I have just noticed on start the idle jumps to about 1000-1500 rpm, then slowly drops to normal. I inspected the vac lines thinking might be a leak. Replaced 2 short peices near the vac canister mounted on the hood, they were badly powering. no fluids in the lines.

about 3 weeks ago I replaced the transfer vac switch. maybe tomorrow i will pull the vac hose off of it and see if any fluid is being sucked in.

any thoughts

97 blazer 3 button 4x4 automatic.

tnx

bernie

 

That is normal.

 

don't think this is normal. never done this before. tomorrow will hook up scanner. no check engine light.

tnx,

bernie

 

could be your iac motor, but on cold start up mine idles at 1000rpm than as it heats up the idle comes down to 500rpms. what are you driving?

 

Mine idles at about 1300 when i start it up cold.. Sounds about normal to me. It only does it in the winter tho. I wouldnt worry to much about it, unless it starts to idle higher than 1500

 

ok, but I have never noticed this before. Have had the blazer 8+ years, this is the first time, the vehicle is stock 97, except for the kn air filter. I will keep an eye on it.

bernie

 

Hmmm... ever clean the MAF? PCM's often up the idle when sensors dont quite add up.

 

Hey!... Longer02,97cherryblazer & pettyfog are all correct-this IS a normal situation(I never liked it much either at sub-zero temps but..) Do look at the MAF-even the slightest restriction there will cause issues.If this occurs when fully warmed up I would be more concerned about vacuum leaks then. No CEL? Then the system is doing what it is supposed to do-upon cold starts getting oil to the cam & valvetrain as fast as possible! step66