Hello everyone. I am new to this forum as well as new to working on trucks. I found a pretty good deal for an 1994 square. The truck has 144k miles on it, original engine, and I was told a new trans around 10k miles ago. I was also told that the truck has been sitting for a few years and would need some love.

It runs and drives under it's own power, but the engine seems to be struggling. I haven't done any maintenance yet or tune up. I plan on doing that soon. But I have already noticed the truck has some issues running and would like to know where to start in diagnosis. I bought this truck to learn a lot of the basics and begin working on vehicles. (It is a 350 small block with an auto trans, 4x4)

Symptoms:
-Hard to start. I have to give her a little gas to get her started. After that I have to give her a little gas to keep her going and then she will idle on her own. (it is 10-25 degree here right now fyi)
-Slight shaking and vibration while running
-The idle is a little rough. It runs strong, and then every few seconds (seemingly random but consistent) it will have a hiccup where it runs a little rough

I was told at the time of purchase it needs it's throttle body cleaned and that should solve the problems. I'm sure that will help, as well as new plugs, wires, distributor cap, etc. But I wanted to hear if anyone had any ideas. Thank you!

 

Hi,
The first thing I’d do If it’s been sitting is some basic stuff. Replace the air filter, check if there is evidence of mice nesting, etc. Change the oil. Look for disconnected hoses and chewed/disconnected wires. Clean the grounds - not sure where they are but I think one on firewall power distribution block, one on engine at thermostat, and at least one other somewhere - someone here might know for sure. Clean terminals on battery.

next I’d check if there are any codes. I assume the check engine light is not on? Here’s link on how to check codes https://www.chevytalk.org/fusionbb/s...php?tid/273660
If there are codes then you can google the code and/or ask questions on the forum about the specific code. (Btw - I think it helps to put helps to put vehicle year engine in the post title as some people know a lot about specific years and they can see which posts may be interesting without opening)

If no codes and still running rough then I’d check fuel pressure and timing to make sure they are right. If that stuff is bad it causes all sorts of problems. Here’s a link on how to check that https://www.chevytalk.org/fusionbb/s...php?tid/253427

its satisfying to be able to work on your own truck though it can be frustrating at times. There are people with a lot of experience and you can be pretty much guaranteed that someone has seen your problem before. Searching these forums can find a lot of info on specific problems.
good luck!

 

welcome from maryland. i have a 94 with a 4.3 with over 350k on it. not really a power horse but she can get up and go. Sabino pretty much hit the nail on the head with what to start with. these computers need to see good grounds to work right. sometimes they can stump me after testing each sensor and dealing with a dead battery i swapped batteries and the problem slowly went away. to this day i dont know for sure but i think it was a poor battery connection. it was good enough to start the truck but not perfect enough to run the computer idk.

i have some links that you may find handy.
OBD1 code retrieval
Trouble shooting sensors and how to test

one other thing to test is the fuel pressure which you have to make a tester or buy one and place it inline. i remove the fuel filter and put it there

 

another thing these trucks arnt "squares" that title is reserved for the 73-87 (91) style

 

Welcome!

 

Thank you very much for this information. I planned on doing the basic services before I freaked out. I know that simple things like a spark plug going bad can cause an engine to run poorly.

I didn't know that there was a way to view the codes without a computer. I had heard a light flashed, but was told you had to have a scan tool of some kind to really see what they were!

I will try these things within the next few days. I am a little busy at the moment. I did do a little inspection under the hood and saw that someone had done a lot of um..."custom" stuff. Hopefully someone did it on their own because if any company put their name on it I would be very sad. Regardless, it doesn't appear to have any connection to the engine or it's performance.

Again, thank you for the awesome information and the warm welcome. I will put this to use!

 

Thank you. I didn't realize good grounding could make such a big upset. I'll make sure to get those cleaned.

My bad. I have always heard the 88-98 trucks called the "old square bodies" lol.

 

Thank you

 

So I did some general maintenance over the past few days. Yesterday I changed the oil (note I did smell gas in the oil. It wasn't a lot but there was some. I heard this could be bad piston rings, but the engine is running VERY rich so I was also thinking it could be that. I also changed the air filter and cleaned the throttle body a little. After those things, it still struggled a little to start, but came to life and ran well faster than it had before. Made me happy.

I did the plugs, wires, distributor cap and rotor today. After I did all that I went to fire up the truck and nothing. It will crank fine, but not start. With the pedal to the floor I get a little crackle from the exhaust it it acts like it wants to start, but nothing else. Here is the image:




My assumption is that I just put something in the wrong place. I didn't have time to check since I finished as the sun was almost down (the truck truck is outside).
[EDIT]: I looked at some more pictures online. Many of them show the order exactly 1 space off from the order I did it in.

 

when you floor the pedal it puts the engine into "clear flood mode" and will limit the fuel. i dont click links to images so i cant tell you if that one is right or not. but number one wire on the distrib should be pointing to number one cylinder and firing order is 18436572