My idle speed sometimes jumps to 2200 or so and holds there. Sometimes, if if blip the throttle, it will slow back down to normal. Sometimes it does not.

I cannot see a pattern... Whether hot or cold or coming off acceleration or deceleration or A/C on or off.

Also, my cruise control is working sporadically. When it does kick in, it sure does it hard. Most of the time, it simply does not engage.

200k + miles.

Is there some vacuum issue or diaphragm issue I need to look at?

Thanks in advance,

JKC

 

What year and model? Have you checked for binding at the throttle body/cable linkage (if not e-gas)?
Cleaned the idle stabilizer (if not e-gas)?

Congrats on 200k+! I have to ask. Original IMSB??

 

2002, C2.

Any help? I am transitioning from dealer/indy maintained to owner maintained. My points of reference are Mustangs from the 60's and Mazda's from them 80's. I'm mechanical but challenged. Wish me luck.

JKC

 

Oh, IMSB and such have been replaced when doing clutch. The car is generally solid and I think (without opening a can of worms) that the key to longevity for these is actually driving them and respecting that they are not race cars.

My two cents.

JKC

 

I was hoping for an original IMSB haha Agree that the best is to drive the car often.

Anyway, 2002 C2 is e-gas so it doesn't have the throttle cable and idle stabilizer. I would suggest:
- clean the throttle body with throttle body cleaner
- check for air leak e.g., oil filler tube
- remove oil filler cap during idling. You should feel a slight vacuum pull and the idle should change to rough
- scan the car with Durametric for any error codes

 

Thanks for the feedback. Just getting it back up and running after a long hiatus. Will keep board posted for those interested.

JKC

 

Anytime. How long are we talking about here? Is the fuel stale?

 

Thanks, again, for your reply.

Let me add more detail. The Heater Core failed last Winter and the car has sat since then. I am in the process of getting it back up and running... So the gas may be stale now, and I will put in additive when I get it running again, but the idle issue was happening before the Heater Core failure.

I'll check the other issues you mentioned.

JKC

 

Oh forgot one important thing to check. Your e-gas pedal connects to the pedal position sensor via a cable. The pedal position sensor is under the dash close to your right shin. If you knee down and look closely at the gas pedal, you could trace the cable. Try to use your finger to feel the sensor and you should feel the movement when you work the gas pedal.

Alternatively, use Durametric or a generic OBDII scanner to check the pedal position to see if its reading sticks at some % when you work the gas pedal for its full range back and forth. I wonder if you have some binding on the linkage.

 

When I read this thread title, this guy came to mind...

link

 

If the car sat nearly a year stale gas has to be a real possibility. I am not aware of any additive that fixes stale gas. If it is not too bad, if the engine runs reasonably well, you might just want to drive the car and use up some gas so you can add some fresh gas. In more severe cases you can have the tank drained of fuel at a shop and then refueled with fresh gasoline.

In this case I would use Techron as per instructions on the bottle to effect a fuel system and engine clean. After you run the tank down to 1/4 then change the oil/filter.

Last but not least with cars that sit unused for long periods of time I'm always concerned about rodent damage.

You need to check the car over very carefully. Mice love to gnaw on wiring and plastic/rubber hoses and lines. I have seen a Cayman with a fuel vapor line chewed through. The chewing stopped as soon as the line was holed and the mouse got a snoot full of gasoline fumes. But the damage was done.

 

I ended up just recently with an erratic idle problem. Mine is also an '02 C2, had the engine out for a couple of months for a rebuild and after being put back together had occasional severe but intermittent performance issues. So far these have turned out to be corrosion on connectors on the engine harness.

Durametric would be very helpful to diagnose. For example, my latest issue threw codes implicating all 6 wires in the throttle valve connector (power, ground, motor, 2 position sensors). There's no one failure that could explain that except that the entire connector was not seated properly or its reinsertion after assembly was just a tiny bit off from the original position and contact was not being made due to oxidation.

In this case, spraying DeoxIT DN5 (magical stuff) on both sides (male and female) of both ends of the harness fixed it. After this you *must* re-initialize the e-gas idle setting: turn ignition switch on (do not start the car), let it sit for 1 minute without touching the gas pedal, turn ignition off for 10 seconds.