lvoithoffer
lvoithoffer
4/6/19 8:25 p.m.

I have a 1993 k3500 454 NV4500... The engine is a semi fresh rebuild(50K miles) with a small cam. I have replaced the following some parts multiple times...  The truck has a stumbling rough idle. Seems to lack power to me but im not sure. If i take the truck for a short drive when i come back and go to instantly restart it has no fire from injectors....hit it with a little ether and shes up and running again. Im fairly positive i have that narrowed down to a weak oil pressure sensor.(changing it tomorrow). The truck runs pig rich and never seems to go into Open loop.(i think heated 02 will change that).  I AM OPEN TO ALL SUGGESTIONS.. out of ideas myself.

I have a ALDL cable with WinALDL & Tuner pro rt but quite frankly do not know what i am looking for I have attached a copy of my logs at a idle.
https://docs.google.com/spreadsheets/d/1ZuvfldSA_rejBc0FAmCb38zTbHMIlfNR4CoTWgblQSU/edit#gid=361545408

Parts replaced less than 300 miles ago.( All new with AC Delco parts)

Completely Rebuilt TBI unit with 2 inch spacer

New TPS & IAC i did my best to calibrate them

New map sensor

Pickup Coil ( Timed at 4 degrees BTDC with connector unplugged) 

Cap rotor & Plugs & Wires

ICM

Ignition coil

o2 sensor ( Re wired from ecu wire was broke assuming when they reinstalled the engine)
*** I plan on switching to a heated o2 due to my long tubes.

CTS

Knock sensor (Wire was also broken)

Newer fuel pump & Filter 15k ago with all new lines 

Im sure there is plenty others im forgetting. The EGR is deleted as are all other vac lines except MAP,PCV. I am at my wits edge with this truck but i love it very dearly. Hopefully the geniuses on here can help me figure it out. At this point any direction is better than none.

Thank you very much you can email me at lvoithoffer@yahoo.com Or text me at 724-570-8672 if that is easier.

Lucas

Picture of said truck causing me all this heartache

Patrick
Patrick GRM+ Memberand MegaDork
4/6/19 8:40 p.m.

What’s your fuel pressure?  You can also hotwire the fuel pump relay to eliminate the oil pressure sensor from the equation so you’re not just throwing parts at the problem.  Under the plastic cover on the firewall between wiper motor and hvac stuff is the pump relay, it should have a red wire with a spade connector(forget it male or female) dangling off it about 4” long, put power to that and it powers the pump for diagnostics 

81cpcamaro
81cpcamaro Dork
4/7/19 9:28 a.m.

I would definitely check fuel pressure. Could also be the ICM, even though it is new. Quality on them has been suspect for a while now.

I did the heated O2 on a 92 454 TBI swap, but ended up after killing a couple O2 sensors, just running a single wire. Even with headers it didn't have any issues. Seems that unless your ECM can control the heated part, having the heater on all the time doesn't help with longevity.

gearheadmb
gearheadmb SuperDork
4/7/19 9:48 a.m.

The oil pressure sensor does not stop the fuel pump relay from working. Its not an oil pressure sensor problem. o2 sensor shouldnt effect startup so not an o2 problem either. If you can start it on ether it is a fuel problem, it could be the fuel system itself or the pcm not giving enough injector pulse width for startup. Check fuel pressure. I dont remeber the exact spec but for tbi you want around 15 psi. Check for codes. Look at the sensor data and look for anything that seems out of whack. Is this a stock pcm or an aftermarket?

ShawnG
ShawnG PowerDork
4/7/19 10:56 a.m.

I'd say fuel pressure as well. Should be the first thing you check.

I've had new EFI pumps last less than a month. Spectra seems to have issues making a Ford in-tank pump that lasts for any length of time.

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