I am trying to get my 93 K3500 7.4 to run smooth. I have done a lot of shot gunning tune up parts and just now purchased an ALDL cable and am trying to learn TunerPro to see what the live data looks like. Very rough idle at cold start, then runs OK.. At steady state drive I get a shudder, but will accelerate fine if I get into it. She has poor gas mileage, but that seems standard with these.
Well hello again and wish me luck.
David
Possibly the 93 K3500 has the 4L80E transmission? If so, gearhead-EFI link with TunerPro information: http://www.gearhead-efi.com/Fuel-Inj...Information-85
Thanks dave w.
Yes I have the 4L80E and TBI
I recorded a few sessions yesterday, but need more knowledge as to what the numbers mean. My O2 is all over, BLMs seem high etc. Is there a way to load the recorded files for others to comment on?
day 2 started and idled.xdldrive to dump.xdlidle after dump.xdl
93 K3500 with 7.4, 4L80E, TBI, 156K miles
There is an overwhelming amount of information about OBD1 tuning:
Perhaps this link will provide useful information: https://www.60degreev6.com/vb5/artic...s/contentpage2
I played back all three data logs. Summary "Averages" screen captures below:Originally Posted by Idaho83813
The data suggests the injectors need service, or possibly cure in a can injector cleaner.
BLM All 3.jpg
SA All 3.jpg
Sample Count All 3.jpg
Wow Dave, thanks.
Curious how you came up with that. Is there a formula you used? X divided by Y times Z etc...?
I have used a few rounds of Lucas injector cleaner as well as Sea Foam over the past several tanks, but they may not have the cleaning ability needed. Probably need to look into servicing the injectors.
I used the information available in the History Tables.
TunerPro RT.jpg
Welcome to the forum.
The 7.4 was always a fuel user. But looking at the recorded data there's definitely room for improvement for your truck.
I am curious how long you've owned the truck and how much you know of service history.
OK, Thanks dave
Hey 1P2many, thanks for input and questions,
I have owned it probably 8 years. I use it to go to the dump, occasional Home Depot runs and plowing snow on our property (600+ foot of driveway).
I had to replace the 4L80 during Covid with my wife as no one was accepting work due to parts etc... I found about the last remanufactured one from Jaspers.... what a pain! Wifey was a trooper though.
I have noticed over the years that the idle was getting pretty high so about 1 month ago I decided to devote some love and attention to the truck. I replaced the following:
O2 sensor
Intake manifold gaskets
Thermostat
Distributor and ignition module, cap and rotor
Coil
Plug wires
Re-gapped the plugs as they are very clean and probably less than 2k miles
New fuel pump and inline filter
Re did the grounds on T-State housing for ECM (Cut to fresh copper, crimped on new ring terminals as well as cleaned up grounds at fuel pump, as many chassis grounds, firewall grounds I could find)
Based on dave w's input, I have a TBI rebuild kit coming Tuesday and will try to address the injector issues...at least what I can with what comes in the kit.
Did compression check yesterday and have 128 to 135 (Engine cold, all plugs out, and throttle closed (learned today I should have opened up the butterfly's...) But I think the 130 range and fairly even seems OK for now.
Started playing with ALDL cable and Tuner Pro RT this last week.
Last edited by Idaho83813; 4 Days Ago at 07:00 AM.
Ok, so it's good to know that a previous owner didn't install the wrong injectors. I think it could be helpful to replace or clean the injectors. It's also important to check the fuel delivery system. One trick I've learned for GM vehicles is to check for rusty colored fuel and junk at the inlet side of the fuel filter. Typically this is copper from the fuel pump armature and it can indicate the pump is in need of replacement or will be soon. If you've already changed the pump then it might not hurt to confirm the fuel pressure is correct.
You could also check the minimum air setting and the IAC motor operation. In order to check / set minimum air, the air inlet for the IAC valve in the throttle body is plugged while the engine is running and RPM is checked against specifications. If the RPM cannot be lowered enough look for a vacuum leak. If engine rpm raises above expected idle speed after correctly setting minimum air suspect the IAC is not working correctly.
Keep us updated. Testing and understanding are the best tools to solve these issues.
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