2001 LS V8 runs rough cold, fine when warm

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twistedwrench

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Hi LS people! I've read and read and read some more on this topic, and tried everything I can think of. I have a 2001 Lincoln LS with 51k, no not a typo 51k original miles. When I start it up first time it runs rough for about 1 minute, after that its fine. No hesitation, not affected by temp, no high RPM issues. I have replaced the spark plus, coils, traced all the vacuum lines, replaced everything even questionable.
the only code that comes up is a p303. I've tested the coils and spark plugs, moved them around, no difference. Tested compression, and everything tests out to 175psi. Oh I should also mention the p303 only sets if you drive it in the first minute while its running rough. Found that out after clearing it and it not coming back for 2 months even tho it ran rough cold. Only had to wait 2 days for it after driving it cold.
I've got good fuel pressure, good spray pattern on the injector, brand new coil, new plugs, no oil leaking into plug holes, no vacuum leaks I can find. This car has been meticulously maintained since new, and tho it doesn't effect how the car drives, it is annoying
 
PCM?
Vacuum leak?
Leaky fuel injector?
 
When we first got our 03 V8, we had a problem on running rough on startup maybe half the time, but it wasn't just when the engine was cold.
I put 2 STP fuel system cleaners thru it with less than half a tank, I believe each time I did it. After the second one,it NEVER did it again. Just a thought. don-ohio :)^)
 
^ Probably just needed to unpressurize a few of the injectors in your case.
 
I'd guess vacuum leak. Buy Forscan app and a dongle to match your phone. With that you'll be able to see fuel trims to see if its lean. You could have a shop smoke test it cold, or you could make your own smoke tester to see any vacuum leaks. My bet is an intake leak between the upper and lower intake.
 
Smoke test and fuel trim

I have a snap on scanner and an OTC, have checked long and short term fuel trims cold and hot, and it's not leaning out. I've smoke tested it too no detectable leaks. I agree it seems like an EVAP leak, but generally vacuum leaks don't go away after 60 seconds. It also runs at 1000 rpms while its acting up (which made me think vacuum leak), but then again its a cold start, and after it kicks down to 700 ish rpms its fine.

My thoughts on it were: bad coil, intermittent coil issue, oil leak onto plug, bad plug, low compression, bad, leaky or partially plugged injector or fuel rail, bad injector o-ring, leak in the vacuum lines, pcv hose, brake booster or intake. After a few months messing with it I can tell you its none of the above, and I've already run 2 bottles of STP fuel system cleaner through it, though not 2 bottles to a 1/2 tank, I ran 1 bottle per tank, also I've been running 93 octane in it. But I'm thinking about having a Castle fuel system cleaning done for $120. I've just run out of directions to go. The only other ideas I've had about it I've ruled out, Faulty PCM(noid lighted injectors and coils) and cam sensor, because I've got perfect signal on the scope.

Here is a list of the things I've found wrong that had no effect on how it runs:
Vacuum hose from brake booster missing clamp at barb connector
PCV hose o-ring bad, PCV fitting at air box cracked
broken lock tab on #3 injector harness
Intake vacuum fittings worn and leaky(the little rubber ones on top)
leaky valve covers

I fixed all of that and I've replaced #3 coil, spark plugs, air filter, fuel filter

I kind of feel like a Ford mechanic at this point (Just replace stuff 'till something works)...hehehe
 
Don't sell STP fuel system cleaner short,BR. It has a purpose sometimes, whether unpressurizing a clogged injector or something else.LOL! don-ohio :)^)
 
We had rough idles until it warmed up on our 3.9 V8... over time I did alot too... coils/plugs... nothing seemed to work... so I purchased all the seals and redid the entire upper intake-manifold/plenum... & since it was down that far I found refurbished injectors... now it runs like a kitten. Oh - and I replaced the fuel filter which I could guess was never replaced. This car has 130K and runs like new. However, I'm still in disassembly of the dashboard to get in a new Expansion Valve.
 
Well I've run it a few more times and I'm using fuel system cleaner. It's slowly getting better, I started it yesterday and almost couldn't feel any vibration, and it only did it for about 35 seconds instead of 1 minute. I'll keep updating, but I've only got 4-6 weeks left before it's put to bed for the winter. Maybe I'll hit 52k before the white crap starts falling.
 
Hope a coupla treatments with fuel system cleaner fixes it for you. It fixed mine. Haven't had a recurrence now for many trips. If you can get Marathon gas, it keeps the injectors and system clean with its STP additives in every grade. don-ohio :)^)

twistedwrench said:
Well I've run it a few more times and I'm using fuel system cleaner. It's slowly getting better, I started it yesterday and almost couldn't feel any vibration, and it only did it for about 35 seconds instead of 1 minute. I'll keep updating, but I've only got 4-6 weeks left before it's put to bed for the winter. Maybe I'll hit 52k before the white crap starts falling.
Click to expand...
 
Well, its back to acting the same again, fuel system cleaning didn't seem to help. Just for haha's I swapped out coils 2 and 3, no change, so I bought a new injector, and all new o-rings. Let you know how that goes when I get the part and install it. It's getting real cold real fast here in the Great North Woods, hopefully I can get this solved before snowfall.
 
Well,you did it NO HARM by running that cleaner thru it. I hope you find the problem. If it were mine,I'd get Ford to run a scan on it. It's worth the cost here at only 65 bucks(they take that charge away when they fix the problem),but the other guys on the forum say it costs them more. don-ohio :)^)
 
Well it took me a while, as I have been very busy, but I tore into the LS again. Spent more money replaced more parts, with a slight improvement. I actually didn't realize my LS wasn't starting up right until after I put it back together! I turned the key and it was like instant on, it had always started with about 2 seconds or so of cranking before, now turn the key and boom its on less than 1 second of cranking. So I fixed something I didn't even know was broken. That said.....OMFG IT'S STILL MISFIRING!!!!!!!!!!!!!! only when cold first thing in the morning for about 30 seconds or so, and then it clears up. Only code is p0303. This particular Gremlin is hiding VERY well. Next up upper and lower intake gaskets and fuel system cleaning, I have no other ideas after that save maybe doing valve seals.
 
I think you are going to need a very good scanner to check injector pulse timing and width. Beyond that... you may have an internal issue you don't want to know about. Best case would be shims for the valve tappets for that cylinder... or replacement, (don't remember if that is the correct terminology). Worst case scenario... start the engine and listen to it through a full temp warm up cycle. If you hear any knocking throught the warm up cycle... try to pinpoint it if you can.

Strange... as I scanned this,,, no one asked or mentioned whether this was a v6 or v8, (unless i missed it). Some of the v6's had issues which were internal.
 
My bad... missed that it was a V8. Still curious as to the noises at idle through full warm up. Use a mechanics stethescope around the problem cylinder.
 
It doesn't make any noises, no valve noises no knocks, even with a stethescope, and honestly you can barely even tell its misfiring. It has a very slight shake when you first start it in the morning, for about 30 seconds, then its fine for the rest of the day, no matter how long its parked. It seems like it has to be parked for at least 12-16 hours to act up at all. I'm pretty sure it's not an internal engine issue. I have good compression, and leak down test looked good. I mean it's totally possible I have a hair line crack in a valve seat or cylinder head that leaks when its good and cold but as soon as the engine warms it seals, but I think I'll swap all the injectors clean the fuel rail and change the intake gaskets before I condemn the head. I will find and solve this issue eventually.
 
I think you have a good plan of attack here. If none of that changes the problem cylinder, keep in mind that the PCM could be the issue.
 
Man I have been chasing the same thing for more than a year now. It only misfires when it is cold, and as soon as it reaches operating temp, misfires are gone. I have become so good at changing plugs and coils, that I can do a full set in about 20-30 minutes. I am about to pull injectors myself and try cleaning those.

Of course this engine has OEM coil and injector prices that make everything a second guess before just replacing.

I am running HEET or whatever through the gas tank now, so far no improvement.

The only codes I can get are P0300 (Random Misfire); P0316 (Misfire on first 1000 Revolutions); P0133 (O2 Circuit Slow Response Bank 1 Sensor 1)

Let me know what you find. We are struggling together, my friend.
 
Andrizzle,

Is it really a misfire... or more of a chugging feel to the engine as it attempts to get the idle right. If a chugging... it may be more related to the throttle body or TPS sensor. The slow O2 sensor may be a symptom,,, rather than a problem. The other 2 codes may be a VVT solenoid that is getting ready to go, (which was mentioned somewhere recently in another thread by Joe, IIRC). Or possibly crank sensor or other issue mentioned by Joe. It was another recent thread.

Lastly,,, even thought there may not SEEM to be any noises from the engine,,, ... pay VERY CLOSE attention to the engine when it first fires up. Do you hear any kind of rattle,,, like BB's in a coffee can... or what may seem like valve clatter???

1999-2002 suffered from bad secondary chain tensioners on the cams... which could be one of the issues described here. If they don't tension the cams fully, (due to poor design and wear), this could be the issue.

Secondly,,, even after the issue with the cam chain tensioners was resolved by 2003... there was still and STILL is an issue with the cam phasers. They wear out... or flat out become faulty when the "check valve" in them doesn't hold oil pressure over a certain number of hours. Then the next time you start it up, (V8's only)... it takes a number of seconds before oil pressure reaches the cam phasers, (not Star Trek related).

It took a couple of people on this forum,,, to start their engine up after sitting for a few hours to realize this problem. First they did it normally... then they pulled the fuse for the fuel pump and cranked the engine for a few seconds... then plugged the fuse back in and tried starting the engine. The engine rattle was then gone,,, and everything was normal.

Not saying this is the be all fix all... but something else to consider. Just because a person doesn't hear the rattle at first,,, doesn't mean it's not there. It sometimes takes a trained ear to hear what is and is not normal.

16 pages long,,, and 389 posts... but well worth a read.

http://www.lincolnvscadillac.com/forum/showthread.php?86480-Engine-rattles-on-startup

Again... I'm not saying this is the issue or problem. Determination is by the reader and his/her own diagnosis.
 
Got another code this morning on my daily misfire adventure.. P2198 (O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 1).

Really close to setting the whole thing on fire.

To the poster above, thank you for the reply. No I don't have any knocking or rattling in my engine. It sounds/feels exactly like bad coil misfires sound.
 
Yea I read that. Brand new coils and plugs aren't changing anything. Unless I am the unluckiest SOB on earth and keep getting defective coils.

I did all new Motorcraft coils in March 2015. And again in February 2016.

I just recently bought 8 Amazon coils and NGK plugs, saying screw Motorcraft, and misfires are still there. So I think there is another problem. However, each time I change coils, the problem changes either better or worse. I have even tried combinations of all the coils (because I have a huge box full of them now).
 
Hope not, would that be cold start only? I am not sure the documenting that has been done on people who had PCM issues.

I am going to try some more coil swapping Thanksgiving morning and try to single out coils. Today the misfire was extremely rapid and basically quick shaking instead of chugging.
 
Sure you don't have a bad harness or coil connector, drizzle?
 
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