Ask oldeerslayer as he is a retired GM technician.
Troubled 2.5
Hey all, I've got a 91 Sonoma with the 2.5 151 in it and she's struggling. It's misses something fierce at idle, low, and high speeds now. It's also got a bad knock that I thought was valve train but after new pushrods and lifters last year, figured out it's rod knock. So I'm gonna pull the ol thing out and go through the whole thing here soon. At this point I'm asking purely out of curiosity because I'm doing a full overhaul. But I'd like to know what may be causing the issues. I've pulled the clogged cat off and got a new muffler on there. Pushrods and lifters (as I said), new coil, plug wires, and plugs gapped to 45 thou. I haven't touched the fuel pump or egr stuff on it and I'm thinking the egr may be the culprit. Just looking for anyone else's 2 cents.
Thanks for reading 👌
Thanks for reading 👌
1 - 5 of 5 Posts
As you are probably expecting, it could be a lot of things, and I usually just start testing everything; timing, fuel pressure, egr, sensor voltages, and vacuum.
A little confused...
If you have a rod knock, nothing you do will solve the issue short of replacing the crankshaft and bearings.
This means pulling the engine out and apart.
Depending on how many miles on the engine, it will almost surely need to be bored for replacement pistons.
I have rebuilt many of these lumps, and have found all of them have a ridge at the top of the cylinder bore.
I am currently rebuilding one and have to sleeve the block since it was previously bored to .060
The top of the cylinders had a huge ridge in them.
Believe it or not... these engines are becoming harder to find in upull yards.
I'm starting a thread soon describing a custom rebuild on this engine.
If you have a rod knock, nothing you do will solve the issue short of replacing the crankshaft and bearings.
This means pulling the engine out and apart.
Depending on how many miles on the engine, it will almost surely need to be bored for replacement pistons.
I have rebuilt many of these lumps, and have found all of them have a ridge at the top of the cylinder bore.
I am currently rebuilding one and have to sleeve the block since it was previously bored to .060
The top of the cylinders had a huge ridge in them.
Believe it or not... these engines are becoming harder to find in upull yards.
I'm starting a thread soon describing a custom rebuild on this engine.
A correct overhaul of your power unit Will solve these Issues if done before internal damage ruins it.Hey all, I've got a 91 Sonoma with the 2.5 151 in it and she's struggling. It's misses something fierce at idle, low, and high speeds now. It's also got a bad knock that I thought was valve train but after new pushrods and lifters last year, figured out it's rod knock. So I'm gonna pull the ol thing out and go through the whole thing here soon. At this point I'm asking purely out of curiosity because I'm doing a full overhaul. But I'd like to know what may be causing the issues. I've pulled the clogged cat off and got a new muffler on there. Pushrods and lifters (as I said), new coil, plug wires, and plugs gapped to 45 thou. I haven't touched the fuel pump or egr stuff on it and I'm thinking the egr may be the culprit. Just looking for anyone else's 2 cents.
Thanks for reading 👌
1 - 5 of 5 Posts
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