Pronounced engine miss, suggestions?

[sgtpoliteness]

So, it runs better once it gets warmed up? That should be 'closed loop', where the PCM uses the O2 sensor to help set fuel trims. However, if there's no O2 I'm not sure if it would actually get into closed loop. In open loop, which is pretty much when the engine is cold or really hot the PCM uses a map to run the engine (spark, fuel, stuff). When the O2 was heated up, it would go into closed loop and use feedback from the oxygen sensor to run. I think yours uses an old-style one wire and it SHOULD be in the driver's side manifold. If not, weird.

---------- Post added at 06:04 AM ---------- Previous post was at 05:55 AM ----------

Make sure you have some paper and a good pen handy. Ok, find your OBD1 port or diagnostic plug in. Now, insert a paper clip or jumper wire into the two far right UPPER terminals. They're the two on the upper row, furthest right. Now, turn the key to the 'On' position but don't start the truck. Remember that paper and pen? Count the number of blinks that the engine light makes. Let's say it flashes twice, short pause and then 2 more times. That's code 22. If there's another code there'll be a longer pause, and then the same deal. Do this a couple of times to make sure you're counting it right and you get all the codes.

If you google '1992 Chevrolet blink codes' it should come back with a list of codes to compare your notes against. Hopefully, that gets you pointed in the right direction.

 

[KevinGn_WV]

The only code I got was 15, coolant temp, but I had unplugged that while it was running last night. Cleared the code, ran it for 15 min at various speeds, let it sit for about 20 min, ran it again about 10 min. No codes.

Talked to a friend of mine at the parts store that actually talked me out of buying a timing light saying it started too good to be out, said the injections didnt look like they were spraying quite right and the fuel pressure reg might be dumping fuel causing the plugs getting wet and the gas smell. Quadrachecked again for an O2 sensor. None.

Def runs better warm but still a rhythmatic miss. Compression check next I guess.

 

[OR VietVet]

Just sayin'. I would have done the compression test a long time before I started throwing money at it. Those gauges are not that expensive and lets you know how mechanically sound the engine is, or at least one of the tests that do that.

 

[KevinGn_WV]

Just sayin'. I would have done the compression test a long time before I started throwing money at it. Those gauges are not that expensive and lets you know how mechanically sound the engine is, or at least one of the tests that do that.

I agree, but I was stuck in the garage, found the nasty ignition parts and was sure that was it, and I guess I am sickened by the possibility of a trashed engine honestly. Denial at its finest you know?

 

[OR VietVet]

I see the reasonable assumption, I do. If it needs engine work and you decide to keep it you have the trashed other parts out of the way. With all the new parts that may influence you to keep it if in fact you wouldn't have. Sounds like you want to keep the vehicle anyways. I hope I am wrong and you can show decent compression. Make sure you take all plugs out and WOT it when you do it and if you end up with some cylinders lower than the others do a wet test to see if upper or lower end. Good luck. Make sure you have a battery charger hooked up so the cranking speed remains constant.

 

[sgtpoliteness]

All of Raiderron's advise is spot on. Compression should be like 1 or 2 on the list of diagnostic steps.

Good work on the code checking though.

 

[OR VietVet]

 

[KevinGn_WV]

Is a 350 from a 1990 a direct swap? Idk why it wouldnt be but then again, the thermo-coil actuated direct fusion gas inhibitor might not be compatible.

 

[OR VietVet]

Took the words right out of my mouth. Compression test results?

 

[KevinGn_WV]

The lowest was between 115 and 120 and the highest was 135. Also, I took apart the TBI found the pres reg diaphram was bunched up on one side but the only improvement is I dont smell gas like I did.

So, while doing all of this Ive found a new ECT sensor, newish looking IAC, what was a recent MAP which also could have been new, the coil is very recent, the plugs and wires while quite nasty were also recent to a point. The ignition module, I'm not sure of. It was also rusty like the rest of the dizzy so its hard to tell if it had been swapped or not. Valve cover gaskets were very recent as well.

My hypothesis is: Someone else was tracking down this problem and quit. Which by now seems like a really good idea. However between the initial purchase and parts Im down close to $2k.

So heres what I know. It still sucks. Figuratively and literally. I can hear it sucking air. Any vacuum I unplug and the idle jumps way up. PCV, or brake booster. Im still losing oil out the top passenger side somewhere and though the previous cleaning I did on that head seemed to slow it down its still leaking but looks like its from the front and I cant really see from where. In P or N, it def has a slight miss. Rev it to around 2k rpm it "seems" to go away, however in R or D the miss is very noticably rythmic and much worse. Also, the hissing seems more noticable from the engine in gear. Under load, the lower the rpm the worse it is. Again, it "seems" to go away as the rpms climb.

PS: Whats the trick to getting at the dizzy hold down? Another "special" tool?

Oh and, theres no oil in the coolant and no coolant in the oil. I looked on my Yuk where the O2 should be and ya its sticking right out there loud and proud. On this truck, theres either a plug in the hole or the O2 is broke off. Cant see in there, just felt for it.