1994 5.7 engine running rough

[acewelderman]

Ok guys you wanted it, you got it, Snap On scan tool results. First let's go thru everything cold on left column and hot on the right column:
One thing on the time columns the truck did stall twice so I don't know if the 4.30 is right or not.
RPM: 1000------------------------------------------ 725
MV: 978---------------------------------------------872
fuel trim: 128----------------------------------------131
open/closed loop:open-------------------------------closed
lt trim:126-------------------------------------------96
exhaust O2: lean-------------------------------------rich/lean
trim cell :18------------------------------------------18
knock: no--------------------------------------------no
knock retard :0---------------------------------------0
base pw/ms:3.6--------------------------------------1.3
tps voltage: .58---------------------------------------.58
O2 cross count: 0-------------------------------------5
throttle percentage: 0---------------------------------0
iac position: 116---------------------------------------53
iac direction:rev---------------------------------------rev/for
iac coil a: on/off---------------------------------------off/on
iac coil b: on/off---------------------------------------off/on
desired idle: 900---------------------------------------675
coolant: 71F------------------------------------------181F
time:2 min 5 sec--------------------------------------4 min 30 sec(??)
prom id: 8135------------------------------------------8135
map("Hg): 13.8----------------------------------------12.1
map V: 1.96-------------------------------------------1.68
barometer V: 4.78-------------------------------------4.96
barometer ("Hg): 29.2----------------------------------30.1
battery V: 14.3----------------------------------------14.1
fuel pump V: 14.3--------------------------------------14.1
CCP selenoid: off---------------------------------------off
CCP duty cycle: 0-------------------------------------0
spark adv: 20------------------------------------------23/15
accel enrich: no----------------------------------------no
decel enlean: no----------------------------------------no
power enrich: no----------------------------------------no
egr selenoid: off-----------------------------------------off
egr duty percent: 0--------------------------------------0
egr position: 0------------------------------------------0
desired egr percent: 0-----------------------------------0
vehicle speed: 0-----------------------------------------0
a/f learned :no-------------------------------------------yes
I hope this makes sense to you, let me know what you think.

[Fireplug]

read this site
http://www.gnttype.org/techarea/faq/BLMINT.html
about long and short term fuel trim
lt trim:126-------------------------------------------96
that is not a good reading
fuel trim: 128----------------------------------------131
a little high reading
looks like its running rich and the ecm is trying to lean it out

[acewelderman]

Layman's terms please...I read the information and it just scares me. New computer, new truck, what's your opinion?

[Cadillakin'98]

Sad to hear a Chevy not feeling well. Obviously something ain't stirring the kool-aid!!! As I was reading your problem(s) you talked about going through everything one last time, including the valves. Well, I totally believe you have analyzed everything outside the motor (like sensors, timing, plugs, wires, vac lines, fuel, etc.) more than a million times. Also believe what you say is true, all that is good. But I don't recall you mentioning double checking the valves except for #1 cyl. You spoke with much confidence about adjusting them correctly. Don't let that confidence get in your way, thats how people fail at things. Not saying you fail and not trying to insult your skills in any way. Just trying to keep you from buying one of them Ford or Mopar things. Start from scratch. These heads you put on came from where? Are they rebuilt, new, or what? Are you absolutely sure thier integity is godd? This would include everything being perfect, like the valve adjustments. Once you can check that all off as perfect (again), then you atleast have a solid foundation to build on. At which point you can check all the external factors for thier integrity since you appear to be excellent at! Your computer is a good possibility, however, start from the bottom up (again) first. In other words, build up on your solid fondation. Computers are very rarely go out. As with all the external stuff to check, I don't really have any suggestions that you haven't aleady checked....4 times! I'm a paint and body guy, not a tecnician (mechanic). However, I do have a strong mechanical apptitude and I will say it sounds like you're on the right track. You're simply forgetting to take a deep breath and walk away. Take a break and rlelax a lttle bit. The answer will dawn on you evenyually. Good luck, keep us posted. And anyone with GOOD RELATIVE suggestions help this guy out.

[Fireplug]

wowowoowo hold the phone m8s
You said it ran ruff when the head gasket blew, right ? And it still runs bad. Ok with the fuel trim readings I can see its rich while the ecm is trying to lean it out. How fast does the o2 swing from lean to rich and does it go just under and over 500 or a big swing. Check the o2 sensor pull it out and look at it because it might be fouled with antifreeze. Also the engine vacuum is low should be about 20hg at idle you have 13.1 hg on the scan tool I would put a true vacuum gauge on a main vacuum and get a reading. The low engine vacuum could be the result of misadj valves or could be the result of the main problem. Before you pull the valve covers please check the o2 with you eyes. If its white or dark black replace it it should be a brownish tan color. You might have more then 1 problem so we must look at 1 area at a time

[acewelderman]

So far, the BLM long term fuel adjustment sounds exactly like what's going on. The buick website you sent me to says to remove vacuum from fuel pressure reg. My truck has throttle body with fuel reg built into it not sure but I have to look and see how many vacuum lines are on mine. O2 sensor is brand new as are heads, plugs, wires, cap, rotor, map & fuel filter. I did say I readjusted valves on left but found adjustments so slight not worth doing the right side. I think that resetting the BLM or ECM is the way to go. When I start the truck it runs perfect for 8 seconds then starts to run rough. Thanks, we're getting close. I didn't really want a Ford anyway, I just figured it would generate some good reading.

[Fireplug]

http://www.customefis.com/GMEFI.html
read this

[Cadillakin'98]

Think I would afree about a few different issues causing all this drama. Good to hear you're getting close. You've heard the expression "Good thing come to those who wait"

[acewelderman]

Originally Posted by Fireplug

http://www.customefis.com/GMEFI.html
read this

OK, enough I'm not a college student, I have no need or use for all of this information. I don't need to understand fuel management and how computers work. I just asked if you knew how to reset the Chevy fuel ecm. You guys have given me a lot of good information but I've been tinkering on this truck for three months and I'm done. I'm going on Monday to buy a new computer for it, found one for $109, that's a lot cheaper than the data computers that the article you sent me to read told me to get. Sorry I'm not a rocket scientist, no problems if it doesn't work I'll just unload it and drive my '83 that hasn't ever let me down becuase there's no f****** computer in it. Again, you have all helped me quite a bit, just not the answer that I needed. I use robotics and lasers at work everyday and they make more sense than this website did.

[RainRider]

Originally Posted by Fireplug

http://www.customefis.com/GMEFI.html
read this

Added that site to my "Favorites."
Thanx for it.
RR

[Cadillakin'98]

First of all, where did you find an ecm for $109? Recon thats used, sure its good, is there a warranty? Not trying to piss you off, just trying to prevent you being pissed off if you buy and doesn't do you any good 'cause its defective or something. As far as resetting your ECM, you can simply disconect your battery for 30 to 90 seconds for it to reset. Sometimes ECM's will have a reset button as well (underneath) but don't recall ever seeing one on a full size Chevy, just on s-10's and other vehicles. Also, if you have access to a scan tool, can't you reset it with that? Never used one myself but would kinda make since if you could. Sorry if this doesn't help you either. Hope you get it runnin top notch soon

[acewelderman]

Thanks for your help. This ecm is brand new but I get jobber price cuz my friend is a county fleet wrench & parts guy wants to keep him happy!! GOOD FOR ME !! Full price was still only200.bones . Auto value in Jackson mich.Also I did unhook ecm and it didnt make a dif last wk.Hopfully will get it installed by wed night I will post what happens good or bad.What about eliminating all the computer shit altogether?? Ive been told its no big deal but dont know for sure.

[acewelderman]

Well tried new ecm & nothing changed still has a miss !!Have about 1600 bones into it now guess Ill have to bite the bullit & take it to the dealer.Scan tool said all sensers are working but still switches from lean to rich back & forth when its warm.

[acewelderman]

BAD HEADS!!!! New wrench pulled heads & found a NASTY loose valve guide .Sent them to mach shop found ALL springs were junk First set they sold me were vortec WRONG!! second set are JUNK Beware of this bs head company Moore cyl headsSo far theyve screwed me for about 2000 bones in parts & labor.Oh yeh the second set had stainless valves in one head & standard in the other .No wonder all my electrical problms couldnt be solved BECAUSE the heads were the problem all along