So I'm on the road right now (or was, when I wrote this) having an issue that started a few days ago and I'm trying to diagnose it. I am not sure what info is relevant, it does feel like more than one problem.
I have a 2001 Honda Prelude SH. For the past few months it's had a slowish (.5-1 qt per week) oil leak out the lower timing belt cover, which from the service diagrams I can only assume is a worn out seal on the crank or cam shafts. I've had some success stopping it with lucasoil oil stabilizer.
About 2 days ago while idling with the AC running it started oscillating between about 400-1100 rpms (normal is ~800-900). First every 20 seconds or so then gradually increasing frequency over the course of 30 minutes until it was every few seconds, blowing gray smoke, and eventually stalled out. Also there were about a dozen small black specks on the ground behind the exhaust pipe. Here's its final moments:
At this point I could no longer start the car. It would turn over but wouldn't start. I checked the oil, it was a little low but not critical. I noticed a larger than usual puddle on the ground.
When this happened the check engine light came on and I read P0170 (fuel trim bank error).
I looked it up, found some similar stories that identified the air pressure sensor as the issue. I took another vehicle out, replaced the map sensor and the air filter.
It looked like it solved the issue, but I let the car idle (no AC or fans on), came back about an hour later and found it stalled.
I put it aside until today.
Today, I started the car and drove it. It ran all right for a while. Suddenly the following happened all at once:
- Check engine light
- Low oil pressure warning
- burning smell
- pressing gas pedal does nothing unless clutch was out. Or something. Some kind of weird long throttle delay.
- With the heater on full blast, cold air comes through the vents.
- VTEC does not kick in at all, and general mild power loss in non VTEC range.
I pulled over, stalled, got it started after some trouble, stalled again.
Opened hood, a medium amount of smoke coming off engine block and a lot of heat, I cant locate source of smoke. Oil looks a bit low. There was smoke coming off the oil on the end of the dipstick.
Read error code as P0177 ECT sensor low input. Looked it up, it said this is thrown when coolant temp is reported 300F or higher. Said most common cause was wiring but the smoke and heat makes me think its correct. I read coolant temp at 309F. Cooled to about 290 after 15-20 minutes of sitting there. Now at about 201, so those readings do seem reasonable to me and not like a sensor malfunction.
I fixed a coolant leak and refilled the radiator about 5 months ago. I have not seen and do not currently see any coolant leaking.
Some other info from comments, etc.:
- No pressure in coolant reserve hose.
- Coolant reserve tank cap is damaged where hose connects.
- Radiator cap o-ring is pretty torn up.
- Upper and lower radiator hoses and radiator itself cool to touch.
- Both the radiator and condenser fans are working properly; at least they both spin at full speed when the AC is on.
- Since replacing the MAP sensor and air filter, the exhaust has been clear and the oscillating behavior during idle hasn't returned, that seems good at least.
- The AC was blowing out lukewarm air at high RPMs earlier in the day when this first all started a few days ago. I assumed the compressor was on its way out but now I'm thinking the air may have just been too hot for it.
- Carpet in cabin is dry, no coolant leaking into cabin.
Currently I am sitting at a gas station waiting for the engine to cool so I can test the ect sensor and check the levels, but I'm out of ideas. The engine confuses me a little because of how heavily computer controlled it is.
Does anybody have any ideas, or know anything else I can check? I only have minimal tools with me (sockets, some screw drivers, a multimeter and some other basic stuff).
Once the engine cooled I checked the coolant. It was bone dry. I couldn't open the reserve tank or check its level because of the damaged cap. The radiator capacity is 3.3L and I put about 3.2L back in. I bled the air, all seemed fine. All the other weird issues I'm assuming were the result of a severely overheated engine.
I drove it about 170 miles with no issue (it was running quite well actually, I think the MAP sensor replacement was a long time coming anyways). I even idled for about 30 minutes in the middle of the trip, AC on. Everything seemed OK. The coolant temperature held in the 190-200F range.
About a mile before my house the temperature gauge shot up suddenly and quickly, and the weird behaviors started again, as well as the burning smell. I put the heater on, the air was extremely hot. I guided it home gently without exceeding 250 F. Once it cooled in my driveway I opened the radiator cap and it seems dry again. I'm out of coolant right now so haven't refilled it yet but I suspect it's empty. I see no puddles on the ground and no liquid coolant anywhere under the hood.
I found http://community.cartalk.com/discussion/2297412/radiator-fluid-disappearing-like-a-magic-trick, the working theories there are blown head gasket, cracked cylinder head, or a leaky heater core. My exhaust is clear which I assume (and hope) means that I'm not burning coolant in the engine, so maybe it's the core or somewhere else in the system. Maybe it's evaporating out the broken seals? Can it do that? In any case, it seems to rule out the theory of a very slow leak, I lost > 3L of coolant in < 200 miles.
I really want to check the reserve tank but I can't get the cap off, can't see the level externally, and don't want to cut the hose and rip it out completely until I can get a replacement cap (the damage to the cap is in the joint where the hose connects, so I cannot unscrew the cap).