rough idle, throttle unresponsive when cold

stumpie

stumpie

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This is my biggest problem with the car right now, I'm hoping you guys have some help for me :(

2003 V8

When I start the car after sitting for a long while, in colder weather especially, the idle is low and very rough, much like a bad IAC (which I've experienced in multiple vehicles before). Sometimes the car will stall out. As long as the car remains in Park in this condition, the throttle is absolutely dead. I can hold the pedal to the floor and get no rise in RPM's. The only way to "fix" it is to put it in gear and hold brake + a little throttle to get any rise in RPM's. Backing out of my spot is down-right embarrassing. The car is shaking and coughing. When I put it in drive and go, things seem Ok until I come to a stop. Then the RPM's are low again, but I can keep them up enough by holding brake + a little throttle, so the car won't stall.

All of this seems to go away when the car gets warm after about 10 minutes of driving.

I've got no CEL codes and computer diags on the engine (the shop had what looked like an iPad (it wasn't an iPad, it just looked like one) hooked into one of the diagnostic ports under the hood while the engine was running) reported no problems, albeit the engine had warmed up by the time the shop got it so they could not test while the problem was happening.

You guys have any ideas or experiences? Any suggestions?

The shop said that a replacement throttle body would probably fix the issue. I thought I'd run the symptoms by the real pros here on the forum to try and confirm.

TIA
 
You don't have an IAC so you can rule that out.

Leaking injector? Joe will know for sure where to start the search! I would definitely pay Ford the diagnostic fee to find out for sure what is happening. Computer controlled mechanicals can be weird.
 
I don't think a leaking injector would render my throttle pedal useless until the car was in gear. I'm hoping joe has some input ;)
 
Well, of course the COPs should always be suspect. I would also check all the PCV and other vacuum plumbing and the fuel pressure.

If you have no luck with those, then you'll need a good scan tool to look at live sensor readings while it is having the problem.

I really don't think it could be the throttle body without you getting an ETC failsafe warning.
 
You really should replace the coils based on your other thread, it would help to narrow it down.
 
joe is that something I can take the car to the shop and have them "check the PCV and other vacuum plumbing and the fuel pressure"?

Where's the PCV on this thing?
 
stumpie said:
joe is that something I can take the car to the shop and have them "check the PCV and other vacuum plumbing and the fuel pressure"?

Where's the PCV on this thing?
Click to expand...

Yes.

The PCV (Positive Crankcase Ventilation) system is part of the engine and some external plumbing between the two valve covers and the intake (manifold and forward of the throttle). It's not a single thing to locate on any car. However, unlike most car engines, there is no PCV valve on the 3.9.
 
stugots said:
Well you'll be doing them eventually... I don't think throwing a throttle body at it is any better.
Click to expand...

What was that old commercial? Pay me now or pay me later (and usually much more!).
 
Can you explain why coils or plugs would only be temperamental when the engine is cold?
 
stumpie said:
Can you explain why coils or plugs would only be temperamental when the engine is cold?
Click to expand...

They're marginal. Ignition is harder on a cold engine, so you can get more misfires then. There are, of course, other possibilities.
 
stumpie said:
That's a $400 "narrow it down" lol
Click to expand...

No, on an LS it's step one for everything. Need to fix a paint scratch? Step one, replace the plugs and coils. Step two, clean the paint around the scratch. Step three, ...

If you don't replace them, nothing else will work.
 
When was the last time the breather element was checked on that thing ? Not sure if you're running an aftermarket
intake or not. It needs to breathe hard under WOT and it needs lots of good clean fuel coming through.

1) Put the 91+ in and stop running the cheap stuff as mentioned in the other thread.
2) Like joegr says, check the fuel pressure, wouldn't hurt to put a new fuel filter on.
3) Be sure it has a clean air breather filter on it.
4) Clean the Mass Airflow Sensor. Inspect housing and fastener clamps.
5) Inspect for cracks and leaks all the way throughout the air intake plenum.
6) Re & Re the Coils & Plugs, perhaps check and see if connectors are clicked in all the way on current set.
7) Inspect for oil and/or moisture in the spark plug wells, if oil replace VCG, if moisture replace cover gaskets.
8) Ensure the plugs are gaped to min. not max.
9) CATs are done already, raw fuel has been going into them for some time now.

10) make sure there is no banana in the tail pipe.
joke.gif



It's running like
censored.gif
because your not firing on all cylinders and raw fuel is
getting into the catalytic converters and thus giving you the "rotten egg" smell.

~ Start fixing !
 
BigRig:

Its got a K&N panel filter in it, which was last cleaned and oiled about a week ago. I also have cut a nice hole in the airbox following this thread:
http://www.lincolnvscadillac.com/tech/Lincoln-LS/Modify-Airbox/
The problem isn't a rich mix unless we're just talking about insufficient combustion.

When I was changing the COPs about 18 months ago, I did notice some oil in a few of the wells and had VCGs replaced at that time. If memory serves me correct, I changed the COPs before the gaskets and the shop put the new COPs back in. I also had a new Motorcraft fuel filter put in during that same visit to the shop.

I will have some time to get in there this Sunday to inspect the wells again. When I'm in there I will replace all coils and plugs again, unless there is oil in the wells, which I'll report back here. They will be BWD coils which are under warranty. I'm also partial to Motorcraft plugs, unless there is a better suggestion amongst the masses here. I will clean the MAF as well.

About the cats... Will the $100 universal magnaflows work on the LS for the front cats?
 
stumpie said:
BigRig:
... About the cats... Will the $100 universal magnaflows work on the LS for the front cats?
Click to expand...

I don't see why not, I personally haven't had to change my CATs so I can't say for sure.
Check with Lee, (Hite337) he did some hiflow CATS not too long ago, IRC they were magnaflows.

I get a little egg smell on mine on WOT as well but it runs fine so I'm not messing with it untill I go to redo my exhaust.
I ran with one failing COP on cylinder #3 for about 2 months. it was enough to put a little buildup of sulfur burnoff into
the screens on the CATS. No CEL's so I'm still good.

Good to hear she's breathing right and getting good clean fuel flow on yours,
as suspected it leaves the COPs and not firing right producing the running rough and egg smell as the end result.


Fred not, you'll get it.
 
BTW, there is only two front CATS on the LS, the middle is the H-pipe, it's combed across, it is not an actual CAT although some do mistaken it for it.
It's often replaced with an open cross-through X-pipe from magnaflow.
 
Thanks for the info on the CATs. I wasn't sure if the universals were equipped with the right holes for the o2 sensors. I'll keep it in the back of my mind to check with hite.

I'm really just concerned about the completely unresponsive throttle when the idle is cold/rough. I know these TBs are electronically controlled and I feel like the problem lies there. Nevertheless the coils and plugs are where I need to start, over, again.

I need to have an A/C Hose Assembly replaced before summer and if things still run like sh!t after Sunday, I'll have them check PCV and fuel pressure.
 
that is all good info from bigrig, but #1 needs to be elaborated upon. if you are running 87 for an extended period of time, then you put in 93 one time and run the car hard at WOT i would not be shocked if you had a sulfur smell among a litany of other undiagnosed issues. clear your KAM which has adjusted itself so far out of whack to try to compensate for low octane fuel before you do any work that is going to cost more than a few dollars. i would check all of these before replacing coils and cats:
1. continue running 91+ octane ONLY
2. clean the maf
3. check the k&n, i dont have one but doesnt too much oil cause problems?
4. check for oil/water in wells and fix whatever is causing it
5. put a bottle of lucas in the gas
6. clear your crappy KAM (crappy from 87 octane) and run a drive cycle.

i bet your proble is solved after that unless the coils/plugs were wrecked by the oil/water in the wells, or the cats were destroyed from general abuse, or the maf is completely destroyed.

I think thats going to save you some cash/time/work. the cats probably are not wrecked, the maf is probably not wrecked, the coils/plugs could be wrecked. if the coils and plugs are wrecked it is because of poor maintenance (potential water/oil in wells) not because of bwd. either way, if you still have problems you should take them back to advance for a free lifetime warranty replacement
 
Is this the drive cycle you're talking about?

1) Begin drive cycle by starting the vehicle and let idle for 15 seconds.

2) Cruise at 40mph for 4 minuites. Bring vehicle to a stop.

3) Cruise between 45mph to 65mph for 10 minutes. Bring vehicle to a stop.

4) Drive in stop and go traffic condition. Include five different cruise speeds
ranging from 25mph to 45mph for 10 minutes. Bring vehicle to a stop.

5) From a stop, smoothly speed up to 45mph. Slow to a stop.

6) Repeat step 5

7) Repeat step 5

8) Idle in Drive position for 2 minutes.

9) In Overdrive position, Slowly cruise to 50mph for 15 seconds then bring vehicle to a stop.

10) In Normal position, Slowly cruise to 40mph for 30 seconds. Continue...

11) While in 40mph cruise, shift to Overdrive and speed up to 50mph
cruise for 15 seconds, then bring the vehicle to a stop.

12) Repeat step 9
13) Repeat step 10
14) Repeat step 11

15) Repeat step 9
16) Repeat step 10
17) Repeat step 11

18) Repeat step 9
19) Repeat step 10
20) Repeat step 11

21) Repeat step 9
22) Repeat step 10
23) Repeat step 11

24) Repeat step 9
25) Repeat step 10
26) Repeat step 11

27) From a stop, Cruise to 65mph, let off the gas - no brakes, slow down to 40mph. Continue...

28) From 40mph, Cruise to 65mph, let off the gas - no brakes, slow to 40mph.

29) Repeat step 28, then bring vehicle to a stop

End of Drive Cycle
 
Back to "calibrating" the LS again, I see.

<shrugs>
 
BigRigLS said:
Back to "calibrating" the LS again, I see.

<shrugs>
Click to expand...

I "like" the overdrive instructions. Like the LS has an overdrive cutoff switch..... And for the LS, WHICH overdrive? There are 2 (actually 3, but one is electronically eliminated) forward gears that uses overdrive.
 
Isn't one supposed to chew gum while rubbing circles on top of head at the same time ?
I think it was supposed to be step 12 before or after you clap hands together twice. Can't remember.
 
Lol bigrig. I think the steps are ridiculous too. I was waiting for the oart where it said "all this has to be performed in an absolute vacuum where temps are maintained at 0ºC."

However, I do think I will go through the D4/D5 steps a few times, mine has seemed a little clunky lately.
 
The whole thing relearns it's self after a couple of drive cycles.

if all fails, try;

30) Maintain 50mph cruise for 15 seconds, then bring the vehicle to a stop.
31) Wet right hand index finger by placing in mouth and removing.
32) Place wet index finger in right ear for 3 second.
33) Turn to your left, while smiling say: "I've just been PUNKED"

End of Drive Cycle
 
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