need some insight on a technical issue i have

[RRice]

i have a 1995 GMC rally STX van (G2500 3/4 ton) i had to rebuild the engine and since i was going to be using for some light towing i purchased the comp cam XE249H-12 and had the engine bored to 4.020.. my question is this..will either of these effect the stock tuning?
when i first fire the engine up it's burning so Rich that inside the exhaust pipe tip is nothing but black soot..i monitors the O2 sensor with a DMM and it starts out at around ~ .5 or .6 and climbs to just over .7V before the ecm goes into closed loop.
the idle is really rough and the O2 stays for the most part right at .7V on the high end and bounces down to around .02V on the low end..and still the mixture is rich..

I pulled the vacuum line off the brake booster to try and see if it would lean out with the extra air added..but it was a no go..

which is why i'm wondering if the cam and bore has altered anything..
the only thing i can see in tunerproRT with bin file BJYN is a setting to set CID which if my math is correct would be 44.16(44.28 in tuner pro) but would that be enough to make it run rich?
or is there other things in the ecm that need adjusted?

Thanks Rick

[steveo]

the bore? no that would not affect things in a noticeable way.

the cam? maybe, but not really. that's a pretty small cam. it should run 'ok' on the stock tune, especially once closed loop kicks in.

you can't monitor an o2 sensor's voltage with a multimeter during operation. all the o2 reads is 'rich' or 'lean'. in closed loop it should be switching too quickly to know whats going on, and in open loop, it wont tell you anything (in fact during open loop warmup it will pretty much read 'rich' unless something is wrong).

you need to monitor it with a datalogger or a fairly silent oscilloscope, preferrably the first.

no idea what's going on, need more information and datalog.

[RRice]

Hi thanks for the reply..i posted another thread about not being able to connect tunerpro to my van..the only headway i made was getting it to say that yes there was an interface present and i got it to finally say DA connecting..but that's all it says..it never goes to DA connected..the other post has a bit more about what i've done ..

Really i just need to know the details on how to hookup..from start to finish with no details left out..
aka..do i need the 10k res..and if so when and how do i use it to get into 8192 since this ecm has no 160 i can't use winaldl.

my other posthttp://www.gearhead-efi.com/Fuel-Inj...2558#post42558

[steveo]

so it's $0D, what is it, a 7427?

8192 baud ecms dont ever need a resistor or magic stuff as far as i know.

try a demo of datamaster instead, if you can't get tunerpro working. if that works, at least you know it's tunerpro config or a problem with your adx or whatever.

[RRice]

Hi again..ok i took your advise and downloaded datamaster ..but unless that program has an automatic detect or something i couldn't get it to connect either and yup $OD 7427 with bin file BJYN.

ok so i don't need the 10k jumper.. will the 8192 line output any data with just the key on without starting the engine.. starting and waiting for closed loop is sucking tank dry lol

[Fast355]

Hi again..ok i took your advise and downloaded datamaster ..but unless that program has an automatic detect or something i couldn't get it to connect either and yup $OD 7427 with bin file BJYN.

ok so i don't need the 10k jumper.. will the 8192 line output any data with just the key on without starting the engine.. starting and waiting for closed loop is sucking tank dry lol

Something is not adding up. I ran a more aggressive cam and TPI heads on the stock tune and it was nowhere near as rich as you state yours is running. In fact even at 14 psi fuel pressure it was lean with any throttle opening at all. I would double check the timing, spec is 0* or TDC with the bypass wire connector disconnected although I have found most like 4-6* BTDC much better. Also check for vacuum leaks, especially the TB base gasket. Finally you should set the minimum air rate aka minimum idle speed so that the IAC itself is a minimal vacuum leak.

[RRice]

what is the process for getting data out of the ecm..is it the following?

Hook the interface to the aldl pin M and pin A(gnd) ..open tunerpro..and start engine..and then click acquire connection..
I have tried starting the engine then hooking up the interface and then starting tunerpro and then acquire connection..actually i think i've tried every which way that i can..
i need to know the exact process so that i can eliminate the hookup process and focus on the connection issue only..


The timing is on 0 used 2 different timing lights since one has an advanced dial which is flaky sometimes..and the other just a straight TL ..both show timing at 0..
it has all new hoses and a new TBI gasket..but i'll pull the carb off and check the gasket just in case ..can't hurt at this point
I'll try and change the timing from 0 to ~4 ~6 and see if that helps any..
i went thru the valve adjustments again,,just in case ..and then checked the cyl pressure on the only cylinders i could get my hose screwed into without breaking my back..which were No 5,6,7,8 all are reading 160Psi... I'd check the others but this van doesn't give a lot of room to move around in there..so for the moment i'll assume they are within this pressure..

on another note my younger bro brought something else to my attention ..i hadn't noticed it until he pointed it out either..ok so this van has been outside for maybe 2 days..to give me more room in the garage to put the motor together....and it rained for those 2 days..and the hood was not on the van..that was about a week ago..once the motor was installed the van got moved back into the garage...now hears where the interesting part is..for the past few days there has been water shooting out the exhaust every time i stomp the gas pedal to something like 1200 to 2000 RPM just a guess on that range..any who..assuming it's not a leaky head gasket..and water had somehow gotten into the manifolds when it rained..i would expect that the water would have been gone after the engine had gotten good and hot..or at the very least would have been gone after 2 days of stomping the RPM up and down..

If this isn't the case then the only other reason i can see for water to be shooting out is a leaking head gasket..but then again if that was the case the temp would go well beyond the 200 degree range and ultimately boil over into the overflow jug lol but that's not happening..dang i just confused myself with yet another odd issue to solve hehe

oh and before i forget..when i pressure checked those cylinders and viewed the plugs they were all black..same soot that was in the tailpipe.
right now i just have straight water as coolant..didn't want to put antifreeze in it until i made sure nothing was wrong..i may have to drain it..put some in..and see if the garage floor turns green where the exhaust tip is..that would at least verify if the head gaskets were at fault..since i can't get into all the cylinders to do a leak down test..
ok i just realized i'm typing my thoughts lol

[steveo]

black sooty plugs from a blown head gasket? nah. blown head gasket shows as a plug being way way cleaner than the rest... (steam clean)

[delcowizzid]

have you tried pin E for data and pin A for earth

[RRice]

Hi this ECM has no pin E.... i kinda wish it did tho..i'm more used to using winaldl.

Steveo you make a good point about the steam cleaning..so the only other conclusion is that there is just a lot of moisture in the exhaust..

i have 2 other ECM's in the garage..a 16168625 and a 16199982 would either of these work as possible substitute to eliminate the ECM as the problem..they both have the same memcal socket as the one in the van now

[RRice]

ok i tried changing the timing..but that didn't help any..it did make it idle a bit faster but still not correctly tho.
carb gasket is good..it past the water bottle spray test..not pulling anything in. i also rechecked all my hoses too
I pulled my DMM back out to verify that i had voltage on pin M..with key on it goes to 5V after turning the key off it stays at 5V for about 5 sec or so then goes to 0V.
so at least there is voltage there..that's about all that test will tell me tho lol

[RRice]

black sooty plugs from a blown head gasket? nah. blown head gasket shows as a plug being way way cleaner than the rest... (steam clean)

went back and yanked all the plugs again to try and get comp readings on the other cylinder and noticed that as i was pulling the plugs out the number 8 plug was a lot cleaner than the others..i'm gonna try and get a pic of the plugs but i don't have much confidence in the camera i'm gonna be using..so hold up for a min and i'll be back with some pics(hopefully) and the compression readings :-)

ok i'm back with the pics first pic is 8,6,4,2 starting from the left and the second pic is plugs 1 ,3,5,7

edit back again :-)
ok i had my lil brother go hookup the comp tester since his hands were smaller than mine..here's the results.

#1 160
#2 150
#3 160
#4 150
#5 160
#6 160
#7 160
#8 150

i think it's safe to rule out compression as well as my thought on the leaky head gasket too..

if i can only get tunerpro to work i can get a little more insight as too whats going on as far as the tune goes..
gonna replace the plug wires with another set..i don't like the color of the current ones anyway hehe

[steveo]

wont connect to aldl + black sooty plugs + runs like shit = running in limp mode?

[RRice]

ok the new plug wires did help a bit..or at least it seems like it did anyway....i'm still wondering about the O2 sensor readings i'm getting from my dmm..the second the ECM goes into closed loop the signal randomly goes from .7V and drops to under .1V ..every time it dips to that low point the motor reacts like it has a miss in it...

Once it's in closed loop i can disconnect the brake booster line and the RPM goes up and steadily goes back down...hook it back up and the RPM goes Down and gradually comes back up..
I know you guys don't think that the DMM is a good way to monitor the O2 sensor..because of the fluctuations in voltage..but if the O2 sensor was bad there would be no voltage since the voltage itself is generated by the O2 sensor itself or if it were locked to a specific voltage ..then a DMM can be used to verify it's functioning..note i didn't say it would show that it's functioning properly but at least show it's active... :-) in my case tho i'm thinking the O2 is defective in some way internally

i tried to get the O2 sensor out to replace it..but the dang thing must be welded in there or something cause all it wants to do is round the edges off the nut.

Limp home mode ... never thought about that since limp home mode completely ignores the O2..or at least i think so anyway.
should there be an error code or something for that..and if it were in LHM wouldn't the engine not respond to the brake booster line being disconnected and reconnected?

sorry guys just tossing idea's as they hit my brain cells hehe

i think my lil bro's 94 GMC sub has the 8192 baud pin M..may catch him after he gets off work tomorrow and see if i can get the aldl to work with his truck..

in the meantime i'm still open for things to try

[Fast355]

Have you checked both ECM grounds, the groundstrap and negative battery cable. The block should be clean not painted where they attach and the connections should be tight. Seen more than one broken ground wire after an engine swap.