Misfire, irratic low idle and stallout

[zep867]

Aye the issues with my transam...

Alright so, my waterpump failed. I replaced the waterpump and through a broken optispark connector that had been taped on by the previous owner, water flooded the opti and it died. I replaced it and the optispark pigtail only to find that when I put everything back together it would start only if I pumped the gas and then wouldn't maintain an idle and died. After deciding it was most likely a timing issue, especially after changing the opti, I took everything apart and found that the dowel pin had just missed the pinhole. So I put it back on, making absolutely sure the dowel pin went in the right place. Started it up and it started and ran, but ran a little rough. I assumed the rough idle to be a result of maf and other sensors being unplugged. So I put everything back together. Now it runs and is drivable but there's a noticeable misfire. It will idle, but it's obvious there's a misfire worse at low rpms and significant power loss in acceleration. If left alone idling, it will stall once the motor warms up it seems.

I dont see/hear any vaccum leaks.

Because the car was sitting for about 2 months while I was working on various problems and projects I figured it was possibly bad gas. I put in a half tank topping it off with 93.

I just replaced the fuel filter while I had it in the garage.

The plugs and wires have maybe 5k miles on them, about 6-7 months old.

I know I need to check my o2 sensors and fuel pressure. It's also been suggested that it could be a bad ICM. Does anyone know a way to test the ICM's functionality? I know 4th Gen LT1 F-body Tech Articles has some information about testing the PCM signal to the ICM but doesnt have anything on actually testing the ICM. Obviously I have spark from the coil, but I don't know if that necessarily means it's working properly.

Also, once the motor gets warmed up, not only does the misfire get worse but my oil pressure drops. Now the oil pressure issue came before the misfire and bad idle issue so I don't think it's the same problem. But it used to drop down to like 10, now its dropping to like 3-5. Possibly a bad oil pump?

[Superman]

You check your coils?
You can use a test light and make a very tiny poke in the boot of the wires on the coil packs. Ground the test light and while the car is acting up, probe the top of the wire boot.
If you experience no change, assume the coil is bad.

[zep867]

There's only 1 coil.

You're talking about essentially using the test light to see if that coil is firing while the car misfiring right?

[NavyVet]

Originally Posted by zep867 There's only 1 coil. You're talking about essentially using the test light to see if that coil is firing while the car misfiring right?

I think Superman was thinking V-6

A failing coil could cause your misfire issues.
As for low oil pressure, what is your idle RPM?
I don't think I've ever seen mine under 30 psi.

[peglegburnout]

Are you absolutely sure you got all the plug wires back on in order?

[NavyVet]

Originally Posted by peglegburnout Are you absolutely sure you got all the plug wires back on in order?

Good point.

[Superman]

I was thinking 98+...my bad.

[zep867]

Yea, I assumed you meant an LS configuration with multiple coil packs. I was just pointing out LT's are single coils. Yea, I'm positive on plug wiring.

[Leonard 3.8L]

Originally Posted by Superman You check your coils? You can use a test light and make a very tiny poke in the boot of the wires on the coil packs. Ground the test light and while the car is acting up, probe the top of the wire boot. If you experience no change, assume the coil is bad.

Yea - I think he's right. I had the same problems with my V6. Coil pack ftw.

[peglegburnout]

I don't think it's a coil problem IMO. That would more than likely show up as a higher rpm problem. Is the check engine light on? If so what codes are you seeing? Does it smell like it's running rich? Using more gas than normal?

[zep867]

Originally Posted by peglegburnout I don't think it's a coil problem IMO. That would more than likely show up as a higher rpm problem. Is the check engine light on? If so what codes are you seeing? Does it smell like it's running rich? Using more gas than normal?

No check engine light. I checked codes and the only code Im throwing is for my bad radiator fan. Yea, it's running rich.

[peglegburnout]

It's possible it could be a coolant temp sensor. My jeep was having a problem a few weeks ago. It would stumble and stall. Sometimes it wouldn't restart when hot. It was running way rich. The connector wasn't getting good contact with the sensor. Just enough to not trip the CEL. The computer will think that the engine is not warmed up so it will keep enriching the a/f ratio. I put dielectric grease on the connector, problem solved.

This will have nothing to do with your temp gauge BTW so you can't go by that to diagnose it. A scan tool or scanning software could confirm this. Maybe put some dielectric grease on it and make sure the connector is firmly in place.

[NavyVet]

You do realize that a dielectic is an insulator?

[peglegburnout]

Originally Posted by NavyVet You do realize that a dielectic is an insulator?

I should have added I cleaned the connection before I added the grease.
I use it on electrical connections I can.

Taken from permatex website "Protects electrical connections and wiring from salt, dirt and corrosion. Extends the life of bulb sockets. Prevents voltage leakage around any electrical connection".