AllThrottle4U

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 last week when it 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.
Paul

AllThrottle4U

*****UPDATE*****

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?
Thanks
Paul

It Wasn't Me

Get a scan tool. With the engine at operating temperature, check the primary sensor's output. If the output is less than 0.3 volts or more than 0.6 volts, replace it.

Have you checked the valves clearances? At 140k, it's overdue for an inspection.


Intake: 0.18-0.22 mm (0.007-0.009 in.)

Exhaust: 0.23-0.27 mm (0.009-0.011 in.)

If the valve clearances are okay, replace the injectors.

AllThrottle4U

Here is a link from civicforums which I posted the same problem.

http://www.civicforums.com/forums/36...n-problem.html

Almost the exact same answer but i'm almost positive the valves didn't just loosen up to the point where I cant start the car. I also unplugged the oxygen sensor to see if there was a difference and nothing changed. Does the sensor even take a reading in open loop?

It Wasn't Me

The freeze data will tell you what's going on with the fuel trim malfunction. It really is unfortunate that you don't have a scan tool.

From what I can tell, when the fuel system status is "open" the ECU ignores signals from the A/F sensor and Ho2 sensors, rather it uses signals from the throttle position sensor, MAP sensor, intake air temperature sensor, barometric and engine coolant temperature sensors to control the amount of injected fuel.


Sorry I'm unable to say "It's this, so do this." as I am not a technician. However, we do have a few techs floating around here, and I'm hoping one of them will chime in and shed some experienced light onto this.

AllThrottle4U

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.

AllThrottle4U

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
Paul

It Wasn't Me

Ah ha! I was wondering about that myself, but figured you would eventually sort things out.


Crank pulley? Jebuz.. tends to be a nightmare. Some people work for hours trying to pry that sumbitch off, while others break it loose without much problem at all. If you have a pneumatic impact wrench (gun), you should have no worries. If you're working with regular ol' hand tools .. yikes .. best of luck to ya.

As for the tensioner, it is recommended to at least inspect it by taking it off, placing it flat on its mounting surface, and measuring the height difference of either (opposite) side of the pulley. If it's more than 0.75mm you're supposed to replace it. I would go ahead and replace it, anyway.

If you buy a kit online, it tends to come with the tensioner, water pump, timing belt, alternator and power steering belts, and necessary gaskets. (depending on who you buy from)