2003 GTP from auction - low MPG

**factory** · 02-10-2014

Former '08 GXP owner here, which I sold a few months ago. I "replaced" it with an '11 Civic Si... big difference between the two! The Civic is fun in it's own way and is a tight, well built car - but no V8.

So I missed my GP and got an '03 GTP

It was had for a reasonable price at auction, knowing I'd need to do some work on it. 120k miles. The body is in pretty good shape, the interior is ok, and I think the mechanics will need the most work.

First thing I noticed is the MPG on the DIC is low. It was showing an average around 13.5MPG. I reset it and it is 11.8 or so, climbing back up slowly.

Went to get emissions and it doesn't have enough data stored to pass, which means the battery was probably removed before I bought it. Wonder how long before the check engine light comes on...

Any suggestions on what to look for in regards to low MPG? O2 sensor? If so, which one? Any other items?

**FordMan77** · 02-10-2014

Dirty MAF, vacuum leaks (especially at the "T" under the S/C snout), fuel filter, air filter, plugs, wires, tires properly inflated. I'm sure you know, but be sure to run at least 91+ octane in it always.

**factory** · 02-10-2014

Originally Posted by FordMan77

Dirty MAF, vacuum leaks (especially at the "T" under the S/C snout), fuel filter, air filter, plugs, wires, tires properly inflated. I'm sure you know, but be sure to run at least 91+ octane in it always.

Great, thanks for the ideas to get started. I have not even put gas in yet, but I'm used to the 93 on a few cars.

**Russosaur** · 02-11-2014

Could be tstat also if the car isn't warming up mpgs go kerplunk.

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**machinegunsquid** · 02-11-2014

Just for peace of mind, I'd go ahead and replace the vacuum lines and tee's, plugs, plug wires, all fluids, filters, check tire pressure, clean the TB and all the sensors in it (with the proper cleaner) check tire pressure, and ensure that the o2 sensors are properly switching.

**Snoop dogg** · 02-12-2014

wat should the MPG be for city diving cause mine show 15.2 on DIC

**Russosaur** · 02-12-2014

Depends on temps

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**osiris94ej** · 02-12-2014

Originally Posted by Russosaur

Depends on temps

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Idle time, driving habits, and traffic movement also have an effect. This cold weather makes mine read about 17-17.5 because I illet it run for 15-20 min to warm up in the morning and after work before I leave. During summer I average around 20.

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**Snoop dogg** · 02-12-2014

^ I let mine warm up about the same time but my temp stay in the middle of 160 and 210 no higher unless I'm low on antifreeze

**coolone** · 02-12-2014

Originally Posted by Russosaur

Depends on temps

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Depends on a lot of things, not just temps! Maintenance, fluids, lube, suspension, gas, tires, elevation, temperature and most importantly... FOOT! The FOOT mod, although little known and understood, is the biggest mod with effect on efficiency! A Bad foot mod could cost as much as 5-10 MPG. Rarely discussed but well known by all the old schoolers, you'd have to search high and low for just a glimpse of a well developed and utilized foot mod. It's a secret not readily shared either and you need to be IN the know in order to get the information n how to use it properly. Many have tried and failed, succumbing to the ever present temptation to abandon it and leave it all to its own. The FOOT...

**Russosaur** · 02-12-2014

Well I said that based on I usually get 16 city then I'm getting 9 now lol. Freaking cold, yes I was s little vague.

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**factory** · 02-18-2014

So I found a leak around the TB gasket and replace the gasket. I don't know how much of a factor this is for the mileage but there was a definite leak on the bottom side. Clean the TB while I had it off.

Also cleaned and oiled the air filter (K&N). Replaced the thermostat.

Can anyone give me a part # for a set of tees and vacuum lines? The coupler for the line from the TB to the evap canister broke off a piece.

Will see how much difference the gasket made... more to come...

**Fivefingerdeathpunch** · 02-18-2014

Only dealerships have the line part numbers, and are the only ones to sell the lines as a whole.

Most people just buy vacuum tubing and some plastic T's and make there own lines, normally it's cheaper and quicker.

**Scottydoggs** · 02-18-2014

i used a fat line that fit the large tube on the TB, then pushed a thinner line inside it, then pushed the stock plastic line into the thin line.

50 cents worth of vac tubing.

dont over oil that filter, they tend to kill maf sensors.

**factory** · 02-28-2014

Thanks to everyone for the help. I'm up to 17.2MPG for short city trips. That's pretty good I figure.

Next on the hit list is replacing the wheel hub assemblies (due to loud road noise when driving) and then LIM replacement. Any tips for either are appreciated! I found some good DIYs for both and I ordered a set of 2003 service manuals off eBay

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