Safety Mode on Cool down lap

benspeed

benspeed

New member
I had a weird deal up at NHIS. After a good race the car went into safety mode or limp mode during the cool down lap. That had happened at VIR also and the problem deteriorated so that the car went into limp mode after 7 laps or so at VIR. Then it wouldn't run for sh*t. My shop diagnosed a broken wires on mass air flow sensor. Fixed that and car was good.

At NHIS the car ran great during the 2 qualifying sessions and race. Then - same deal, limp mode and check engine light on during cool down lap. Runs perfect now and no check engine light. Ran the car hard in the driveway and had to shut it down when water got to 190F. Haven't bothered to look for codes because the car runs awesome and no check light. Can't wait to race at LRP in about a week - but nervous this probelm will reappear at a bad time - like with 2 to go and a podium finish in hand (got to think aggressive).
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Any suggestions? I have a spare oil metering pump. If this is the problem - how tough is it to swap the OMP out at the track?

Do other cars seem to have some funkiness on cool down after being run hard? Temps and pressure were on the money.



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BenSpeed
#33 ITS RX7
BigSpeed Racing
NNJR BoD - Treasurer
[email protected]
NNJR
 
Not certain what things on your car can send it into limp mode...but:

My Honda Civic has gone into limp mode during a cool down period after some spirited driving. Code came back as low oil pressure at VTEC sensor or something like that...

Turned out that at speed oil pressure is good (rpms up) and oil level is fine (despite moderate g's). During the cool down lap rpms are down, but still high enough on the HX model to trigger the VTEC (3000 rpms). While the engine is just cruising around "cooling down" at 3500-4000rpms the oil is hot and pressure is lower while we are still going around the track at a little higher speed than the engineers who wrote the programs anticipated as being likely.

My solution was to a)make sure there was enough oil in the pan b)while cooling down keep the rpms in corners low enough to not trigger the VTEC.
 
Thanks - that might explain why some folks have suggested an oil metering pump issue. During the qualifying runs, I didn't really back it down much until pit which might be why it only occured after the race. At VIR, I backed it down each time and that's when the issue surfaced.
 
An OMP fault is the only thing that will send the car into limp mode. I've also been told that once a pump goes bad it can take the ECU out with it. I also have a sporadic problem. After swapping three ECUs with the same apparently bad pump (and probably screwing up the ECUs in the process) I just learned to live with it. When the car goes into limp mode a quick off/on of the master switch clears the condition and it's off to the races.
 
I have had the oil metering pump problem a few years ago also. The switch off then back on did not always clear it. Sometimes it had to cool off awhile before it would run again. Its a pain in the butt until you change out the pump. I just started experiencing it again in February. I had a spare installed last week. I'll know next weekend if the spare is any good. You really need to check the codes after an issue or you just won't know what caused it and you are taking a chance that the problem will come back again at an inconvenient time.

Just what kind of signal is the oil metering pump putting out? Is it a pulse? Does the ECU do anything proportionally to the change in signal? Or is it a go, no go type of indication? I'd like to find a way to duplicate the signal because the pump still works but the darn ECU thinks the pump is faulty when the pump sensor starts to mess up the signal.
 
Well - good news. Ran the car very hard during a test and tune at LimeRock and no issues. Might have been backing the car down too slow during cool down and making it go funky. That's the only circumstance that created the issue.

Chris - thanks for the quick on-off trick and I'll keep that in the hip pocket if it makes trouble again.

"Riding with a spare OMP" Cheers
 
Chris - the "quick on/off trick" saved me a podium finish in the race at Pocono this weekdend - Mucho thanks for the tip!

On two laps, one being the final lap of the race, the car went into limp mode after slowing down for a second gear chicane. Lost power, saw my check engine light go on and did the on/off. Regained power immediately and finished third!

Thanks dude!

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BenSpeed
#33 ITS RX7
BigSpeed Racing
NNJR BoD - Treasurer
[email protected]
NNJR
 
Originally posted by Mike Guenther:
Just what kind of signal is the oil metering pump putting out? Is it a pulse? Does the ECU do anything proportionally to the change in signal? Or is it a go, no go type of indication? I'd like to find a way to duplicate the signal because the pump still works but the darn ECU thinks the pump is faulty when the pump sensor starts to mess up the signal.
Click to expand...

There is a variable resistor with a plunger on the end that rides up and down on the metering piston in the pump. The ECU for a constantly varying signal from the pump that is proportional to the TPS and MAP sensors. More load and more throttle angle should equal more oil. If it doesn't you get limp mode. It's kind of like a downstream O2 sensor. You can't just plug in a single value resistor and make it go away. The computer needs to see a complex variable voltage signal. The pump is shimmed so that the plunger depth is accurately set. The current pump in my car was reshimmed with output values measured under load to confirm proper setup....and it STILL gives me fits.

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Chris Ludwig
08 ITS RX7 CenDiv
 
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