I’ve got a '94 Suzuki Swift GT, manual transmission.
Recently (the last week to two weeks), when I start it in the morning, it runs normally for the first minute or two, then it goes into this deal where the rpms fluctuate - the tachomoter bounces between 1500-2000 rpms, and you can hear the engine revving and falling.
Once I start driving, it will quit doing it about 7 minutes (hey, I paid attention to how long it was happening this week) after I start moving - it doesn’t seem to matter how long I let it warm up for before I start moving. From that point, it’s fine. It will do it again in the evening when I leave work, after the car has sat in the cold all day. As I’m driving, until it stops doing it, I only notice it when I’m slowing down or stopped at a light.
It doesn’t seem to be the clutch - it does it whether I’ve got the clutch pressed or not. Fluid levels are fine and they look fine - I had the oil changed last weekend, and while it was a little low (I know it has a very slow oil leak and I knew I’d hadn’t checked it in a while).
The only thing that’s relatively new is that the car, like me, is in Ohio. The first instance (at least that I noticed) was after I hadn’t driven it for a few days during a cold spell - single digit days and wind chills below zero. Since then, the temperature has been mainly back up above 30 degrees most of the time. The other thing I realized Friday is that I haven’t done any major driving for a while - it’s typically been tooling around town with multiple stops. I’m only 7 miles from work and I’m fairly close to shopping centers and the like. I’m going to go for a longer drive tomorrow (but stick to populated areas and off the interstate, just in case) to see if it helps.
Did you try resetting the computer? My '92 Toyota did that, we disconnected the batery for 5 minutes. Then it was all better.
Or it might be an O[sub]2[/sub] sensor.
It could also be a problem with the oxygen sensor. My '93 Pathfinder had a similar problem. The 02 senser is located in the duct work AFTER the air filter. I screwed up once and did not get my air filter all the way clamped down and that messed up the 02 senser. In my case the 02 sensor has a little fillter on it. Rinsed it out and I was good to go.
I’m going to guess that you don’t have a check engine or emissions system light lit, yes? If the O2 were out of range, it should set a diagnostic code. The vehicle is fuel injected, so there isn’t a choke. It seems as though the vehicle is unable to stabilize on a cold curb idle.
If you lightly rest your foot on the accelerator, can you feel the pedal moving in response to the changes in RPM?
What is the status of filter changes-air/fuel, etc?
See what your answers are to these and we’ll go from there.
It can’t be the oxygen (HEGO) sensor(s). The computer doesn’t even use them until the engine warms up, and in this case, the engine runs fine when it’s warm it sounds like.
It could be a lot of things. The first thing that comes to mind is the Idle Air Controller. It’s the primary device in control of the idle speed. Perhaps in the cold, frost is getting in it and making it stick. Then, of course, the engine warms and it starts working. On a Ford, you can check it by unplugging it with the engine running. If it’s working, the engine should die immediately. Get someone to verify it for Suzukis.
I’d check that first, but there are many other things it could be. Has it only happened once, or every time you start it? If you know how, you may want to pull your spark plugs to see if they tell you anything. Any additional information you can provide would help narrow it down. It would help a lot if you could drive to Autozone and have them do a diagnostics test too, if they have the equipment for your model.
Thanks for the suggestions, folks. I’ll start with the simplest of them and make my way up - ideally one will work and EZBake (the car) will be happy again!
The symptom does not presage breakdown-type problems. I would have no concerns about getting onto the interstate, and it’s possible that running at highway speed for a while could help. If the problem progresses, the most likely next symptom would be dying at stops (i.e., not idling – would restart immediately and stay idling if you kept your foot on the accelerator).
Nothing mentioned suggests even the possibility of a clutch or thermostat problem.
For everyone’s general information – if your engine is low enough on oil, it can be mechanically damaged or destroyed, as in busting apart or melting together. But unless it’s on the verge of the aforementioned, which is virtually always accompanied by nasty noises, being low on oil does not relate to it’s ability to start, run, idle, develop power, etc.
I would suggest 10 minutes or more of highway speed driving, a can of Techron (fuel system cleaner) in the gas tank, and possibly reset the ECU memory (by disconnecting the battery, as previously mentioned). If the symptom is then still present, I’d suggest having a competent shop test and evaluate it.
I’m still trying to figure out what you’re describing here, but I assure you it’s not an oxygen sensor. Oxygen sensors are not located in the air intake ducting, are not affected by the air filter or air cleaner condition, and do not have filters on them. They are invariably installed in an exhaust system component.