Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - 93 Civic VX: Tuning up hesitation and rough idle

GTR · 07-24-2012, 08:27 PM

Hello all,

First off I want to thank everyone here for the wealth of great information! I just bought an unmolested VX with 228K last week and have been learning all I can about it, and the posts here have been a huge help.

When I got it, the radiator was cracked (overheated and blew all coolant out before I got 4 miles hah! putty to the rescue!) and it idled a bit rough around 800-900 rpm and had some dead spots and hesitations when accelerating, and had trouble delivering torque when at <1600 rpm at times.

So far I've replaced the radiator, spark plugs, spark plug wires, fuel filter, and cleaned the IACV.

The plugs and wires and fuel filter made a nice difference. I think it had original plug wires, they were nasty. I replaced with Denso 671-4183, for 30 bucks.

The spark plugs themselves were in good shape, but someone got lazy and had put ZFR5F plugs in it, which I replaced with ZFR4F.

That made a huge difference in the hesitation, and in the steady pull of the motor. Very happy. Idle seemed smoother as well.

Then I pulled off the IACV, and it was 80% blocked I'd guess. Lots of carbon dust on the filter. Sprayed it with brake cleaner and aired it out. Put it back on and WOW, huge difference!

The idle is completely different now. When cold it idles at around 1000-1200 now for a bit. It seems to stay there, unless I blip the gas, then it drops down very, very low. I thought it was going to die. At its lowest idle, the tach needle is between 0 and the first line. It seems to adjust it's idle up and down a LOT more now as well. Generally from around the first line up to about 7-800.

So I'm not sure about the idle. Clearly it's more efficient since it's often 50% less rpm than it was before. When it drops down to the lowest point, the car does a fair amount of shaking. At around 5-600 it seems to be pretty smooth.

Driving wise, it's much better than before. The previous owner said he got 45-52mpg city/highway for the last 16 years. We'll see what I get. MPGuino is on the way.

Do I need to reset the ECU or anything for the car to relearn some parameters since I changed so much?

Thanks everyone!

07-24-2012, 08:27 PM	#1 (permalink)
GTR EcoModding Lurker Join Date: Jul 2012 Location: United States Posts: 22 Red VX - '93 Honda Civic VX Teal VX - '94 Honda Civic VX Godzilla - '09 Nissan GTR Premium Thanks: 1 Thanked 3 Times in 2 Posts	93 Civic VX: Tuning up hesitation and rough idle Hello all, First off I want to thank everyone here for the wealth of great information! I just bought an unmolested VX with 228K last week and have been learning all I can about it, and the posts here have been a huge help. When I got it, the radiator was cracked (overheated and blew all coolant out before I got 4 miles hah! putty to the rescue!) and it idled a bit rough around 800-900 rpm and had some dead spots and hesitations when accelerating, and had trouble delivering torque when at <1600 rpm at times. So far I've replaced the radiator, spark plugs, spark plug wires, fuel filter, and cleaned the IACV. The plugs and wires and fuel filter made a nice difference. I think it had original plug wires, they were nasty. I replaced with Denso 671-4183, for 30 bucks. The spark plugs themselves were in good shape, but someone got lazy and had put ZFR5F plugs in it, which I replaced with ZFR4F. That made a huge difference in the hesitation, and in the steady pull of the motor. Very happy. Idle seemed smoother as well. Then I pulled off the IACV, and it was 80% blocked I'd guess. Lots of carbon dust on the filter. Sprayed it with brake cleaner and aired it out. Put it back on and WOW, huge difference! The idle is completely different now. When cold it idles at around 1000-1200 now for a bit. It seems to stay there, unless I blip the gas, then it drops down very, very low. I thought it was going to die. At its lowest idle, the tach needle is between 0 and the first line. It seems to adjust it's idle up and down a LOT more now as well. Generally from around the first line up to about 7-800. So I'm not sure about the idle. Clearly it's more efficient since it's often 50% less rpm than it was before. When it drops down to the lowest point, the car does a fair amount of shaking. At around 5-600 it seems to be pretty smooth. Driving wise, it's much better than before. The previous owner said he got 45-52mpg city/highway for the last 16 years. We'll see what I get. MPGuino is on the way. Do I need to reset the ECU or anything for the car to relearn some parameters since I changed so much? Thanks everyone!