S2meowzan

Hello all, my names is Sada and I'm new to the s2000 world. I picked up a 2002 ap1 with 145,000 miles about 2 months ago. It was running strong with no problems and then out of no where it begins hard starting and rough idle after acceleration. I've been stalking all the threads I can and trying to research everything I can. I started with all the normal routine stuff so I replaced the spark plugs with the NGK Laser IRs, and the hard start continued. Then I replaced the coil packs with all new Denso coil packs and still had the hard start. Next I ran a compression test and all four cylinders came up in the 195 - 205 range so that all seems good to me. After doing more research I saw the MAP "Wack" and how to clean the MAP sensor and port that feeds air to it so I got some compressed air and sprayed them both out to clean and I cleaned the throttle body while I was at it. I also saw the ECU reset where you start the car up and rev it to 3,000 RPM till it reachs operating temp so I tried that and yet still, hard start. At this point I got a CEL so I was excited about being able to run the codes. It came up with random misfire codes and a cylinder 4 misfire code and I saw that could be caused by the valves being out of spec. I took it to the Honda dealer in my area (Spreen Honda) and told them about my situation and they told me they would do a diagnostic and let me know what's going on. They later called and said it would need a valve job and since I've never done one I told them to go ahead and handle that. When I went to pick my car up they explained to me how the valve job is all done but it's still hard starting and they believe it's the O2 sensors because they were getting bad readings from the upstream O2 sensor and the car is running rich, but they didn't have one to replace it with to check. I asked what brand they suggested for O2 sensors and the mechanic told me to go with Denso so I replaced both upstream and downstream O2 snesors with new Denso ones. I then did another ECU reset and still I can get rid of this hard start. The car seems to be driving just fine, it's not thrown any more CELs, and it doesn't have any lag or sluggishness through any RPM range but I don't know what to check next. Also, the battery is new, the alternator is putting out the correct voltage, the starter is cranking over strong, and I check all the fuses under the dash and everything appears to good so any help or advice would be appreciated at this point. If you need any more information please let me know. Thanks in advance, Sada.

windhund116

Did you try cleaning the IACV valve?

https://www.s2ki.com/forums/s2000-un...k-iacv-943369/

S2meowzan

I did not check that. I'll see if I can get a new seal for it and pull it off to check it out and clean it, thanks. Also it popped up with the cylinder 4 misfire code and the DTC definition not found again so I don't know if that could also be caused by the IACV but I'll check it out.

S2meowzan

Just read the thread on how to clean it and saw it doesn't need a new gasket as long as you don't mess up the rubber seal so I'll clean it and see if that helps.

windhund116

Good luck!

Keep us posted.

S2meowzan

Okay sorry for the late reply but I've been working on a lot of different things. As far as the car goes, it started throwing random misfire codes again. I pulled off the IACV and cleaned it inside and out but when putting it back together I accidentally broke the top of the plastic piece so I ordered a new one from Rock Auto. The new IACV came in, I installed it and started it up. The first start was hard still but after it did it's warm up sequence I turned the car off and let it cool down again. When I went back and started it up it fired up just fine and I thought I was done but I drove it around, parked it, and then when I went to start it I had the hard start again. It appears that the IACV is helping with it but that's not the full problem. Or maybe the ECU is just working on relearning? I don't know. I cleared the random misfire codes so I'll drive it around some more and see if they come back and see if it gets better with starting. Thank you guys for the help but I think I'm still searching.

S2meowzan

Okay so I got an update. CEL popped up again today on my way home from work, got home and ran it. Came up with misfire codes on all cylinders and the random misfire code. All I can think at this point is the CPS? That's all I can think that I haven't touched yet. Any reply would be helpful, thanks.

Hfreak

Might want to get your injectors checked, can and will cause the issues you have described. Good luck.

S2meowzan

I thought it might be injectors at first but after I replaced the spark plugs I checked them a few days later and they are a little dark (unburnt fuel). So I don't think it would be that. Idk I'll check it out while I'm at it cause it won't hurt to check.

S2meowzan

Sorry for the stupid late reply but got to the bottom of it! After doing so much my last thought was injectors but I decided to replace the Fuel Pressure Regulator before I mess with the injectors and wouldn't you know it, that was the problem all along. Been daily driving it for about 2 months now with no problems, that was all it was. Thank you guys for the help.