2.5L Questions: Running poorly - S-10 Forum
S-10 Forum is the resource on GM S-series trucks, Suspension, engine information, Body Modifications, painting tutorials.  Modifications to suit every need, budget and whim

2.5L Questions: Running poorly

Go Back   S-10 Forum > Engine and Drivetrain Tech > 2.5L - 1st gen 4-banging
New User? Register Forgot Password


 
LinkBack Thread Tools
Old 03-13-2008, 10:57 PM   #1
Registered User
 
DarkRose's Avatar
 
Age: 35
Join Date: Nov 2005
Posts: 91
Location: Columbus, IN
User is: OffLine
Question 2.5L Questions: Running poorly

Got a few questions, I'm working on a 2.5L 85 S-10 (Well, S-15 Sonoma), Manual, no PS, no A/C, for a friend's son. I know enough about my 4.3 to tune it decent, but know almost nothing about a 2.5L...

Truck was running rough, I did some initial checks, timing was 12° BTDC, engine tag called for 8, adjusted it, with the plug under the dash jumped, and battery unplugged after to reset the computer. He told me the longer it ran, the worse it ran.
Idles better, but when if you stab the gas, or even blip it a little, tries to die, if you give it gas VERY slowly and gradually, revs up and runs fine, as long as you creeeeeeeep up on the gas. No check engine light (it does work). Checked #1 plug wire with a spark tester, good spark, plug wires are new.
Tested alternator (handheld tester), charging fine. Ran it for about 5 minutes, quite a bit of water coming from exhaust pipe, condensation from sitting too long? Didn't run it too long because the coolant is a few inches low. Battery is new.

Here's my planned course of action, lemme know if I'm on the right track:

Truck has been sitting quite a while, talking period of 2-3 years, siphon the crap in the tank, put in decent gas.
Replace o² sensor.
Check cap and rotor for condensation or corroded contacts, test remaining wires for spark.
Seafoam... But... no brake booster, like on my 4.3 where I pour some through the booster vaccum line while running, where would I get the Seafoam into the vaccum system in the 2.5?

Am I on the right track or should I be looking at something else?
Sponsored Links
Advertisement
 
Old 03-13-2008, 11:18 PM   #2
The Eye is watching you!!
 
kamesama980's Avatar
 
Age: 30
Join Date: Nov 2007
Posts: 963
Location: dekalb, IL, USA
User is: OffLine
Re: 2.5L Questions: Running poorly

my suggestion (though I've never seafoamed a 2.5) would be the smaller PCV hose going just under the throttle body. it'll get sucked in via vacuum and have a nice distribution. just be careful not to bog it down too bad, thats a big hose for introducing liquid.

hate to say it but blown head gasket isn't out of the question from the low coolant and excess condensation. smell the exhaust, if there's coolant in it, you can tell. it's kinda sweeter smelling (like coolant go figure). make sure you have oil in it, then drain and refill it. compression test wouldn't be out of order either.
Old 03-14-2008, 05:29 PM   #3
Registered User
 
DarkRose's Avatar
 
Age: 35
Join Date: Nov 2005
Posts: 91
Location: Columbus, IN
User is: OffLine
Re: 2.5L Questions: Running poorly

Ok, let me add some more data... Engine is supposedly rebuilt with 50k on the rebuild, so head gasket is possible, but hopefully not likely, the engine was recently installed and the guy who installed it never got the troubleshooting or tuning done, due to an unfortunate (yeah right) incarceration.
The water coming from the tailpipe looks and feels and smells to be just that: water. No sweet smell, no color, no gas or any other odor other than the soot from the tailpipe. The radiator is low for 2 reasons: the 19 year old kid who worried more about his dirtbike than the truck, until he now has a g/f, and a split heater hose which I just fixed, but will be keeping an eye on the level after I get it topped off.
I'm hoping to check some of the stuff I mentioned earlier next weekend and maybe start it up and let it run 20-30 minutes to possibly "dry" anything out and get things lubed good and circulating. Oil looked decent, he said it hadn't really been driven at all since the change, still looks good and light-colored.

As for the Seafoam, I don't recall seeing a PCV valve, but might need to take another look, valve cover just had oil cap, and a grommet/elbow going to an "L" hose hooked around into the back of the breather for the breather filter... Unless I completely overlooked the PCV...
Old 03-14-2008, 11:53 PM   #4
Registered User
 
wi11ie's Avatar
 
Age: 55
Join Date: Jan 2007
Posts: 326
Location: Houston,Tx.
User is: OffLine
Re: 2.5L Questions: Running poorly

Nope that is it!
I just ran a pint of SEAFOAM thru mine today (that elbow thingy) and it smoked like a bitch! After letting it sit for 10 mins or so ,started it up.
Ran like shit and smoked for 5 minutes then cleared out and runs better than it has in A decade!!!
SEAFOAM!!!! Good stuff!
wi11ie
Old 03-15-2008, 03:04 PM   #5
The Eye is watching you!!
 
kamesama980's Avatar
 
Age: 30
Join Date: Nov 2007
Posts: 963
Location: dekalb, IL, USA
User is: OffLine
Re: 2.5L Questions: Running poorly

yea I don't know that there even is a vavle. might just be an open hose but I doubt it. *shrug* doesn't matter much.
Old 03-30-2008, 03:05 PM   #6
Registered User
 
DarkRose's Avatar
 
Age: 35
Join Date: Nov 2005
Posts: 91
Location: Columbus, IN
User is: OffLine
Question Re: 2.5L Questions: Running poorly

Ok, updating this because I'm still having problems, so far have Seafoamed the motor through the PCV vaccum to the TBI, replaced the fuel filter, checked spark, replaced cap and rotor (old ones were worn off center, rotor dug into cap on one side), replaces air cleaner, adjusted timing to 8 deg. BTDC, replaced O2 sensor. Drained old gas, filled with a couple gallons fresh 87 octane. I think that covers it.
Starts fine, still has problems when you try to push down on the gas pedal, wants to die until you get it almost to the floor again, or accelerate VERY slowly (this is all in neutral), my next thought is testing/replacing the TPS, seems to run fine at the start and end of the accelerator travel, and wants to die in the middle of the pedal travel, which could indicate a dead spot in the TPS, right?
Also due to a tool shortage that I didn't know about where the truck is at (kid has NO tools, I didn't realize that, so I didn't bring enough tools with me), I haven't yet been able to pull and check the spark plugs, just checked for spark.
If checking the plugs and TPS don't fix it, I'm stumped. If you push VERY gradually on the gas pedal, it does ok, but any sudden pressure (like you would taking off from a stop light, sign, etc, just normally) tries to kill it, haven't been able to figure out if it's flooding or starving...
Any other ideas to check would be MUCH appreciated.
Old 03-30-2008, 03:34 PM   #7
Rarely goes over 20mph
 
beaniebmx's Avatar
 
Join Date: Jun 2007
Posts: 3,164
Location: Iowa
User is: OffLine
Re: 2.5L Questions: Running poorly

TPS, clean the IAC, its on the TBand has 2 t-15? torqx screws, clean that and the IAC port.

then pull off your EGR valve and clean that out and make sure the tiny vacuum port isnt clogged.

the EGR builds up with carbon after awhile and can sometimes stop working enough to make the engine run like crap.

but then the tps could be one of the factors.
Old 04-01-2008, 11:08 PM   #8
Freaks Of Nature
 
tacobell's Avatar
 
Join Date: Jan 2007
Posts: 48
Location: Lafayette,IN
User is: OffLine
Re: 2.5L Questions: Running poorly

sounds to me like a fuel pressure or volume problem. visually check the injector ( while revving) for a steady, constant fan pattern. The little diapraghm that sits between the fuel pump and the sending unit is notorious for taking a shit allowing just enough fuel for it to run but dumping fuel back into the tank. But it could be a couple of things, plugged exhaust (cat), timing etc.
Old 01-13-2010, 03:23 AM   #9
Registered User
 
Join Date: Aug 2009
Posts: 14
Location:
User is: OffLine
Re: 2.5L Questions: Running poorly

why is everyone so worried about the egr valve? not to sounds dumb but mines been plugged off since the day the truck drove off the lot in 1990 lol
and has never had a problem ( that was egr related ) lol
Old 01-14-2010, 12:16 AM   #10
Wire Splicin Fool :-)
 
lesterl's Avatar
 
Age: 35
Join Date: May 2008
Posts: 8,691
Location: Harrisonville, MO
User is: OffLine
Re: 2.5L Questions: Running poorly

Well if you have thought about it, the EGR is a problem child of the Duke. Blocking the EGR off without retuning the ECM causes the ECM to run LEAN because of lack of uncombustible gases in the intake mix when called for. (Lean can be bad, I had my EGR's vac port plug and it burnt a hole in a piston in two different engines, the second engine within a few minutes of operation, granted I think the fuel pump was weak at the time also.)
Old 01-14-2010, 01:43 AM   #11
Cool, Tight, & STRONG....
 
Steady Eddie's Avatar
 
Join Date: Mar 2008
Posts: 1,939
Location: The Great Pacific Northwet
User is: OffLine
Re: 2.5L Questions: Running poorly

Quote: Originally Posted by jabez006
why is everyone so worried about the egr valve? not to sounds dumb but mines been plugged off since the day the truck drove off the lot in 1990 lol
and has never had a problem ( that was egr related ) lol
================================
jabez--

You are not the first person the has said that they de-nutted the EGR valve and suffered NO issues after...

I could not do it. I neutered mine by dis-connecting the vacuum line to it. Soon the SES light came on and would not go out. At that point, the brainbox goes into an open loop condition and operates the motor by using fixed timing and fueling, designed into the brainbox programming.

Sure, it'll run, and fairly well, too. But any performance and economy goes out the window. Or tailpipe...

sigh...I guess a guy could just put black tape over the SES light...
Sponsored Links
Advertisement
 

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the S-10 Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 11:05 PM.

Powered by vBulletin® Copyright ©2000 - 2011, Jelsoft Enterprises Ltd. SEO by vBSEO 3.2.0
SEO by vBSEO
vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.