03-17-2010, 06:04 PM #1
Any HONDA mechanic's? NEED YOUR HELP!!!!
I have a 2003 civic 1.7L vtec with some issues. Have 6 codes
missfire code cylinder 1,2,3 & 4
Intake air sensor
Now i just checked the fluids. oils good BUT coolant is a "very dark green" colour and it's way way to full for some reason and doesnt smell like coolant, is almost like carbon in it but not sure why its overfull car also when cold the rpms drop to 300 for a sec then revs to 2000-2500 the back to normal and does this a couple time till the car is warmed up.
03-17-2010, 10:50 PM #2
The drop in the rpms is caused by your bad intake air sensor. especially while the car is cold and the ecu is running in open loop, the ecu is telling the injectors to dump more fuel while the intake air sensor is saying something diffrent. Does the car jerk when driving. is the car a 5-speed or auto? when the car is at proper operating temperature and you come to a stop, do the rpms drop then? Also on the easier side, make sure your air filter is not crazy dirty or cloged.
Reguarding the coolant. does is fill thick or more like water? does the motor overheat? is there any dirt at the bottom of the resevour? smelling like carbon could mean a possible bad head gasket or a small puncture in the head gasket. it could be mixing with the exhaust. This one is easier to diagnose after you let us know if the car overheats while driving, or better yet standing in one spot? and do the radiator fans turn on? also if the fans do kick in, after one fan cycle carefully touch the top radiator hose going to the motor and see if its hot and does it feel like it has pressure inside, or can you easly push on it?
Let me know some of the answer to the questions i asked. Im sure I can help you out.
I build and race Honda's
03-18-2010, 07:01 AM #3
this is a on going problem the last year. intake air code is new though. Ive replace all the plugs and gaped them. 02 has never been changed. car has 180,000km's and it is not overheating and after 45 min of city driving coolant is still cool to the touch. once the car is warmed up it 100% fine. dont think its plugs or coils as the would cause all 4 to missfire.
03-18-2010, 05:47 PM #4
also like to note the coolant is full of what apears to be carbon this issue really has me stumped. what would cause a misfire on ALL 4 cylinders. Im thinking head gasket could be gone but cant see the afecting all 4 cyl
03-18-2010, 08:35 PM #5
Is the coolant a really dark blue? Just to let you know Honda's coolant isnt the regular green or pink. they have a very unique Dark Blue color for their coolant.
Checking the Intake air sensor is fairly easy. If the Pcm is setting a code for it, it means that there's a fault in the circuitry.
I would check the wires to and from he IAT sensor and the iat sensor itself. Depending on the circuit if there is a open the pcm could be getting bad info thinking that's its super hot or cold outside. The bad info will play a major role in fuel delivery possibly causing a bad idle or hard start or even a misfire depending on temps. If i were you i would Tackle the IAT circuit and see if that all checks out good.
03-18-2010, 08:42 PM #6
Here's a schematic for your car NON VTEC.
looking at the schematic looks like the IAT wires and O2 sensor has a similar path. So you might have a electrical fault somewhere in that connector or something along those lines. Get that test light and DVOM out !
03-18-2010, 09:15 PM #7
yes dark greenie blue but im concerned about the carbon like deposits in it and why it was cool to the touck after 45min of city driving the IAT code is new but i will check it. going to do a leak down test on saturday as i have a feeling it the head gasket.
03-25-2010, 07:02 PM #8
i'm a honda mechanic. Many of the 01-05 civic have headgasket problems. I've even fixed some with mileage as low as 75K. Honda kinda brushed this one under the rug, but if you google it you'll find thousnads of people with the same problem. At our shop we replace the entire engine assembly to avoid issues if there's a problem with the block of head (we've been faced with cracked blocks before). So unfortunately if you're smelling exhaust in the coolant then you're probably screwed.
The O2 is probably just getting fouled out from burning coolant, and the coolant RESERVOIR is probably full because the exhaust gas is pushing the coolant in there. You need to check the radiator, it's probably very low.
I'd ignore the IAT code for now, they rarely go. Reset the PCM and see if it comes back.
I'd suggest saving up for some expensive repairs and keep nursing it along by adding coolant. Good luck.
03-25-2010, 10:24 PM #9
thats the thing im not going through any coolant if it needs a motor no big deal only take a couple hr to jam a new on in. but iv had these missfire codes for 2 years maybe more. It would only do this in the cold but now it constant. and it never throws the same MF code. 3 then 4 then 2cyl MF its very peratic. I had it at a friends shop he say the head gaskets fine.
03-26-2010, 12:48 AM #10
Does it actually missfire ?
I'm not that familiar with Honda
If it drops to 300 rpm,that's lower than expected,the PCM might see that as a missfire. the cars I'm used to,Ussually with an actual missfire below 3-400 rpm, should show a P0300=random missfire.
Is the IAT clean ? Does your car have an oil coated air filter? ( K&N )
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