I have a 99 civic si, pretty much stock. Just recently i was driving the car on the highway and i realized my fuel gauge dropped pretty damn quick. After i filled up i realized im only gettin 15miles to the gallon. Then i get back in teh car to drive it and its hesitating like crazy and misfiring at idle and while driving. I have no codes at all. When i drive first and 2nd gear are decent but 3rd - 5th barely accelerate. It takes forever to get to 60 mph and when i do the car wont go any faster. I can put it in 3rd and floor it and it just stays at 60mph. Does anyone have any idea what this could be? I changed out my coil about 2 weeks ago, if that matters. Thanks.

 

OEM plugs, wires, cap rotor? Make sure everything in the distributor has a good connection, and none of the plug wires are loose or coated in oil or water in the plug wells. You can also unplug each of the plug wires while it's idling and see if the idle changes. If it doesn't, you have found (one of) the offending cylinders.

 

Checked the plugs and they are good...then again they only have 3k on em, the wires have 30k on em and they all seem good. The cap doesnt look corroded at all, however the fin on the edge of the rotor looks a lil burned. Would this cause those problems?

 

weird.. no smoke?
hows your fuel pressure?

just for the hell of it check cam timing.

 

cam timing is perfect, no noticable smoke outta the exhaust or anywhere else, fuel pressure is good. i got the b&m gauge, aem fpr.

 

something is wrong. if your car is really doing that; the plugs should not look normal.

you say it does not accelerate on 5th or 3rd, whatever gear.

Do a run on a high gear high load, right after that park and check the plugs.

I mean.. its either fuel or ignition..

 

The plugs all have a light brown tint to them. 2 of them look a slight bit darker all the gaps are good. and they are all pretty new plugs. I think im just gonna run to napa and pick up a cap rotor and wires and see what happens.

 

Also, some things that have been eliminated from being the cause are fuel pump, injectors (put 4 other injectors in to see if the problem stayed and it did), coil (was replaced two weeks ago.

 

Just changed the cap, rotor, plugs, and wires and no change in my problem. Does anyone know if a clogged cat could be causing this?

 

Hmm, come to think of it, that's just what my car did when this happened:



I could get to 50mph, and that was all... I wouldn't call it normal below that, or in lower gears. I would describe it as "unbelievably shitty" or "annoying to the point of being a hazard".

Can't hurt to check it out.

 

alright then...time to go pull that...

 

yup plug cat

 

alright guys....thanx for all ur help...i pulled the cat off and it runs a million times faster. Problem solved. Thanks for all ur help.