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Hello, this is my first post on the forum. I bought this 2002 honda civic lx about 6 months ago with 140k miles. I have had no problems until yesterday when i started a low rpm stumble. It happened immediately, no previous symptoms. When idling, if i push the gas any more than say 25 percent it would bog the engine and almost stall. If i feather the throttle to about 2500 rpms it's responsive and i can go all the way to to the higher rpm band but it still feels low on power. I have a cel and it was a p0172 rich mixture. I was going to change my fuel filter but apparently it's more of an in tank strainer. I also thought is was a clogged cat but it happened so suddenly. I changed the spark plugs about 5k miles ago, air filter was ok. I don't know a lot about these cars but i did have a 99 z28 that i used to mod myself, ie..cam, headers, intake, suspension, clutch, tune, ect.. so i do have a strong mechanical sense. I just don't know all the tricks on the civic yet. If any of you had the same issue or know where to check for a common problem, please chime in. Any ideas are appreciated. Thanks.
Ok gentlemen. I really need some help. I downloaded the manual and went through everything step by step and then some. As i said before the only code that i am getting is p0172- mixture too rich. The same symptoms are there. So here's what I did since i posted this last:
Checked fuel pressure- good 44 psi throughout rpm range no leakdown
Checked EVAP valve- holds vacuum
Cleaned PCV valve- dirty but now clean and functioning
Checked for vacuum leaks with propane- none
Cleaned upstream O2- soaked in gas, no previous symptoms, no codes
Cleaned throttle body-dirty but not sticking, replaced TB gasket
Cleaned IAC valve- dirty but not bad, it is functioning
Checked spark plugs again- all good no unusual bias, it is sparking/coils are ok
Checked fuses- none blown
Visually inspected MAP sensor- is there a way to check values with multimeter since i don't have a scanner? Voltage values for different vacuum ranges?
Gas is good- ran a whole tank through
Battery and alternator are good- Battery replaced 7 months ago
So here is where it gets interesting. After I took the throttle body off and cleaned it the car started right up and there was no change in the way the car was acting. It was still idling funny and taking a little while to rev while feathering the gas. So i decided to reset the computer by pulling the ECM fuse. I went to restart it and no dice. It will turn over and almost catch, real lopey but wont fully start. So i have narrowed it to the injectors or the ECM itself.
I am assuming the fuel trims were reset when i reset the computer. I took all the spark plugs out after some cranking and there is raw fuel on all of them even though i know the plugs are firing. So for some reason the injectors are squirting too much fuel on startup and through the rpm range. Any ideas? What sensors are used to determine how much fuel is released when cold cranking? Map? I unplugged it and tried cranking to no avail. I found a used set of injectors on ebay for 30 bucks but i have to wait for them to ship. Can i try anything else? What about the ECM, is there a way to check it?
Does your scantool have data feed (reports sensor signals in realtime)? Idling at operating temp, in Park or Nuetral: does the Primary O2 sensor read 0.3V- 0.5V?
To check valve clearance look in the manual under "Valve Clearance Adjustment" under "Cylinder Head" in the engine chapter. Sorry I can't just tell ya, it's rather involved and has lots of pics. It was 108 today AFTER 30 straight of 100+ and I'm just worn.
There are also very good videos of a valve clearance adjustment on YouTube:
Thanks for the reply, i probably will adjust the valves eventually but im 98% sure that's not what it is at this point. Thanks for the video though. I cant imagine it being mechanical as everything was somewhat working until i reset the ECM. I wish i had scanning software but i sold it when i sold my Camaro. Now i'm at the mercy of autozone for reading codes. Can i tap in to the reference wire on the map? Is there a way to tell if the ECM is bad without taking it to the dealer?
check the egr valve, take it off to make sure its not stuck open becasue of some debris. ive seen this on a brand new car before. 2ndly check the fuel prssure regulator and the rail. ive seen them have a leak thats not super obvious.
So apparently I don't have an EGR. This car is different than those i'm used to working on. I can't believe there is no mass air flow sensor either. I guess the less components the better for fixing, ha ha. I measured the fuel pressure with the inline gauge i rented at autozone. I took off the hose from the firewall to the rail and used 5/16 tubing, it was a little too big but i use clamps and it was not leaking. It read exactly 44 psi throughout the rpm range, idle to wot. I know its not the regulator, pump or fuel filter. Here's a pic of the area that the EGR should be located.
I will take a look at my valves tomorrow, i just have to get a new gasket first and it's hot as hell in Houston right now. Thanks for the replies guys, this is really annoying me. What are the chances a clogged cat is causing this? It has run to the higher rpms when it would start so i kind of ruled that out.
Last edited by AllThrottle4U; 08-03-2011 at 06:50 PM.
I'm still hunting down this problem, i was able to borrow a scanner and read some of the sensors. Everything looked ok, the o2 was switching fine and everything was in range. The one thing that stood out to me was the MAP sensor. It was reading around 65 kpa at idle. In the service manual it says it should be below 40 kpa at idle within 1 second. Could a mechanical issue cause a low vacuum scenario at idle? Another thing that bugged me was the voltage of the map when the car is off. It was sitting at 2.7 volts. Shouldn't it be close to 5 volts with no vacuum? I just want to make sure i don't waste money on a new MAP and it turn out to be a slipped timing belt or something major.
Thank you to all who replied with suggestions. I want to let everyone who might have this problem know what it is. It turns out my TIMING BELT SLIPPED. It was off two teeth. It was so loose or stretched i could actually pull it off by hand. All i did was pull the valve cover and upper timing cover. I know this is not recommended but just for grins i slid the belt off and set up top dead center on the crank and lined up the cam pulley and put it back on, by hand. I just wanted to see if it fixed it before i went out and bought the timing belt kit. It runs just like before, so that was my problem. I was almost ready to throw up my hands and take it to a mechanic but pride stood in my way, thankfully. It looks like I will be replacing the timing belt and gaskets soon. Any tips on pulling the crank pulley? Other tips? Do i need to replace the tensioner? Ect...Thanks
You'll need a friend and a fence post as a breaker bar, impacts usually won't do it. May need a long extension to bring the breaker bar outside the tire to get maximum leverage. Also the crank pulley tool is almost essential.