hello , I am new to this forum , and been searching,through here and other Honda forums like CRAZY these past few days trying to find help diagnosing my car.

I just bought this little accord a few weeks ago and it gave me a p1399 (ithink that's the numbers) saying random misfire on all cylinders. Has no CEL light on . I changed the sparkplugs , wires, seafomed the car , changed oil air filter etc. The dist cap looked new so idid not change it , also the O2 sensor looks new . The car sounds fine when driving but at idle sounds weak and rpms go low sometimes but usually stay at about 750, muffler sounds like crap puffing sounds, I was also told by the previous owner that the CAT was new , when I looked at it from the bottom it looked like a crappy weld job but it was there and looked fairly new(Ftermarket ofcourse).

I really need help trying to find the cause i don't want to keep replacing parts if the motor is crap already I rather start looking for a new engine somewere on eBay or CL. I paid 2500 for the car its clean title has 111K on the odometer , and really straight body irather shell out another 1000 for a diffrent motor than taking a loss on it .. thank you in advanced for any advise or info I'm,open to anything as of now I just want a good running car

 

Suggest first resetting the ECM/PCM by pulling Clock/Backup fuse (#13) in under-dash fuse box for 10 secs.

P1399 is a temporary DTC that may indicate a pending miss code, P0300-P0304.

Is the car missing? Listen carefully to exhaust at idle for putt, putt sound of miss. Vibration of miss can usually be felt though steeing wheel. A sustained miss should set codes P0300-P0304, where P0300 is random missing.

Low idle is usually a dirty idle air control valve. It can be removed/cleaned along w/ throttle plate/bore. See DIY forum for additional guidance. check following video of cleaning which should be similar to yours.
See this recent thread: https://www.hondaaccordforum.com/for...ere-iac-58631/

good luck

 

hey TexasHonda thanks for the advise . I meant p300 it says random misfire on all cylinders . I do hear the exhaust putting , it sounds bad , everyday that goes by the car sounds worst and worst . you think the misfire could be caused by the EGR or IAC ?

 

EGR might cause a lean miss.

IACV can cause idle stability and wrong idle speed but usually not missing.

Did you reset and Check Engine Light came on? What code/s.

Check for intake air leaks by spraying throttle body cleaner or brake cleaner around intake manifold, throttle body, and vacuum lines. A change in idle speed indicates a leak.

good luck

 

i did reset the computer but there was never a CEL and the check engine light has not came on , but I scanned the car and that's what comes up on the scanner still . And okay I will try that today at work during my brake , I hope I can find the problem soon I start a new position at work Tuesday and its out of town so I'm going to need a good running car , rite now I only work litterally 2mins aaway so I'm fine, any other suggestions would be great or if anyone else has anything they can think of thanks

 

the p300 is whats on the car when i scan it

 

Is your scanner able to show Long Term and Short Term Fuel Trims (LTFT & STFT)? This may provide a clue.

Also some scanners will provide data on conditions when code was set. These also may help.

Confirm your car is 4-cyl or V6.

good luck

 

my car is 4cyl and im not sure if it does I'm taking it to my buddys house who usually does my mechanic work that I can't do and ill let him know this info to try on his scanner he has a better one than I do

 

Hey so we did a compression test today and all were 180 except cylinder 3 had about 30... leakdown test aswell and did very bad . my buddy said probably the headgasket .. would you or anyone else who might be reading this recommend replacing it and possibly some machine work , or should I buy a JDM engine ? I found one here in CA and I can go pick it up , they told me it has 47k miles and 30 day warranty, do you know anything about how the swap would be ? since I have a ULEV engine I understand a few components are different , would I need a new ECU ?

 

I suspect it would be cheaper to repair your engine, assuming the problem is head gasket or valve leak issue. You will for sure need a new ECU and perhaps other problems w/ sensors that are no longer have a place on new engine.

Adding a bit of oil to cylinder and observing whether compression increases or stays the same will isolate if rings are leaking or valves are leaking. A very bad head gasket leak might make determination between rings and head gasket difficult. However, it unlikely that one cylinder will have worn rings, which would suggest head gasket or valve leak.

I think it would be worth the effort to pull the head and determine source of compression loss before going to a replacement engine.

One low compression doesn't account for P0300. It should show a single cylinder, unless water is getting into other cylinders somehow.

good luck