RPM - What's it supposed to be when stopped?

[GMCritic]

When I'm in drive, sitting at a stop light, my montana runs just a wee bit rough and idles at 600 RPM. It doesn't sputter or anything when giving gas and runs well when driving (if I don't use cheep gas). Is this a normal idle speed when stopped? Any thoughts as to why it's running a bit on the rough side when stopped at a light? 2000 Montana, 40,000 miles.

[GMMerlin]

Originally Posted by GMCritic

When I'm in drive, sitting at a stop light, my montana runs just a wee bit rough and idles at 600 RPM. It doesn't sputter or anything when giving gas and runs well when driving (if I don't use cheep gas). Is this a normal idle speed when stopped? Any thoughts as to why it's running a bit on the rough side when stopped at a light? 2000 Montana, 40,000 miles.

Well first question is what fuel are you using (octane wise)?

You may have some dirty injectors, this would cause a rough idle condition.
Over the counter fuel treatments will not properly clean the injectors..the proper way to clean the injectors is to use a 10% solution of TOC and gas at 75 psi..perform this procedure twice and the problem will be resolved.
Then you need to use Top Tier gasoline (87 octane) and you should have no more problems

[GMCritic]

I typically use Chevron standard. However, lately I've been switching back and forth between standard and plus. If I put any bargain gas in the Montana it tends to stall.

The shop that did my lower intake manifold quoted me $125.00 for a complete injection cleaning service. So, you're recommending that I do this?

BTW, can you answer my question about idle speed? I'm just curious.

Thanks for the reply!

[GMMerlin]

Originally Posted by GMCritic

I typically use Chevron standard. However, lately I've been switching back and forth between standard and plus. If I put any bargain gas in the Montana it tends to stall.

The shop that did my lower intake manifold quoted me $125.00 for a complete injection cleaning service. So, you're recommending that I do this?

BTW, can you answer my question about idle speed? I'm just curious.

Thanks for the reply!

The idle speed is controlled by the PCM and there is no spec for the RPM.
What you are looking for is the IAC counts to be within a certain range.
Your van is designed to run on 87 octane fuel..using higher octane fuel can cause cold start and driveability concerns.
Use a fuel that is Top Tier (look it up on the net.)

It is obvious that you are not using a GM dealer to do your repairs, so I will say this...having your fuel injectors cleaned by any other product then a 10% solution of TEC and gasoline has not been proven to be effective...the fuel injector pressure drop must be checked prior to cleaning the injectors to see if the injectors are dropping equally. If there is a difference in pressure drop outside of specs, then the injectors are to be cleaned 2x using the formula stated above..then the injector drop is to be checked again to see if the cleaning procedure was effective..any injector that does not drop equally is to be replaced.
The problem with maintance fuel injector cleaning with products other than TEC may cause damage to the coils inside the injectors and could cause issues later on.
The ONLY way to be sure that your fuel injectors have been properly cleaned is to check the drop before and after the cleaning process and compare the results.

[cdru]

Originally Posted by GMCritic

I typically use Chevron standard. However, lately I've been switching back and forth between standard and plus. If I put any bargain gas in the Montana it tends to stall.

The only difference between standard or plus from a reputable brand is the octane level. The higher the octane level, the less predetonation (knock) is present. Our minivan's aren't high enough performance for knock to be a real issue, so save the $.10 per gallon and just go with the standard grade.

But as you say, stay away from the discount el-cheapo gas. Should you go with the Top Tier gas (retailer list here)? It's up to you. I use Speedway, Marathon, or BP gas mainly and don't have issues.

[GMCritic]

Ok, thanks for the replies. Cheveron is on the top tier list, so I'll stick with them. Since the lower intake manifold was changed, I'm not having the problem with the knocking and pinging that I was having before. Thanks for the information. I'm just suprised nobody has stated what their vans idle at under normal temps.

[gls02]

To answer your question. My Silhouette idles about 550-600 rpms in drive, around 750 rpm with the A/C on in drive.

[GMCritic]

Originally Posted by gls02

To answer your question. My Silhouette idles about 550-600 rpms in drive, around 750 rpm with the A/C on in drive.

THANK YOU!!! Ok, mine does the same. Strange thing, today it rained and it seemed to run smoother when idling.... go figure.