Help! I need some diagnostic help ... 95 Civic

[kev99sl]

My wife's '95 Civic is displaying some low-grade issues that I can't quite say are related, but can't quite pass off as coincidence, and that aren't really that bad, but bug me enough to want to check it out.

Before I begin, FYI there is no MIL lit, and no codes in memory. It is a '95 SOHC with about 120,000 miles.

First of all, the car displayed some hard-starting issues a couple of months ago -- only after the car had sat for quite a while -- accompanied by a slip in mileage -- nothing drastic, but noticeable -- from 36 MPG to 33 MPG. I replaced a vacuum hose on the fuel pressure regulator, and the hard-starting issue was solved, but the mileage remained where it is.

Next, we noticed that the temperature gauge was creeping up higher than usual when the car was idled a lot. The fan kicks in and cools it down with no problem, just a lot later than it used to. It never gets near the red, but it was enough for even my wife to notice. In other words, it's doing what it's supposed to do, but it's not behaving the way it used to. When the car is driven, it's fine.

Finally, while I was idling the car to see if the fan would kick on, I noticed that every two minutes or so the idle would kick up a few RPM, stay there for 10 seconds or so, and then go back down. It isn't "erratic" -- it occurs in regular cycles. Since I haven't made a habit of idling the car and listening to it for long periods of time, I don't know if this is normal or not.

All that to say, I'm thinking that the thermostat is starting to go. I say "starting" because it isn't exhibiting any of the symptoms of all-out failure, open or closed. Am I crazy? I'm thinking the thermostat is starting to go, and the ECM is compensating by running in open loop, or some such thing, hence the mileage drop.

Any thoughts would be appreciated.

[ July 23, 2003, 06:17 PM: Message edited by: kev99sl ]

 

[got boost?]

my GUESS is that the oxygen sensor is bad, a bad o2 sensor can cause the computer to go into open loop mode, I'm surprised you have no codes though. other (more remote) possibilities are clogged injectors, general tune up stuff. start with a tune up (new plugs, cap, rotor, check wires, new fuel filter, air filter) including a new o2 sensor.

 

[kev99sl]

quote:

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Originally posted by got boost?:
my GUESS is that the oxygen sensor is bad, a bad o2 sensor can cause the computer to go into open loop mode, I'm surprised you have no codes though. other (more remote) possibilities are clogged injectors, general tune up stuff. start with a tune up (new plugs, cap, rotor, check wires, new fuel filter, air filter) including a new o2 sensor.

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Thanks for the reply. Unfortunately, I failed to mention in my original post that I did replace the O2 sensor, plugs, cap, rotor, wires, fuel filter, and air filter in the attempt to fix this! I wonder about the injectors though ...

 

[Propflux01]

You mentioned the car sat for some time....how long?? My first thought is bad or sour fuel caused gum in the fuel system. 30 day old fuel is sour. You idling up and down sounds like a vacuum leak. This is indicative of hotter than normal temps, erractic idling ( car is leaning out, ecm is trying to compensate, hence the up and down idle)
My next question is when is the last time you flushed cooling system? if never, it may have rust that has settled in the radiator, partially restricting it. If it was a daily driver before it sat, the rust is moving around with the water every day. when it sat, the rust settled and 'coagulated' so to speak, and now won't move around much. Just a thought. I think this only because problems started after it sat awhile. check EVERY vacuum line ( you know there is one thats hidden somewhere in the engine that you didn't see, there always is!!!)and post back to let us know.

 

[smeltjr]

my integra has an ECT-engine coolant temp sensor that i replaced along with thermostat when my temp was bad-but the other way. they are both cheap-i believe the ECT can throw into an open loop. if you have a helms for your car, check there. also, flush out your coolant and make sure that the system is bled. the dreaded thing that obviously can cause temp issues that will not throw a code is your head gasket. if you have means to check compression or do a leakdown, try it. my 2cents.

 

[Drew99GT]

You wouldn't be going to open loop if the temps are above normal, like if your thermostat was stuck open. I'd start with everything in the cooling system. With 120K or so, replacing the thermostat now is cheap insurance even if it turns out to be something else. If you've seen what a stuck closed thermostat will do to an engine, especially n the highway, well then you know (warped cylinder heads etc.) Also, perhaps the radiator pressure cap is starting to vent pressure too early. That will occasionally increase operating temp a bit. After that, pressure test the system and see if it is holding pressure. My Dad's blazer was exhibiting the same systems, and then one day after shutting it off, the coolent just suddenly boiled out of the overflow after sitting from coming off the highway in high temps with the A/C on. New pressure cap solved everything. If all else fails, perhaps your water pump drivebelt isn't tensioned to spec and is slipping a tad bit

 

[manualman]

Hey Kev, how's the Saturn running? 140k on my SL, but my sister drives it now.

My wife's old Olds had a tiny pinhole leak inside the fuel pressure regulator that allowed the pressure to bleed down between starts and also leaked a small amount of fuel into the vacuum line. Symptoms were slightly lower fuel economy and hard starting.

Knowing you, its had Techron every 5,000 miles so injectors should be decent.

On the temp side, I guess it could be the thermostat. Try it, they usually aren't too expensive. Is the idle rpm normal? If it is on the low side, the pump just may not be spinning fast enough at idle. Need an IAC cleaning? I can't believe its any inherent flow problem in the system if you have no trouble at higher speeds. Did it once have a hanging down air deflector that has been ripped off by a parking bumper? That would affect low speed cooling, but not high speed. (That would definately be my prime suspect if this was the Saturn.)

 

[kev99sl]

Thanks for the replies, everyone. The car has been regularly maintained, including complete coolant flushes every 30,000 miles. When the car exhibited hard starting, it had sat for about a week, but like I said that hasn't really been an issue since I replaced the vacuum line on the fuel pressure regulator.

The car really is just fine as far as it never actually overheats -- it's just that the temp gauge gets higher than it ever used to before the fan would kick in.

I'm thinking I'll replace the thermostat just as a matter of course -- it's cheap and it's the original one with 120k on the clock. Besides, it definitely needs new radiator hoses, so I might as well do the whole thing at once.

Beyond that, it sounds like I'd just be throwing parts at it to try and pinpoint the issue. I hate to say it, but it might be time to have the local Honda folks take a crack at it, or maybe wait until some more clearly defined symptoms crop up.

 

[mph]

If your cooling fan is coming on late, suspect the electric fan thermoswitch. This is different from the gauge sender or the ECT sensor for the ECU, is located on the thermostat housing, and costs about $35 from the dealer. Replacement is easy, if you have a big enough wrench or socket.

Mine became erratic and came on too late, leading to overheating when stuck in traffic or driving hard in hot weather. I pursued other options at first, because it did come on eventually, but it turned out that the switch can indeed fail in this way.

 

[mph]

quote:

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Originally posted by Drew99GT:
If all else fails, perhaps your water pump drivebelt isn't tensioned to spec and is slipping a tad bit

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On Civic engines (at least of this vintage), the water pump is driven by the timing belt. If it's slipping, he's got bigger problems to worry about!