I just picked up a 1994.5 7.3 PSD 4x4 supercab truck. zf 5 speed, 3.55 gears. 240000 miles. It needs a little TLC and cleaning up. I bought it from my friend he has had the truck a couple of years and has maintained it fairly well. It has started to develop a cold skip. It goes away when the engine temp gets up to 130-150 deg. So I know an injector or two are going to be crapping out soon. No major blowby, the oil cap off trick doesnt spit oil out or blow the cap off the filler neck. No blue smoke or white smoke on startup. Revs quickly from idle to 2500 sitting with no load on engine. Straight 3.5" exhaust no cat or muffler.

On to the questions, anyone with similar gearing have trouble pulling small hills in 5th gear at 55-60mph? The truck feels like its pulling a boat but it is completly unloaded. My friend who sold it to me always ran it with the MAP sensor unplugged for more power. I plugged it back up and it is gutless. No power, with the MAP unplugged its better but not like it should be, and there is NO black smoke at all.

So I think the injectors are crap. Or the HPOP is weak. Is there a good way to check these parameters since the truck is an OBD1 setup. I know the OBD II port can be enabled somehow but will it read info from the pcm like the later trucks so I can read ICP and so on?

The truck is up to date on maintenance, it is so slack on power an IDI would outrun it and outpull it. I need some help.

Thank you any suggestions and guidance would be GREATLY appreciated.

 

AEFO reflash for the PCM I recall to utilize OBD2.

Sounds like your map is bad.

 

I'll check the tubing to the MAP sensor tomorrow and replace sensor if needed. I didnt know unplugging the MAP would make it run better if the MAP was bad, I was ill informed. My friend who sold me the truck said that was a cheap "mod". I know better now.

 

If you unplug the map and it runs better it means your map is bad as it defaults to known factors in the PCM.

Many people route the factory map line over to the hot side of the IC as it increases the boost loss over the intercooler, as it injects additional fuel.

Outside of the map being bad a clogged hose is also common. Pull it off and blow through it.

If you need a map I pulled one from a truck I've been parting. I assume it is in great condition, but I don't know that for a fact.

 

MAP sensor and tubing changed, power is great now. I still have a check engine light to check out, CEL on at idle when going down the road CEL goes off comes back on at every stop.

 

Get the codes

 

Gotta find a way to read them first. There is no OBD II port under dash just wires hanging where its supposed to be with wirenuts and tape on them. Im gonna have to patch in a port from a junkyard truck I guess. I have read that the OBDI port under hood does not read proper codes I am still researching the subject right now.

 

Are you kidding me? I've seen some bad wiring in my life, but I can't think of 1 reason to **** with the obd 2 connection.

 

No kidding it has been cut, sliced and diced. Its got #6awg house wire run to the tail lights, wire nuts and all. Its a project but she sure runs like a raped ape now.

 

Glad to hear that bud!

 

Oh I changed the oil today too, oil was supposidly 4-5k miles old mileage wrote on filter was 226000. So it had 14k miles on the oil or at least the filter. No more injector sticking. No cold skip. Also fuel filter was about stopped up with biodiesel scum.

 

Lol 14k is so so far to much! No wonder it had all those problems. New filter and oil every oil change!5k miles is about the farthest you want to go on the oil. You can go further,but that is reccomended interval and it is fun for me so I do it every 5k. It is also cheap insurance that you can maybe spot a problem before your motor is destroyed due to lack of inspection/proper maintenance.