98 civic erratic idle
 

Good day,

98 civic LX 5 spd with 285000kms.

After being on the highway during my 35km commute, when I pull up at a red
light, my RPMs stay at around 2500. After a few seconds, or if I pump the
gas pedal, the RPMs go down to about 1200-1500.

This just recently started happening. Don't know if its related, my AC
recently stopped cooling. Sounds like the compressor doesn't come on. Is
there anything in the AC mechanism that affects idle speed?

Also, have recently done the following, all with OEM parts from the
dealership:

Spark plugs
Distributor Cap
Distributor Rotor
PCV valve
Air Filter
Front wheel bearing
rebuilt all struts
all new suspension components front and rear
4 wheel alignment

When I did the distributor cap, I actually had to remove the distributor so I
could drill out 2 of the bolts holding the cap on. (They were rusty and
broke). I was expecting the removal of the distributor to be harder, but it
was pretty much idiot proof. It appears that you can only put the
distributor back in the block either the correct way or 180 degrees wrong.
So if you are careful, you should be OK.

Also, since my distributor had never been removed before, it was easy to put
it back exactly the way I had removed it as I could see where the washers for
the adjustment bolts had been before (good old corrosion at work here again).
Checked the timing with a timing light after, and all is well.

Note that the idle fluctuations occured before I did the tune up work (which
was overdue anyway).

I am also fairly certain the car is running pretty rich. Fuel economy is
relatively poor (around 11-13km/liter or 25-30 US MPG or 31-36 UK MPG), and
the exhaust pipe is pretty black. I have run several bottles of injector
cleaner and Lucas Oil Upper Cylinder lubricant over the past few tanks and
seen no real improvement here.

The car has great performance, when you want to step into it, it accelerates
really well. However, I have also measured fuel economy on a light foot, and
the mileage is about the same.

Driving pattern is mostly highway, we live about 20km outside the city.

Any ideas of what I could check would be greatly appreciated.

Thanks
Terry in Winnipeg

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