dbittinger

Probably not your typical question, but I drive a 2000 acura TL at a local speedway and recently it has developed a bad misfire between 2000 and 3500 rpm while at partial throttle. However, when I either get in the gas at that rpm, or have the car up to racing speed (4500 rpm or more) the misfire vanishes. I have a link to an in car video of the misfire occurring below. I have already checked coil packs, cleaned out the egr ports, and done the basic troubleshooting. It just seems like a weird occurrence to only happen at that rpm. Any input would be greatly appreciated!!!

http://www.youtube.com/watch?v=36n4q...ature=youtu.be

03 tls nc

iTrader: (6)

First off that is awesome! From the video I kinda sounds like a fueling issue. Are you running the factory ecu? piggy back? standalone? What have you changed from stock?

Karanx7

iTrader: (2)

And there's absolutely no misfire at idle? Just because there is no CEL doesn't mean there's no misfire. How is the idle in terms of roughness?

I suspect small vac leak if rough idle.

If smooth idle, then check plugs and injectors. Start with SeaFoam.

Karanx7

iTrader: (2)

Lol nvm, just watched the video.

That's not just a 1 cyl misfire. You could disconnect a coilpack and have a smoother running engine than that.

dbittinger

03 tls nc - Thanks, it is a lot of fun. Nothing has been changed from stock, the track doesn't allow modifications to the car except some camber in the front suspension and choosing a wheel and tire size that suits the track best...I thought maybe fueling too, but wouldn't you expect the misfire to get worse with more load on the engine, not better?

Karanx7 - Idle is fairly smooth, and the car fires right up after a couple cranks every time. I'll still check over the vacuum lines carefully though. Thanks

dbittinger

03 tls nc - I should have mentioned, it is getting plenty of pressure to the fuel rails, haven't checked the injectors yet, but like Karanx7 said, it isn't just one cylinder misfiring which leads me to believe it isnt just an injector issue...

Karanx7

iTrader: (2)

Mmm, any CELs other than misfire? Might be worth checking TPS, IAT, and O2.

Nicks2001tl

If it is the injectors and they are super clogged no over the counter cleaner will do the job.

Injectors would have to be removed and cleaned by a professional. You might be able to DIY if you have that skill.

03 tls nc

iTrader: (6)

I was thinking along the same lines as Karanx7 sensors TPS, IAT, 02. Its clearly missing on all cylinders. I would start with the O2 and then the TPS. I'm not 100% certain of the ECU operation but the WOT circuit could be run on a open loop w/ no O2 involvement, while the rest is run on closed loop and it could idle because the IAC system. If the IAT is bad then it will not feed the correct amount of fuel and timing. Does it miss all the time or just after the eng is hot? If it gets worse with heat start with the IAT. If you have access to a scan tool so you can see what the ECU is reading it would help in the diagnosis. It could even be as simple as a water temp sensor starting to go bad which make the ECU fuel and fire incorrectly. I don't think it would be the injectors because if they were clogged or not working properly it would get worse with eng speed. Let us know how its going

03 tls nc

iTrader: (6)

After watching the video several more times it sounds like the eng is starting to lean out causing the knock sensor to pull timing. A scan tool would be really help full to see what is happening during the actual event, not to check after the fact. You might want to hook up a little led with the knock sensor just so you know what is going on if the problem continues. Either way it most likely is going to be a sensor that is effecting the ECUs ability to control fuel and spark.

dbittinger

Only codes the computer is throwing are:

p1399 - Multiple Cylinder Misfire (no kidding, right?)
p0420 - Catalyst System Efficiency Below Threshold (Bank 1)

The cat was removed with teh rest of the exhaust when we built it, which is why I would guess the p0420 is being thrown, but it has been that way for three years and no issues have developed from it for that time.

I will consult the haynes manual procedures and check the sensors you mentioned with a multimeter. Just because they aren't tripping the CEL doesn't necessarily mean they are working properly either...Thanks, will keep you posted

3.2TLc

If ya want more detailed info, I'd suggest downloading a copy of the Factory Service Manual. It's the Bible's gospel for detailed trouble-shooting.

dbittinger

3.2 TLc - I have a copy of the repair manual and have consulted it to check the sensors mentioned in the above posts, they all came up normal function

03 tls nc - The intake wasn't tightly connected down to the throttle body, had it apart to clean stuff out and apparently never tightened the clamp back down after stuffing it back on. I would assume the two vacuum lines on the black intake connected to the throttle body were not getting sufficient vacuum as a result...do you know what they are connected to and operate? Would that possibly cause the condition I am experiencing?

03 tls nc

iTrader: (6)

If your talking about the two lines that connect to the intake pipe in front of the TB, the big one is a breather from the front valve cover and the small line is an in take for the IAC. Neither are vacuum lines, all the vacuum lines are after the TB. You said you have a Haynes manual but that will not give you near the information that the Acura Factory Service Manual will give you. I would be very curious to see what its has to say about the p0420 - Catalyst System Efficiency Below Threshold (Bank 1). This car only has o2 sensors pre and post cat, how is it only calling for an out of spec reading on bank 1.


It may be a long shot but since you didn't have the intake pipe connected tightly, it could be possible the you just have a loose connection that only is affected under certain eng. vibrations. I would go back to the basics and check all connections. It might be something very simple.

Juicebox00

iTrader: (2)

I had an issue very similar to this. stuttering under initial acceleration. beyond 3.5K it was incredibly smooth, and was also smooth at idle. I believe that I may have had the same code too. I just needed a valve adjustment and it went away.