94 C3500 350 Basket Case

[tanman_2006]

Truck has 110k miles. So far I've replaced the distributor, plugs, wires, fuel filter, t-stat, ect sensor, and fixed some chewed up wires going to the injectors. It's gone from barely ran to runs speed limit but still isn't right.

So here goes the list of issues:

Takes pushing the gas pedal and some cranking to fire up cold.

Idles ok cold but still has a lope to it.

Take off cold and it sputters in 2nd, 3rd, and 4th to the point of giving whiplash at times.

Idle warm is all over the map from trying to stay running at 400 rpm, 750 RPM but has a slight miss, 1000 rpm with a surge to it.

driving warm it had the same cut out issue at cold but not near as extreme.

Top speed floored is 70mph and loses speed on hills.

Truck is an ex DOT truck, cab and chassis 2wd 5 speed likely has 4.10's but doesn't have a factory tach to be sure and the rpo codes are worn off.

any help you can give me would be great. Just looking to make a cheap/reliable service truck

 

[tanman_2006]

Oh and when I flushed the coolant it was like mud. I don't seem to have coolant in my oil so I guess I will see if this is junk from a previous repair or mixing coolants and see if it gets nasty again or stays clean this time

 

[magimerlin]

First thing I would do is check the fuel pressure and also check the egr system... both can cause those bucking and cutting out issues as well as the IAC on the throttle body....

sent from what use to be a great country...

 

[vic_v8]

Start with the basics.

Check timing, fuel pressure, and compression.

 

[tanman_2006]

Timing is at 0 with the tan wire unhooked and bout 7 when hooked up.

A buddy checked fuel psi an said it's good. I ordered a kit and will be checking myself this time.

The previous owner said compression was bout 140 across the board but it is consistent. Seems low but I'm used to checking diesels at 400.

What do I need to do to check egr and IAC?

 

[tanman_2006]

Hooked up a radiator tester holds 20 psi for over an hour.

Checked cold Compression and got 125 plus or minus 5 on all cyinders. So a hair low

 

[90halfton]

I think I would pull the tb off and give it a good cleaning, ohm out the tps, look at injector spray pattern, clean IAC. If coolant was mud maybe pull the temp sensor, inspect, ohm it out at various temperatures, and clean and/ or replace it. Change out base gasket under tb.

 

[tanman_2006]

Swapped in a new temp sensor at the t-stat housing. Is that the only one?

TPS? Throttle position sensor? What numbers should I see over the throttle shaft range?

Do I take the IAC out of the throttle body? Just pull vacuum hoses out or is there something else holding them on? Never really worked on one much.

Had a 95 K1500 and me and a couple friends did the TBI mods but I can't remember how I did any of that, it was bout 10yrs ago that I sold the truck. I'm having a case of mental block and don't want to break anything and add to my head aches.

 

[90halfton]

Tps? Dunno. Should have low reading at 0 throttle and increase upon opening throttle, without jumping all over the place. I'm sure exact specs are on here somewhere but it's pretty obvious if it's not good.
Yes, the sensor at tstat housing is the one I was referring to.
IAC will unscrew out of the tb. Clean it up real good and put small drop of oil on shaft. There is a much better way to do it I'm sure but so long as the thing can retract and extend unobstructed like it should be good.
Have you pulled any codes?

 

[90halfton]

Check for injector spray pattern while running too. Should be a translucent, clean, cone spray. Dribbling injector is a horribly inefficient thing.