Fast Idles on Start-up

[Uphill_Both_Ways]

Fast-idle cold starts long preceded catalytic converters and all the rest of the anti-pollution plumbing added over the decades. Cold starts were fast idle with my three-on-the-tree 1953 Pontiac (Canadian model) with Chevy's "Blue Flame" six and automatic choke.

I hate fast-idle starts, winter or summer, but especially in the winter. What's the point of gentle driving until the engine warms up if the thing's grinding its guts out at 1,600 rpm with stone-cold 35- or 40-below-zero oil, either temperature scale?

I drop it into drive immediately after starting, to slow the revs as much as possible, 950 to 1,000 — still too fast — and have with every automatic-transmission car I've owned. A pox on the catalytic converter (and the 235,000-kilometre four-speed transmission remains trouble-free).

That's why I never use the remote start unless the engine is warm, it's snowing to beat the band and I'm in a grocery store.

 

[OVERKILL]

Originally Posted by Uphill_Both_Ways

I drop it into drive immediately after starting, to slow the revs as much as possible, 950 to 1,000 — still too fast — and have with every automatic-transmission car I've owned.


The point of driving it gently until the engine warms up is to keep the load low. When the engine is sitting there high idling and you stuff it in gear to bring the revs down, you are also increasing load as it flails away against the torque converter, which is full of equally thick and cold transmission fluid. Not a better scenario.

 

[demarpaint]

Originally Posted by OVERKILL
Originally Posted by Uphill_Both_Ways

I drop it into drive immediately after starting, to slow the revs as much as possible, 950 to 1,000 — still too fast — and have with every automatic-transmission car I've owned.


The point of driving it gently until the engine warms up is to keep the load low. When the engine is sitting there high idling and you stuff it in gear to bring the revs down, you are also increasing load as it flails away against the torque converter, which is full of equally thick and cold transmission fluid. Not a better scenario.



Which is exactly I will wait until the idle drops to about 1,000 rpm before dropping it into drive. I also keep my foot off the brake when putting into drive or reverse after a cold start if conditions allow it.

 

[StevieC]

We would see engines grenading all over the place or living short lives if fast cold idles made a difference. Heck look back to the old carburetor days. Those ran fast idles choked with very rich mixtures and while it does increase wear (rich mixture) those engines never seemed to suffer from the cold fast idles even with thick conventional in the crank case which you know was providing less than superior lubrication on cold starts most of the time in the winter.

 

[Uphill_Both_Ways]

Originally Posted by OVERKILL

The point of driving it gently until the engine warms up is to keep the load low. When the engine is sitting there high idling and you stuff it in gear to bring the revs down, you are also increasing load as it flails away against the torque converter, which is full of equally thick and cold transmission fluid. Not a better scenario.


Hmm. I need a six-speed stick.

 

[PimTac]

Fast idles have been around for decades. There is nothing new here.

Interesting side note, my Mazda has a temperature icon that is blue when the engine is cold then disappears when normal operating temperature is reached. A nice visual to remind the driver to take it easy.

 

[StevieC]

With the Journey although the idle would be higher than hot idle it wasn't too much different unless it was really cold outside. The Highlander is noticeably higher idle on cold start if the coolant temperature is below 100F. This is fine by me, I was just questioning why is all because it was different than previous vehicles.

I kind of like having it now that I do because it will remind me to leave it in park until the fast idle drops to a more normal idle. Then I know the emission components are warmed up properly and the oil is circulated. I live close to a main highway and so having this all done before I get to the highway about 2 miles away is important IMO.

 

[440Magnum]

1) heats up the catalysts quicker, gets the O2 sensors hot and the engine into closed-loop quicker than sensor heaters alone would
2) Maintains a hydrodyamic oil wedge in high-friction areas until the oil pressure comes up, reduces engine wear
3) Gets oil circulated throughout the engine faster, reduces engine wear
4) Faster airflow through the intake and valves encourages fuel vaporization and better air/fuel mixing than slow airflow would

 

[demarpaint]

Originally Posted by StevieC
We would see engines grenading all over the place or living short lives if fast cold idles made a difference. Heck look back to the old carburetor days. Those ran fast idles choked with very rich mixtures and while it does increase wear (rich mixture) those engines never seemed to suffer from the cold fast idles even with thick conventional in the crank case which you know was providing less than superior lubrication on cold starts most of the time in the winter.

They also idled a lot faster and dumped a lot of gas into the oil. EFI seems to have helped a lot with that problem, and at a cold idle they don't idle as high or as long as a carb. And we don't have to mash the gas to get EFI to kick down from a fast idle.

 

[billt460]

Originally Posted by PimTac
Interesting side note, my Mazda has a temperature icon that is blue when the engine is cold then disappears when normal operating temperature is reached. A nice visual to remind the driver to take it easy.


My mother had a 1965 Chevy Impala. It had a green "COLD" light that would go on after a cold start. It would remain on until the engine warmed up enough to where the thermostat would open. In the Winter that could take quite a while.

 

[SwampSurvivor]

Some are worse than others. Our non - turbo/di Fords have always been ridiculous with the fast idle. My Focus would run at 2500RPM on a cold start and that is what the engine was going to run at, end of story, until the catalyst lit off. So, taking off on a cold morning was fun. Trying to shift when the engine won't slow down and there's molasses in the gear oil. Both of my parents' GTDI escapes just are above 1000rpm cold.

Right now my F350 has a very rotted out / cracked exhaust manifold. I'm pretty sure I wake up the dead in the cemetery on the other side of town when that cold starts.. You can definitely hear it popping and coughing at the end of my street. Luckily, it's warm enough out that it hits closed loop in 20 seconds or so and idles right down.

 

[Brigadier]

Originally Posted by StevieC
I have spent most of my time working on Asian and American vehicles and haven't come across any. I have seen Air Injection pumps on German vehicles but we don't refer to them as Smog Pumps. Smog pumps or so they were called were compressor looking things that were belt driven and forced air into the catalytic converters and that type I haven't seen since the 1970's vehicles. Gasoline based anyway.


My 85 Z-28 LG4 had one.

And it had a choke that ran a cold engine at high idle until it warmed up.

Every car we have ever had has done this - 72 Chev C20, 78 F-150, 78 VW Rabbit, 85 VW Jetta, 13 Mazda 3, 17 Santa Fe, 15 Escape,.....all had/have cold start high idles.

 

[billt460]

Originally Posted by Miller88
Some are worse than others. Our non - turbo/di Fords have always been ridiculous with the fast idle. My Focus would run at 2500RPM on a cold start and that is what the engine was going to run at, end of story, until the catalyst lit off.


In the cooler Winter months here in Phoenix, my 1991 EFI, F-150, 5.0 V-8 cold starts at right around 2,000 RPM. It's been doing it since I bought it. I took it in several times only to be told by 3 different dealers that it was "normal", and "within spec". I can kick it down to around 1,200 RPM as soon as it starts. Both my Jeep and my new Toyota cold start right around 1,200 RPM. And quickly come down to 650-700 RPM within 60 seconds or less if it's warm out. Once the engine is warmed up they start at around 650 RPM.

 

[Trav]

Originally Posted by StevieC
We haven't had Smog Pump's here since the 1970's.

You may have one or 2 in the 2018 Toyota. This is for a 2018 Tundra, they may also be used in other models, but I didn't look for it.

2018 Toyota air pump

 

[bunnspecial]

Originally Posted by Uphill_Both_Ways
Fast-idle cold starts long preceded catalytic converters and all the rest of the anti-pollution plumbing added over the decades. Cold starts were fast idle with my three-on-the-tree 1953 Pontiac (Canadian model) with Chevy's "Blue Flame" six and automatic choke.


It's not even automatic chokes.

At least on an SU carburetor-of which almost all are manual choke(I think Rolls Royce was the only company to shoehorn an auto choke onto one)-the first 1/3 or so of the choke cable pull ONLY serves to move the fast idle cam(s) into place. The "enrichment circuit"(which isn't a true choke but instead uses moves the fuel jet to make the mixture richer) only starts engaging past the 1/3 point of the pull. The spec idle speed for the little 1.8L 4-banger ranges from 500rpms for the earliest 3-main bearing engines to 850rpms for the late 5-main, low compression single carb engines(in-between 5 main dual carb engines are speced at anywhere from 700-850rpms-I tend toward the high end of that). The fast idle for all engines is given as 1000-1300rpms.

Even on a 90º morning, the engine on that car will stall at stoplights when cold if I don't keep the fast idle engaged until it's warm. The auto choke installed on the '75 and later single carb is bad about seizing(it's a water choke, so will corrode if the cooling system is neglected) and those cars can be a royal pain to get warmed up if the fast idle won't engage.

 

[StevieC]

I had an SU on my Austin Mini.

 

[SwampSurvivor]

Originally Posted by billt460
Originally Posted by Miller88
Some are worse than others. Our non - turbo/di Fords have always been ridiculous with the fast idle. My Focus would run at 2500RPM on a cold start and that is what the engine was going to run at, end of story, until the catalyst lit off.


In the cooler Winter months here in Phoenix, my 1991 EFI, F-150, 5.0 V-8 cold starts at right around 2,000 RPM. It's been doing it since I bought it. I took it in several times only to be told by 3 different dealers that it was "normal", and "within spec". I can kick it down to around 1,200 RPM as soon as it starts. Both my Jeep and my new Toyota cold start right around 1,200 RPM. And quickly come down to 650-700 RPM within 60 seconds or less if it's warm out. Once the engine is warmed up they start at around 650 RPM.


The focus was awful in traffic. Just idling along in a traffic jam in stop and go traffic, the catalyst wouldn't stay at temperature, so it would start bumping up the idle. There were a few times where I had to pull onto the shoulder or against the barrier because the engine wouldn't stay below 3000 rpm. It had horrible gearing so 3000 rpm was like 20 mph.

I had it to a few dealers and I was told it was a strategy to keep the catalyst 100% to maintain the PZEV rating.

 

[StevieC]

My 2.4L 4 Cylinder Journey would bump up the idle in the winter time and it made the downshifts coming to a stop light or stop-sign very jerky because of it. Was really annoying.

 

[KrisZ]

Originally Posted by Miller88


The focus was awful in traffic. Just idling along in a traffic jam in stop and go traffic, the catalyst wouldn't stay at temperature, so it would start bumping up the idle. There were a few times where I had to pull onto the shoulder or against the barrier because the engine wouldn't stay below 3000 rpm. It had horrible gearing so 3000 rpm was like 20 mph.

I had it to a few dealers and I was told it was a strategy to keep the catalyst 100% to maintain the PZEV rating.


Your Focus had something wrong with it and your dealer simply fed you lies. No car has to rev. at 3k RPM just to keep the catalityc converters up to temp.

 

[SwampSurvivor]

Originally Posted by KrisZ
Originally Posted by Miller88


The focus was awful in traffic. Just idling along in a traffic jam in stop and go traffic, the catalyst wouldn't stay at temperature, so it would start bumping up the idle. There were a few times where I had to pull onto the shoulder or against the barrier because the engine wouldn't stay below 3000 rpm. It had horrible gearing so 3000 rpm was like 20 mph.

I had it to a few dealers and I was told it was a strategy to keep the catalyst 100% to maintain the PZEV rating.


Your Focus had something wrong with it and your dealer simply fed you lies. No car has to rev. at 3k RPM just to keep the catalityc converters up to temp.


That's' what I always thought, but I had it to different dealers and they all said the same thing. it was very aggravating to drive in traffic.