Need help 350 in my 91 caprice runs bad after 4 years

[racecar]

I had the 350 swapped into the 91 Caprice 4 years ago it was from a 1992 C1500, it ran good the whole time, recently in the winter time it was close to about -30c and I hadn't plugged the car in overnight. When the car started it sounded like a tractor really high idle, I changed all my spark plugs, distributor cap, rotor, ignition coil, coolant temperature sensor, fuel filter, spark plug wires, intake air temperature sensor and EGR valve. The map sensor had been changed just a couple months before I got the engine changed 4 years ago. After replacing everything and scanning the OBD1 I don't have any engine codes and the car continues to run bad but not at such a high idle. I'm wondering if anyone knows what it could be. I'm currently replacing my throttle body gasket and the fact occurred to me that I have 305 injectors on the 350 and the ECU and the TBI unit had not been changed when the engine was changed. The TBI units were kept to there same vehicle for Hood clearance reasons. I tested the TBI injectors with a 9-volt battery and they both make the clicking sound. I'm wondering if the ECU could also be damaged from that. Also if I need to change my injectors to the 350 ones.

I don't have any vacuum line leaks but I am wondering if it could be intake manifold gasket. It bogs out and dies under acceleration especially in drive and reverse. When it is in park or neutral I can rev it more, like it is an underload issue? It still does not sound like it's running normal like it did about a year ago from now. THX

 

[Hipster]

Nothing lasts forever and especially not if it's been frozen without enough anti-freeze. I would probably pressure test cooling system and then cylinder/compression pressures. Make sure you didn't split a cylinder. Water in oil or vice-versa.

 

[Erik the Awful]

Please, before you post, re-read what you've written to see if it reads clearly. It took me a couple minutes to understand your post.

It sounds like you're hoping to find a $20 part, replace it, and the truck runs like new. This is going to take some diagnosis.

What's your fuel pressure?

Vacuum leaks don't typically cause a high idle, but you can spray WD-40 around every gasket and vacuum hose and see if your idle raises. It sounds like your car is idling good, but struggling to accelerate. Is that correct? If so, it's not likely a vacuum leak.

 

[racecar]

Please, before you post, re-read what you've written to see if it reads clearly. It took me a couple minutes to understand your post.

It sounds like you're hoping to find a $20 part, replace it, and the truck runs like new. This is going to take some diagnosis.

What's your fuel pressure?

Vacuum leaks don't typically cause a high idle, but you can spray WD-40 around every gasket and vacuum hose and see if your idle raises. It sounds like your car is idling good, but struggling to accelerate. Is that correct? If so, it's not likely a vacuum leak.

I haven't pressure tested anything on the vehicle yet

 

[racecar]

Please, before you post, re-read what you've written to see if it reads clearly. It took me a couple minutes to understand your post.

It sounds like you're hoping to find a $20 part, replace it, and the truck runs like new. This is going to take some diagnosis.

What's your fuel pressure?

Vacuum leaks don't typically cause a high idle, but you can spray WD-40 around every gasket and vacuum hose and see if your idle raises. It sounds like your car is idling good, but struggling to accelerate. Is that correct? If so, it's not likely a vacuum leak.

Also thanks for letting me know of the typing errors.

Yes, it sounds like its idles and runs on all cylinders but bad acceleration especially underload. If i try to continue to push the gas when in gear it stalls/dies out

 

[Hipster]

I haven't pressure tested anything on the vehicle yet

You mentioned the temps it was subjected to, so if there was a chance it froze the engine might be junk now. I would start with those tests. One night is enough to destroy stuff, and no need throwing money at it that won't fix it.

 

[Erik the Awful]

Have you replaced your fuel filter? If not, I'd do that out of hand, then connect a fuel pressure gauge and see what the fuel pressure is. If you have the factory fuel lines you'll probably have to build adapters.

You mentioned the temps it was subjected to, so if there was a chance it froze the engine might be junk now.

His symptoms don't point to a cracked block, but yes, a compression test might be a good idea after checking the fuel pressure.

 

[racecar]

Will do both

 

[racecar]

I had the 350 swapped into the 91 Caprice 4 years ago it was from a 1992 C1500, it ran good the whole time, recently in the winter time it was close to about -30c and I hadn't plugged the car in overnight. When the car started it sounded like a tractor really high idle, I changed all my spark plugs, distributor cap, rotor, ignition coil, coolant temperature sensor, fuel filter spark plug wires, intake air temperature sensor and EGR valve. The map sensor had been changed just a couple months before I got the engine changed 4 years ago. After replacing everything and scanning the OBD1 I don't have any engine codes and the car continues to run bad but not at such a high idle. I'm wondering if anyone knows what it could be. I'm currently replacing my throttle body gasket and the fact occurred to me that I have 305 injectors on the 350 and the ECU and the TBI unit had not been changed when the engine was changed. The TBI units were kept to there same vehicle for Hood clearance reasons. I tested the TBI injectors with a 9-volt battery and they both make the clicking sound. I'm wondering if the ECU could also be damaged from that. Also if I need to change my injectors to the 350 ones.

I don't have any vacuum line leaks but I am wondering if it could be intake manifold gasket. It bogs out and dies under acceleration especially in drive and reverse. When it is in park or neutral I can rev it more, like it is an underload issue? It still does not sound like it's running normal like it did about a year ago from now. THX

Also i should add that my oil and coolant are not leaking out anywhere nor do i see milky oil or contaminated coolant

 

[Hipster]

Also i should add that my oil and coolant are not leaking out anywhere nor do i see milky oil or contaminated coolant

ok, good.