Here's a brief recent history of my 1996 4.3 vortec;

Rough Idle, 11 - 12mpg
[ul][*]Replaced Plugs, wires, distributor cap.[/ul]
Still Rough Idle,11 - 12mpg
[ul][*]Replaced Injection spider and regulator for updated MFI one along with O2 sensors.[/ul]
Still Rough idle, 14 mpg
[ul][*]Replaced EGR[/ul]
Still rough idle, now 16 mpg.

Can someone tell me what else I may be overlooking? The MPG should be around 17 - 18 mpg with a smooth idle (as it was when I bought it). I have ordered a vacuum guage to check there are no other vacuum leaks - this has a direct effect on the fuel pressure regulator and MPG.

The engine itself has good compression with no oil burning.

I know these are notorious for rough idles, I have gone through most things, if I can find out the problem then I may be able to help other Blazer owners. Is there anything else I am overlooking?

Thanks in advance.

 

when you find out let me know...... i replaced EGR valve and still ruff idle. I'm doing fuel pump next

 

Thor, I would not recommend you change the fuel pump without first verifying that the fuel supply is causing the problem you are experiencing. But that is a topic for another thread.

GGA, do you experience this condition more when it is raining? What was the compression on each cylinder (list 1-6 please)? How did the plugs look? Was there any indication of which cylinder may be causing the misfire?

 

do a simple pressure test on the exhaust . a clogged converter seems to foul things up and will give a misfire or rough idle .or if its not to rusted drop the exhaust just enough for it the breath.

 

Easier way of doing it is to pull an O2 sensor (disconnect it as well).

 

My Old Blazer had a similar idle issue due to the Throttle Position Sensor (TPS).

 

Also make sure you installed correct plugs, OEM i know certain brands dont work well with the vortech.

 

Mine too has a very rough idle. It gets worse the hotter the truck gets. haven't replaced anything yet as it JUST started this. It does seem to be worse in the rain though hmmmmmmm[]

 

vaccum leak?