Sputtering at Ignition, MPG dropping, & low rpm power loss
 

Hey guys. Want to say thank you for all the info provided on this site. Bought my 04 new in August of 04. Manual 6 with Grand Touring Package.

I change the oil and filter every 5k and plugs every 30k. Now have 125k on my 8.

This summer I started to have fix some things. Had a bad coolant tank and a bad O2 sensor (rear one). This site was integral in getting both of these fixed. Thanks again.

Ok.. now the problem(s).

Spring 2012 started to get the coolant tank sensor issue... that is resolved with new tank.

Changed tank as well as rear differential fluid, coolant, and transmittion fluid. (should have done the fluids every 30k but had not. it made a big differency.) I also changed the oil and I think I over filled by a quart. (must have been tired or rushed by wife)

After that car ran great for a about a 1000 miles then my CEL came on... The CEL turned out to be a bad O2 sensor (which i just replaced in November 2012). Before I replaced the O2 sensor I did a Seafoam, and took apart my intake and cleaned it out with the purple all purpose grease cleaner (and plenty of water). towel dried it and put it back together. I took my intake valve off the engine and wiped it down. I was happy with my results. (everything looked cleaner and I didn't break anything) The other thing that I did while the intake was off was remove the 2 plastic baffles inside the intake filter housing (and changed the filter). This (intake cleaning) was back in August 2012. Car felt new again but still had the CEL in August due to O2 sensor.

Since the weather turned colder (October) my MPG started to drop slightly. This is normal I've noticed over the years but this year it's a little more this year. Usually Summer 250-270 on appox 14 gallons (my light comes on around 13.5) now i'm down at 210-225. It's usually 240-260 in the winter.

I'm thinking the MPG drop may have to do with the baffels on the intake. (????) Not sure as I was getting normal MPG after the baffel removal in August and September.

But what i'm really concerned about is now while starting the car it sputters before ingnition. (cranks over for like 5-8 second then starts) This sputtering has happened occasionally to me in the past but it's a regular occurance now. Cold and hot starts. (crank duration is less on hot starts)

I'm thinking the sputtering is due to a dirty or bad fuel pump but wanted to get some opinions before I replace or take apart my fuel pump.

I've also begun to notice a slight loss in power from 2500 - 3500 rpms it starts to pick up at 4k then takes off at 6k. For the most part the car is running fine but I'm wondering what the drop in MPG the slight loss in low rpm power and the sputtering starts all have in common.

Thanks in advance for any help.

John

You said you changed the plugs, but have you ever changed the ignition coils?

Nope. Haven't replaced the ignition coils yet. I've seen the DIY for that and was thinking that could also be the problem. Just wasn't sure if that would contribute to some of the other symptoms.

Thanks for the advice.

Ok spent a day or two reading and you have me convinced that the ignition coils need to be replaced. 126K on same coils appears to be unusual so I will replace and see what happens.

Thanks again
Thanks again.

126k miles on coils???? This has to be some kind of record:)

I got 113k on my coils original owner never replaced. i also have around 75k on my plugs. I just got the car and the previous owner has all his service records from when he owned it and they were never changed confirmed by him and the records. I too have teh rough idle and it will dip to around 500 then pickup to 1000 and slowly bounce between 750 and 900. I have orderd new coils plugs and wires. Also plan on doing a full fluid flush of and change of all fluids.