Erratic idle, what else i can check?

[wingrg]

Hi, 1998 Expi, 5.4 L, this it my second expi,
problem erratic idle on parking and while driving, no check engine light or codes.

work already done, new spark plugs, water pump, thermo.

What else i can check, in the morning everything works greats but about 5 min Driving start like missfire and when stop a little rought idle start, any sugestion or advice going to be apreciate.

 

[Eric]

My 05 does something similar and I can't find what is causing it. Mine runs smooth when the AC is on or when the engine is cold as the RPM's are up a little higher around 550 vs. about 500. In my case I'm starting to think its a lean condition purposely caused by the computer because as soon as I bring up the rpm's the idle smooths out, but I do get another shake at 1,200 ro 1,500 RPM when reving in park or neutral.

 

[tonydiv]

Do a search on the forum for "rough idle" There's a vacuum elbow that is problematic on the 5.4.

It could also be an IAC motor or coil packs, but look for vacuum issues first.

 

[wingrg]

TX for the advice apreciate this problem is giving me hard time and want to resolve by myself prior to start looking for a shop, I going to start to look if i can find that elbow.......

 

[tonydiv]

With all the vacuum lines running around that engine bay, it's so easy to disturb one when doing simple maintenance.

A can of starting fluid can help. Spray it around the vac lines, when the idle jumps up, you found your leak.

 

[wingrg]

Thanks for the advice i already buy the starting fluid can to make the test, i already check the elbow on the intake, but was prior replace with direct hose to the pvc, i can hear what i think is a little air leak going to test tomorrow morning and if no results was found going to verify coils, for my bad luck i already replace all the spark plugs this week and forget to check the coils arrrggggg.....OMG have to take out one by one again during this days to test the ohm reading on ea one, I have two xtra coils on my things one reads .5ohms the other one read is erratic that mean that one is bad right?, can anyone have an idea whats the reading in ohms for a good coil? thanks to all for the help.....

 

[burksfinancial]

I like that method. Another method is to get dish soap and water - put it in a spray bottle.....then spray the hoses. If it starts bubbling up - there's ur leak.

 

[wingrg]

Hi just a update on my case just verify cop only #7 was bad but problem continue, get to a racing shop of my friend and he scan the vehicle with a incredible scanner i dont have cel light on but scanner found open tps sensor, based on anyone experience is posible a bad tps cause rought idle autozone ask 45.00 for part any advice going to be apreciate. TX

 

[Eric]

One would think the throttle position sensor would not affect idle, but why would the scanner come back with a faulty code if it was good? $45 is not a huge chunk of change to spend by any means if it solves the problem. Can you buy the part, try it and if it does not change return it?

I have been through too many "diagnose by replacement" scenarios on vehicles so I'm cutting my losses on my Expedition and living with the rough idle. Still convinced it has to do with the coumputer controlled valve timing.

 

[wingrg]

Thanks its true, if i buy the tps i dont think i can return a electronic part but in my case when i buy this expi runs smooth later the cel light came on missfire on #7 change cop everything fine again later 3 weeks rought idle symptoms when stop and when driving and if i take a hill more rought also the cel lights blinks soon as i get home i try to pull any code with my little scanner no codes came up, i dont know what else to do i already chane spark plugs, 1 coil, going to verify for additional vacum leaks or bad cop, i dont know if i can spray the iac with carburator cleaner i just make once on my mustang and resolve the issue, well any results going to be post TX for the help

 

[mic_1011]

wingrg did you check the line all the way in the back behind the throttle body. its kinda hard to see and to get to. i'm 6 ft and had to lay across the engine bay to get to it was completely off in my case and kept my expy from staying on. the next thing is to get a code reader even though its not throwing a code you might be able to pull one. this will help if its a bad coil. instead of changing all off them. the code will pinpoint which coil it is then you can just replace that one, also happened to me

 

[KWT2000]

have you cleaned the MAF sensor and the IAC yet if not do those just may solve the problem

 

[wingrg]

Going to check first thing in the morning the pvc hose again im 6ft too and my delicate hand is too big lolololol but going to try again, can a yone direct me to a link on how to clean the MAF because i once clean my mustang IAC spraying some carb cleamer and a lot of dirt came out and fix problem, i dont konw if MAF is just the same take out and spray it, i really aprecite the reply's and always help here, The only code that i can get was TPS open i dont think thats can cause rough idle. TX

 

[gijohn45]

take the air cleaner off the maf and take a spray bottle of rubbing alcohol and just spray the inside... there is a little wire that gets dirty specially if you use a K&N air filter....

And yes the TPS can cause rough idle.

 

[wingrg]

TX let me work on this on Sunday and i post results, apreciate the help.

 

[wingrg]

Hi to all, I just change TPS and clean MAF Sensor but the problem gets worse, I asume is the MAF i just spray a little with CRC cleaner and get worse, I going to take to the shop on monday to find out whats the problem, TX.

 

[wingrg]

Hi guys,bring thebexpi to the shop they change the spark plugs to the factory ones thats reduce the erratic idle very well but not completly they want to replace all the cops but too expensive for me they ask 45.00 for ea, do you thing i can buy the complete set on ebay for 79.00 plus shipping or i have to go for OEM cops . Any review for ebay cops going to be apreciate tx.

 

[Stoned06]

Was the new TPS adjusted after installation, or just replaced?

 

[wingrg]

Was just replaced , i dont see or find in the haynes manual that can be adjusted if it can i going to apreciate if you can send me any advice how to do it, tx

 

[Stoned06]

http://f150online.com/forums/lightning/104839-i-finally-got-tps-adjusted.html

It's for a Lightning, but the same general procedure applies to your Expy. Take a close look at the pics and see where the leads of the voltmeter go. You want the readout to be as close to .99 as possible.