[Rick_crew]

I can't remember what a smooth idle was like on my '05, it's been years since it idled anything but rough, the way 4-cylinder carb'ed engines idled 30 years ago.

My truck has 130K on it and is running great. Stills accelerates and runs like new.

My TB is clean and I have new plugs, the factory Delco iridiums.
Would have gone with the Nippondesnso plugs but my opportunity to pull the plugs came unplanned a couple weeks ago and the Delcos were all I could lay my hands on.

I've had the Nippondenso plugs previously and it didn't make any difference in the idle that I could feel.
The coil packs have less than 15K on them. Idle was bad before I replaced the coils also.

I've tried every gas I can buy, and I run 92 octane (which has nothing to do with idle, but..)

Thing is, if I go 5 miles to pick up groceries, it may idle reasonably smooth at one traffic light, then at the next it'll be idling like an old tractor.

I run either Lucas Deep Clean or Sea Foam in the tank about twice per month.

What else can I try?

 

[OJwerks]

any codes or check engine light? My truck idled very rough when my Map sensor was bad.

 

[pittman]

Does it idle better when the AC/defrost is NOT on? I find my truck idles worse when the blower is set to one of those (as the AC pump is running).
Also, I believe the idle speed was increased a bit in the newer trucks. My 07 idles at 650rpm on the dot.

If you've tried everything and there are no sensor or mechanical problems you could consider getting a tune.

 

[Rick_crew]

any codes or check engine light? My truck idled very rough when my Map sensor was bad.

Did have... my thermostat was bad and she ran too cold.
The code was "temperature lower than expected"
Replaced the t-stat, CEL went out.

I replaced the plugs the same day. They looked fine, but I already had them out, so I popped-in the new ones anyway. Only about 13K on the old plugs at the time.

Does it idle better when the AC/defrost is NOT on? I find my truck idles worse when the blower is set to one of those (as the AC pump is running).
Also, I believe the idle speed was increased a bit in the newer trucks. My 07 idles at 650rpm on the dot.

If you've tried everything and there are no sensor or mechanical problems you could consider getting a tune.

Pretty-much the same with or without the AC compressor..

I'm thinking of a tune also, just to bump-up the idle speed.
I never was comfortable with the idle so low.

I've tried holding the throttle very slightly open at idle to try and gauge the difference a higher idle speed might make and it feels the same.
I realize though that isn't the same as a higher idle speed setting.

I may go for the tune.. Wish I were back home and I'd drive up to see the nice folks at PCM For Less. Won't be back there until October though..

 

[Goros]

I can't remember what a smooth idle was like on my '05, it's been years since it idled anything but rough, the way 4-cylinder carb'ed engines idled 30 years ago.

My truck has 130K on it and is running great. Stills accelerates and runs like new.

My TB is clean and I have new plugs, the factory Delco iridiums.
Would have gone with the Nippondesnso plugs but my opportunity to pull the plugs came unplanned a couple weeks ago and the Delcos were all I could lay my hands on.

I've had the Nippondenso plugs previously and it didn't make any difference in the idle that I could feel.
The coil packs have less than 15K on them. Idle was bad before I replaced the coils also.

I've tried every gas I can buy, and I run 92 octane (which has nothing to do with idle, but..)

Thing is, if I go 5 miles to pick up groceries, it may idle reasonably smooth at one traffic light, then at the next it'll be idling like an old tractor.

I run either Lucas Deep Clean or Sea Foam in the tank about twice per month.

What else can I try?

We have the same year, and mine runs smooth as a baby's butt.

I have done a ton to it to get that back, however.

Fuel Filter every 30-40k
Fuel Pressure Regulator at 75-100k (200k for me, was weak/leaking)
MAP Sensor (200k for me)
MAF Sensor Cleaned every oil change
Oversized Dryflow Air Filter (possibly unrelated)
Ported TB (unrelated, keep it clean and lube the joins with deep creep)
Exhaust Camshaft Actuator Solenoid (200k, needed it long before)
Denso Iridium ITV16's (yours are fine, NGK makes Delco)
Supersparkz
Upstream o2 sensor 80-100k
Replaced PCV hose to resonator
Replaced Brake Booster hose to intake manifold
Seafoamed head every 10k w/seafoam in the crank case for 30-50 miles just before oil change
Gumout Regane in the tank every 3rd or 4th.
Mobil 1 Extended w/good filter

Skip the seafoam in the gas tank, it's too weak and diluted to help clean anything. You want something with a ton of PEA in it, which leaves Gumout Regane All-in-one, Gumout Regane high mileage, or Redline SI-1. Start with a shock treatment of 2x whatever the recommended dose is. You'll lose gas mileage for that tank, but it will help get your injectors clean.

I'm still on original coil packs @ 227k miles. I clean my grounds under the hood, and at least 1/yr clean my QD connectors on each coil pack and at the back of the engine with QD electrical contact cleaner to make sure I'm getting the right spark.

 

[Rick_crew]

We have the same year, and mine runs smooth as a baby's butt.

I have done a ton to it to get that back, however.

Fuel Filter every 30-40k
Fuel Pressure Regulator at 75-100k (200k for me, was weak/leaking)
MAP Sensor (200k for me)
MAF Sensor Cleaned every oil change
Oversized Dryflow Air Filter (possibly unrelated)
Ported TB (unrelated, keep it clean and lube the joins with deep creep)
Exhaust Camshaft Actuator Solenoid (200k, needed it long before)
Denso Iridium ITV16's (yours are fine, NGK makes Delco)
Supersparkz
Upstream o2 sensor 80-100k
Replaced PCV hose to resonator
Replaced Brake Booster hose to intake manifold
Seafoamed head every 10k w/seafoam in the crank case for 30-50 miles just before oil change
Gumout Regane in the tank every 3rd or 4th.

Skip the seafoam in the gas tank, it's too weak and diluted to help clean anything. You want something with a ton of PEA in it, which leaves Gumout Regane All-in-one, Gumout Regane high mileage, or Redline SI

Thanks much!
Fuel pressure regulator was done at the same time as my thermostat and plugs two weeks ago.
(it was leaking... in my opinion every 355 owner should consider replacing the fuel-pressure regulator as preventive maintenance)


(put up this thread hoping to help out any with an older 355...)
http://www.355nation.net/forum/i4-i5-engine-drivetrain/104001-also-got-leaking-fuel-pressure-regulator.html

Camshaft solenoid was done almost four years ago, got it before the screens had deteriorated. Thinking about it though, it made a definite improvement then..
I think I'll replace it this week just in case.

I'll look at everything else you listed...
Thanks much to you and everyone (pittman and OJwerks) who took the time to offer suggestions.
I do appreciate it. This nation is populated with the very best sort of folks!.

:355group: