1994 Honda Civic EX, Manual, 1.6L, 1 Owner (yup, almost 24 years...)

I was driving on the interstate when the engine suddenly overheated. I noticed the temperature gauge was pegged high and the air from the vents started blowing cold. Took the first exit and pulled into a gas station just as smoke/steam started coming through the vents and was billowing out from under the hood. Coolant hose had split and sprayed coolant over everything in the engine compartment.

Fixed the hoses and changed the oil (it was time) and it cranks right up. But now it runs rough. If I really baby it on acceleration (grandma would complain I'm going too slow) it can be completely smooth, but pressing on the gas a little extra makes it run rough during acceleration. Definitely lacks power on acceleration, too.

There is no CEL. (And I confirmed that the CEL bulb still works)
Cold idle is rough, but seems to improve as it warms.
After its warm, the idle RPM sometimes drops to the low peg on the tachometer and is rough, but it doesn't die.
At constant RPM, can be rough or smooth depending on throttle position.
No visible smoke in the exhaust (I don't think it's burning oil.)
Some burning anti-freeze smell, but that could still be from the initial leak.

I know it could be a lost cause, but what should I check before I give up? Could the coolant have caused any sensor issues?

I plan on checking spark plugs and compression. Maybe throttle position sensor? Maybe O2 sensor? (but there's no CEL....)

thanks for any suggestions.

 

I would, bleed the coolant. Then get a headgasket tester from your local auto part. See if the headgasket took a dump during the overheat.

 

Yeah, good call on bleeding the coolant, I'll see if that changes anything. The oil looks normal though, doesn't appear to have any coolant in the oil.

 

warped head is a good possibility

 

I know, I'm just looking for the things to check to confirm or deny that's the real problem.

 

compression/block test are good starting points

 

Well, I can't get the spark plug boots off of cylinders 2 or 3. Probably not a great sign. They twist, but won't come off.

I wanted to check what lack of spark was doing when the engine is idling. 1 and 4 are clearly working, but 2 and 3 made no difference to how the engine was running when I pulled the distributor cable (from the distributor end, since I can't get the spark plug boots off). Sounded like good spark when the cables went back on.

Any tips for how to remove the spark plug boots? I've seen a couple forum posts where other people have had this issue ...

 

The ends of the wires can melt onto the plugs when the engine overheats. You will have to rip them out and replace later. Once you get the wires and plugs out, do a compression test. Zero compression on two adjacent cylinders is often because the head gasket has blown out of the gap between them. This will cause those cylinders to be dead but it is in a "dry" place where coolant will not leak through the blown gasket.

 

Good news bad news. Got the boots out, but they left the rubber tip behind, so can't get a socket on the spark plug. At least I'm bleeding now, so I've got that going for me.

I've got the replacement wires already, kinda expected that. How do I get that last 1/2" of rubber out of the bottom?

 

Probably a combination of breaking it up with a screwdriver and fishing out with long pliers.

 

Flathead screwdriver plus shop vac and soda straw for the win! We'll see what the compression test shows in a minute.

 

165 160 160 165

didn't expect that. Two of the plugs look not so good. Here's hoping new plugs help.

 

not awesome numbers. done warm or cold?

 

Cold, maybe luke warm. 1.5 hours after last driven.

I put new plugs and new distributor cable and its running just like it did before overheating! CEL turned on during the first test drive, so I unplugged the battery to let that reset in case it was leftover from cranking during the compression test. Now it's running smooth, no CEL, and frankly I can barely believe it. I was ready to write it off as a lost cause.

Let's see if it lasts.

 

you are a lucky individual. odds are your numbers would jump significantly warm.