Resetting ECU After Coil Replacement and MAF Cleaning

[ouzo12]

As part of my preventative maintenance list, I went in and put in new coils and cleaned the MAF. After replacing them, I still noticed a strong gas smell when starting from cold and I would have assumed replacing these would have cleaned that up. There is also a slight vibration when in put in Drive and holding the brakes at a light.

I will say I do feel a bit more power once the old beast gets up and going and the engine spins as smooth as silk. The 4.7 is a great motor. 200k miles on these is nothing.

The FSM does not mention needing to reset the ECU but several posts indicate that this is advised. Do i just disconnect the battery?

 

[ramangain]

A fuel smell is a fuel issue. Are you throwing any codes?

 

[ouzo12]

No codes being thrown and it goes away after it warms up. I will continue checking to see if I see anything out of the ordinary when I do my next project - replacing the starter and alternator.

 

[kruisinkid]

Sounds like vac leak. Cracked or loose hose, evap system, etc

or running rich. Check around throttle body and fuel trims if possible

 

[gregnash]

So dumb question, but you replaced plugs when you replaced the coils? Get a hold of techstream if you can or a good OBDII scanner and see if you can see any issues.

 

[dogdaysindurham]

To reset, just disconnect the battery, but I do believe you need to let it sit disconnect for 20 or so minutes. I usually disconnect before cleaning the MAF and the throttle body.

Once you reconnect and start back up, it may be running rich. You can let it idle for 15 minutes or so as the ECU relearns the mapping. Also did you clean the throttle body?

 

[gregnash]

To reset, just disconnect the battery. Once you reconnect and start back up, it may be running rich. You can let it idle for 15 minutes or so as the ECU relearns the mapping. Also did you clean the throttle body?

Aren't you supposed to let it sit disconnected for like 20 minutes or something? Seems odd that just simply disconnecting would be good to "reset" the ecu.

 

[ouzo12]

So dumb question, but you replaced plugs when you replaced the coils? Get a hold of techstream if you can or a good OBDII scanner and see if you can see any issues.

The spark plugs and throttle body cleaning were performed at 189K miles under previous ownership at the Lexus dealer. Checked everything on the Lexus site.

The car is now at 204K miles and figured those items were new enough not to bother replacing them. Its really something minor but i have a habit of being OCD with things.

 

[gregnash]

The spark plugs and throttle body cleaning were performed at 189K miles under previous ownership at the Lexus dealer. Checked everything on the Lexus site.

The car is now at 204K miles and figured those items were new enough not to bother replacing them. Its really something minor but i have a habit of being OCD with things.

Nah that should be good. Might be worthwhile to pull them and check each one to ensure gap is proper and that one doesn't look more burnt than another or anything.

 

[dogdaysindurham]

Aren't you supposed to let it sit disconnected for like 20 minutes or something? Seems odd that just simply disconnecting would be good to "reset" the ecu.

@gregnash Yes I believe you are correct, will update my post. I usually disconnect before cleaning the MAF and throttle body.

 

[Brentok]

I noticed mine idling up a little after doing this. It seemed to go back to normal after a few drive cycles. I assumed it just had to go through a re-learning process.