tbi esc

[STEBS]

So im working on my company work truck (94 2500 with a tbi 350/4l60)

my boss's dad bought it at an auction, heres the history that i/we do know:
-Was on propane at some point, and propane system was takin off
-dumping fuel, barely idled and poured black smoke (fuel would fill 1/8" on throttle plates)
-engine swap with a '90 tbi350 (assuming from emission label on air cleaner)

First thing i did was check ground points, found a broken ground strap from head to frame, installed temporary ground wire from exh manifold to frame... Fixed the over fueling

Next, full tune up - plugs, wires, cap, rotor, air and fuel filter, oil change

Rebuilt t/b (previous spray pattern was cone shaped but pretty heavy, new pattern is cone mist)

Vac lines on front of t/b were in wrong order

Its thrown a bunch of codes so far, some of which ive resolved, others i havnt had a chance to investigate yet

Runs great, even on highway, plenty of power... has intermittant low idle and die (usually starts as intitial start up, will run and die... Will stay running after giving a little throttle on start up. After dropping trans into gear, barely stays running and sometimes dies) this is an "every now and then" intermittant, not a regular intermittant

Hard 1-2 shift with light or hard throttle
Sometimes acts like tcc doesnt lock up reverse
2-3 shift is sometimes delayed a few rpms on hard or light throttle(intermittant, good firm shift rest of the time)


hell of a spark knock - open and closed loop, almost all the time... Sounds like a diesel

Fuel mileage is garbage, 9.1 avg

Code 42 for ESC never goes away

Raw fuel oder when standing near truck

There may be other symptoms that i cant quite remember right now


No access to live feed scan tools, but heres what ive come up with so far
Compression test around 120 around all 8
Vac 15hgm at closed loop idle, steady needle
Base timing at dead nuts 0°
dont have tbi adaptor to test fuel pressure, but id like to see it to rule out a blocked return line (which i dought is the case)

as of this afternoon ive been thinking o2 sensor... Ive been meaning to pull it to clean the tip after running black smoke rich for so long, also after inspection i have a 1 wire o2 that is pre cat/post y-pipe... i suspected upstream o2 @ manifold was missing maybe durring engine swap and down stream sending ecm crazy signals. Called gm today the parts guy only shows 1 o2 for my vin, but shows location is at manifold near flange (not sure if the farther distance will affect the heat range of plug readings) not after y pipe.

The esc code i never really did look into at all till tonight, went out to check wiring at the module (assuming maybe if the ecm can adv. or retard it to alleaviate the knock, that may fix alot of my other problems) and found NO esc module on the bracket (no clue why i just now noticed it was gone or how i looked over it) even the pigtail for the module is missing (will check wire loom in the morn to see if wires have just been cut due to propane swap)... Timing wire under glovebox is still intact and works

Did gm ever mount the esc anywhere else but the egr solonoid bracket on these trucks?

Im thinking trace down the esc wiring along with install or find the esc module, and replace o2 sensor and see what that does for the fuel trim...

Anybody else want to chime in on thoughts or ideas

[stevejohnson48]

Originally Posted by STEBS

So im working on my company work truck (94 2500 with a tbi 350/4l60)

my boss's dad bought it at an auction, heres the history that i/we do know:
-Was on propane at some point, and propane system was takin off
-dumping fuel, barely idled and poured black smoke (fuel would fill 1/8" on throttle plates)
-engine swap with a '90 tbi350 (assuming from emission label on air cleaner)

First thing i did was check ground points, found a broken ground strap from head to frame, installed temporary ground wire from exh manifold to frame... Fixed the over fueling

Next, full tune up - plugs, wires, cap, rotor, air and fuel filter, oil change

Rebuilt t/b (previous spray pattern was cone shaped but pretty heavy, new pattern is cone mist)

Vac lines on front of t/b were in wrong order

Its thrown a bunch of codes so far, some of which ive resolved, others i havnt had a chance to investigate yet

Runs great, even on highway, plenty of power... has intermittant low idle and die (usually starts as intitial start up, will run and die... Will stay running after giving a little throttle on start up. After dropping trans into gear, barely stays running and sometimes dies) this is an "every now and then" intermittant, not a regular intermittant

Hard 1-2 shift with light or hard throttle
Sometimes acts like tcc doesnt lock up reverse
2-3 shift is sometimes delayed a few rpms on hard or light throttle(intermittant, good firm shift rest of the time)


hell of a spark knock - open and closed loop, almost all the time... Sounds like a diesel

Fuel mileage is garbage, 9.1 avg

Code 42 for ESC never goes away

Raw fuel oder when standing near truck

There may be other symptoms that i cant quite remember right now


No access to live feed scan tools, but heres what ive come up with so far
Compression test around 120 around all 8
Vac 15hgm at closed loop idle, steady needle
Base timing at dead nuts 0°
dont have tbi adaptor to test fuel pressure, but id like to see it to rule out a blocked return line (which i dought is the case)

as of this afternoon ive been thinking o2 sensor... Ive been meaning to pull it to clean the tip after running black smoke rich for so long, also after inspection i have a 1 wire o2 that is pre cat/post y-pipe... i suspected upstream o2 @ manifold was missing maybe durring engine swap and down stream sending ecm crazy signals. Called gm today the parts guy only shows 1 o2 for my vin, but shows location is at manifold near flange (not sure if the farther distance will affect the heat range of plug readings) not after y pipe.

The esc code i never really did look into at all till tonight, went out to check wiring at the module (assuming maybe if the ecm can adv. or retard it to alleaviate the knock, that may fix alot of my other problems) and found NO esc module on the bracket (no clue why i just now noticed it was gone or how i looked over it) even the pigtail for the module is missing (will check wire loom in the morn to see if wires have just been cut due to propane swap)... Timing wire under glovebox is still intact and works

Did gm ever mount the esc anywhere else but the egr solonoid bracket on these trucks?

Im thinking trace down the esc wiring along with install or find the esc module, and replace o2 sensor and see what that does for the fuel trim...

Anybody else want to chime in on thoughts or ideas

I don't see were you changed the fuel filter of course I getting tired And sleepy??/ Check all the fuel related senors in the EGR line up ??/ Maybe something small like a throttle positioning sensor or something else in the EGR system??/ Remember propane is some dirty stuff I don't care what anybody says ??/

[STEBS]

Originally Posted by STEBS

Next, full tune up - plugs, wires, cap, rotor, air and fuel filter, oil change

lol... its okay, i look over stuff all the time haha


well until yesterday, ive been wondering that the o2 was the causes of all my problems (from being fouled during the extreme over fueling) but now with the ESC missing, now im wondering just what it might affect, and if its absence isnt the root of all the problems

i mean i totally agree, i feel like there something with the fuel system (more something that tells the fuel system what to do, rather than what it actually does if that makes sense). i really wish i had a tech1 to hook up to read live data and get a better idea of whats going on

ive always heard that propane is supposed to burn clean?

[stevejohnson48]

Originally Posted by STEBS

lol... its okay, i look over stuff all the time haha


well until yesterday, ive been wondering that the o2 was the causes of all my problems (from being fouled during the extreme over fueling) but now with the ESC missing, now im wondering just what it might affect, and if its absence isnt the root of all the problems

i mean i totally agree, i feel like there something with the fuel system (more something that tells the fuel system what to do, rather than what it actually does if that makes sense). i really wish i had a tech1 to hook up to read live data and get a better idea of whats going on

ive always heard that propane is supposed to burn clean?

You need to relay all that info to your Boss ??/ Brownie points ??/

[ChevyTech]

Originally Posted by STEBS

So im working on my company work truck (94 2500 with a tbi 350/4l60)
...Did gm ever mount the esc anywhere else but the egr solonoid bracket on these trucks?

In 1994 that should be a 4L60E.
There is no ESC module under the hood. That has a PCM. The ESC is built into the PCM.

Originally Posted by STEBS

... has intermittant low idle and die (usually starts as intitial start up, will run and die... Will stay running after giving a little throttle on start up. After dropping trans into gear, barely stays running and sometimes dies) this is an "every now and then" intermittant, not a regular intermittant

Sounds like IAC problems.

Originally Posted by STEBS

hell of a spark knock - open and closed loop, almost all the time... Sounds like a diesel

Fuel mileage is garbage, 9.1 avg

Code 42 for ESC never goes away

The knock will be picked up by the knock sensor and the system will retard the timing. That will cause the bad gas mileage.
Are you sure it is not a code 43?

Originally Posted by STEBS

No access to live feed scan tools, but heres what ive come up with so far
Compression test around 120 around all 8
Vac 15hgm at closed loop idle, steady needle

Compression is to low. Vacuum is to low.

Originally Posted by STEBS

as of this afternoon ive been thinking o2 sensor... Ive been meaning to pull it to clean the tip after running black smoke rich for so long, also after inspection i have a 1 wire o2 that is pre cat/post y-pipe... i suspected upstream o2 @ manifold was missing maybe durring engine swap and down stream sending ecm crazy signals. Called gm today the parts guy only shows 1 o2 for my vin, but shows location is at manifold near flange (not sure if the farther distance will affect the heat range of plug readings) not after y pipe.

1994 is an ODB1.
It should have one oxygen sensor. It should be in the manifold close to the flange. If you mount the oxygen sensor down steam you must convert to a heated oxygen sensor.

Sounds like it needs an overhaul!
CT

[STEBS]

Sorry bout the trans, i always forget there was the 4l60 prior to the 4l60e, and when im referring to the electronic version, i have a bad habbit of leaving the e off (same bad habbit if im talking about a 3406 cat b, c or e models)

I did not know that about the esc, every tbi ive ever worked on had the module right with the egr soloniod, hense y i assumed this one had disappeared... Learned something new lol

I agree iac was my first thought with the low idle, what gets me is its only an every now and then and not a regular basis which would lead me to beleive its not a complete senser failure. Thinking on it now, i wonder if maybe the pintle is getting intermittantly "hung" ?

Now that u mention it, im pretty sure it is code 43 for knock sensor circuit

Speaking of knock sensor, i know that it will feed the esc a signal to retard or advance the timing, but what i dont understand is what is causing the knock... I know a spark knock is detonation, but not exactly sure what would cause detonation

And yes i agree that vaccume is too low, i have a hunch that once the spark knock releives itself it should pull better vaccum

I was pretty sure there was supposed to be one in the manifold... The odd thing tho, my personal pick up is a 92 k1500 4.3/5speed and it has 2 sensors, one in the manifold as we both mentioned but also one pre cat, post y pipe... Which led me to beleive this truck was missing one. I mean i understand the concept of an o2 sensors function for affecting air/fuel in order to set short and long fuel trims, but am having a hard time figureing out why it would just have the 1? How would the system be able to moniter itself for malfunction and "learn" fuel trims based off of the data from one sensor? I could maybe understand it having one in early 87 or late 80's body change etc due to the fact of lack of r+d on new technology, but in 94 things were progressing technology wise, like todays vehicles that have 4 o2 sensors if not more.


Truth be told CT, ive come across a couple other of ur diagnostic assistance replies on other posts, and was actually hoping ud stumble across mine. I admire your skill and knowlage... and at the same time i do have to appologise for the "lack of hard info" im mechanicing for a local farmer/rancher and so im usually on the go quite a bit in (of.course) the service truck or have this tractor to.fix, or that truck to repair or that field to plow, etc... I dont always get the opportune times to be able to stop and see whats going on. Since my last fuel up avg of 9mpg tho, im going to make a better effort on finding time. I try to save my boss as much as i can, especially with the biblical drought this region has been in for the last 12 years.

[ChevyTech]

Usually the IAC does not go bad electrically, but it is common for them to stick and stop moving.

The IAC is a stepper motor and uses short pulses of electricity on the wires to move its position.

If the IAC sticks as does not move as it should for each pulse, the IAC count will get off because the computer does not know the actual position of the IAC, but the ECM tracks the commands it has sent to the IAC and assumes it has moved every time it has been sent a pulse.

I would not worry about the IAC until the knocking is taken care of.

With all the knocking that you hear, I would expect a code 43.

This system will not run well if it has excessive knock counts.

You should focus on the knocking.

With the compression that low, it is less likely to ping.

My best guess at this point is the engine has a rod knock or other mechanical issue that you are hearing.

[STEBS]

Got cought up on a few of the rush jobs that needed done, before i start the next project tomorrow im going to do a little work on this one in the morning. I cant stand spending any more of the bosses money on un-nessacary fuel.

I can definatly attest that its not a rod rod knock

I bought a new o2 sensor for it (assuming the prior is extremly fouled from the previous overly rich condition) will be installing tomorrow. So according to the local chevy house from my vin, the o2 is located on the manifold by the flange, currently its post y-pipe, pre cat. I havnt yet inspected the wiring to see if its been extended or tampered with by prior owner(s). But if i remember correctly the wiring for the o2 came directly off the trans harness just as it would from the factory. According to alldata, it shows o2 location where its at now. The wiring for the o2 aswell as the o2 it self is single wire. You mentioned something about o2's mounted that far back must be heated. So if this one is not heated, and theres a difference of information between alldata and the parts guy @ gm, im not sure which to follow. I have another manifold here at the house with an o2 bung in it if i need to switch it.



Next ill be addressing a couple wires i found laying on the manifold the other day, after that will be addressing the esc curcuit... How would i go about testing the esc curcuit?

All the material on mitchell OD and alldata show a knocksensor module on the intake same area as iac and egr sensor(which i dont see or find). Wiring to the module shows a fused 10a in (ecm/ign), a lead to the ecm (pin b7) for ks input, ground, and ks feed.

You said the esc is controlled through the pcm, so since this seems to be the case, im assuming there would be a lead from the ks straight to the ecm, and a lead from the pcm to the ign. module to advance or retard timing, am i right?

What kind of voltage should i see at the ks? Being 1 wire, i dont see how it transmit back to the computer with out either a 5v reference or some sort of supplied voltage.

What kind of voltage should i see coming from the computer to the ign module?

[STEBS]

Doing some looking on the ecm layout on alldata.

It shows pin A6 as the ign feed from the same 10a ecm/ign. It powers the ecm, air bypass valve (never heard this before and assuming this is non equiped) and the knock sensor module

It also shows pins D4, B5, D5, B3 to the ign module

D4 - ignition control from ecm
B5 - ic reference high
D5 - ic bypass (timing indicator)
B3 - ic reference low
im assuming "ic" is ignition control

[STEBS]

Did a little more digging, the pins listed above were for the ecm layout... I just found more for the pcm, all of which are different

Pcm shows pin
- B15 for ks input directly from ks

And for the module
- F11 for ic signal
- A4 for ic reference high
- B2 for ic bypass
- A5 for ic reference low

So from what im thinking, alldata is providing info for an ecm which would be the older (basic) electronics, pcm is for the newer (more safisticated) electronics... And that i have a pcm and not an ecm... Am i correct or way in left field?

[ChevyTech]

You said the esc is controlled through the pcm, so since this seems to be the case, im assuming there would be a lead from the ks straight to the ecm, and a lead from the pcm to the ign. module to advance or retard timing, am i right?

Yes you are correct.

Pcm shows pin
- B15 for ks input directly from ks

That matches the 1993 manual I have in front of me.

So from what im thinking, alldata is providing info for an ecm which would be the older (basic) electronics, pcm is for the newer (more safisticated) electronics... And that i have a pcm and not an ecm... Am i correct or way in left field?

Your correct that you have a PCM. If it had a manual transmission then it would have an ECM with a separate ESC module on the bracket to the passenger side of the TBI unit. This is why it is so important people state which transmission the vehicle has when asking questions. So many question asked here on the board do not have enough information to give a answer to in the limited amount of time I can spend here on the board.

All the material on Mitchell OD and alldata show a knock sensor module on the intake same area as iac and egr sensor(which i dont see or find). Wiring to the module shows a fused 10a in (ecm/ign), a lead to the ecm (pin b7) for ks input, ground, and ks feed.

A knock module by the intake is correct for a manual tranny or a older vehicle. Do the people copying GM information to make Mitchell manuals know the system well enough to sort out the GM information which also has errors? I doubt it!

What kind of voltage should i see at the ks? Being 1 wire, i dont see how it transmit back to the computer with out either a 5v reference or some sort of supplied voltage.

The PCM sends out a 5 volt reference and the knock sensor pulls that voltage down to 2.5 volts. That is how the PCM detects if the sensor is unplugged, by watching the voltage.

Unplugged = around 5 volts on the wire.
KS connected = around 2.5 volts on the wire.

[STEBS]

that makes alot of sence on the ecm/pcm... Now it makes me wonder about the computor i ordered online for my v8 swap in my 92 chevy. Its a manual trans and im not sure which computer i bought if its an ecm or pcm.

Okay, so next question. Did some looking today while i was working on it, and the ks pigtail is nowhere to be found which means tracing wires

Which harness does the ks wire run through? Im guessing it runs through the starter harness and route up around the bellhousing into the main harness on the firewall between the distributor? Im also assuming that wire would run through the firewall connection on the pass side since its straight to the pcm rather than to the driver side by the fuse block and then to the pcm through the dash

[STEBS]

Also, once i get the wire found, ran, solder a new pigtail on, and plug it in, im going to test it to make sure everything is working proporly. The normal voltage range for the ks would be 2.5v as u stated, when it senses a knock, does the voltage drop or raise? Ive heard of a test with takeing a hammer and tapping the side of the block to test for propor function. Im assuming i would do this with a multimeter hooked inline with knock sensor and would see a voltage drop with the hammer taps.

[ChevyTech]

1993 was the year the switch was made from 4L60 to 4L60E for the C/K1500 line.
The 4L60E trucks used a PCM
1992 C/K1500 trucks used a ECM, with a manual tranny or the 4L60 that was used in them.
There were CK2500 trucks with a 4L80E before 1993 which used a PCM.
The C/K 1500 manual tranny trucks used an ECM up through 1995.

Tap on the exhaust manifold and watch the timing to see if the knock sensor works.
Note: The truck may have to be in drive for the system to use the knock signal. This varies between vehicles and I can't remember which vehicles are which way.

Looking for a knock signal with a volt meter on this system is not done. You are mixing testing on the separate ESC module system with this system. The circuit you would want to monitor is internal in the PCM.

The knock sensor wire goes through the firewall on the passenger side. It does run next to the starter wires. Keep it away from spark plug wires, or it can cause false knock counts.