454 TBI Swap Problems

Mac5005

Mac5005

Well-Known Member
Joined
Oct 19, 2005
Location
Rocky Mount
Here is the background and I'll get on with the problems.

78 K30 Frame and Running gear, 454/TH400/205
88 S10 Cab,

My dad (Moldman05) bought the truck a year a go to wheel while we dovetail, bob, shorten, and turn his 84 suburban on 1-tons into an 84 Avalanche. When we bought the truck it had a street avenger carb that someone had attempted to convert into a truck avenger. Truck ran good on flat ground, but sucked in the hills with fuel spilling out of vent tube into the venture. Truck would run rich on full throttle and very lean on part throttle. Ditched the carb, and bought parts to swap to fuel injection.

Howell Harness for 95 C3500HD 7.4L, and Prom to remove VSS and EGR functions
95 ECM, 16197427, BHMH Bin95 GM OEM 7.4L Throttle Body

We installed the harness and all sensors. ( IAC, MAP, Heated O2, TPS, CTS). Running a factory style GM HEI....

Bottom line is, the truck runs super rich, and Howell has not been very helpful.

Using a Volt meter, as well as a borrowed OBD1 Scanner, we have checked all the sensors and everything is working correctly. Vacuum is steady at idle at 18.5-19". Idles choppy at 750-900 rpms. Small cam in 454, not too much overlap, considering idle vacuum. No other mechanical problems or vacuum leaks. Checked and rechecked all the typical easy fixes, and checked for leaks using propane, and found nothing.

The Heated O2 Sensor is in the Pass side header, just downstream of the collector, and measures around .89V at idle, pointing out the Rich Condition.
The Map Sensor voltage is between 1.5-1.8V at idle, again 18.5-19".
The Tps sensor was reading 1-2% at idle,
The IAC works and could been seen stepping in/out on the borrowed scanner.
The Base ignition timing is set at 12 degrees advanced with the connect closed (jumping out terminals)
The CTS is reading 298 ohms at 190 degrees, and 617 ohms at 150 degrees. Whether the engine is cold or warm, no change in AFR.
Fuel Pressure is 30psi, and the regulator works. From Howell -> 1995 HD 7.4 models used a higher 30psi fuel pressure to get needed flow from injectors. At first startup we had 15psi tbi pump and it definitely ran worse. Swapped to e2000 pump. Confirmed Regulator is working by pinching off return line and pressure runs up quickly. All new fuel lines so I doubt a blocked return line with the confirmed regulator operation.

As you crank up the truck the O2 sensor voltage starts at .45 volts and just creeps upward to .89-.9 the longer it runs. The exhaust will burn your eyes and is obviously rich, as well as plug fouling doesn't take too long. Tried 3 different heat range plugs with no effect.

Once engine is warm, when you drop it in gear, truck will stumble and stalls 50% of the time.

Replaced O2 sensor, TPS, MAP, and CTS and makes no difference. Only difference is truck runs better with the O2 sensor unplugged.

This brings me to building an ALDL cable per instructions on several forums. Can run it on either direct serial port or Serial to usb converter. Verified cable operation by plugging it in to 89 4.3L s10 blazer, and had all functions of WINALDL and Freescan. I have downloaded tunerproRT, Winaldl, and Freescan and nothing will communicate with the 95 ECM. The goal is to further diagnose the terrible rich condition by using TunerproRT as a glorified scan tool, and decide how to fix the truck, and get it to run better.

I downloaded the BMHM bin file, as well as the $0D Mask, and the $31 mask from gearhead-efi
Pretty sure I have done necessary steps with TunerproRT but not positive because I have no communication with 95 ECM.

Also, when I try to open bmhm bin file, tunerprort says unable to open.

First off, not sure If I am doing correct things in the correct order with TunerproRT, and not sure if I installed the BIN file and Mask correctly. I'm not fluent with TunerproRT yet, but tested the ALDL cable using WINaldl on the 89 4.3, to rule out that it is a cable problem.

Any Ideas on why it is running rich? and Any advice appreciated on how to use TunerproRT with the masks for my ECM.

Thanks,
Scott.
 
We set timing with the EST disconnected (Tan wire) initially at 4 degrees, and then disconnected battery per howell instructions. To get the truck driveable we set timing at 6,8,10, then 12 degrees advanced using the same methods in stages to track progress. O2 sensor voltage fluctuates but never goes below .75 even while driving and "blipping" the throttle open under load, and always returns to .87-.9 volts, not only at idle. The fuel smoke coming from the exhaust was a better hint than my nose...that and fouled plugs saturated with fuel. We do have a nice conical spray pattern with injectors that are opening like normal.


Not sure if it ever goes into closed loop, it idles in open loop.

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we have had the timing set at every 2* increment from 0-12. Only at 10* and above will the truck stay running when put into gear. Maybe im missing something but how is that base timing going to cause the super rich condition that has existed from the beginning? Tried with howell chip plugged in and removed, and with 95 4.3 ECM, and no change.
 
From all of the 5.7 TBI's I have messed with here is what I have found out the distributor is what fires the injectors and now if the distributor is going bad it will cause the injectors to increase the duty cycle which will cause it to flood. One thing I would look at is grounds the only other thing I see is a bad ECU
 
Mac5005 said:
Tried with howell chip plugged in and removed, and with 95 4.3 ECM, and no change.
Click to expand...
Here is the answer to your question . If you have replaced all of the sensors and changed every thing except the ECM then there is your answer the ECM has a bad driver in it that coud cause the issues as well, If you could borrow an ECU then you could test to see if it was bad.When you removed the prom the truck should have differently. also the Prom could hav has a static dis charge which will erase them .
 
The Check Engine Light operates as follows

Key off position: obviously light off
Key run position: light flashes once and then remains on
key start, then to run: light remains on, until engine fires and runs, light goes off and remains off

Only DTC shown is 1-2 : verifying operation of "Short" in ALDL cable asking for DTC display

I have two laptops and two cables,

Laptop A: Dell with Tunerpro RT with all same .bin, .adx, and .xdf Has serial port and usb port. Loaded with all same drivers as Laptop B
Laptop B: HP with usb only ports, loaded with tunerprort, same bin,adx, and xdf files. same drivers as laptop A

Cable 1: Homeade cable with switch to allow direct "short" to retrieve DTC codes, 3.9K ohm resistor can be switched on, 10k ohm resistor can be switched on. This cable goes direct ALDL to Serial.

Cable 2: ALDL to USB cable from www.aldlcable.com Has moveable bar to change from open to 10k ohms, to direct short.


To explain in better detail.

I hooked Laptop A and cable 1 to 89 4.3 s10 blazer, and view ALDL information using FreeScan program. I was able to view dashboard as well as sensor data. Switched to direct "short" condition, and viewed DTC code for TPS voltage low, which matched sensor data and flags. This confirmed that the cable we had built was working correctly with 89 4.3 S10 blazer.

I then hooked laptop A and cable 1 to 78 K30 454, and using Freescan, and nothing happened. This is when i downloaded and installed TPRT on both laptops, and installed all corresponding bin files, adx files, and xdf files, all for $31 mask. I also ordered the cable 2 at this point.

Then I hooked cable 1 to laptop B using usb to serial adapter and TPRT failed to recognize cable, with correct drivers and COM port settings.

Next I hooked cable 2, to laptop B direct to usb, changed COM settings and TPRT failed to recognize cable.

Next I hooked cable 1 to Laptop A, direct to serial port, TUNERPRORT recognized the cable!!!. Next i hooked to 78 K30 7.4 Still using $31 mask files, still failed to connect to ECM. I then verified that cable 1 is still working with ECM, by switching to direct "short" to display DTC, and i get a code 1-2, verify operation. I then tried Freescan, Winaldl and tunerprort again, with no info from ECM.

My thoughts were then, maybe the ALDL plug was wired incorrectly from howell: But-> we had our resident tune up guy bring himself and an OBD1 scanner, early on trying to make sure all sensors were working correctly and he could view all data, and see that all sensors were working correctly. The fact that he could, and I witnessed the data on his screen, makes me think the Chip Howell did and the aldl plug they wired are both correct. He had the truck for over a month going over everything and could find nothing wrong with any sensor, or any other hardware or wiring issue.

So where we are now:

Laptop A, with cable 1, is the only way TPRT will recognize any cable, but still no data stream from ECM on 78 k30 7.4. When I click the double arrow button to connect to ECM, for 1.5 seconds, it says DA Connecting: then goes back to DA not connected.

Capture1.PNG



P.s. IIRC it is switching between open and closed loop, this info from when tune up guy had his professional scanner plugged in.

Base Timing with tan wire disconnected is set at 4 degrees. Note: when i unplugged that connector to check timing, the idle definitely got much smoother, and truck ran better. Then disconnect battery, reconnected the tan wire connector(for setting timing) and truck is back idling terrible.



With base timing at 4 degrees instead of the 12 degrees before, the truck runs moderately better through the rpm range and varying loads.

however, the terrible idle quality is worse than before, and will immediately stall when dropped into gear once warm, and stall if you do not keep some throttle opening while driving. Truck is definitely surging at idle.

From what Ive read it seems like if I adjust the idle screw, i need to get the IAC counts in a certain range, but I can't view the counts bc i'm not getting any aldl data. Catch 22. Thinking that the idle blade position and IAC counts are hopefully causing the terrible idle issue, stalling on deceleration, stalling when dropped in gear problem that I was band-aiding by advancing the timing more than normal before, inadvertaintly increasing idle speed.



So been trying to fool this thing all day with no notable progress.

I warmed up engine to operating temp and made sure tstat was open at 200 degrees. I revved and held engine at 2k RPM to ensure IAC was completely closed, and unplugged IAC, and shut motor down. Next I cranked engine back up with IAC disconnected and shifted into gear while hold brake, and set minimum idle speed before stalling at 950 rpm. Anything below that and the engine is erratic and completely stalls. I shut everything down, and reconnected IAC.
Next, i back probed the TPS, and adjusted it so the voltage is back at .59v so that the ecm thinks we are back zero throttle opening.

Took the truck out, and now idle in park is around 1700 rpm, and when you drop it in gear, idle speed drops to 950 and only now stalls 50% of the time. Drove around, no noticeable difference other than wanting to push through the brakes almost all the time, and no longer stalling on deceleration.

Put the truck in low range, and it still stalls everytime its placed in gear. If i finesse the throttle while putting it in gear it will stay running, but pushes through the brakes like they are not even there.

1) To me, its dumb to have it idle so high if it still is going to stall when dropped in gear,
2) My first thought is that the cam has too much duration & overlap, and this is why its stalling at anything below 950 rpm. However, idle vacuum was 18.5-19.5 inches at 950, more vacuum than my bone stock 97 7.4L.
3) Torque converter stall speed is just two low for the cam specs.
4) Im almost positive having the throttle opened this far at 1700 rpm idle is confusing the ECM seeing different MAP voltages and TPS voltages...
5) still no luck scanning or datalogging
 
Wwildman said:
Here is the answer to your question . If you have replaced all of the sensors and changed every thing except the ECM then there is your answer the ECM has a bad driver in it that coud cause the issues as well, If you could borrow an ECU then you could test to see if it was bad.When you removed the prom the truck should have differently. also the Prom could hav has a static dis charge which will erase them .
Click to expand...

We swapped ECMs and Truck definitely ran even worse. Tried with and without Howells Eprom and it is worse without it, and kicks on all the extra DTCs having to do with the 4l80E.

Identified Problems:
1) Truck wont idle when put in gear unless minimum idle speed is set at 950, and TPS is adjusted back to .59V at idle. Makes idle in park around 1700 rpms. In 4low with idle adjusted up, truck still stalls when dropped in gear, unless throttle finesse is applied.

2) Still runs rich at idle according to checking the plugs after being brought up to temp.

The only good thing is that the truck runs pretty darn good once warmed up, off idle. :driver: roasting 42's.
 
Wwildman said:
Check all grounds. I have seen this happen before.
Click to expand...
My task for first thing this Morning is to add extra grounds to the system and see if anything changes. I know we checked all the grounds in the harness when we installed, and the block to frame, but I'm going to add extra to completely rule it out. Thanks for all the help man. I really appreciate it. Ill post up any results.
 
I checked and cleaned all grounds. Highest Ohm I got from any point to battery was 1.8 ohms, which to me is not enough to be concerned with. Main ground runs from battery post to pass side of block. Additional ground runs from alternator bracket mount on intake to battery post. Additional ground run from battery post to inner fender. Also has ground cable from back of passenger head to firewall, and from firewall to frame.

No change in the way it behaves.

base Timing is set at 4 degrees with bypass plug disconnected, per specs for 95 model year, I re-adjusted idle speed back down to 850, and truck will barely run, and stalls immediately when put in gear and on decel when throttle is lifted. Timing at idle with bypass plug connected is around 20 degrees. my pointer stops at 16, having marks every 1/8": 2 degrees, and timing mark is 1/4" before 16 degrees. Vacuum at idle is 19-20"

I have logically ruled out torque converter or cam being the problem. Before with the carb, truck idled fine at 750 rpm, and never missed a beat when dropped into gear. Only problem with carb was the truck ran bad on hills,and anywhere off idle.
 
Here is an update with data from back probing with multimeter.
Checked Map Sensor wiring, we have 5V accross two outside terminals with Key On
we have 4.9 volts on Map sensor signal wire with key on engine off.
we have 1.5-1.7 volts on map sensor signal wire engine idling.

Checked TPS wiring, 5V accross two outside terminals with key on,
.58 volts at closed throttle on signal wire
4.06 volts at wide open throttle on signal wire

Checked o2 sensor voltage, have .635 volts across purple and tan wires with sensor unplugged. key on, engine off
we have varying voltage that creeps up to .9 volts at idle, frequency of variation fairly low compare to 2k rpm reading
at 2000 rpm in park, O2 sensor voltage varies greatly but sweeps back and forth from .1 volts to .8-.9 volts but spends more time at higher voltage

with timing bypass wire unplugged, idle smooths out not stumbling and O2 sensor voltage stays hovering .78-.98 volts, doesnt stall when shifted into gear, and shows loop mode change by showing o2 voltage changing on higher requence between .2v and .8v

(video 1)
with timing bypass plugged back in, battery disconnected to clear codes, idle erratic and stalls easily. at first startup o2 voltage hovers between .76 volts and .79 volts, then stalling

(video 2)
re-cranked engine, and inital o2 voltage was .88 volts and hovered and crept up .998 volts and even showed 1.026 volts. when revved up to 2k rpm, voltage change frequency speeds up dramatically and shows fluctuation between .2 volts, and .9 volts, when dropped back to idle, o2 voltage shows over 1.0 volts and hovers between .998 and 1.056 volts.

(video 3)


(Video 4) shows cranking the engine, and dropping it in and out of gear and shows the o2 voltage fluctuations while having to finesse throttle to keep engine from stalling
 
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From what I am seeing is you have a bad distributor because when you unplug the spout connecter it sets it in base time mode. I know you said you replaced the distributor but I ended up going thru about 4 before I got one to run right.
 
Got some data from a borrowed scanner today. Here is a video of the replay of the truck at idle.


Wwildman, you are very good sir. Truck had a stored code about bad Ignition signal, didn't show up with CEL flashing mode, but scanner showed it. Gonna try two different ditributors.

Thanks again.
 
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Here is data stream of warm engine start, open loop then switching to closed loop, at idle.


Swapped old Ignition module in and runs better but just barely. No more IGN malfunction code.

Don't understand why now it looks like oxygen sensor is slowing down its frequency change in closed loop.
 
This thread made me realize how ignorant I am on these topics.....really impressed at this effort and diagnostic ability.
 
I may have missed it but have you verified the coolant temp sensor and IAT sensor are ready correctly? A faulty CTS defaults to -40°F and that will most definitely cause it to run rich.

🤦🏽‍♂️ just saw CTS in one of the videos and it was reading fine. Still gonna post anyways. Outside of whats mentioned above I'm not sure what direction I'd go other than checking grounds.
 
Chris_Keziah said:
Outside of whats mentioned above I'm not sure what direction I'd go other than checking grounds.
Click to expand...
And by checking grounds that doesnt mean look to see if they are attached in some way. Grab them and move them around, check where they're bolted in and see if they will move, Take them loose and see how the connection looks, sand them down to get metal to metal contact. Having had Jeepsters my whole life it never ceases to amaze me that people say the ground is good just becaue it's there!
 
Chris_Keziah said:
I may have missed it but have you verified the coolant temp sensor and IAT sensor are ready correctly? A faulty CTS defaults to -40°F and that will most definitely cause it to run rich.

🤦🏽‍♂️ just saw CTS in one of the videos and it was reading fine. Still gonna post anyways. Outside of whats mentioned above I'm not sure what direction I'd go other than checking grounds.
Click to expand...
R Q said:
And by checking grounds that doesnt mean look to see if they are attached in some way. Grab them and move them around, check where they're bolted in and see if they will move, Take them loose and see how the connection looks, sand them down to get metal to metal contact. Having had Jeepsters my whole life it never ceases to amaze me that people say the ground is good just becaue it's there!
Click to expand...
Ya'll this thread is from 2014...you know back when people on this sight did some real work to their rigs.....
 
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