Vacuum for 95 blaze 4.3 - 1995 Chevrolet Blazer

Its a vacuum line that comes from the transfer case vacuum switch that controls the four wheel drive shifts it in and out of 4 WD at the front carrier also runs through an accuator like a diaphragm that controls the vacuum. You need to remove the battery and the tray to see it.

Are the vacuum lines properly connected and have vacuum available to the switch?

Vacuum leak often causes surging. At the age your truck is, vacuum hoses are a likely problem check for cracking and such. Replace as needed.

Use V Power European cars same deal 95 RON is a minimum. The 98 you will get slightly better performance and cleaner burn.

I have the same issue with my '95. I'm combing salvage yards - will advise if i find more than one

First I would check all those pesky little rubber vacuum hoses that are used for pollution control. They tend to go hard and split if they are over 10 years old, allowing air /vacuum leaks and also prevent functions that operate on good vacuum from working.

There is a vacuum actuator mounted on the front differential that locks the shafts to engage four wheel drive.

Try replacing the vacuum lines that go to the transfer case from the engine. I had the same problem on a 95 Jimmy and was told to do it.... I changed every piece of vacuum hose that had anything to do with the 4x4 and it worked. Hope this helps you out

I had the same problem on my 95 jimmy. I could get it into 4 lo but 4 hi would not work. I replaced all the vacuum hoses that went to the transfer case and it fixed my problem.

What is the fuel pressure it has to be at least

1. Ignition "OFF" for 10 Seconds.
2. With ignition "ON," engine "OFF" and fuel pump running, pressure should be 333-376 kPa (48-55 psi). For additional fuel pressure testing, See: Computers and Control Systems\Testing and Inspection\Symptom Related Diagnostic Procedures\A - E Charts & Related Test Procedures\A Charts\Chart A-7 Fuel System Diagnosis
3. Have you tested the compression?
4. A totally plugged cataltic converter can cause tis too because the engine cannot breathe
5. to verify a plugged cat connect a vacuum guage to manifold vacuum and ccrank the engine you should get at least 2-4" of cranking vacuum providing the timing chain has not jumped and the cat is not plugged

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