Miss on acceleration
 

My 2008 ls has developed a miss on acceleration and gas mileage if off 25%. To start in the morning takes 3 tries exactly. Has 80k. Plan to change plugs and would welcome any ideas as to cause.
Thanks
John

I would get the codes read. If there is a misfire then there should be a code that will tell you which cylinder it is.

Code is for random misfire

There are a lot of things that can cause a random misfire.

There is a tsb for carbon build up causing a random misfire on the 2.4 engine.

I would start checking the basics. Fuel psi being my first test.

Shall I assUme that means ONLY p0300? That's pretty rare.

Fuel pressure is a pretty good starting guess.

If it's a random mis-fire and as donbrew mentioned above, could I suggest a Fuel Pump/Filter?

May I concur with these suggestions and throw in a dirty throttle body! Or battery about to expire! Or loose ground wires! The infamous low oil level?
Please check these suggestions and get back to us.

How many miles on it?

Good suggestions especially interesting fuel pressure. Has 80k.
Thanks
John

I see from searching the forum several cases like mine where the fuel pump was the cause. I will go get the codes read and try to get a test gage for fuel pressure. Is there a fitting for this on the fuel rail?

Yes. In a word !

Here is a picture of the fuel rail test port. When you install the gauge (with the engine not running).

Turn the key on a few times then shut the key off.

Look for leaks and note the gauge psi. With the engine not running the fuel pump should hold some pressure and not bleed off.

Then start the engine and record the readings.

Many thanks
John

codes read
 

Went to OReilly auto today to have the codes read. They saw p0171 diagnosed as fuel trim system lean.
Could not rent the fuel pressure gage from them as they require you to buy the requisite part as part of the rental. Autozone has a better rental policy. The pump is 180 from amazon so that will be my source if required. Any ideas as to poor gas mileage? These symptoms seem to fit (hard starting missing poor gas mileage) with other members who have had to replace their pumps
Many thanks
John

Okay, now please follow the link in my sig for troubleshooting Check Engine Lights.

P0171 probably means a cracked flex pipe, or a broken canister purge valve (the one under the hood just above the arrow shaft in the pic above). What it means is too much air in the system between the MAF and the #1 O2 sensor, not too little fuel.

I concur Don! Please have a listen to the flex pipe area , have somebody move the muffler tip to see if there is a change in the sound at the flex pipe.
The purge valve is a lot less the $180.00, it is attached to the pipe where the white tape is at the right end of the red arrow in Lucky's picture, above^

solution
 

Just to bring closure to this problem. Fuel pump test 30 running immediate fall to 0 on shutdown. Replaced fuel pump problem solved. Many thanks to those who helped out. You're great.

Well that is great to read the problem is resolved!!