I have a 95 4WD Blazer and it has recently, and suddenly, started missing or hesitating under load. It has had a slightly rough idle, not too bad, for quite a while. I changed the plugs,wires, rotor and cap this past summer.

I replaced the fuel filter (kind of a bitch on a cold night w/o the right size wrenches) and drove it up the mountain here in Santa Fe and it seemed to drive just fine, no misses. Pat myself on the back for saving a bunch of money on the repair shop. Well, not so fast..... It is doing it again and gets worse each day. I assume the side of the filter (Autozone) that says "out" faces the front of the vehicle. Wondering if I could have put it on backwards.

Doesn't seem like it could be the fuel pump if it worked for a short while after changing the filter does it?????

How does one check the fuel pump pressure? Can you check it from the schrader valve?

I'm sure this is posted somewhere but I'm short for time today.

got to run...

 

Actually, the pump is still a possibility. When a pump gets weak, any kind of resistance can cause a low pressure situation. To check the pump, follow the list in THIS THREAD.

 

If it ain't the pump it could be the Fuel Pressure Regulator.

 

Thanks guys.

I assume that I need a special gauge?

Is it available at Autozone?

Does it sound like the filter is on the right way?

Any other likely reasons for the rpm to be dropping by 100-200 RPM while under load? I still am able to drive up steep mountain roads, but it is jerky and surely not good for the tranny.

Wasn't able to find a post about how to change the fuel pump yet....

 

Standard fuel pressure test gauge available from lots of supply stores (I bought mine from Northern Tool).

From your initial post, yes.

Quite a few of them. Use 'search' for 'change fuel pump', etc.

 

Thanks.

I found that they have them at Autozone and also have a description on how to change the fuel pump. I have a full tank of gas though. What the heck do you do then? Keep driving it or siphon into a big tank?


Besides the fuel filter and pump, is there a common failure for '95 blazers in particular that cause this missing/hesitation? My wife is driving it today and said it is getting pretty bad even in town.

 

I bought a fuel pressure tester. Gets up to about 60 psi when engine is off. When engine is on it drops (as it should) to 57 psi. It goes up to 62 upon intial revving and then goes to around 54 or so upon sustained revs.

When I turn off the pressure drops right away, but slowly.

The manual mentions pinching the lines to see what is causing the pressure drop. Anyone have any suggestions on where to pinch it?

Also, although clearly I have an issue with the pressure dropping after turning it off, would that cause the now horrible hesitation I have - now at idle and under load? I know this is not the EGR since I went through all that years ago and got a new EGR valve and screened gasket.

Also, I tried having Autozone check my codes and the unit kept saying "link error" and would not connect. What would cause that?

 

Sounds like you have a leaking FPR. When this leaks, it allows unmetered fuel into the lower intake plenum where it can get into the intake as well as drain into the engine oil. It is very common for the CPI motors to have this type of failure. Check out Lindertech.com for their update kit which allows you to install a newer design FPR from the SCFI motor onto the CPI spider. Do not forget to replace the internal lines (nut kit) whenever you pull the spider.

About reading codes. Well, 1995 was the bastard year for on-board diagnostics. It is not fully OBD2, but it cannot be considered OBD1 either. It is commonly referred to as OBD1.5 and most off the shelf scan tools cannot read the stored codes.

 

Thanks. I know you are the expert, but why would my data tell you that it isn't the fuel pump?

And again, could a bad FPR cause all the hesitation or is it another problem that hasn't shown symptoms yet?

I saw that the FPR R/R thread has been chopped off....how big a job is that including the "nut kit"?

 

here's a full walk through with pictures it should tell ya all you need to know http://www.automotiveforums.com/vbul...d.php?t=473110