OK guys, here is a weird one. My Blazer only does this after sitting out in the hot sun all day, not in the AM, and not if it has been parked in the garage all day. At about 70 mph, it feels as if the engine cuts out and there is a loss of power for a split second. This occurs on flat ground, hills, with the AC on or off. After coming out from work in the evening and starting the Blazer, it usually takes about 5 miles for it to start this problem, and it usually stops after like 15 miles. I can not get it to repeat for the mechanic. He thinks it is possibly an intermittent transmission problem.

No codes are being thrown, tranny was serviced recently, fuel pressure tests good, injectors / fuel system was just cleaned.

Any ideas are appreciated!

 

How about plugs wires cap and rotor? My girlfriends Blazer had similar probs, I figured it to be a miss fire. Replaced plugs,cap, and rotor, and so far so good. knock on wood. lol

 

I had much the same problem however mine would not quit. New MAP sensor and my blazer is smooth as silk now. Plus it seems to have more mid-range power than it did before because it doesn't need to down shift to make it up one of the hills on my commute to work.

But yeah, I'd check out the plugs, wires, cap and rotor first before dropping money into any sensors. If you don't know when the last time they were replaced, it is good preventative maintenance anyway, but the plugs, cap and rotor are very easy to inspect.

 

Well, the shop hooked it up to the diagnostic tool and said that the plugs, wires, and cap were good. The guy said he pulled four of the plugs and they looked good, and inspected all the wires. They were quite certain that the plugs, wires, and cap were not the problem. It has 70K on it, I plan to do those at about 85K. The Blazer came from up North, and it had a couple of electrical ground issues underneath when I first got it. Don't know if that could have any bearing on it...

How much was the MAP sensor, is it hard to change, and where is it? Perhaps I can do that one myself over the holiday weekend?

Thanks for the input guys, and if anyone else has any similar experiences, please let me know.

 

Is it a very trustworthy shop?

I have a problem with not believing half the stuff any shop tells me.

 

The MAP sensor is a tool-less change. It is located on the passenger side of the upper intake manifold about 3" behind the throttle body. It'll have an electrical connection into it from the side and it just pulls straight up out of the plenum. I changed mine in the parking lot of the AC Delco store here in town. I believe that the new MAP sensor cost me $56 or something like that. It was almost the same price as the ones from Advance Auto or Napa so... I went genuine.

You might also want to check and clean your MAF sensor. A dirty MAF sensor will make the engine do screwy things. Same with the MAP sensor. Both of these sensors affect how the transmission shifts as well.

Here's a shot of the MAF apart. It really doesn't show the elements that need cleaning very well, but you'll see when you open yours up:

I would first try to just spray electrical parts cleaner on the elements. If that doesn't work, get the cap off the electrical parts cleaner can and spray some cleaning fluid into it. Using a Q-tip VERY carefully wipe the crud off of the elements. They should turn out to be almost white when clean. Clean both sides of the elements and reassemble your MAF.

I'd give that a try first before replacing your MAP sensor.

Good luck!

 

Pardon my ignorance, but where is the MAF located? Also, the pic didn't come through. I will try cleaning the MAF, and then if that doesn't work, replacing the MAP sensor.

Oh, and I believe the shop to be trustworthy, there were a couple of things they could have got me on in the past that I know they didn't, but, you never know.

 

Hmm.. Pic works fine both here and at my home computer. Weird.

Anyway, The MAF sensor is located in the intake pipe between the filter and the throttle body.

 

Pic works at home. Thanks for the info, and I will give these items a try over the weekend.

 

Well, tried cleaning the MAF, and replaced the MAP sensor, and the darn thing is still doing it. But, only when it is hot out. Anyone have anymore ideas as to what to try next?

Thanks for all your info, thus far.