So I finished swapping a 46,000 mile 2.8 V6 into my '85 GT with 100,000 miles (the original V6 threw a rod) last month. The car was running like a champ for around a week (minus an oil leak) and then I dropped it off at BrakeMax to have them pull a stuck front hub off for me. When I got the car back this past Monday, I started it up and noticed that it was running terrible. (I spoke with the manager and the mechanic that worked on my car, and they said they did not touch anything engine-related at all.) It idles around 1000 RPM but is really rough, the engine vibrates quite a bit, and there's absolutely no power. It is so low on power that when I try to start off in first gear or reverse, it comes very very close to stalling. It doesn't rev happily at all, it sounds terrible, and it doesn't seem to have the effort to rev up past like 4k. And if it does, it takes longer than usual to get up there.

I replaced the fuel filter yesterday, but that did nothing. I can hear the fuel pump come on when I turn the key to the "on" position, so I know it's neither of those. So far, I haven't seen any coolant/water in the oil or on the oil cap. I have also flushed my cooling system multiple times. I put straight, clean water in, and flush it out a couple days later, and its very brown or black. I'd say I've flushed at least 4 times, even with BlueDevil radiator flush for two of the flushes.

I know I have the spark plug wires connected correctly, I followed the firing order that I found here on the forum.

At this point, I have no clue what direction to go next, so once again, I turn to the forum. Anyone have any suggestions?

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'85 Fiero GT [4-speed]
‘86 4cyl (Parts Car) [5-speed]
'95 Mitsubishi 3000GT VR4 [6-speed]

On my 86 2.8 I had this exact thing happen. It turned out to be a blown fuse for 3 injectors. For some reason Pontiac decided to fuse it that way. It was one of the fuses on the block under dash by your left knee, and it's labeled as such... It was only running on three cyls...

[This message has been edited by FX (edited 07-10-2019).]

quote Originally posted by FX: On my 86 2.8 I had this exact thing happen. It turned out to be a blown fuse for 3 injectors. For some reason Pontiac decided to fuse it that way. It was one of the fuses on the block under dash by your left knee, and it's labeled as such... It was only running on three cyls...

You are truly a lifesaver. After spending a whole month of my time swapping that engine (I'm not all that experienced, this was my first big project) I was very stressed, angry, and upset that it all might've gone to waste. I made the mistake of assuming the worst when the engine started acting up. You saved me plenty of hours and effort trying to track that down! Many thanks to you!

quote Originally posted by jaredaltizer: I made the mistake of assuming the worst when the engine started acting up.

A perfect example of needing to check the simple things first! Glad to hear that's all it was. Hopefully there's not some recurring issue that causes the injector fuse to blow repeatedly.

quote Originally posted by Patrick: A perfect example of needing to check the simple things first! Glad to hear that's all it was. Hopefully there's not some recurring issue that causes the injector fuse to blow repeatedly.

I don’t think it will be a repetitive problem. I put seafoam in the tank a day or two before I dropped it off at BrakeMax, so maybe that contributed to the blown fuse.

I would suspect a short... but it's also possible I suppose that an old fuse just lets go eventually.

I have “heard” that the injector wires have some sort of issue and makes the fuse pop. But my experience in blowing injector fuses are usually related to having a bad injector. It’s possible the fuse just fatigued and failed on its own but that has not been my experience. I sincerely hope it’s nothing...

-David

quote Originally posted by Patrick: I would suspect a short... but it's also possible I suppose that an old fuse just lets go eventually.

quote Originally posted by Crasian: I have “heard” that the injector wires have some sort of issue and makes the fuse pop. But my experience in blowing injector fuses are usually related to having a bad injector. It’s possible the fuse just fatigued and failed on its own but that has not been my experience. I sincerely hope it’s nothing... -David

I ended up figuring it out, and it was a short. One of the wires going into the EGR sensor (I think?) has been chewed up to where the bare wire was exposed.

jaredaltizer, I don't know a whole lot about these infernal contraptions, Mostly what I read on here, and experience. I replaced that fuse over two years ago, and it's still running fine. Fuses do fail over time, and heat. Glad to help out when I can...