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-   -   2.5 running rough (https://forums.off-road.com/gm-small-trucks-suvs/11646-2-5-running-rough.html)

**DONOTDELETE** 02-28-2000 12:31 AM

2.5 running rough
 
I have a GMC S-15 4x4 with a 2.5L engine. I have changed the O2 sensor and timed the thing but it still runs king of rough. Yes, I checked all the vacuum hoses and they are good. I checked the computer for fault codes and I found none. The only thing in question is a vacuum line on the very back of the base of the injector. Someone has plugged it and I cant seem to figure out what it goes to. The manual dosnt help me none. I was thinking that if someone else has one of these motors they could check and see where it runs to. Anyone?

92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke

**DONOTDELETE** 02-28-2000 05:54 PM

Re: 2.5 running rough
 
couple Q's
does it act up at idle or all the time?
manual or auto?
how is the vac port pluged?
the general also used two diffrent TB's models 300 and 700
could make a diffrence.
later

HAWG WILD
<font color=red> ALL THOSE WHO WANDER ARE NOT NECESSARLY LOST </font color=red> [img]/wwwthreads_images/icons/cool.gif[/img]

**DONOTDELETE** 02-29-2000 01:58 AM

Re: 2.5 running rough
 
ok the truck has a 4 speed manual trans. And it idles very rough but seams to be running rough all the time. The vacuum is pluged with a bolt that the previous owner or someone put there. So I know that its not "factory" I'm not sure what TBS is on it. I did just change the O2 sensor because the old one was bad and that allowed me to time it at the recomended 8 degrees. But it still runs rough. Like it is missing or something. I've got spark at all 4 cyl and checked everywhere for a vacuum leak because thats what it acts like. Thats when I found the line at the very back of the base of the TBS plugged off and I cant find where it goes.

92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke

**DONOTDELETE** 03-02-2000 01:04 AM

Re: 2.5 running rough
 
can anyone tell me where this vacuum line goes?

92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke

J.R. 03-02-2000 11:54 AM

Re: 2.5 running rough
 
Well, when you stated the line is in the back of the injector I assumed some sort of fuel vent/return line. Doesn't make much sense on a fuel injected vehicle though. Does the 2.5 have a vacuum modulator to the EGR valve? If those vacuum lines are bad they will cause surging in the idle speed.

Sorry, my only experience with four-bangers is with a Toyota...

J.R. [img]/wwwthreads_images/icons/cool.gif[/img]
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