slugges starts

[ThomS]

I know this topic has been addressed and if so I am sorry.
When I have a cold start the RPM's are only around 500 and if I do not keep the engine running a little fast it wants to stall and after 30 seconds of so It is fine. I have turned the idle screw up about 1/4 turn and no effect. What have you guys done to fix this problem?
Thanks for any ideas you might have.

[Tom @ Fast Forward]

It seems to be an 01-05 phenomenon. Not sure if there is a cure for the cold start idle for the first 30 seconds. Thats part of what the old VTCS used to do before we removed it. Good news is that it is "Gone in 30 Seconds". I think they made a movie about that? :)

[ThomS]

It seems to be an 01-05 phenomenon. Not sure if there is a cure for the cold start idle for the first 30 seconds. Thats part of what the old VTCS used to do before we removed it. Good news is that it is "Gone in 30 Seconds". I think they made a movie about that? :)

Yes if they did make a movie then it must have our yellow car in it. hahaha.
We are taking the yellow car to PA this week for the Pace Miata club get together and wanted to adust it if possible for the trip. Does not sound like it is possible. If you ever hear of a fix let me know.

[elerner]

I think I noticed that this became less of a problem for me when I moved the white plastic restrictor from the vacuum hose by the IAC to right next to the passenger side valve cover breather.

I'm only getting the low idle for about 8 seconds in the morning. It's worse if I haven't driven the car the day before.

[Tom @ Fast Forward]

It became a lot less of a problem for me when I stopped using Mobil 1 and went back to regular oil. The Oil control valve really doesn't seem to like synthetic oil.

[elerner]

I'm running Mobil 1 5w-30. Does the Oil Control Valve come into play during idle? I thought it was only when the "variable valve magic" happens, around 3-4K.

[maggie]

Has anyone tried Mobil 1 0W-40? I wondered if the 0w end of the blend would alleviate the cold start issue.

[Tom @ Fast Forward]

I don't think it comes into play at idle? I think the idle issue for the first 30-60 seconds cold is the lack of the VTCS. A lot of the engines, like Honda, have the cam switch at around 4500 RPM from one set of lobes to another. It is a hard switch and is basically RPM controlled. The Miata VVT is continuously variable. It changes a little or a lot at almost any RPM based on load.

Next oil change, I think I might try 0-30 or 5-30. Once the oil gets even a little warm, all the problems go away. For my 05, that is about 2-3 blocks of driving on a cold start after sitting overnight. If it is parked for a few hours during the day and then started and driven, no problem.


I'm running Mobil 1 5w-30. Does the Oil Control Valve come into play during idle? I thought it was only when the "variable valve magic" happens, around 3-4K.

[elerner]

Even though this may be obvious, I thought I'd throw it out. Once my car starts , I keep the clutch in until the rev's are up above a grand. I figure the additional resistance of the cold tranny might keep the engine lugging.

[Tom @ Fast Forward]

Evan, take care of your back.

Actually a lot of boosted Miatas add a jumper to eliminate the clutch switch so they can be started without depressing the clutch. Some think that starting the engine cood with the clutch depressed, especially with a heavy competition clutch,
is hard on the thrust bearing.

[lowboy72]

Hit or miss for me is to blip the throttle immediately after the engine fires up. The trick is to catch it right before the rpms drops. It will sputter a second or two with the accelerator in but at least it is the idle is not hanging 500 RPM for 5 to 10 seconds.

[ThomS]

It became a lot less of a problem for me when I stopped using Mobil 1 and went back to regular oil. The Oil control valve really doesn't seem to like synthetic oil.


Well have made the change from synthetic oil to reg dyno oil and the car is running a lot better especially at a cold start.. SO smooth it is scary....

[Tom @ Fast Forward]

Pretty soon you will need a new title. :)

[ThomS]

Pretty soon you will need a new title. :)

You might of spoke too soon.

I will post something in Misc section .

[ThomS]

After the car sits overnight or even for four or more hours that cold start problem has returned. after I start it if I blip the gas the car is fine, but can not drive it to good till it warms up. I have changed to reg oil and the problem went away for a short time, now is back. There has to be a reason for this. Maybe try 5w30 reg oil.

[Tom @ Fast Forward]

Doesn't the owners manual suggest 5W30?

[ThomS]

No for the 02 it says 10W30

[John Miles]

After the car sits overnight or even for four or more hours that cold start problem has returned. after I start it if I blip the gas the car is fine, but can not drive it to good till it warms up. I have changed to reg oil and the problem went away for a short time, now is back. There has to be a reason for this. Maybe try 5w30 reg oil.

Honestly, this really doesn't have a darned thing to do with oil. It is purely a consequence of the removal of the VTCS solenoid.

The ECU is using a fuel map that assumes that airflow is being restricted by VTCS under cold-start conditions. But it isn't. There's too much airflow for the fuel map being used. As you note, if you step on the gas a bit, it will switch to a richer fuel map, and the stumbling will go away until you come off the gas agani.

As far as I'm aware the only remedy is to rig up a circuit to artificially bias the TPS value high, forcing the ECU to switch to the richer map until the water temp comes up enough to initiate closed-loop operation. I've posted a few notes about this before.

If there were a simpler solution, it'd be great, and maybe there is, but if so, it won't involve monkeying with oil viscosity. It's just a mixture issue, plain and simple. The best course of action is probably to ignore it, or allow a bit more warmup time before taking off.