LS First Gen Rough Idle

[LincolnSedan]

Have rough idle most noticeable with foot on brakes, stopped. Mileage is 138k. The car displays no codes. A short while ago, within 20k miles, all cops (bought expensive aftermarket ones on amazon, not $23 pack one bay) and plugs where replaced, platinum either motorcraft or bosche, have to look. Paid careful attention, making sure they where grounded, checked the pre gaped gaps, have proper gaping. Idle did improve a noticablly after replacing cops and plugs. Used either dialectic greese or anti seize (only a bit on threads) to avoid corrosion for next service. This has a newer air filter. Recall spraying maf cleaner on maf a while ago but not very recently.
Asking for budget reasons due to expenses with multiple cars. The car has the original o2 sensors, no errors. Believe it has original egr. No knowledge of anything wrong with cats the car does not exibit any symptoms related to bad cats, loss of power gas mileage on hwy is 26.5 avg. Not aware of manifold vacuum leaks. The car has new valve cover gaskets which are installed perfectly. Timing is dead on, there are no known issues with slipped chains, chronic issues. Am trying to look at common, simple issues with no codes.
Considering o2 sensors, someone suggested

 

[joegr]

I really don't think it will be O2 sensor related. I think you would be wasting money on those.
My (and many others) experience is that Ford and Bosch spark plugs don't mix. (Specifically, I had rough idle when I tried them.)
Some have had good luck with aftermarket coils, but many have not. If you bought expensive ones ($50 a coil), why not buy the OEM ones at that same price. They got it right with the last ones that I bought, over 100K life.
How is the idle with it in park, but with you foot on the brake?
This is a first gen LS? This is the V8 or the V6?

 

[Antony]

Had rough idle with my 2003, after throttle body, coil overs, new plugs, 02 sensors, I found that my injectors were bad. had it in the dealership a couple of times and they did not even figure it out, they said it was throttle body( hence the replacement). so , if you have not replaced them, the I would say you have some bad/very dirty injectors. PS - I got my injectors from Rock Auto and they were Ford motorsport, very reasonable.

 

[04_Sport_LS]

Vacuum leak somewhere might be something to check into also.

 

[LincolnSedan]

I really don't think it will be O2 sensor related. I think you would be wasting money on those.
My (and many others) experience is that Ford and Bosch spark plugs don't mix. (Specifically, I had rough idle when I tried them.)
Some have had good luck with aftermarket coils, but many have not. If you bought expensive ones ($50 a coil), why not buy the OEM ones at that same price. They got it right with the last ones that I bought, over 100K life.
How is the idle with it in park, but with you foot on the brake?
This is a first gen LS? This is the V8 or the V6?

gen 1, title in post. think they are motorcraft platinum, cannot find the doc right now, they are gapped. though possible, think it would be odd that bosch may not work but recall motorcraft. the plugs are a basic platinum. this is mainly with it idling, brake on, at a stop sign. noticed an improvement in idle with new coils. spending $60 a coil on a car with little resale, hoping may be problematic. I have a number of cars to maintain. did not buy the $20 ebay set. v8.

 

[LincolnSedan]

Had rough idle with my 2003, after throttle body, coil overs, new plugs, 02 sensors, I found that my injectors were bad. had it in the dealership a couple of times and they did not even figure it out, they said it was throttle body( hence the replacement). so , if you have not replaced them, the I would say you have some bad/very dirty injectors. PS - I got my injectors from Rock Auto and they were Ford motorsport, very reasonable.

played the injector game once on a maxima, replace all. they have particular tests they seem to do on reman injectors. some of them are not bad when going through testing on a random car. they are the original ones, fuel cleaners, yeh right. sea foam, maybe not. tried different octane, did not make a huge difference. do not know, it seems like a possible issue. the car has plenty of fuel pressure.