2000 blazer auto trans. Lately my truck has developed an interesting feature. About 80% of the time I'm driving and I take my foot off to coast my rpms go from 1000 to about 600 very quickly and jump back up. Will do it three times and be fine for a second. Then do it three more times etc... I'm baffled and am hoping someone can point me in the right direction. Thanks

 

Have u scanned it for trouble codes?

 

Ya. She's code free other than a 0442 code once in a while.

 

Noone? This is driving me crazy. Tried cleaning egr, maf and iac. No luck. Mileage is terrible now. I'm getting less than 350 kms to a tank.

 

I am having a very similar problem on my 95 blazer. While driving at 40-50mph and I take my foot off the gas and the tac reaches 1700rpms it will start to bounce, going down in intervals more so then jumping up until it reaches 1300rpms. The car 161,000miles and seems to accelerate the same as it always has and and seems to down shift normal it's just when I'm in the range of 40-50mph when I start to experience the tac problem. I'm meeting with a mechanic tomorrow to take a look at the vehicle but if anyone could give me an idea to what they might think the problem is that would be much appreciated and greatwhitenorth after I talk to the mechanic I'll give you. Years up on what he tells me. Best of luck

 

I should also mention that I have a leak in my oil cooler line and it has gotten worse since this problem has occurred but only seems to leak a small puddle in the morning once I start and let the car warm up and I will only see a few drops throughout the day but at the end of the day when I get home it will only drop one drop of oil and be done until the next morning when I start the car. Also I have noticed a difference in my mileage as well since this problem, I am defiantly not getting the same gas mileage.

 

Any word on that problem? I'm driving almost 1000 kms a week for work. This is driving me crazy

 

Have any of you guys tried seafoam running through your engine from the vacume port?