Skip the auto shop - Our mechanics make house calls

Q: Engine tapping noise related to short term fuel trim but only on cold start up.

asked by on

I have an OBD reader. When engine is cold and at first start up. It run and sounds perfect. The obd reader .stft is showing 0.0. O2s haven't started registering yet. As o2s start stft starts to move. Bouncing from -02 back to 0. Engine still sounds great. Now the stft starts to move into the positive and the tap or tic starts. Starts very faint. Then builds in sound. As the stft increase so does the sound +10.00 on bank 1. 2 to 3 on back 2. Stft falls back to 2 or 3 tic disappears. Then it comes back. Now if it's in the middle of a tic tic tic. I turn the engine off and start it right back. No tic. Until the stft starts to move again from 0.0 back to+5+8+10 on back 1. Back 2 stays around +3+4. Advance fluctuations from +5 ° to 10°. Once engine warms to 170. The tic is gone. Stft on both banks is now bouncing -2 ±0 +2. Engine runs like a top. Quiet enough to hear the injectors ticking away. New cam, crank, knock map sensors and O2s. No codes ever. Thanks

My car has 198000 miles.
My car has an automatic transmission.

Has a mechanic’s stethoscope been used to track down the specific location of the noise? There are several solenoid valves in the engine bay that do not run all the time and may be pretty loud once they start, such as an evaporative emissions purge valve and the like. The high fuel trims on one bank sound like you may have a problem on one side with a vacuum leak. A positive trim means air is being added and the computer is trying to add fuel to compensate.

I recommend having an experienced technician, such as one from YourMechanic, come to your location to determine why the engine is making a noise and suggest the proper repair.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • Engine tapping noise related to short term fuel trim but only on cold start up.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I pulled up to a gas station and filled up with gas. As I tried to start the vehicle just gave clicks. Jump starting did not work.

Hi There, If the vehicle previously overheated, it may be possible that it could have damaged a cylinder head gasket, which could cause it not to start as you describe. A blown head gasket may cause a number of different...

Q: Popping noise when turning the car

Hi and thank you for contacting YourMechanic. There are 2 main causes for this popping sound. First off, your tie rod end needs to be replaced. A quick check for this is if you notice that when you turn...

Q: My 96 Jeep Cherokee Classic does not start up when it has been sitting for hours or overnight

Hello. The symptoms you describe can be caused by a wide variety of issues. Issues with the fuel and engine management systems can often produce these symptoms. A few things I would look at are the fuel pressure, fuel pump,...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...