SHAKYBRAKE

Hello all. I haven't been very active on here in a couple of years (old screen name was OVER 9000!), but I just wanted to post up a problem that I was able to chase down in MY02. I am at 135,800 miles on the odometer currently and recently did a valve adjustment at 135,200. About a month ago I noticed that I started getting worse fuel economy than usual (barely 160 miles on a tank) and popped a CEL for misfires on all 4 cylinders and random misfires (P1399). I would clear the code and it would wait about a week then come back.

So I started chasing down likely causes. I pulled the spark plugs, which had maybe 1,500 miles on them and were rather dark (showing signs of running rich), and swapped in new NGK laser platinums. CEL still came back a week later. After this the CEL started coming on within a few minutes of starting the car. I switched coil packs (one was replaced earlier this year) and still came back. At this point I had bought a bluetooth OBD2 reader for the S and ran Torque Pro to see what the engine was doing. My short term fuel trims were constantly seeing -20% on my STFT and would rarely get in the positive. I found that the negative values corresponded to running rich and that it was running very rich most of the time.

Finally, I decided that it was likely a fuel issue. I took my injectors to Deatschwerks since they are local to me and had them clean/flow test my injectors. They came back with some interesting news that one of my injectors is outflowing the others! it was putting out almost 1.2 gallons more fuel an hour and had a slighting higher flow during the low pulse testing (simulating idle). I went about replacing the failing injector and learned a lesson about injectors along the way. Injectors are flow matched from the factory. Basically injectors are a mixed bag of flow rates (within a certain range of course) and the factory pairs 4 of them together with similar flow rates (likely within 1–2% variance). Chances are low that you will get an injector with a matching flow rate when ordering a single injector. Luckily a friend of mine found his 3 oem injectors from when he supercharged his S and I took all 3 of them into Deatschwerks and they picked the injector with the closest flow rate to the other injectors. I got the injectors back in about 4 days ago and it has been running like a champ and pulling a lot harder too since its not running super rich anymore! I just wanted to post up because it was a pain to go through and figure out, so I want to help the rest of you if you are having similar issues.

Edit: Here are the Fuel Injector Test Results. The first and second picture are from the first test with the original 4 OE Keihein injectors. The 3rd pic is from the second test with a refurbished injector labeled as a 2000–2003 Honda S2000 injector from USCarburetors on Ebay. Obviously it was a different injector or a faulty one. The bottom line was that it was a stupid decision even if the injector was working properly because chances are, it would not have matched the other 3 injectors' flow rates. I have already requested to return it. I will upload results from the third test with the 3 additional OE injectors sometime tonight.

cgarrett23

That's good stuff, thank you for sharing.

SHAKYBRAKE

No problem! I found a similar thread that had traces of the same problems and he had fixed it with new injectors, so I wanted to help out others too with my own experiences.

Soviet

You should consider posting this in the Misfire thread if you haven't already

HarryD

I assume it will be good advice to tell you to dump your oil and do an oil change, because the leaky injector probably diluted/contaminated your oil? Better safe than sorry!

Thanks for posting a follow-up!

P.S. Here's a dude who used a 9V battery, tube, zip tie, and can of carb cleaner to test his leaky injector on the fly:

92gli

Yep. Same situation as you. Car is dumping fuel and throwing codes at idle. I'm pulling my injectors and sending them off for cleaning and flow matching next month. Already wasted $ on unnecessary coil packs because thats what everybody keeps saying. Injectors are mechanical, coil packs are not. People need to stop harping on the coil packs and use some common sense

SHAKYBRAKE

Update Time! Well, it's been a bit of a rollercoaster ride this week with the S. I put the flow-matched injectors in on Friday 11/30 and the car ran great for the weekend with no CEL's. Then on Monday starting up the S after work, there was a CEL waiting for me. I pulled the attached freeze frame from my Torque Pro app, so it was back to the drawing board.

After some thinking about the situation and some digging on here, I found a potential solution. I've seen many people debate whether the OEM fuel pressure regulator can handle the increased fuel output by an aftermarket fuel pump. I installed an AEM 320LPH fuel pump with the SOS Easy Wiring Kit earlier this year, but thought my fuel pressures were normal due to so many estimations on what the OEM fuel pressure is and whether that number was for static fuel pressure (WOT) or at idle. So my fuel pressure was at around 57–61psi....at idle. I finally found some verification that fuel pressure should be around 43psi at idle and 54-57psi at WOT. So I put on an AEM adjustable FPR and set it within OEM specs and cleared the check engine light. That was Wednesday and it's been running great with better short term fuel trims and no misfires or check engine lights. Hopefully it holds up and resolves the issue for good.

noodels

60 psi at idle

SHAKYBRAKE

Update #2 Getting really tired of this problem. It waited a week and a half before popping the check engine light yet again. It seems to happen only at idle. The CEL came on sometime this morning when I was warming up the car (garaged, but its 35°F and very windy in OK). Then after I got in and scanned the codes it started flashing (probably adding the random misfire code to the rest). As usual it's running and driving great, save for the times when I don't clear the check engine light. Does anyone know if 20in/hg vacuum is normal under load? Also I'm not sure why it's showing load at almost 40% at idle

Edit: Damn, I forgot to take a screenshot of the codes. Oh well. It was just 3 codes for random misfire, misfire on cyl #1, and misfire on cyl #2. Freeze frame was taken from when these codes popped.

SHAKYBRAKE

Yeah, I'm kicking myself for not researching the OEM pressures sooner. You live and learn. It's been a long, but informative journey for me since I've had to learn everything about cars and tools on my own.