Rough starts - poor mileage

1995 S10 PU 2.2 227,000 miles

Started as intermittent rough idle at startup - more frequent now, idles and runs fine once it levels out, throws no codes.
Mileage is down to 22-23 compared to my usual 26MPG.

Probably 30,000 miles on 100,000 mile AC delco plugs, new Acdelco wires. Replaced fuel filter and oxygen sensor, tested map sensor, did basic EGR tests, removed EGR, the pintle valve seemed to move fine and I didn't see any major carbon build-up.

What's next?

I noticed on the way home tonight the heat was going up and down. This happened a couple of months ago and I was low on coolant.

The reservoir was full so I thought maybe it was the thermostat. When it cooled I opened the radiator and it was quite low. I don't know why its not flowing from the reservoir to the radiator, and where is all of the coolant going. I have no leaks as far as I can tell.

Head gasket or intake? I have no oil in the coolant, or coolant in the oil.

Pull your plugs and see what color they look. I had a 95 that had a head gasket problem and id did exactly what you just said. Look for greenish tint to the plugs. Otherwise, start the engine - just after the idle starts to smooth out, stop it and pull the plugs and look at it. I bet that one or two of them are wet with coolant.

I highly doubt your intake because it's not the same as a v6 where the intake has coolant running through it.

Hope that helps diagnose your problem.

I tried to remove the plugs last night and could only get two out. (I didn't want to break something and not be able to get to work this morning, so I didn't try too hard for the two that are seized) Do the seized plugs mean anything?, I have never experienced this in any car I have ever owned, (around a dozen or more over the last 25 years) Also, I haven;t mentioned it yet, but this was never overheated. it got hot bet never in the orange on the guage, and no steam or discharge under the hood.


The ones that came out didn't look bad to me, but the did have a very thin white/gray powdery residue, no green. Is this an indication of burning coolant? The exhaust seems normal to me, so if it is burning it, it is not a great amount.

I am stuck right now not knowing exactly what the problem is, the temp goes up, goes down when stat opens, goes up, back down, several times, with the range between decreasing each time, until it finally stays steady.

I have the gurgle when I shut it off, still not sure why the coolant isn't flowing from the resorvoir to the radiator. Any help would be appreciated. If I can't figure it out I will take it to a shop for diagnosis, but I hate to pay $75 for something I already know, but I don't want to replace the head gasket on a hunch either.

Thanks

If you are not getting flow from the rad to the overflow, then check your cap. might consider replacing since it's only 14 years old. Pull the small hose that goes from the rad to the overflow and try blowing through it. That is all I can figure for you on the issue of overflow. If it's not circulating, then there's a chance that you are building too much pressure and the coolant is being forced somewhere else that it isn't supposed to go.

Seized plugs - not too normal, but I know two of them are PITA's. The color of your plugs are ok - grey/white and chalky kinda...normal colors. Black sooty or greenish tint are bad.

Head gasket is leaking, shop tested antifreeze for exhaust and found it.

Head gasket is leaking, shop tested antifreeze for exhaust and found it.


Are you going to repair it yourself? It's not too bad, and I think I might have some pics somewhere too. I can give you some pointers...:cool: