally find my intake leak. Your mileage may vary...
Thread Starter
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
Yes. I disconnected the vac hose from the brake booster and blew smoke into the tube. Of course there was a good vacuum to suck in the smoke so I know it went into the hose. Is this the correct procedure? I did it with the engine running and then turned it off and blew plenty of smoke it the hose and started it up and looked. Never saw any smoke.
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Thread Starter
|
Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
The I6 intake manifold is known to warp and crack over the years. A few have found leaks by doing a smoke test. A few threads on here for how to do it. The vacuum reservoir on the passenger side fender is known to rust through on the bottom. The brake booster is another common failure.
Highly suggest to replace ALL of the vacuum hoses as preventative measure.
Simple test to eliminate all outside sources of vacuum leaks is to remove all the vacuum lines from the manifold tree. Run a single dedicated line to the MAP sensor. If the idle is still high it's a gasket, cracked manifold issue or something else on the engine. Bad throttle body, worn throttle body bore, leaking/stuck IAC, etc. You already know you need to move the TSS back to factory position.
Highly suggest to replace ALL of the vacuum hoses as preventative measure.
Simple test to eliminate all outside sources of vacuum leaks is to remove all the vacuum lines from the manifold tree. Run a single dedicated line to the MAP sensor. If the idle is still high it's a gasket, cracked manifold issue or something else on the engine. Bad throttle body, worn throttle body bore, leaking/stuck IAC, etc. You already know you need to move the TSS back to factory position.
Fleet Owner
Joined: Oct 2005
Posts: 20,784
Likes: 1,751
From: Kentucky
Not my preferred method. All your smoke in the intake system went out the tail pipe. Several YouTube methods available. Short story is you need to pressurize the intake enough to reveal the leaks.
My home made smoke tester was a 5 gallon shop vac, cigar of unknown age, duct tape and tubing of varying sizes. Set the shop vac to "blow mode", use adapters, duct tape, etc. to hook the output to the brake booster line (it's one of the larger ones). Do not turn the truck on. Turn the shop vac on. Look for smoke.
I used this recently to find a supposed exhaust leak (tick) on my 2005 Navigator. Worked like a charm to prove the exhaust manifolds were not leaking. It was a very loose spark plug. Saved me ~$150.
My home made smoke tester was a 5 gallon shop vac, cigar of unknown age, duct tape and tubing of varying sizes. Set the shop vac to "blow mode", use adapters, duct tape, etc. to hook the output to the brake booster line (it's one of the larger ones). Do not turn the truck on. Turn the shop vac on. Look for smoke.
I used this recently to find a supposed exhaust leak (tick) on my 2005 Navigator. Worked like a charm to prove the exhaust manifolds were not leaking. It was a very loose spark plug. Saved me ~$150.
Fleet Owner
Joined: Oct 2005
Posts: 20,784
Likes: 1,751
From: Kentucky
Manifold vacuum. Trying to eliminate any other potential vacuum leaks since the factory typically has that line teed to other things (HVAC).
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
[IMG]https://cimg6.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/2000x1124/80-vac_leak_dd5dbf38bc42d1b60f36f387d184ad1cf081face. jpg[/IMG
I was going to use my air compressor to force the smoke but I saw smoke before I used it. Here is where it is leaking. The other side of the line is if front of my finger and goes into the large wireing harness.
I was going to use my air compressor to force the smoke but I saw smoke before I used it. Here is where it is leaking. The other side of the line is if front of my finger and goes into the large wireing harness.
Thread Starter
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Lead Driver
Joined: Oct 2016
Posts: 6,185
Likes: 633
From: Houston/Sugar Land
I am going to have to replace the line or the vac end to fix this leak. It goes into the large harness and the line broke at the large vac end where it attaches to the part. Can I replace the vac part where it broke or am I going to have to go into the harness? Thanks