Car losing throttle response/ power / horsepower while driving

[jus_nation]

Car model: Honda Civic (Tenth Gen) 1.5 Turbo (bought it brand new back in 2018 August)

Issue: Very very poor throttle response. Throttle feels very very tight and repulsive. Only hard steps on the throttle can the car push forward and even that the push factor feels very poor. I have leg and back aches now whenever I drive the car. This is how bad the issue is!

When did it happened: Issue started immediately after original headlights were changed to after market custom headlights. My initial thought was I was being paranoid and sensitive. However, I have no issue nor had leg and body pain while driving my dad's and wife's cars. Both cars are of lower litre and horsepower/torque

Observations of the issue:

- After the installation, the custom headlights worked except the high beam. The installer had to stick his hand in and adjust the headlights sockets/connectors to make it work
- After the installation was complete. The audio player froze. I had to do a reset
- After the installation, one of the charging port was not working as well. Issue was solved after I off and on the engine
- Weak sounding car starts lately
- Throttle response always seem to get better when the car is not driven for a few minutes to hours but issue will re-surface after a few minutes of driving

The following was done to the car to try to solve the problem but to no avail:

- Changed the headlights back to the original set
- Car battery had fallen to 79% (no idea if it was caused by the after market headlights). Changed it to a brand new one
- Turbo oil and filter were changed recently
- Took the car to the service center and they did an ECU reset
- Took the car for a dyno test and found out that the car's horsepower has dropped from the original 174hp to 163
- Did an ECU remap to boost the hp to over 174hp. Car felt like a monster for a day before the problem re-surfaces
- Went to the service center again and they ran a system/diagnostic check. No error message found. Service center proclaimed the car is in a clean bill of health
- Left the car overnight at the service center but was informed the next day that they could not reproduce the problem

I do not know what is wrong with the car. Has the after market headlight screwed up some eletrical component? I am at my wits end! Can anyone shed some light on this? What could be the problem. Where to look?

Thanks in advance : (

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[Hollywoo0220]

I do not believe a clear and concise answer can be concluded from what you provided.

Is your AirFilter clean?
Did the Headlight installer somehow not reattach the AirBox correctly? Make sure that is seated and attached correctly, so you are taking in the correct amount of intake.
Brush off the front of your Intercooler - it may be loaded with road debris like bugs etc.
Try using some MAF Spray cleaner and cleaning of your MAF sensor? Perhaps obtain a higher flow air filter to assist with your throttle response.

I think what you are experiencing is probably more "Heat Soak" than anything else. You won't get everything out of the engine when the conditions are not optimum.

 

[shoegazer]

Just adding on to the list above:

Personally... I'd return everything back to stock and inspect every area that the tech had to touch. Trying to piecemeal something that isn't obvious can be an endless pursuit.

If your battery was good before the headlight upgrade; then whatever you have installed may be beyond the capacity of the electrical system.

Agreed: re checking all the induction/throttle body stuff. Again... check *everything* that someone had to touch.

My gut says that this is electrical in nature. Can you post a link or a manual to whatever lights you had installed? And was it installed per those instructions? When you say that you returned the lights back to stock; did you also remove every aftermarket transformer/ballast/resistor/etc... from the system?

And just to be tin-foil-hat sure; I'd test the battery/electrical system again.

Just my amateur thoughts. Not an engineer or a mechanic.

 

[Pbergmann]

Another reason to leave things stock.
Seen this type of thing over and over.

 

[jus_nation]

I do not believe a clear and concise answer can be concluded from what you provided.

Is your AirFilter clean?
Did the Headlight installer somehow not reattach the AirBox correctly? Make sure that is seated and attached correctly, so you are taking in the correct amount of intake.
Brush off the front of your Intercooler - it may be loaded with road debris like bugs etc.
Try using some MAF Spray cleaner and cleaning of your MAF sensor? Perhaps obtain a higher flow air filter to assist with your throttle response.

I think what you are experiencing is probably more "Heat Soak" than anything else. You won't get everything out of the engine when the conditions are not optimum.

Hmm, no checks on the airfilter were made as the car was fine prior to the headlight change. The headlight is a plug and play accessory. I think this MAF sensor might be worth a shot. Let me get it in my checklist. Thanks alot

 

[jus_nation]

Just adding on to the list above:

Personally... I'd return everything back to stock and inspect every area that the tech had to touch. Trying to piecemeal something that isn't obvious can be an endless pursuit.

If your battery was good before the headlight upgrade; then whatever you have installed may be beyond the capacity of the electrical system.

Agreed: re checking all the induction/throttle body stuff. Again... check *everything* that someone had to touch.

My gut says that this is electrical in nature. Can you post a link or a manual to whatever lights you had installed? And was it installed per those instructions? When you say that you returned the lights back to stock; did you also remove every aftermarket transformer/ballast/resistor/etc... from the system?

And just to be tin-foil-hat sure; I'd test the battery/electrical system again.

Just my amateur thoughts. Not an engineer or a mechanic.

Appreciate your suggestions

The headlight is plug and play. Forgot to mention that I installed the after market headlights along with a pair of after market fog lamps. These fog lamps have transformers, the headlights do not. They have all since been removed

I agree, high chance my issue is electrical in nature which will make things alot more complex unfortunately

I will try test the battery again now to see if there is any leakage. Battery is new. I will also try to run the car on a dyno again to see if my car's hp drops again

 

[jus_nation]

Another reason to leave things stock.
Seen this type of thing over and over.

yeah. I guess I have learnt my lesson after this episode

 

[jus_nation]

Something just hit me. Could my car's problem be caused by a faulty camshaft sensor? Sensor could have been short circuited during the headlight installation? Service center did a car circuitry check and they found no error code though

 

[Hollywoo0220]

You would have far bigger issues if that were the case.

 

[charleswrivers]

Are you seeing full boost pressure?

My thought of a mechanical issue other than the ones stated would be something with the wastegate... it’s sort of near the passenger headlight.

My other thought that isn’t a problem at all would be a noted power loss from going from cold winter days to a warm snap of the 70s and 80s as were coming into spring. Going from 30F to 80F is probably good for about 10 whp (there was an off-site thread that I think calculated 1.1% power gain from every 10F due to the change in air density). Your dyno isn’t out to lunch power wise though... the throttle response piece is most the thing I’d go after. If you have the dyno graph and post it, we can see if it is what it should be... shape-wise. Peak numbers aren’t telling the full story of your experience.

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