Runs terrible when cold, fine when warmed up...

[fitefanSHO]

When I start it cold (and I don't mean cold like freezing outside, I just mean cold like has not started in 8 to 10 or so hours) it idles badly. First it surges up past 1K a bit a few times, tries to settle down at 600ish but it drops below that (below 5 hundred) and seems like it might stall out. Gets as close to 6 hundred as it's gonna get (all shaky and stumbly) and I put the car in drive and it runs very sluggy, feeling bogged down when I put foot on gas. Get her out on a little open road and after a few minutes of driving (without having to stop hopefully because the first few stop lights are rough) and she settles down and starts to accelerate much better and behave better at stop and starts. After a good ten minutes of driving, she's fine and if you shut it off and restart her, the idle goes right to 600 and only barely flutters, if at all with no acceleration issues.

Cams weld service by Kirk.
New plugs but with "new" aftermarket coils.
K & N air filter.
New fuel filter.
New TPS.
MAF cleaned.

Oh and of course NO CODES

Thinking maybe IAC or a clogged cat? Or maybe them coils suck? At a loss, help appreciated.

 

[stephen newberg]

That sounds like it is the air meter sensor. Its dirty and needs cleaning. I forget its name. AIP, something like that.

pax, smn

 

[fitefanSHO]

I threw a new IAC at it today, not sure if helped or not.

We'll see in the morning.

Car runs and idles great warmed up, like **** cold. I read that if you unplug the IAC with the car running it should die out. Well, unplugged the old one with engine cold, engine died. Tried same thing when engine hot with old one and new one, car did NOT stall out.

air meter sensor, ok, I check that too Thanks

 

[Funmart6]

A dirty MAF sensor perhaps????, nevermind, I see that you had that cleaned already. TPS, maybe????

 

[1998v8sho]

Check the MAF and the TPS sensor.

If it was a misfire it would continue to stumble or shake when it warms up. So misfire could be ruled out.

One other area that might slightly display rough idle during a cold start are the secondaries. The could be stuck open. Make sure they are working properly.

Vacuum leaks?

 

[stephen newberg]

MAF, right. Always forget the name. A dirty one creates the indicated problems, though they certainly could be something else as well, or in addition to.

pax, smn

 

[fitefanSHO]

New IAC did not clear it up.

Still rough and sluggy on cold startup, then fine when warmed up. At that point it roars on the highway and has a pretty nice clean idles at stops and restarts.

 

[tqmx1]

Odds are it's the engine coolant temp. sensor (ECTS). The wife had the same thing with her Eagle Talon. When the ECTS screws up it lets the engine think it is all ready up to opperating temp (even when the engine is stone cold) so all the cold start inrechment is removed so it runs like S^%T when cold and OK when warm.

 

[SHOZ123]

I bet it is coils. The cold start strategy is limited more by time than temperature.

 

[stephen newberg]

Dirty MAF or coils are my bet.

pax, smn

 

[fitefanSHO]

Maybe I need to replace the MAF, I have cleaned it very well and very properly.

It's really more or less a tolerable problem because it only runs like ass for 5 to 10 minutes and then just like that, it's a well kept V8 SHO with attitude, new sporty ties, and nice growl.. good to go all day. It's just the first start and initial driving experience that blows.

and new real Motorcraft coils are bookoo money.
Maybe I will throw a new MAF at it, or see about the ECTS, I dunno, any more ideas?

 

[stephen newberg]

If the MAF is clean and working properly, I am then with Paul and suspect you have one or more plug coils going, and after they warm up, they start to work better.

pax, smn

 

[1998v8sho]

That has not been my experience. Even after the engine is warmed up, if there is a faulty coil it will still misfire. But worth a look though.

 

[Vnuk1]

Maybe I will throw a new MAF at it, or see about the ECTS, I dunno, any more ideas?

Try unplugging it and driving it, that'll tell you if it's the MAF..

 

[fitefanSHO]

OK so the rough erratic idle/misfire condition continues to be problematic at start-up and then gradually as the car warms up it gets better. Anyway, I finally got a CEL light today while letting the car warm up after starting it and got some codes, here they are.

P0303 cylinder #3
P0300 random cylinders

This leads me to believe that one/some (all?) of the aftermarket coils I recently had installed are bad/problematic.

Should I replace just #3?

All them them?

Have my head examined for ever doing the SHO thing again?

Thoughts?

 

[stephen newberg]

Yes, replace just #3. If you do it one at a time you will eventually end up with a full goos set installed.

pax, smn

 

[fitefanSHO]

My thought is to put my 4 best Motorcraft ones in the back, 1234
with my best/newest coil on #3?

 

[newshofan]

My thought was when I get the money. To get four from the local parts store. I've checked on the borg warner at orielys good quality parts and slightly cheaper than motorcraft. And put them on the back and then try some cheaper ones on the front and see how they work

 

[fitefanSHO]

I was never so excited and happy to see a check engine light in all my car owning life, this SHO finally told me what was wrong with her so I can get it fixed...