M42 cranks but won't start

[Mohit]

Cleaned the ICV, and idling doesn't seem to irradiate now. It's a bit steadier but still pretty rough. When I apply throttle, it's very hesitant to increase RPM, and does so slowly, and once you let off, it drops slowly and almost to 400 RPM, where it wants to die. It also still smells like gas in the exhaust, and I see some droplets blowing out the muffler.

Here's a video of the current idle, I dunno if it will help.

https://www.youtube.com/watch?v=P8XaeMoexog

[roguetoaster]

I'd start by raising the idle to spec with either the throttle screw or the twist adjustment on the cable just to see where that takes you.

Then if it's not exhibiting any change in operation, but the idle does stay up I'd check timing. Frankly, the odd bucking when you apply throttle seems like a timing issue.

[AndrewBird]

Sounds like a vacuum leak. I'd pull the intake boot off and check for tears/cracks. Might also try unplugging the O2 sensor and see if it changes anything. Do the same with the AFM.

Also, don't set the idle with the throttle body screw or the throttle cable. This will not allow the ECU to go into closed loop and you will have worse idling problems. The screw on the throttle body is a stop, not an idle adjustment.

[roguetoaster]

Sounds like a vacuum leak. I'd pull the intake boot off and check for tears/cracks. Might also try unplugging the O2 sensor and see if it changes anything. Do the same with the AFM.

Also, don't set the idle with the throttle body screw or the throttle cable. This will not allow the ECU to go into closed loop and you will have worse idling problems. The screw on the throttle body is a stop, not an idle adjustment.

While it might be, I don't think it's a simple vac leak. I say that partly due to the no start initially and the condition of the plug he showed, but mostly due to the idle staying stable despite being at a lower than spec'd RPM.

Yes, the screw is the throttle stop, but can be used for the purpose I suggested. I'm not saying you should leave the throttle open/adjusted to compensate permanently with the adjustement I suggested, but rather just as a diagnostic tool. To be sure, you don't want to leave the throttle open 100% of the time.

Still very worth checking for vacuum leaks.