ECU/Fuel/(A/F) Problems
06-27-04, 02:12 AM
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ECU/Fuel/(A/F) Problems
I hate cross posting, but my thread in the advanced tech section isn't getting any love, so I figured I'd get some more traffic to it. The problem is getting worse and I need to see if I can figure it out before too long:
https://www.rx7club.com/showthread.p...hreadid=321226
Blake
https://www.rx7club.com/showthread.p...hreadid=321226
Blake
06-27-04, 02:18 AM
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Text of post:
*edit*Turns out to be longer than I thought, but I'm trying to make sure I provide as much info as I can.*edit*
So hears the deal...No shop can pinpoint whats going on with my car, and its running like crap. I need to figure out what I should check before having to fork out some money.
Symptoms:
Off idle, from a stop sign/light, etc, I'll be in first gear, have the car revved to right around 2k rpms, and slowly let the clutch out (ala normal driving). As I let the clutch out, the rpms, of course, start to fall as they should for a fraction of a second, then they fall to idle and the car almost dies if I don't get to the clutch in time. Then after putting the clutch in, I'll try it again, and sometimes it'll repeat, other times its just fine. Sometimes if I short shift into second gear after it happens into first, same thing happens, but not as bad.
Then today, while at a stop light, I notice the idle RPMs fall, and the car almost dies, so instinctively (the tranny is in neutral) I push the clutch in and RPMs return to normal. I assume that helped by taking the extra load cause by the half of the tranny connected to the engine via the clutch/flywheel off the engine.
And yet again, a while later, on my way back home, the same thing happened at a stoplight, only I put in the clutch, and the RPMs STILL kept falling and the car almost died. So I kept it revved up by tapping the accelerator. Each time I did, it would backfire repeatedly.
Thats the worst thats happened. I of course have the 3k RPM hesitation. Then other seemingly unrelated problems include letting out a bit of brown smoke right before shifting when doing a full throttle run, and then white smoke at startup.
And last, a one off incident, when running around 14 lbs of boost while trying to dial in my boost controller, we did a partial throttle run that still got into boost. Then the next full throttle run, brown smoke billowed out the tail pipe (solid plume, enough to not see the car behind us through it). Never happened again though.
Seems to not do it as much in hot weather, but if it gets cooler or a lot more humid it seems to do it a lot more.
Mods are: streetport, full exhaust, intake, boost controller set to ~14 lbs, Crane HI-6 ignition, Competition fuel pump, SX FPR, set 1:1, and running about 32 lbs. (or whatever its measured in) around idle. What I think is the culprit is this: non-sequential twins, with XS Engineering ECU, which was reprogrammed a long time ago, for the seq. setup and mods I assume. I get a EGR code periodically, on a non-cali '93 year car, so we're pretty sure they did a core exchange and sent back a Cali ecu.
My first thought is its running really rich all around, since its programmed for seq. twins, and the boost doesn't come in nearly as early. And after the incident today with it almost dieing then backfiring when keeping the revs up, leads me to believe its running really rich at idle.
So is there anything I should check before I go get a PowerFC? I'll probably put it on the dyno in the next couple of weeks to get the a/f readings and see if that shows anything funny.
Blake
*edit*Turns out to be longer than I thought, but I'm trying to make sure I provide as much info as I can.*edit*
So hears the deal...No shop can pinpoint whats going on with my car, and its running like crap. I need to figure out what I should check before having to fork out some money.
Symptoms:
Off idle, from a stop sign/light, etc, I'll be in first gear, have the car revved to right around 2k rpms, and slowly let the clutch out (ala normal driving). As I let the clutch out, the rpms, of course, start to fall as they should for a fraction of a second, then they fall to idle and the car almost dies if I don't get to the clutch in time. Then after putting the clutch in, I'll try it again, and sometimes it'll repeat, other times its just fine. Sometimes if I short shift into second gear after it happens into first, same thing happens, but not as bad.
Then today, while at a stop light, I notice the idle RPMs fall, and the car almost dies, so instinctively (the tranny is in neutral) I push the clutch in and RPMs return to normal. I assume that helped by taking the extra load cause by the half of the tranny connected to the engine via the clutch/flywheel off the engine.
And yet again, a while later, on my way back home, the same thing happened at a stoplight, only I put in the clutch, and the RPMs STILL kept falling and the car almost died. So I kept it revved up by tapping the accelerator. Each time I did, it would backfire repeatedly.
Thats the worst thats happened. I of course have the 3k RPM hesitation. Then other seemingly unrelated problems include letting out a bit of brown smoke right before shifting when doing a full throttle run, and then white smoke at startup.
And last, a one off incident, when running around 14 lbs of boost while trying to dial in my boost controller, we did a partial throttle run that still got into boost. Then the next full throttle run, brown smoke billowed out the tail pipe (solid plume, enough to not see the car behind us through it). Never happened again though.
Seems to not do it as much in hot weather, but if it gets cooler or a lot more humid it seems to do it a lot more.
Mods are: streetport, full exhaust, intake, boost controller set to ~14 lbs, Crane HI-6 ignition, Competition fuel pump, SX FPR, set 1:1, and running about 32 lbs. (or whatever its measured in) around idle. What I think is the culprit is this: non-sequential twins, with XS Engineering ECU, which was reprogrammed a long time ago, for the seq. setup and mods I assume. I get a EGR code periodically, on a non-cali '93 year car, so we're pretty sure they did a core exchange and sent back a Cali ecu.
My first thought is its running really rich all around, since its programmed for seq. twins, and the boost doesn't come in nearly as early. And after the incident today with it almost dieing then backfiring when keeping the revs up, leads me to believe its running really rich at idle.
So is there anything I should check before I go get a PowerFC? I'll probably put it on the dyno in the next couple of weeks to get the a/f readings and see if that shows anything funny.
Blake
06-27-04, 02:19 AM
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Oh, and when driving and having the throttle on, but no load (I.E. cruising down the highway or trying to keep a constant speed, and at the same time having no load on the engine) it starts to kinda buck. Essentially losing power, getting power, etc. Usually its just audible, but rarely you can actually feel it.
06-30-04, 12:10 AM
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Man i used to own a probe that ran like **** just about like that. I know that its a probe and all but the engine did the same thing. Now im not sure what was all done because my grandpa fixed it (hes been a mechanic for over 30 years so he knows a lot) he replaced spark plugs and wire for sure and i dont know what else but i suppose i could find out for ya
Justin
Justin
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06-30-04, 03:36 PM
#10
Originally posted by infinitebass
Hrm, thats a good idea. Do I unplug from under the car at the O2 sensor itself?
Blake
Hrm, thats a good idea. Do I unplug from under the car at the O2 sensor itself?
Blake
06-30-04, 04:31 PM
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Ok, I'll check it out. If the problem stops, what does that indicate? Bad O2 sensor?
Would I expect any other problems to pop up with the sensor disconnected?
Blake
Would I expect any other problems to pop up with the sensor disconnected?
Blake
06-30-04, 04:56 PM
#12
It would indicate a bad O2 sensor and/or a bad ground circuit associated with it. I ran for a couple of years with mine disconnected with no terribly ill effects. If it does solve or reduce the problem, get a new sensor and add a heafty ground strap to the downpipe.
06-30-04, 11:47 PM
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jxy, I know that needs to be done, but since this is an issue that is progressively getting worse, I don't think thats the main cause. I'll get that taken care of, but I need to know what this problem is first.
Blake
Blake
07-01-04, 06:45 PM
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So I disconnected the O2 sensor...
In response to suggestions for this problem:
https://www.rx7club.com/showthread.p...hreadid=321545
And I had some interesting results. First, with the limited driving time I put on it, none of the problems with idle and almost dying when starting from a stop happened. Its promising, not conclusive since it wasn't that much driving. Gonna try when it cools down this evening and see if that'll cause the problem again.
Next, after driving slowly around my apartments, I stopped in my parking spot, and noticed a lot of white smoke coming out (Not a lot, but similar to when it starts up, which is unusual unless the car is cold). Not sure if this is a side effect of having the sensor disconnected.
The third, and most interesting result, which again, is not conclusive due to low drive time: No 3k RPM hesitation.
I've read a bit on the 3k RPM hesitation, and no one mentioned that it goes away with the O2 sensor disconnected. Anyone else experience this? If so, is there a reason why it would have this effect?
Blake
https://www.rx7club.com/showthread.p...hreadid=321545
And I had some interesting results. First, with the limited driving time I put on it, none of the problems with idle and almost dying when starting from a stop happened. Its promising, not conclusive since it wasn't that much driving. Gonna try when it cools down this evening and see if that'll cause the problem again.
Next, after driving slowly around my apartments, I stopped in my parking spot, and noticed a lot of white smoke coming out (Not a lot, but similar to when it starts up, which is unusual unless the car is cold). Not sure if this is a side effect of having the sensor disconnected.
The third, and most interesting result, which again, is not conclusive due to low drive time: No 3k RPM hesitation.
I've read a bit on the 3k RPM hesitation, and no one mentioned that it goes away with the O2 sensor disconnected. Anyone else experience this? If so, is there a reason why it would have this effect?
Blake
07-02-04, 12:19 AM
#17
yeah, only one wire. The connector is near where the UIM bends down towards the LIM, on the firewall side.
I'm curious to see if that works. My car used to do that, altough not nearly to the degree that you describe, and just by unplugging the O2 sensor it made a night and day difference.
I'm curious to see if that works. My car used to do that, altough not nearly to the degree that you describe, and just by unplugging the O2 sensor it made a night and day difference.
07-02-04, 05:07 PM
#23
Re: So I disconnected the O2 sensor...
Originally posted by infinitebass
In response to suggestions for this problem:
https://www.rx7club.com/showthread.p...hreadid=321545
And I had some interesting results. First, with the limited driving time I put on it, none of the problems with idle and almost dying when starting from a stop happened. Its promising, not conclusive since it wasn't that much driving. Gonna try when it cools down this evening and see if that'll cause the problem again.
Next, after driving slowly around my apartments, I stopped in my parking spot, and noticed a lot of white smoke coming out (Not a lot, but similar to when it starts up, which is unusual unless the car is cold). Not sure if this is a side effect of having the sensor disconnected.
The third, and most interesting result, which again, is not conclusive due to low drive time: No 3k RPM hesitation.
I've read a bit on the 3k RPM hesitation, and no one mentioned that it goes away with the O2 sensor disconnected. Anyone else experience this? If so, is there a reason why it would have this effect?
Blake
In response to suggestions for this problem:
https://www.rx7club.com/showthread.p...hreadid=321545
And I had some interesting results. First, with the limited driving time I put on it, none of the problems with idle and almost dying when starting from a stop happened. Its promising, not conclusive since it wasn't that much driving. Gonna try when it cools down this evening and see if that'll cause the problem again.
Next, after driving slowly around my apartments, I stopped in my parking spot, and noticed a lot of white smoke coming out (Not a lot, but similar to when it starts up, which is unusual unless the car is cold). Not sure if this is a side effect of having the sensor disconnected.
The third, and most interesting result, which again, is not conclusive due to low drive time: No 3k RPM hesitation.
I've read a bit on the 3k RPM hesitation, and no one mentioned that it goes away with the O2 sensor disconnected. Anyone else experience this? If so, is there a reason why it would have this effect?
Blake
The white smoke is likely a coolant seal starting to go...sorry to be the bearer of bad news, but that is the most likely cause. Does it smell sweet?
Now for the O2 sensor...
Originally posted by ISUposs
If it does solve or reduce the problem, get a new sensor and add a heafty ground strap to the downpipe.
If it does solve or reduce the problem, get a new sensor and add a heafty ground strap to the downpipe.
I connected my ground from the UIM grounding point to the portion of the DP that connects to the trans. You could also connect it to the midpipe/cat flange.
I suspect that the computer is not seeing an accurate voltage from the O2 sensor, therefore it keeps adjusting the fuel incorrectly and that's why it runs crappy.
Last edited by ISUposs; 07-02-04 at 05:22 PM.
07-02-04, 05:21 PM
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I'm pretty sure the smoke is fuel, its done that since the engine was rebuilt. Again, usually just on startup.
Now when I started it today, it barely ran for a few seconds, then started to die. When I revved it up, it seemed unresponsive, again like it was running really rich. I'll go play around a bit more and connect the O2 sensor back up. And I know the white smoke this time was fuel. One sniff and it was obvious.
What exactly did you use to ground it?
Blake
Now when I started it today, it barely ran for a few seconds, then started to die. When I revved it up, it seemed unresponsive, again like it was running really rich. I'll go play around a bit more and connect the O2 sensor back up. And I know the white smoke this time was fuel. One sniff and it was obvious.
What exactly did you use to ground it?
Blake