I have a 94 civic hatch with the original d16z6 and 5spd trans, 142,xxx miles. I've owned the car for about 8 years and just recently it's been giving me issues.

The gas mileage has dropped down from what used to be 38-40 highway down to 28 highway. It also takes 5-10 seconds to start, seems to crank forever compared to my 99 civic and every other honda I've ever owned.Those issues seemed to have started at the same time.

I did all the maintenance stuff years ago but went ahead and replaced all this recently within a week or so. cap and rotor, coil, spark plugs, o2 sensor, fuel filter, engine temp sensor(the one down by the distributor on the corner of the head), thermostat.

The fuel pump started to go bad last month so that was replaced with a new denso and new fuel filter sock. I removed the main relay and resoldered it. Air filter has been cleaned, catalytic converter was replaced a couple years ago too. My driving style is still the same, still living in the same area, still using the same gas stations. New wheel bearings in the front, no sticky brakes. New gas cap, tire pressure all good. Oil changed. Timing belt changed 42,000 miles ago with valves adjusted. No new changes with bolt ons, no wheels and tires changed.. no triple decker spoilers or 10" hood scoops. No added weight. No check engine lights either. New pcv valve too.

I've completely run out of ideas. My other 99 civic has 264,000 miles on it, still gets 36-39mpg with the a/c running and it starts right up. My 94 civic hatch is driving me crazy with the crappy gas mileage and these long starts.

Does anyone have any ideas?

 

Have you done a compression test?

 

That is one thing I have not done yet. I am planning on doing a compression test and possibly a leak down test too. I was wondering if I could have a cylinder low on compression causing the issues?

It doesn't seem to use much oil if any at all and doesn't smoke. I suppose I might have something else going on inside there.

 

Are you using the same gas station? what brand?

 

I still buy gas from sheetz or pilot. Same place I go to for both my cars. Still using 87 octane.

For the 8 years I've owned the car, nothing has really changed in the way I drive or where the fuel is purchased from. I'm thinking it's a mechanical or electrical issue?

 

Injector sticking maybe?

 

It idles normal. I don't notice any rough idle issues but maybe I could run some injector cleaner through it. Not sure that stuff really does anything but worth a shot.

 

Anyone else have experience with a similar problem?

 

Friday bump for help

 

check/replace spark plug wires

 

Bump for help. Gas mileage still down.

 

If you let the fuel pump prime first does it start right up?

 

I always let it prime first and it doesn't make a difference.. it's an intermittent problem. Some days it'll start up normal and the rest of the time it cranks 5-10 seconds before starting. Warm or not.

 

Did you use OEM honda ignition components? I've had bad luck with various aftermarket brands. Can't go wrong with factory parts.
How did the old plugs look? Sooty?
How's the new plugs looking?
As mentioned, may not be a bad idea to put some fresh plug wires on. If they're old anyways, it couldn't hurt.

A compression test and or leakdown test isn't a bad idea either.

 

I just wanted to post the solution to my problem.

After a compression test and a few other parts tested, i had almost gave up. I finally decided to swap out the aftermarket AEM fuel pressure regulator for an oem honda pressure regulator i had laying around the garage. Finally, after putting up with bad gas mileage and long starts, everything is back to normal. The previous owner had installed the aem regulator for some reason.

 

Interesting. Do you have a fuel pressure gauge on the filter? B&m plus others make kits for these now.

Glad you got it figured out.

 

Interesting. Do you have a fuel pressure gauge on the filter? B&m plus others make kits for these now.

Glad you got it figured out.