[Scotts Acura]

Hi,

I'll try to be detailed enough for some good ideas here.

2 months ago I got an 04 TSX from a buddy with 238k miles.

When I got it:
1. He told his mechanic said it's okay to use 87 octane fuel. He's been doing this for 2 years approximately. For the last 2 fill ups, I switched back to 93 octane and plan to keep it that way.

2. His mechanic told him the connector for the TPS sometimes gets loose and will cause the RPMs to fluctuate, sometimes roughly. Told me to make sure it's plugged really snug and tight.

3. RPMs constantly fluctuate even to the point that it almost feels like the car downshifts several times during a usual 15 to 20 drive. Now it seems to happen even more.

4. A Crack in the air hose between the engine and air filter (where the mass air flow sensor goes) is taped with electrical tape.

5. Top gun mechanic friend of mine says it sounds like the car is burning lean. (In a Facebook message because we no longer live close enough for him to see it in person)

After I got it:

1. 3 weeks into owning it I get a misfire code and the misfire made it run crappy of course.

2. I replace and gap all 4 plugs and 1 ignition coil.

3. 2 weeks after fixing first misfire, another misfire made me need another ignition coil.

4. The same day I replaced the ignition coil I began getting to P0420 code that mentions "low threshold" at B1 (bank 1 -what is this?).

5. It's running exactly as well as it was the day I got it, except the RPMs fluctuations and making it feel like a downshift kinda, at times.

6. I ran a can of cat cleaner through and still have the engine light for the P0420 code.

I have maybe 100 bucks right now to spend on the car. However, soon I will begin putting a little more money in it to get it running tight.

Any suggestions would be great. Thanks in advance.

 

[Sahilah123]

the loose throttle plug can definitely cause rpm to fluctuate.
that hose is most likely the pcv hose that recirculates oil vapor into the intake, not that important to function i dont think its causing the issue.

A couple things i would try.
I would take the injectors out, clean them and replace all the o rings on them.
Inspect air filter

Also give the spark plugs a good look,
you can try to pull the o2 sensors out and clean them.
You can also try some injector cleaner and some oil flush like marvel mystery oil.

 

[Scotts Acura]

Thank you. The hose I mentioned is the air intake hose where the mass air flow sensor usually is. It's cracked and taped...lol

 

[bluetegjoe]

With any car that age, attempting to diagnose a misfire beyond swapping coils and plugs is a challenge to a non professional. You are likely to spend a lot of money without solving the problem. Though it's not the cheapest option, your best bet is to have the car diagnosed by a professional.

 

[john.m.sabato]

I also own a 2004 TSX and have put 40,000 miles on it in the last two years. Current mileage is over 250,000 miles. I have only run 87 octane regular gas the entire time except for maybe the first two tanks of gas. I have had ZERO issues, fantastic gas fuel economy (30-35 MPG Highway) and amazing response and performance. I have no idea why anyone would run premium gas in this car, especially at today's prices and when running the two tanks of premium, I found NO difference in performance.

 

[Jpig6]

Loose/worn timing chain is a known issue on the first gen TSX (I replaced the chain on my 2006 5AT base at about 180,000). Presents as misfire, coil replacement. If you can rule out timing chain that would be good, but you need a good / honest mechanic to sort it out. Not a cheap job, but if that's your problem, you don't want to throw money at peripheral stuff that won't fix it. Also, they "recommend" premium gas, but by law all vehicles in the U.S. have to be able to run well on 87 octane. You will get a little better MPG with premium, but not worth the difference in price. ** BE SURE to keep oil in this vehicle. Check your levels regularly. Timing chains fail because of the VTEC being run on low oil. This cannot be overemphasized!

 

[merlinj79]

I also own a 2004 TSX and have put 40,000 miles on it in the last two years. Current mileage is over 250,000 miles. I have only run 87 octane regular gas the entire time except for maybe the first two tanks of gas. I have had ZERO issues, fantastic gas fuel economy (30-35 MPG Highway) and amazing response and performance. I have no idea why anyone would run premium gas in this car, especially at today's prices and when running the two tanks of premium, I found NO difference in performance.

Reason is this: Modern cars including the TSX can adapt to low-octane fuel using their installed knock sensors. Once the ECM detects that knock is occurring, it adjusts the engine's operating parameters to stop the knock.

Problem is in order for the knock sensor to detect knock, the knock must actually occur. That's bad for your engine although not as bad as continuous knock.

If you drive like a total granny, or don't plan to keep the car for two long you can probably get away with it.

 

[1bryantmjb1]

With any car that age, attempting to diagnose a misfire beyond swapping coils and plugs is a challenge to a non professional. You are likely to spend a lot of money without solving the problem. Though it's not the cheapest option, your best bet is to have the car diagnosed by a professional.

Do a cylinder compression test. They burn oil cause of rings. You would need to visually check ur cat. Take out o2 sensor n look with one of those cameras. With the above mentioned

 

[TSX_008]

Following your thread as I am also experiencing idle RPM drops. It’s like the rpm dips like a trigger pull when coming to a stop or in park.