hey all im matt, i have searched and read alot of the posts on here thinking check those first i have done all that i have read and my 1997 2wd 4.3 blazer runs badly. it surges and sounds like vacume leak but i dont have one, i have changed the iac, tps, maf, plugs, wires, cap and rotor, cleaned tb and egr, but im still getting this problem. anyone go through all this and still have the same problem?? if so let me know. this is my daughters blazer and she has a new born, and i cant have her broke down. it will throw the maf and o2 sensor one time then the next two times or more it wont. i was thinking fuel pump, but im pretty sure they either work or dont. i do oldd vehicles so this is ticking me off. anyyyyyy help would be much appreciated.

thanks

matt

 

What are the exact DTC codes it is showing?

 

sorry for slow response. it varies from one time 02 to next time maf(new) and the timing/shift solenoid stays on. just for giggles i unplugged a vacume line and it idles up high but more consistant, and smoother(not smooth but better) replace tps and got ignition module check both good. this is blowing everyones minds here. 2 master mechanics and me being a pretty darn good one myself and still no answer. grrrrrrrrr. im at point now of trying to trade it, but im sure most are hesitant with no 100% positive answer on the problem. thanks

matt

 

You say that it sounds like a vacuum leak.
Does that mean that you can hear the hissing noise? Or that it runs as if there is a leak?

With the codes that it throws and the idle problem it sounds like you have a leak somewhere in your intake. A new upper plenum gasket kit may be in order for your truck. This is doubly likely if you have ever had the intake off the truck in the past.

It could be any of the seals such as the one around the top of the spider assembly which would let in the most air.

Unmeasured air entering the intake would cause the 02 code due to the fuel air mix being off, as well as the MAF code as that sensor is the one reading the incorrect amount of air entering the intake. The surging is usually caused by the computer attempting to balance the air fuel mixture based on the info from the sensors that is incorrect due to the leak.

If the problem goes on for long enough you may also end up damaging your oxygen sensor(s). (not sure off hand if the 97 has one or two 02 sensors though I think it is 2)

Depending on the size of the leak it could also lower your overall vacuum system pressure enough to start causing you problems with anything else in the truck that uses vacuum to run properly.