2013 TL rough start up
 

I have a 2013 TL with 108,000 miles. I recently changed out the MAF sensor because I had a code and even after cleaning it and resetting it still ran awful and kept stalling. I put the new MAF sensor and a new air filter too. Good improvement in performance, but not 100% so I put new NGK plugs in and ran a can of Royal Purple Max Clean through it. After all this, I'm still getting a rumbling sound at start up and a little hesitation too. Any ideas ? Thanks

Did you do the 105K service with a new timing belt and waterpump?

I looked it up in owner's manual and it recommended 60k. Also, I was told the previous owner had taken care of it, but you never know. Probably a good idea to pull the cover and check it anyway. Thanks.

It's 60K in severe service conditions, but in FL you are fine to 105K miles or 7-10yrs as rubber does age. A mechanic should be able to check for you based on any marks on the bolts that are commonly removed such as side engine mount.

I'm planning on taking a look this weekend. Do you think it may also be possible that its an issue with the EGR valve ? I'm not showing a code, but wondering if this could be the problem. Thanks

Well, good news ! The belt looks really good. No signs of wear. Also, the bolts looked almost new and I didn't have to break my back taking them out. I ordered a new gasket from my EGR valve. I'll remove it and give it a good cleaning and check that it operating properly. Thanks again for the suggestion.

Update
 

Well, I apologize for late response. I pulled the EGR valve and cleaned it. I also replaced the canister purge valve. I got rid of the tighten fuel cap light, but I still starts rough and hesitates in the morning. It’s mostly noticeable if it’s been raining. Once I’m at operating temp for a few minutes it smooths out and the car runs fine. I’ll try pulling the throttle body next. Any other suggestions? Thanks

Your upstream O2 sensors could be getting lazy. That's kind of an expensive job and not a guaranteed fix though. Those sensors are around $80 each.

Do you use Top-Tier premium fuel?

Thanks
 

I’ll look into the O2 sensor. It’s weird that it’s just in the morning after the car has been sitting all night. It’s also weird that I don’t get any codes either. I always run premium 93 in it and I run a bottle of STP once a month in it too.

The O2 sensors have a heating element that brings the temp up to the level needed for the sensor to operate correctly. If that element isn't working correctly, it could be taking a while to kick in and provide the correct information to the ECU. However, that would likely throw a code (P0135 or P0155 depending on which bank) so I'm not sure that would be the culprit. It would correspond with your symptoms though since the problem would go away once the exhaust gas warmed up the O2 sensor enough to begin operating accurately. Until then, the ECU would be running the A/F mixture rich, which would be the equivalent of keeping the choke on when the engine has warmed up enough.

Does it run rough immediately after starting it or after a few seconds after starting? It doesn't take long for it to heat up but it would be cold for the first few seconds which is also exactly when the ECU will run rich. If it's struggling right away, then I don't think the theory above would be the case. If the heating element wasn't working, you'd likely see a smooth idle for a moment, then rough, then smooth again.

Some of that is speculation though. I haven't personally had this problem.

Good info
 

Well, went through and checked my sensor connections and put another bottle of STP in with my last fill up. It’s only a little rough at start up on warm and damp mornings and it’s just for a few minutes. Still no codes. My mechanic is going to help me with pulling the throttle body. It may be dirty. Thanks for the info.

Off to the shop !
 

Well I'm still getting a little hesitation/shudder first thing in the morning and even my mechanic friend can't figure it out. Also with neither myself or my mechanic having actual Honda diagnostic equipment; I have decided to take to a local shop that can do the scan and send the results to Honda for me. It's still not showing any codes, but maybe there's something in the data that solves the mystery for me. I'm truly hoping this ends well.

Rough start up now just a slight rumble
 

I brought the car to a local shop that has a dealer level scanner. They told me the engine was misfiring, but they didn't know why. They had it for 2 days when they informed me I had the correct spark plugs, but they had the wrong gap. They regapped the plugs and that really seemed to help. The car still has a little rumble at start up, but it accelerates smoother and there is no more hesitation in the lower gears. They also told me a valve adjustment would most likely eliminate the rumble at start up. I'm going to wait on that recommendation since the vehicle is running good now and they want $600 to do it. Any thoughts on the valve adjustment recommendation are welcome. Thanks

Valve adjustment is about 2 hrs labor and gaskets, shouldn't be more than $300 dollars. Call up your local honda dealer, they'll probably do it for around $325 total.

I figured that was high for that. Based on some of the other posts I've read this valve adjustment is seems to be an issue with these cars. I'll get a quote from Honda. Thanks !