2.8 timing way off/failed emissions - S-10 Forum
 
LinkBack Thread Tools
post #1 of 10 Old 11-18-2015, 12:11 PM Thread Starter
Registered User
 
Join Date: Feb 2009
Age: 37
Posts: 130

User is: slicknick13 is offline
2.8 timing way off/failed emissions

So I went for an inspection today and failed all of my idle tests:
CO: limit 1.2, actual 8.88
HC (ppm): limit 220, actual 1059

2500RPM tests were good:
CO: limit 1.2, actual 0.01
HC (ppm): limit 220, actual 50

We poked around a little in the garage with the tailpipe still hooked up, cleaned the EGR, plugged the evap, pulled the PCV etc. with no change in the idle emissions.

Next step was to check timing, which was retarded by a long shot. We're talking like the timing mark is in the 3 o'clock position. At that point, I had to leave the shop.

Got the truck home, the distributor loosened, and the base timing wire unplugged with no change. Tried to advance the timing but it naturally won't even get close to the marks. Plugged the scan tool in to make sure all of my sensors were sending data, though I don't know what to look for on a lot of them at idle. Temp and everything was OK.

Any suggestions out there? I just can't fathom why that timing mark was so off unless the balancer ring slipped or something.

Truck runs fine, but is pretty rich at idle. I put a kit on the throttle body very recently, so it's all cleaned out.

slicknick13 is offline  
Sponsored Links
Advertisement
 
post #2 of 10 Old 11-29-2015, 02:26 PM Thread Starter
Registered User
 
Join Date: Feb 2009
Age: 37
Posts: 130

User is: slicknick13 is offline
Re: 2.8 timing way off/failed emissions

Following up to this since I hate dead end threads:

Changed the O2 sensor. That got me some action that I didn't have before on my scan tool.

Rotated the engine to TDC and marked the balancer. I guess it slipped. Got the motor timed to what I think is around 10 degrees. The 'ol screwdriver in the spark plug hole technique has a little room for error.

At this point I was running pretty good. I had reset the ECM and was out driving to relearn everything. Took it up to the inspection shop and hooked it to the tester, numbers were a lot better but still not where it needed to be. A bump to the throttle to keep the engine off idle, but still within the idle specs of the testing equipment brought it in to passing. Barely.

Only "problem" I have left is that the truck won't go into closed loop at idle. Which is why I think we had to bump the throttle during the test to get it to pass, it would go into closed loop at that point and clean up.

New vacuum hoses and a hot air riser should get me into a pretty reliable state for the winter.
slicknick13 is offline  
post #3 of 10 Old 11-30-2015, 05:22 AM
Registered User
 
Join Date: Aug 2011
Posts: 854

User is: damanx is offline
Re: 2.8 timing way off/failed emissions

Quote:
Originally Posted by slicknick13 View Post
Only "problem" I have left is that the truck won't go into closed loop at idle.
What BIN is in the ECM?

I have the 1228062 ECM with ATKX BIN and it goes into open loop at idle.

It does this to keep the engine cooler by dropping the BLM value to whatever amount is programmed in the BIN.

What scan tool are you using?

If you can see these numbers with it, what is the IAC count, and, what is TPS voltage value?

1985 GMC S-15 Gypsy ext cab.
3.4l, Edelbrock intake, a 4.3l throttle body controlled by an '88 TBI ECM. 700R4 with 3.73 rear. Real time tuning using a CF-30 Toughbook with a Moates Ostrich 2 emulator.
damanx is offline  
 
post #4 of 10 Old 12-26-2015, 09:09 PM
Registered User
 
Join Date: Dec 2012
Age: 49
Posts: 92

User is: sparkybuoy is offline
Re: 2.8 timing way off/failed emissions

It has to get to certain coolant temp to go into closed loop so if you have scan data...if you don't see it go over I think it was 140 degrees farenheit...it won't go into closed loop which usually points to a lazy thermostat - if it needs a thermostat get the correct 195er from NAPA and get the Premium - it's made by Robertshaw and is warranted forever against defects including laziness or sticking closed
sparkybuoy is offline  
post #5 of 10 Old 12-28-2015, 10:30 AM
Maybe later.
 
tytotheler92's Avatar
 
Join Date: Aug 2011
Location: Northeast Ohio
Age: 27
Posts: 9,334

User is: tytotheler92 is offline
Garage
Send a message via AIM to tytotheler92
Re: 2.8 timing way off/failed emissions

I agree. It sounds like a lazy thermostat at this point.



I've had wayyy to many of these trucks. (Currently...on number 7)

1988 S-15 - 5.5/6 drop

1985 S10 Blazer 4WD

1998 Blazer ZR2 5 Speed!

Quote:
Originally Posted by fackinsteve View Post
3 doors for 1 and a half whores
Quote:
Originally Posted by svmcgover View Post
He only bought one wheel. So every picture we see is going to be a pic where either the rear or front is conveniently out of frame.

tytotheler92 is offline  
post #6 of 10 Old 01-03-2016, 04:59 PM Thread Starter
Registered User
 
Join Date: Feb 2009
Age: 37
Posts: 130

User is: slicknick13 is offline
Re: 2.8 timing way off/failed emissions

Thermostat is a 195, brand new.

Here's a snapshot after warming up to operating temp.
slicknick13 is offline  
post #7 of 10 Old 01-06-2016, 08:05 AM
Registered User
 
Join Date: Aug 2011
Posts: 854

User is: damanx is offline
Re: 2.8 timing way off/failed emissions

You've checked for vacuum leaks?

As stated, a lot of the BIN's for these ECM's go into open loop at idle and that is why you see the short term fuel trim locked at 128.

Has the maybe it's a cat problem?

What ECM are you using and do you know what the 4 letter code on is?

1000 rpm at idle after warm up seems high.

1985 GMC S-15 Gypsy ext cab.
3.4l, Edelbrock intake, a 4.3l throttle body controlled by an '88 TBI ECM. 700R4 with 3.73 rear. Real time tuning using a CF-30 Toughbook with a Moates Ostrich 2 emulator.
damanx is offline  
post #8 of 10 Old 01-08-2016, 08:07 PM
Registered User
 
Join Date: Dec 2012
Age: 49
Posts: 92

User is: sparkybuoy is offline
Re: 2.8 timing way off/failed emissions

That's REALLY fat at idle

Idle speed is too high however that's not going to cause you to be that fat

you might have weak spark and at idle that's gonna hurt ya

what's MAP voltage at wide open throttle?

Check MAP vacuum line for leaks
sparkybuoy is offline  
post #9 of 10 Old 01-08-2016, 08:14 PM
Registered User
 
Join Date: Dec 2012
Age: 49
Posts: 92

User is: sparkybuoy is offline
Re: 2.8 timing way off/failed emissions

what year is yours?

I remember back then they'd go into open loop at idle and that mostly because they have the oxygen sensor way down stream without it being a Heated oxygen sensor
sparkybuoy is offline  
post #10 of 10 Old 01-08-2016, 08:26 PM
Registered User
 
Join Date: Dec 2012
Age: 49
Posts: 92

User is: sparkybuoy is offline
Re: 2.8 timing way off/failed emissions

you can convert it to a HEATED Oxygen sensor and fix that issue and also gain mileage and driveability
sparkybuoy is offline  
Sponsored Links
Advertisement
 
Reply

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:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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

 
For the best viewing experience please update your browser to Google Chrome