I'm new here and I am having serious problems finding my way around. I hope I am in the right place for this post, so here goes nothing! I recently purchased (kind of) a 98 Accord 2 door with the 2.3 VTEC. I was told that it needed a new cat and O2s, so I replaced them and drove it home. Oh boy did it run bad! I started with the simple stuff- new cap, rotor, plugs and wires. I cleaned the intake and the EGR ports. Still ran bad but only gave the codes of P0300 and sometimes P0301- P0304 completely randomly. I tested the coil, which was bad so I replaced it. There is no real test for the ICU, so since the inputs tested good I replaced it. Still no change. Since it seemed low on power, I checked the cam timing. It was off one tooth and the belt was loose, so I adjusted it and checked the valve clearance. Surprisingly, there are no obviously bent valves. At 240k all the valves were within spec. Everything I can think of has either been tested or replaced, and I am still having a rough idle both hot and cold, no power and it seems to like to foul plugs. To me, that says weak spark, running too rich or cam timing off. I've cleaned the plugs and checked for spark and it gives a beautiful hot blue arc. I am at the end of my wits and all I can really think of would be a matter of throwing parts at this thing and hoping for the best. Please help!!

 

If I understood your post, the problem began w/ replacement of O2 sensors. Were they correct part? Any chance of damage?

Suggest checking fuel pressure as you have eliminated spark and timing as likely issues. Low fuel pressure would account for symptoms, however I would expect a high positive long term fuel trim if you scan the ECM.

Any chance the spark plug wires were installed to wrong cylinders or distributor outlets?

good luck

 

When I got the car it was not running. I am pretty sure that the O2s are correct and not damaged, but the readings from them are all over the place. I was assuming that low fuel pressure would cause it to run lean, but I stopped working as a mechanic a long time ago and I am not all that familiar with OBD2 systems. I have tried switching plug wires around in the hopes that I had messed that up and boy did that make it act up! I have noticed that the fuel trim seemed pretty high to me, but I'm not all that sure of what I am looking at. I was also assuming that it was more of an ignition timing issue and looking at the Cylinder Position Sensor (even though there is no code for it), a wiring issue or maybe a bad ECM. I haven't checked any of that because I just found out my multimeter is giving incorrect resistance readings. Looks like when I go get a new multimeter I will also need to pick up a new fuel pressure gauge. I will keep you posted on the progress and I thank you very much for the info! I have 20 years of fuel injection technology to catch up on, so I appreciate every little tip and trick. Thanks again!

 

Low fuel pressure would cause high positive Long Term Fuel Trim (LTFT) as PCM compensates for reduced fuel pressure. See attached fuel pressure test for your car.

Partially blocked fuel injectors would cause similar LTFT.

good luck

 

That would make sense. Apparently I ordered a fuel pressure regulator one night after too many drinks, so I will put that on after work tomorrow and see if it helps. There is also another fuel pressure diaphragm (?) on the fuel rail. It did have a plastic cap on it at one point, but I found the plastic cap under the car today. It seems to just be a cover, but Honda usually doesn't use stuff that's not needed. Any ideas on that? I am finally realizing just how smart these computers are! I just wish the OBD system could tell me the fuel pressure. It seems to know everything else! Thanks again. I am seriously in your debt!

 

The fuel pressure regulator is on the fuel rail and has a diaphragm. It also has a vacuum reference line connection. They can fail but very rarely.

good luck

 

What else (other than the fuel pump) would cause low pressure? The only filter I can find is the "sock" filter on the pump pickup. I wanted to check that, but I believe it was replaced about a year ago when the fuel pump was replaced. Please tell me there's no connection with the evap system..

 

It's possible to have a leak in a fuel line or fitting that would reduce fuel pressure (and increase gas consumption).

Partially blocked fuel injectors would have similar symptoms to reduced fuel pressure.

good luck

 

The pressure regulator made quite the difference! I still have intermittent misses, but I feel comfortable that it is fouled plugs. I'm going to go over the entirety of the fuel system as I have time, but your help has been incredible! Next pay is getting another set of plug wires- this time no Advance Auto Parts crap. Any advice on where to get plug wires? I have absolute faith in your advice! I am also probably going to replace the injectors. I made a drunken cocktail of chemicals to clean them and I fear that I may have done more harm than good. I sure miss the days of carburetors! Thank you so much for getting me headed in the right direction. I really can't afford to be throwing parts at anything!

 

NGK or Honda wires are good options. Check sponsors, ebay, amazon, etc for best prices.

Injectors can be professionally cleaned and tested. I did this for outboard motor injectors. Check ebay for vendors for this service.

good luck