94 C3500 350 Basket Case

[tanman_2006]

No codes when checked with paper clip other than me screwing with the temp sensor while running.

 

[tanman_2006]

The spray pattern looked ok at a glance didn't look real hard though.

 

[sntrym]

I had the same issue with my 350 recently. New TPS fixed it. It messed up the idle, shift points, and general drivability. IAC can also mess up idle, but does not affect the rest of the operation.

 

[tanman_2006]

I'm up for checking anything. Just tell me what it is and roughly how it needs checked.

TPS and IAC are on my hit list for 2mro

 

[skylark]

Tps will be .5v with the throttle closed to usually a bit over4.5v wide open. You can probe the wires if you don't have a scanner. The 3 wires are a 5v reference from the computer, ground and the signal back to the computer.

 

[tanman_2006]

Haven't found my volt meter so I haven't gotten to test the TPS.

Yesterday the truck was a complete dog and had to climb hills in 1st gear that it typically climbed in 5th just lost 10-15 mph.

Today it runs 80-85 on flat ground and only loses about 5 mph on that hill. Not full power but better. No cutting out or stuttering but does seem to lose some power about mid rpm range.

So my current thoughts are it had a bad case of a gummed up fuel and tbi system. I have sprayed to sea foam through pcv and cleaned all visible varnish off the inside of the throttle body while it was running. After it cools I will pull the EGR and IAC and try to clean those.

I will check the fuel psi while I have the rig rented and see what I get.

while I cleaned the throttle body I did confirm the injectors and spraying a good and strong.

My theory of the gummed up fuel system comes from the 6 bottles of sea foam I have poured in its tank, one bottle per fill up. It gets 9-10mpg and I fill up every 150-200 miles so it is getting a strong dose by now.

 

[tanman_2006]

IAC looks new. Cleaned just a little gum off it, lubed it, added sealant and reinstalled.

Egr looked pretty clean, gave it a shot of seafoam and opened and closed it a few times. Seemed to operate as intended.

Currently idles good. Hunts around 900 rpm on cold starts and settles at a smooth 750 after just a couple minutes.

TPS and fuel pump are about all I have left before I come full circle.

 

[sntrym]

My TPS was behaving intermittently like this until one day it completely died. I was hesitant to replace it because I didn't want to just throw parts at a problem, but in the end the truck drives much better now.

 

[tanman_2006]

Today the truck ran rough first thing this morning to the deer plot (3 miles back road), ran better but still rough home, ate a piece of pie and we took it to check cows. Was rough the first 5 miles then ran flawlessly all morning (still seems a touch low on power). Shut it off for lunch, came back out and it was a bit rough through the parking lot and getting on to the main road but cleared up within 2 blocks.

So, is there a chance I am loosing fuel prime? Is there a way to test this?

On my 6.5's I've had the pick up tube in the tank rot and get pin holes. Any chance I'm getting air in my fuel and loosing prime after shutting off for a time?

 

[tanman_2006]

The psi's have it. 6-8 at idle, 2 psi foot to the floor, my wire harness is faded but I have one wire at 13.5v (greenish), one at 6v (yellowish) and 2 seem to be grounds. Does this sound right for voltage?