power-drop gremlin

OK - I'm at the end of my rope on this so I thought I'd ask the crowd and see if anyone can help diagnose this issue.:shrug:

ITA Civic EX (2000) with OBD1 P28 ECU with Boomslang OBD2b-OBD1 adapter and otherwise stock wiring and sensors (OBD2) - no loose connectors or obvious damage / bent pins that I can find. The car runs fine, but occasionally power just drops out. toggling the ignition or kill switch (3 pole) brings it right back, otherwise it takes a few seconds for the power to return. when the problem occurs, the car will idle, will rev to ~3000, then drop. with the throttle open and clutch disengaged, this will repeat for a little while then clear itself up. when reset, the car will blow a nice fireball, so it appears to have fuel during the problem. All gauges, etc.. stay on, and no engine light on dash (light works).

problem occurs on cool down, warm up, and at speed. Happens anywhere from 3000 to 9000 RPM (car moving) and doesn't appear to have anythign to do with VTEC (happens with P06 ECU, which doesn't supoort VTEC). Occurs typically braking for, or just after exiting corners, but occasionaly it will die mid-strait or mid-corner, which is about as much fun as I can stand... right and left turns, non-discriminant.

we have replaced the distributor, map, TPS, and tried multiple ECUs (P06, P72, P28x2), all stock. We have bypassed the ignition switch and the kill switch to rule them out. we have unplugged various sensors such as IAC, TPS, MAP with no replication and the problem continues. I bypassed the EFI main relay, connecting the ign. power to the pump and batt power to the ECU directly, and the problem will not reset with a toggle of the kill switch. As the ECU would remain energized at all times in this configuration, I believe it to be resulting from a sensor energized via the ECU.

We can't make this occur in the paddock, garage, or on the midway at sebring (shhh). We can do it driving like an ass in a parking lot and at CFRC.

ideas? thanks for any help!

Have you checked fuel pressure when the motor falls off?

Almost sounds like a fuel pickup issue or a return line issue.

fuel pressure is good.

Check your kill switch. These can go bad and cause a similar problem. Search for Jay Griffin's HP Runoffs video to see the sympton (car dies, comes back to life after cycling kill switch)

Also check your grounds. I had a similar problem that would cause the engine to die in left hand corners that I thought was fuel related, and spent a lot of time checking the pick-up, baffles, surge tank, etc. Turned out to be a loose engine ground that would only act up when the motor mounts flexed during left hand turns.

Limp home mode? Chuck

That sounds like a ground issue to me. I'd check yours and just add a bunch. They don't hurt.

Quote:

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Originally Posted by chuck baader

Limp home mode? Chuck

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most definately - but why??

I'm headed out to CFRC again wed with the S300 dataloging ECU from our FP car to see if I can identify anything.

I'll add a few grounds too. Thanks - see you at Savannah (don't pass me on the outside unless I get this fixed!!:blink:)

Something is out of spec. Maybe the O2 sensor...is the ECU looking for a narrow band and the OBD2 system use a wide band? Something as simple as that? Chuck

Sounds like it is going into a CAT protect mode. That is it starts leaning the fuel back at WOT to avoid burning the CAT out. Quite common practice, and another reason to do standalone.

You got my phone number? If not get it from David. I think I could get you some time at the office.

Thanks Derek. - I appreciate the offer to maybe use "the office."
Thinking about the problem a bit more - looking for previous experiences that are similar, the best parallel I have is in my first MR2 - the TPS wiring fell off of the sensor and hanged low and to the rear of the engine room. I was young and it ran fine so I hadn't noticed. once driving in the rain the car slowed and spurted only to 3-4k then dropped to something ~1k and allowed itself to rev to 3-4k again. horribly rough while doing so. suddenly cleared up after a short idle rest. the 2 systems couldn't be much more different, and all of my sensors are attacked, acting as described in the troubleshooting guides of the FSM, and have been dry.

do 92-95 hondas have this cat-protect mode? from what I understand they run open-loop over ~4k at >50% or so throttle. - I checked the PNs for the O2 and the ECU-era (OBD1 - single O2) unit matches the car-era (OBD2) downstream piece, while the OBD2 upstream (the one we are using) is a separate number. worth looking into?

Since we are using the "downstream" O2 sensor as an "upstream" O2 sensor I guess there could be a problem there, but wha tis the difference? However I still don't see why it would be intermitent. I hope we learn alot from the logged data. This is getting annoying. It would be nice to have two strong running cars at savanna.

Re-reading this, it looks like limp mode for a lost sensor. Are you sure it is not throwing a code even though the light is off?

Wouldn't limpmode just cause it to run poorly not cut off and cause the idle to jump from 1k to 3-4k and back again?

Since you guys are running an OBD1 P28 ECU, I'm assuming that you're then tuning it with something (otherwise what's the point?). If so, what are you tuning with? Some software's can actually mask problems/codes from ever being displayed.

Kevin- We have been using Hondata S300 in the FP car, but using stock P28 for the moment in the ITA car (car in question). Eventually it will also be an S300 or a Moates Demon or simply chipped. We run it because OBD2 is a huge PITA with all of the emissions system verifications (both O2 heaters, cats, tank evap, etc.) and because we can eventually chip it. For the S300 we tune with sManager, for Moates-type we use Chrome.

Derek - no evidence of codes. we have gotten CELs for various problems, usually self-induced, but never when the power problem happens. unfortunately the "clearing" method of toggling the power switch kills what codes we might have had. agreed on the dropped sensor or anomolous signal but when sensors drop it tends to run pretty well, considering. we have unplugged and run without just about every sensor to check that. only MAP was a real drivability / idle issue - so a new sensor is installed there, wires look OK ECU-Sensor.

Stock P28 in limp mode would limit rpms to 3500.

Soft error mode like no VSS signal or VTEC pressure switch, rpms would be limited to 6800.

Has it ever ran right with the P28 in the car? Could just be a bad ECU.

Talked with some of the guys. The Honda strategy for limp mode is to pull timing (retard timing) and dump fuel. That alone will cause some rough idling. As for the check engine lights, seems Honda takes the we only throw it when the extreme situations.

Not know some of the exact specifics some of the suggestions:


Have you mad sure all of the harness connectors are in the right plugs (some of the sensors have similar connections)?

Have you run it with an ODB2 ecu? This would eliminate the adapter harness. From what I have seen of the adapter harness and heard from other people as they can cause problems.

Are there any sensors or controls that change in the OBDI to OBDII model crossover (someone thought the injectors changed)?

Is the only time it is happening is during a heavy load scenario?

Is it only happening during engine movement thus harness movement?

Couple of the guys would love to see the car and help out with it. Let me know.

Derek

D- Got your number from DL late last night, will call today. We'd love the help!

went through and replaced all of the sensors of note + dicsonnected the power steering pressure sensor wich is not used by the P28 but shares power with other sensors.

OBDI - OBDII map/TPS are the same internally if not externally. put the ECU-year O2 in, we'll see if that helps. Injectors are different plugs, but still 240cc. this is a very common ECU swap and no one on the honda fora recomends any sensor changes so none of this seems too bad. all we had to do to change from OBD0 to 1 on the FP car was use an OBD1 distributor, which isn't an issue here.

bonespec - thanks, that about sums up the issue. at least now we no that it is in limp for sure. why no light???

Kevin - 3 P28s, 1 P06 (slow AND still troublesome), and a P72 all error out. I'll be flogging the car with the S300 (dataloging, tunable) in it tonight at the CFRC to see if I can see what sensor is droppingout if the problem persists. I have the stock P28 to use if the problem goes away as a sanity check.

if the hondata fixes it, we will swap the S300 from FP to ITA with a calibration change between sessions this weekend.

thanks all for your help, will update tonight.

I sure hope we find something.. I would hate for everything to work fine at CFRC then start acting up at RRR. I am staring to belive that it is going into limp mode in conjunction with the orignal error, since you can't control engine RPM at all untill the problem clears itself which you normally should be able to do with in "normal" limp mode correct? So engine cuts our from what ever casue that causes the car to run irradically and idle surging between 1000 rpm up untill the limp mode 3500 limit.

Well... I went to CFRC and flogged on the car yesterday - using the Hondata S300 there were no issues. technically this ECU belongs to the FP car, but we will be sharing it for the weekend and getting another very soon.

As a sanity check, I ran the stock P28 again with the same results that have plagued us since the start. whatever the "problem" is, it appears to be with the programming of the factory ECUs, and whatever Hondata changed works for me.

Thanks for all the help, see you at Roebling!!!!