Last post was posted in the wrong place

I am getting really frustrated with my AP1. My car would have unstable idle where engine is hot/cold. If I rev above 3000 rpm then release throttle the rpm would just drop to ~500 and the car shakes badly, sometimes even stalls. Same stalling problem happens when I come to a stop at traffic light. I have learnt heel & toe to maintain idle at stop

The stalling problem only started after I had a "Honda specialist workshop" to adjust my valves. I sent the car back to them for a fix. They rechecked the valve clearance and said they were within spec. They denied responsibility and said my car had had this problem before valve adjustment. I argued many time and finally gave up. Don't want to waste any more time on these "specialists". I decided to fix it myself

I have looked at all relevant posts and tried many things on my car:

1. MAP whack with zip ties
2. Cleaned IACV
3. Reset ECU - when I reset ECU I found the 'back up' fuse was blown, I thought that was the culprit. After I put a new fuse in (I followed the ECU reset post -> 3000 rpm ->fan on->idle for 10+ minutes -> fan on)

I still have no luck....

My question is.
1. Do you think the bad valve adjustment can cause idling issue? The "specialists" seemed to know what they were doing and I just don't think valve adjustment is rocket science for any profession workshops...
2. The ECU doesn't seem to relearn idle. Can this be the ECU fault as the back up fuse was blown once? Although I checked the new fuse after my ECU reset and it did not blow a second time.
3. Can anyone point me in the right direction if there is anything else I can try.


Thanks in advance!

 

How did you clean the IACV?

Sometimes cleaning it can make it worse. Splitting the halves and freeing up the shaft is the best way to do it.

 

Hey op this is something I have been chasing on my friends car as well that has a similar issue.

Car runs great through the revs but at idle it stutters, sometimes stalls, shakes violently.

So far we have:
Replaced the iac
Replaced ecu (then swapped back)
Checked grounding
Valve adjustment
Measured and adjusted tps
Numerous idle relearn and Ecu resets
New plugs
Changed fouled O2 sensor
Logged fuel trims via obd2 reader

What hasn't been done:
Coil packs
Clutch is in need of change
Check flywheel
Check injectors
Check fuel filter
Check fuel pump

Our temporary fix is to increase the offset on the throttle body plate screw. This keeps the car from stalling but increases fuel consumption.

What is your cars configuration? How many miles do you have? Mehta kind of driving do you do?

Btw apparently this can happen clear out of the blue without throwing and CEL. So you shouldn't necessarily blame your mechanic.

 

You check all vacuum hoses for cracks or leaks? Clean all electrical connections, under the hood?

 

I followed this thread to clean my IACV

https://www.s2ki.com/s2000/topic/492...ean-iac-valve/

 

Thanks for your reply. My car has 52k miles on the clock. It is my daily drive so I don't drive aggressively. Vtec once a month? Its getting pretty good mileage though ~23 mpg. The worst thing about the mechanics is that they offset the throttle screw after the valve adjustment to keep the car from stalling. Car was idling at ~2k rpm only after the valve adjustment. It was obviously done by them and it seems they did this deliberately to cover up their fault.

 

I did not check this myself but when I sent the car back to the mechanics for recheck they reported they checked vacuum and electrical connection. No fault found..

 

How does it drive at lower rpm? (2000-3500)

Is it jerky and unstable at those rpm's?
What happens if you try to keep your revs at 3000rpm in neutral? Do they drop on their own or do they neatly keep the rpm's?

 

You sent it back to the same shop to check the valves? Have you tried sending it to a different shop or using a write up on s2ki to recheck their work? If this problem did not occur until after the valve adjustment then that is likely the variable. Sometimes you cannot trust others to work on your car correctly; for instance, my dealership quoted me a new engine for a dirty fuel injector. Get a second opinion or DIY.

 

All sorted . Turned out to be the throttle position sensor. It was sitting slightly off the center and when I reset its position the problem was gone! Isn't it amazing how 0.01m movement make such a huge difference....