rought running

[gmoutdoorsman]

My buddy just picked up an 89 stepside and seems to have some issues. Its originalky a 350 truck but someone replaced it with a 305 out of a monte. We got it idling smooth,but when you try acceleratingit falls on its face like somethings holding it back. I played with the distributor a lil and got it to idle better but it wants to run like crap otherwise

 

[woody31]

need to set the timing with a timing light the right way..then do the basic check list,,,plugs ,, wires,,cap,,ect ect

 

[scoob8000]

Has it always run this way after swapping the motor? Did they swap the computer over with the motor?

 

[IOWNJUNK]

need to set the timing with a timing light the right way..then do the basic check list,,,plugs ,, wires,,cap,,ect ect

This^^^^

 

[gmoutdoorsman]

Not sure about the computer and engine swap. My buddy bought it yesterday and wasnt aware of all the issues. But bought it anyway lol smh. What is the factory timing,28°?

 

[gmoutdoorsman]

Also the coolant temp sensor is broke off. The iac sensor isnt hooked to anything.

 

[SAATR]

Also the coolant temp sensor is broke off. The iac sensor isnt hooked to anything.

That would be a good place to start.

Sent from my XT912 using Tapatalk

 

[Scrufdog]

You need to start with replacing the coolant sensor and IAC. If the IAC is unplugged, its probably bad and the Previous Owner unplugged it.

Google up how to set base timing on the truck, and how to set idle when replacing the IAC motor.

Right now its likely over fueling the engine when you try to drive it. I would assume it still has the 350 computer in it. If the computer cant find any one sensor or control (example, coolant temp or IAC), then it will switch to the default fuel and timing tables it has. These tables are for a 350, bigger engine, more fuel, too much for a smaller 305. Once you replace the broken stuff, the computer will be able to switch into closed loop mode and will use the oxygen sensor (primarily) to adjust the fuel to proper levels. The computer wants to put a certain amount of fuel out, but it has enough fuel trim in it to cut fuel down to adapt to a 305.

The only real future problem you will encounter is if another sensor goes bad. If in the future a sensor or control goes bad the computer will then again go into default maps and cause the engine to run rough again.

So, replace the coolant temp and IAC, reset the computer (disconnect battery for a bit), set base timing, and reset computer again. Then go for a drive with a combination of 'city' and highway driving for about 20 minutes and the computer should adjust itself... assuming no other sensors or controls are bad.

 

[slippy3002]

Not sure about the computer and engine swap. My buddy bought it yesterday and wasnt aware of all the issues. But bought it anyway lol smh. What is the factory timing,28°?

Base timing is 0°. You need to unplug the wire from the computer to do it.

Sent from Robl@nd

 

[gmoutdoorsman]

You need to start with replacing the coolant sensor and IAC. If the IAC is unplugged, its probably bad and the Previous Owner unplugged it.

Google up how to set base timing on the truck, and how to set idle when replacing the IAC motor.

Right now its likely over fueling the engine when you try to drive it. I would assume it still has the 350 computer in it. If the computer cant find any one sensor or control (example, coolant temp or IAC), then it will switch to the default fuel and timing tables it has. These tables are for a 350, bigger engine, more fuel, too much for a smaller 305. Once you replace the broken stuff, the computer will be able to switch into closed loop mode and will use the oxygen sensor (primarily) to adjust the fuel to proper levels. The computer wants to put a certain amount of fuel out, but it has enough fuel trim in it to cut fuel down to adapt to a 305.

The only real future problem you will encounter is if another sensor goes bad. If in the future a sensor or control goes bad the computer will then again go into default maps and cause the engine to run rough again.

So, replace the coolant temp and IAC, reset the computer (disconnect battery for a bit), set base timing, and reset computer again. Then go for a drive with a combination of 'city' and highway driving for about 20 minutes and the computer should adjust itself... assuming no other sensors or controls are bad.

Thank you^^ very helpful. It has the IAC in it,i ment to say Intake air temp sensor is absent. It has the original air lid/snorkel from the monte on it and has no sensor in it. I do have a computer from my pld 305 (L03) camaro. Think we should swap that in? Last night we replaced the intake gaskets and cleaned everything up and it wont start at all. Plenty of fuel and spark just no fire. I tried every tooth on the distributor and still nothing. Tonight im gonna make sure to set it TDC #1 on comp stroke n start from square one.