jimrankin Posted October 16, 2011 Share Posted October 16, 2011 OK, I'm kind of stumped. S2000 motor but the Honda dealer is no help. A little background before I explain the problem. (Just venting a bit here so unless your just kicking back or have seen this problem before you can skip reading this without missing much) The car has been running perfectly till this. I was at Thunder Hill raceway a couple of weeks ago, running great until late in the day when it suddenly felt like I was having a fuel problem, sputtering, not reving etc. Went off and refilled the fuel cell, seemed to run OK at low speeds in the pits but back on track it was right back to crap. Have checked the fuel pump, fuel filter and all of the wiring for something coming loose, all good. Took it to the Honda Dealer to have a diagnistic done but they called to say that the harness was missing some of the sections that are not needed for the motor to run correctly, but do have to be there for the Honda diagnostic machine to work and said they would have to order two "under dash" wiring harness sections for about, I couldn't beleive this, approx. $700 each, not installed. Sinced there is now no where to hook them to as there are no Honda dash components I'm not sure what they planned to do with them. I went to see the dealer and asked to talk with the tech. I explained that the motor seemed to run OK at a "fairly low set speed" but stumbled at any sudden throttle movement but this was most pronounced at higher RPMs. I had had the same problem with a 5.0L Ford motor in the past and it was the throttle position sensor. We agreed to have that fix priced out and maybe start there. The dealer ordered the throttle body without calling me and when I called them I learned that it was about $750 plus tax and install and no guarantee it was the problem because "no computer read outs to go by". I stopped the part order and told them I'd just pick up the car, ($832.00 for "diagnostic examination", labor only, No determination. Just learned a lesson the hard way). Purchased an aftermarket TPS unit ($65.00 vs $750.00 Honda complete throttle body) and installed it on the existing throttle body. Set it up with the digital multimeter and set right on specs. As it was too late in the evening to go for a test drive I decide to check out the existing TPS. Jumped the 5V imput to it and, UH OH!, it read perfectly, could not get it to show even an intermitent fault when running it through from.35V all the was to 4.99V (exact Honda spec.)again and again. Took the car out yesterday and same problem. Seems to run "OK" but not quite as as smooth at low RPM (>3K)as before the problem and the higher RPM you get to the worse any throttle movement seem to bring on a problem. This really goes to extreme when you get to VTec range ( Anyone who has read the original Honda S2000 service manual will already know that every single line seems to start with "monitor the OBD status for the DTX####'s with the HDS (Honda Diagnostic System). Every section also seems to end with "substitute a known good ECM and repeat". To make matters even worse they cover EVERY wire harness in the car with a color coded easy to read diagram EXCEPT the wiring for the motor. Just shows the wires all as black lines to the hook together links for each harness. At the end of the harness the wires show as black lines going "wherever" but no idea where it came from on the other end. I had planned to replace the stock Honda ECM with an aftermarket unit this winter but now don't think that's a good idea until I resolve the current issues. Anybody know of anyone with a "known good ECM" for an '04 S2000 they might want so loan/rent/sell? Hate to start down a long path of checking contuinuity wire by wire and replacing sensors only to find out it's a bad ECM. Fixing things with points and carburators was so much easier. LOL. Link to comment Share on other sites More sharing options...
a.moore Posted October 16, 2011 Share Posted October 16, 2011 You mentioned refilling the fuel cell- does this cell have foam by any chance? Link to comment Share on other sites More sharing options...
jimrankin Posted October 16, 2011 Author Share Posted October 16, 2011 but no foam in the filter and had the cell out to relocate it and all new fuel lines and new filter this spring. Foam is in great shape and not shedding. Going to add a fuel pressure gage to the system as that was my "first" thought. Since it seems to supply plenty of fuel to run at a constant semi-high speed the stumble at lower speed when the throttle is blipped seems to be more ignition/ECU related. Link to comment Share on other sites More sharing options...
a.moore Posted October 16, 2011 Share Posted October 16, 2011 Any chance a ground loosened or a vacuum line developed a leak? How do the plugs look? Link to comment Share on other sites More sharing options...
jimrankin Posted October 16, 2011 Author Share Posted October 16, 2011 Took just about every connection apart and sprayed with electronics cleaner. No cracks/slipped off/leaking vacuum lines. Almost none anyway since everything seems to have a sensor in its place. This problem isn't just "getting out of tune". It came on almost "instantly" as I can state exactly when it first happened. I had come up on a slower car in a tight section of the track, sat behind him till he saw me and waved me buy in an uphill corner. I went from steady throttle at about 4K+ to near WOT on the pedal but got three sharp bog/gain/bog/gain/bog/gain cycles of about one second each instead and then steadied out and I went by him. Was perfect till that happened and crap after. Plugs are good as are oil level and the sensor for water temp/oil pressure are sending. Link to comment Share on other sites More sharing options...
powderbrake Posted October 16, 2011 Share Posted October 16, 2011 I am sure that Loren or Chuck would be better sources of info, but the DLC (obd port) only has 5 wires according to Brian's schematic. ECMA 10 to DLC 1 ECMA 21 to DLC 15 +12v to DLC4 ground to DLC 12 & 13 I have never plugged a tool into the DLC, and I am not sure this wiring is correct, so if it isn't someone let me know. I haven't found the DLC connector diagram in the manual, so if anyone can verify this please let me know. Won't the codes give the info you need? (discounting those that are associated with the missing air pump and idle circuit) Link to comment Share on other sites More sharing options...
Mondo Posted October 16, 2011 Share Posted October 16, 2011 (edited) Man, that Honda dealership ripped you off. You can buy a little scanner/reader like the one I got http://www.actron.com/product_detail.php?pid=16361 . As long as you have the OBII plug on your harness, it'll say that your smog pump isn't working (because you don't have one) etc.. but it'll tell you useful things like misfires, VTEC issues etc.. You'll have to do a google search to find the code definitions but no biggie. Plus you can erase the codes to try again. And it's good for your other cars when they say (check engine) and it ends up only being a problem with your fuel cap. I think it's a fuel problem too... I had a problem similar to yours, it was that my fuel line was coming loose inside the tank, near the top, as the fuel pump swang back and forth under Gs. I have foam in my tank too but that didn't stop it from swinging around. Don't know how your fuel cell is set up but if it's a honda fuel pump just sitting at the bottom of the cell with a fuel hose hooking up near the top, I'd check that it's tight at both ends. If partially off, it won't supply enough for full throttle... and it's about ready to come off all the way and leave you stranded out in the boonies. Wait that was just me, twice;) Thought I did damage to the motor the way it sounded too. I ended up putting the fuel pump outside the tank after trying to reach into the tank to fix the loose hose and pushing/grounding the wire for the fuel pump... can you say BOOM and FLASHFIRE! There's pros & cons to having the fuel pump outside I know but I feel better now. Edited October 16, 2011 by Mondo Link to comment Share on other sites More sharing options...
BusaNostra Posted October 16, 2011 Share Posted October 16, 2011 Anybody know of anyone with a "known good ECM" for an '04 S2000 they might want so loan/rent/sell? Is yours 2.2 or ap1 2.0 ? Can you use the 2001 Honda ECU ? Link to comment Share on other sites More sharing options...
Off Road SHO Posted October 16, 2011 Share Posted October 16, 2011 Did you get a fuel pressure gage on it yet. I think your regulator is hosed, if it has one. If it's the returnless type, make sure that what is supposed to be grounded to the battery's negative post, is in fact grounded to it. Tom Link to comment Share on other sites More sharing options...
jimrankin Posted October 17, 2011 Author Share Posted October 17, 2011 My brother is a mechanic back in N.H. and scanned and emailed me all of the color coded schematics for the engine harnesss from a data base he subscribes to. Also told me just byt the universal scanner as our government was smart enough to require that all cars have a generic system as well as anything manufacturer spacific. May not be quite as easy as the Honda diagnostic but still basic enough that he thinks his dumb older brother can manage it! LOL. I'll be checking out, or have checked already, most everything noted so far. Thanks for all the help, and I may still need an ecu if this one is kaput. Thanks to all, I'll keep progress/hopefully solution posted. JR Link to comment Share on other sites More sharing options...
danilo Posted October 17, 2011 Share Posted October 17, 2011 My thoughts too, a Canbus gizmo will give 90+% of what the Honda reader does. But then I'm not a big fan of the S2000 lump.. Too much coin, too much weight and bugger all torque. Link to comment Share on other sites More sharing options...
WestTexasS2K Posted October 17, 2011 Share Posted October 17, 2011 Just give me a call check your PM. I likely know the cause I need a little more info. It sounds like you are going into limp mode which wont allow the car to rev past 4k or so. It sounds and feels like fuel issue because the computer pulls the the fuel and timing out of the engine. Has the car always run well in the Vtec range? Were you speeds over 100mph? Have you been at that speed before? Depending how your car is wired the ecu power might stay on even with the battery switch off. So disconnect the battery positive terminal for 15 seconds and then reconnect and go for a drive. If its a VSS limp code it will run fine again until it gets up to near 100 mph. Then it will kick in again. The problem most likely is the VSS signal going into the ecu. Its the blue wire / white strip. It should be going to connector A pin 9 on the ecu. Connector A is the plug with just a few wires in it. Pin 9 is located by looking at the wire side of the plug with the retaining clip up the top row starts with pin 1 on the left and goes in order left to right. It may be plugged in another location let me know if that is so. Also and check the blue/white wire isnt connected to the speedo signal input. That will cause the car to mis-behave as well. The speedo needs to be run off a magnetic pickup sender not off the VSS. This has caused problems before. Link to comment Share on other sites More sharing options...
WestTexasS2K Posted October 17, 2011 Share Posted October 17, 2011 I just purchased a 2.2 ecu for a customers car in Houston last week. Keep in mind if you swap the ecu if you have the Honda key switch they wont work together and it cant be reprogramed without the OBD2 plug. It wont start. If you dont have the Honda key switch then you have to remove the anti theft section from the ecu before it will start. Fuel pressure gauge is very useful to trouble shoot these type of issues. Its well worth the little bit of hassel to install one. It takes about 30 min to install and clears up issues like this in seconds. I doubt it is a fuel pressure regulator. The Honda one is a simple spring loaded return bypass regulator very unlikely it failed. It is unlikely that the fuel pump came off the hose. I has happened before but it usually just wont run if that happens. You can hear the pump humming and no fuel flow. (fuel pressure gauge tells you this very quickly). As mentioned in the previous post its sounds like limp mode. Link to comment Share on other sites More sharing options...
jimrankin Posted October 17, 2011 Author Share Posted October 17, 2011 I'll give you a call but a couple of quick answers. Speedo is fed off a mag senson on the axle. Car has always run fine and over 120MPH on a fairly regular basis. Honda Imobilizer is installed and I don't have the original VIN from the donor S2000. Thanks, JR Link to comment Share on other sites More sharing options...
WestTexasS2K Posted October 17, 2011 Share Posted October 17, 2011 Check the blue/ wht wire if that's good then you install a dlc connector. It's fairly easy. You can go to any salvage yard and remove the dlc plug from any make. The plug is the same wiring varies. I can email you a diagram of the wiring. Link to comment Share on other sites More sharing options...
jimrankin Posted October 17, 2011 Author Share Posted October 17, 2011 Downloaded a couple of diagrams off the web but could use yours if you have it scanned. Not a lot of time this week but will get a fuel pressure gage/sender and a code reader ordered so I have them for the weekend. Not a lot of junkyards in silicon valley but I'm sure one of the used parts houses (no cars, strip them and send out the rest for scrap as soon as they get one, but lots of shelved parts) will have something. Thanks, JR Link to comment Share on other sites More sharing options...
WestTexasS2K Posted October 18, 2011 Share Posted October 18, 2011 Here is a scan of the wiring diagram. As you can see the DLC has been corrected it was all flipped 180. I think you can see the changes pretty clearly. I will check a few local yards to if I can locate a DLC for you. I can wire it and label it and send it to you if that helps you any. Pin 16 is 12v unswitched. The ignition will need to be on to check the codes. Link to comment Share on other sites More sharing options...
jimrankin Posted October 18, 2011 Author Share Posted October 18, 2011 Got the fuel pressure gage and the code reader on order last night. Good old Summit Racing, not the cheapest but has it all. The code reader is one of the really full function units and I will even be able to get the original VIN of the donor etc. Cheap b-----d that I am I went for the free ground shipping so won't see it till Friday and will be out of town all weekend so my next update on what the problem actually is will be delayed a bit. Thanks for all the imput so far. Link to comment Share on other sites More sharing options...
jimrankin Posted October 18, 2011 Author Share Posted October 18, 2011 Going to swing by an "all Honda" used parts yard in Santa Clara before thursday and I would think they would have one. Hope they don't correspond with my local Honda dealer or they will want $823.00 for it. LOL. Link to comment Share on other sites More sharing options...
WestTexasS2K Posted October 19, 2011 Share Posted October 19, 2011 If you don't want to install another gauge. You can use the oil pressure gauge just install the sending unit and run the signals to a toggle switch so you can flop from oil and fuel pressure without cutting another hole in the dash. Just a thought. Link to comment Share on other sites More sharing options...
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