[Gmecm] TBI and EFE

Mon Dec 4 00:29:22 UTC 2006

You also may want to check the o2 sensor and make sure it still working 
properly after all that excess fuel. I have a wideband controller and sensor 
in my 95 TBI truck (simulating the narrow band signal) and have just run 
across where if the startup voltage is too low for too long on the 
controller, it shuts off and my o2 signal is basically non-exisitant... when 
that happens the ECM will try and adjust to whatever voltage it thinks it 
sees and it will idle all over, surge and loose power as you drive until it 
finally trips a code and goes into open loop. It takes quite a while to 
finally trip a code though....  Just my 2 cents! :)

Garrett Herning

>From: Jared Ryan <jryan at caminofx.org>
>Reply-To: gmecm at diy-efi.org
>To: gmecm at diy-efi.org
>Subject: Re: [Gmecm] TBI and EFE
>Date: Sun, 3 Dec 2006 10:14:58 -0600
>
>OK, here is what happened, from the beginning.  The exact sequence is  
>important.
>
>I discovered the busted fuel injector O-ring that was the cause of the  
>too-rich problems I had been chasing since April.  (The lower O-ring on  
>the left-side fuel injector was mashed, letting fuel under pressure  down 
>into the barrel).  I replaced that, and the engine ran perfectly.   It 
>idled very slow (at the target idle speed programmed into the ANLU  chip, 
>about 550 RPM) but very smooth.  Drivability was excellent.
>
>Then, after a few days, I noticed it would sometimes idle faster than  it 
>had been.  It was still smooth, but about 1000 RPM.  It would flare  up 
>when I shifted out of drive into Park or Neutral and not come down  as fast 
>as it had.
>
>All of the preceding is with the daytime highs in the mid-70s and lows  in 
>the 60s.  Warm weather.
>
>Well, I wondered if the IAC valve might be sticking.  I took out the  valve 
>and cleaned it.  It wasn't very dirty, hardly any carbon, but I  sprayed 
>Gum-Out on it and also sprayed it in the passage on the  throttle body.  I 
>put the IAC valve back in.  I didn't drive it after  doing this.  Later 
>that night, the arctic blast came through (well, for  Houston, TX; lows in 
>the low 30s, highs in the 50s at the most).  Since  the day I cleaned the 
>IAC valve, it has not idled well.  It acts like  it might be too rich, and 
>it won't idle slower than about 700 RPM.
>
>I've done the IAC reset, grounding the diagnostic pin to force the ECM  to 
>extend the IAC plunger fully, and the slowest I can get it to idle  with 
>the IAC valve unplugged is about 600, and it's rough.  It's rough  with the 
>IAC valve connected, both cold and hot, and it idles faster in  Park or 
>Neutral than in Drive.  In Drive it's right about at the target  idle 
>speed, but still rough, but it won't idle down when taken out of  gear.
>
>By "rough" I mean a bad smell from the tailpipes, car shaking, surging,  
>having to really hold my foot on the brake to keep it still at a red  light 
>due to the surging.
>
>So could I have damaged the IAC valve with the Gum-Out?
>
>I broke the scientific method and changed two things at once (OK, so I  
>can't control the weather), and now I don't know if I have an acting-up  
>IAC valve, a fuel leak, or if it just doesn't like the chilled air.
>
>The pintle of the IAC valve looks like it could possibly wear over time  
>and not seal against the throttle body, with or without carbon buildup.
>
>  ---> Jared Ryan <---
>jryan at caminofx.org | http://www.caminofx.org
>
>On Dec 2, 2006, at 9:31 AM, davesnothereman at netscape.net wrote:
>
>>
>>  The TBI trucks w/ 7747 expect intake air temp around 90 deg F or  
>>greater.  The intake air heater is calibrated for this temp.  Most  folks 
>>with older tbi trucks don't seem to know / care.  In an area  where 10 
>>year old trucks are rotted out due to salt, snow, and  humidity it's not 
>>uncommon to see the few left running with no heat  stove left on the 
>>manifold and no tube connected to the snorkel.
>>
>>The question you need to answer is "How good is good enough?"  I have  
>>open element air cleaners on my truck which used to run in temps well  
>>below zero without causing any issues which I can remember.
>>
>>The old carby 2.8 S10's had an electrically heated grid under the carb  to 
>>prevent icing.  A 15-20 mile drive at highway speed at 50 deg temps  could 
>>cause enough restriction to bring vehicle speed below 30 mph if  the 
>>heater was inoperative.
>>
>>Zaphod
>>
>>-----Original Message-----
>>From: jryan at caminofx.org
>>To: gmecm at diy-efi.org
>>Sent: Fri, 1 Dec 2006 1:28 PM
>>Subject: [Gmecm] TBI and EFE
>>
>>
>>Do TBI engines typically need the EFE ThermAC setup to run smoothly in  
>>cold weather?
>>
>>I have an El Camino that has a heat stove on the passenger side, but I  
>>recently changed to a Camaro air cleaner that puts the snorkel on the  
>>driver side (this fits MUCH better with my Camaro serpentine belt  setup). 
>>I will need to put a heat stove on the left-side exhaust  manifold in 
>>order to use the ThermAC.
>>
>>I assume it wouldn't be there (on '88-'92 TBI F-bodies) if it didn't  
>>help. It made a BIG difference in cold-weather running when I had the  
>>QuadraJet carburetor, and TBI is also a wet-manifold system.
>>
>>The reason I ask is that the temperature has dropped into the 30s F,  
>>which is cold for Houston, TX, and the idle is a little rough.  However, 
>>the cold weather moved in on the same day I removed and  cleaned the IAC 
>>valve. It is entirely possible I just need to reset  the minimum-air 
>>setting and the idle will smooth out.
>>
>>Off-idle performance has been perfect, just a little bit of a rough  idle 
>>since it turned cold. I will do the IAC reset this afternoon, but  I still 
>>wonder if making the ThermAC operational will help a lot.
>>
>>I notice that the TBI intake manifolds no longer have the exhaust  
>>crossover under the carburetor/throttle body mounting pad.
>>
>>I hear a lot about ThermAC, like "It only closes in *really* cold  
>>weather. When I had it set up properly with the QuadraJet, it would  close 
>>at least a little bit on sunny warm spring days! It would open  quickly, 
>>but it didn't only work on very cold days, for sure. On very  cold days, 
>>like what we have here, it often wouldn't ever open  completely.
>>_______________________________________________
>>Gmecm mailing list
>>Gmecm at diy-efi.org
>>Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
>>Main WWW page: http://www.diy-efi.org/gmecm
>>_______________________________________________________________________ _
>>Check Out the new free AIM(R) Mail -- 2 GB of storage and  
>>industry-leading spam and email virus protection.
>>_______________________________________________
>>Gmecm mailing list
>>Gmecm at diy-efi.org
>>Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
>>Main WWW page: http://www.diy-efi.org/gmecm
>>
>
>_______________________________________________
>Gmecm mailing list
>Gmecm at diy-efi.org
>Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
>Main WWW page: http://www.diy-efi.org/gmecm

_________________________________________________________________
Share your latest news with your friends with the Windows Live Spaces 
friends module. 
http://clk.atdmt.com/MSN/go/msnnkwsp0070000001msn/direct/01/?href=http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mk