Honda city idsi sticking rpm

[umair610]

Salam everyone. The car in question is city '05 manual. When i rev up the engine and let go, rpm sticks for some time like at 1500 for 3 to 4 seconds then comes down to normal 750. Same happens when ac clutch engages. Rpm jumps up by 300 to 400 then comes down. Even on cold start,the rpm jumps up to almost 2100 and then settles down at approx. 1400. Recently i had the entire engine swapped along with throttle body,coils,plugs and everything but the problem was there even before the swap. Check engine light is off. I recently cleaned iacv and it's rotating freely. Coolant is topped up. Fuel filter was changed some time ago. Any input would really be appreciated.

[hash4u]

Accelerater cable thoroughly checked ?

[umair610]

Yes accelerator cable is fine

[Hassan1991]

Looks normal to me.
In old toyota engines there's a spring mechanism which operates in this way.
It doesn't allow the rpm fall all sudden. It holds it at certain rpm(which can be set) then slowly brings it to idle.

[umair610]

Nah it takes very long to settle down. It used to be ok before. I have checked almost everything and running out of ideas. The first thing these local mechanics fiddle with is the throttle stop screw so i had to change the throttle body but the problem is still there after changing it again with new engine.

[Hassan1991]

You should double check the accelerator cable and paddle.

[umair610]

Checked it with accelerator cable off. Still acting the same

[Hassan1991]

Remove the wiring grip of IAC then try again

[umair610]

I'm not sure what you meant there. Anyway removed the connector grip to iacv and rpm rose up. I think the connector is fine

[Hassan1991]

No remove the connector and accelerate then see of rpms stays at 1500k or not

[umair610]

Ok will update soon

[umair610]

Did as you suggested. Rpm stays up continuously.
Also checked for vacuum leaks with a carb cleaner. Rpm stays constant so i think there is no vacuum leak either.

[hash4u]

check for black smoke
if so, its might a faulty O2 sensor

[umair610]

There is no smoke. Also pre facelift version did not come with cat convertor

[babarhyd]

Idle relearn is what you need. Go to some good diagnostics shop and have it relearned.

[Hassan1991]

Without IAC it stays up?
If there's no vacuum leak then check TPS position

[umair610]

Ok planning to visit honda peshawar road tomorrow. Will update once done

[umair610]

Tps is fine i guess. Its 0.47 V at CT and 4.4ish at WOT. The transition is smooth too

[umair610]

Visited honda peshawar road yesterday. The said it would need a complete tune up and they can't assure it would fix surging. Anyway need your opinion on this whether i should go for it or visit some other diagnostic shop. If you know any good shop, kindly share.

[arbaz03]

Check crankshaft position sensor.