Are you an expert? I've got a good one for you!
06-23-02, 03:19 PM
#1
Are you an expert? I've got a good one for you!
93 Base model, 5spd, all stock.
Here are the symptoms.
Rev to 4500 rpm and it gets a HUGE stumble. This will happen while parked (running with clutch in or in neutral) or while under boost or part throttle on the road. It doesn't want to pass 4500rpm, it will stumble through in 1st or 2nd gear and after abou 6000-6500 rpm it will clear out and run smooth to redline. In 3rd gear or higher the car doesn't have enough power to accelerate through the rough spot and will stay at 4500rpm. This is independent of throttle position, WOT, or very slight throttle, it will not rev smoothly past 4500rpm.
When I got the car the check engine light didn't work, fixed it (replaced bulb) and I got two codes. Code 13 for the pressure sensor and another one for the EGR. I fixed the EGR code (broken wire) and ran through the procedure listed in the manual for the Pressure sensor. Everything checked out OK. Took the car for a drive and I still have the same problem, but now the check engine light doesn't stay on, it flashes when the engine stumbles. I also swapped out the pressure sensor for a known good one and I get the same problem. I swapped out the ECU for a known good one and I also still get the same problem.
Checking the codes by jumping the GRD and the TEN pin turns up nothing. How do I capture the code when the check engine light flashes?
Any ideas?
Thanks,
Jeff
Here are the symptoms.
Rev to 4500 rpm and it gets a HUGE stumble. This will happen while parked (running with clutch in or in neutral) or while under boost or part throttle on the road. It doesn't want to pass 4500rpm, it will stumble through in 1st or 2nd gear and after abou 6000-6500 rpm it will clear out and run smooth to redline. In 3rd gear or higher the car doesn't have enough power to accelerate through the rough spot and will stay at 4500rpm. This is independent of throttle position, WOT, or very slight throttle, it will not rev smoothly past 4500rpm.
When I got the car the check engine light didn't work, fixed it (replaced bulb) and I got two codes. Code 13 for the pressure sensor and another one for the EGR. I fixed the EGR code (broken wire) and ran through the procedure listed in the manual for the Pressure sensor. Everything checked out OK. Took the car for a drive and I still have the same problem, but now the check engine light doesn't stay on, it flashes when the engine stumbles. I also swapped out the pressure sensor for a known good one and I get the same problem. I swapped out the ECU for a known good one and I also still get the same problem.
Checking the codes by jumping the GRD and the TEN pin turns up nothing. How do I capture the code when the check engine light flashes?
Any ideas?
Thanks,
Jeff
06-23-02, 04:26 PM
#2
Hamado things my way!
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I'm not an expert, but make sure you have good plugs in the engine. Also, buy a boost gauge(it can be a $20 auto parts type) and see how much boost you are getting. This might help in the diagnosing. If you know anyone who has a power FC ask if you can borrow it. Plug it into your car, and watch the sensor outputs in the "etc." mode. My car was having problems with severe jerking and hesitation while the check engine light flickered on and off. I plugged up a PFC and found out that the ECU was resetting itself from an electrical short.
06-23-02, 04:46 PM
#3
Thanks for the reply. The electrical short is an interesting idea. Was your hesistation happening at different RPM or the same RPM consistantly?
The car has a boost guage but I don't think boost is the issue here since it will stumble while in the driveway
.
Plugs and wires were installed in January, 3K miles on them since. Again I don't think that is the problem since it stumbles off boost at exactly 4500rpm.
This isn't a slight miss, it is a huge stumble. It isn't fuel cut because there is no boost while it is in the driveway.
Thanks,
Jeff
The car has a boost guage but I don't think boost is the issue here since it will stumble while in the driveway
.Plugs and wires were installed in January, 3K miles on them since. Again I don't think that is the problem since it stumbles off boost at exactly 4500rpm.
This isn't a slight miss, it is a huge stumble. It isn't fuel cut because there is no boost while it is in the driveway
.Thanks,
Jeff
06-23-02, 05:00 PM
#4
Hamado things my way!
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My car would buck at any rpm and just about jerk your teeth out. I ended up replacing the main engine wiring harness, the ignition wiring harness, and the harness going from the battery to the starter. I'm not sure where the short was, because once I got the old harness out I could see wiring insulation cracked off and missing all over the place. You can do a search to find out all of the details.
As far as yours goes I would look into what electrical things change at 4,500. Since it's happening in neutral I wouldn't think it to be related to the turbo control systems. I'm not home, so I can't check my service manual, but if you have one (if you don't then download one from www.iluvmyrx7.com) look towards the end of section F (I think). It's the fuel and something section. They have a table of what happens at different rpm.
As far as yours goes I would look into what electrical things change at 4,500. Since it's happening in neutral I wouldn't think it to be related to the turbo control systems. I'm not home, so I can't check my service manual, but if you have one (if you don't then download one from www.iluvmyrx7.com) look towards the end of section F (I think). It's the fuel and something section. They have a table of what happens at different rpm.
06-23-02, 05:59 PM
#5
Big Snail
Have you tried...?
Hey bro have you tried resetting your ECU...? Just unplug your negative cable from your battery and depress the brake pedal 6 times and leave the cable disconnected for a few minutes. Then reconnect and restart. One note when you disconnect the negative cable you will loose memory from your car stereo head unit. Hope this helps if not its a start ....Tony
06-23-02, 07:27 PM
#6
Hey Gordon,
It stumbles from 4.5K to 6-6.5K rpms. After that it clears up and goes to redline just fine.
I checked the coils connections and checked for "oozing", they look good.
I'm thinking it isn't a boost problem since it will occur in the driveway under no load. I don't think the engine is really getting any extra air, the second turbo shouldn't come on under no load should it?
Sorry, I don't live near you, actually I can't get much farther away, I'm in Oregon.
I've reset the ECU, I also tested another known good ECU.
Thanks,
Jeff
It stumbles from 4.5K to 6-6.5K rpms. After that it clears up and goes to redline just fine.
I checked the coils connections and checked for "oozing", they look good.
I'm thinking it isn't a boost problem since it will occur in the driveway under no load. I don't think the engine is really getting any extra air, the second turbo shouldn't come on under no load should it?
Sorry, I don't live near you, actually I can't get much farther away
, I'm in Oregon.I've reset the ECU, I also tested another known good ECU.
Thanks,
Jeff
Originally posted by gmonsen
first, if it stumbles at 4500 and then at 5000 is pulling strongly, it is probably notan ignition-related problem. if it is stumbling and stuttering all the way up, then you need to check the plugs. if you are running very rich, they will be very black and wet from gas. make sure that there is "clean metal" between the electrode and the housing.
physically check your coils to see that the connections are solid and that there is no dark oily substance oozing from the coils. also, check that you are getting good spark.
those are the easy things. it is interesting that you are getting a stumble at 4500 rpm, since that is approximately where the second turbo comes on. if you get the stumble there and it goes away, there could be something wrong with the actuator that brings the second turbo online. that's why i asked if the problem occurs and goes away. if it is related to the second turbo, it could also be that the map is rich and you aren't getting enough spark energy, so the huge amount of air that is all of a sudden going through the motor isn't getting enough fuel or is getting too much fuel. stumbles due to air fuel problems can be due to either of these.
go to any good dyno shop in your area (call first to be sure they have a wideband a/f meter) and have them plug in a wideband heated o2 sensor where the stock one goes and then they'll plug that into a meter and read it while you goose the throttle. (might as well do a few pulls at the same time.) i say this rather than plugging it into a power fc, because that doesn't have a wideband capability. a narrow band is only going to maybe give you a clue. this is the right way to do this. (if you live near me in bethlehem pa i can do this for you at my house.)
-gordon
first, if it stumbles at 4500 and then at 5000 is pulling strongly, it is probably notan ignition-related problem. if it is stumbling and stuttering all the way up, then you need to check the plugs. if you are running very rich, they will be very black and wet from gas. make sure that there is "clean metal" between the electrode and the housing.
physically check your coils to see that the connections are solid and that there is no dark oily substance oozing from the coils. also, check that you are getting good spark.
those are the easy things. it is interesting that you are getting a stumble at 4500 rpm, since that is approximately where the second turbo comes on. if you get the stumble there and it goes away, there could be something wrong with the actuator that brings the second turbo online. that's why i asked if the problem occurs and goes away. if it is related to the second turbo, it could also be that the map is rich and you aren't getting enough spark energy, so the huge amount of air that is all of a sudden going through the motor isn't getting enough fuel or is getting too much fuel. stumbles due to air fuel problems can be due to either of these.
go to any good dyno shop in your area (call first to be sure they have a wideband a/f meter) and have them plug in a wideband heated o2 sensor where the stock one goes and then they'll plug that into a meter and read it while you goose the throttle. (might as well do a few pulls at the same time.) i say this rather than plugging it into a power fc, because that doesn't have a wideband capability. a narrow band is only going to maybe give you a clue. this is the right way to do this. (if you live near me in bethlehem pa i can do this for you at my house.)
-gordon
06-23-02, 09:42 PM
#7
Hamado things my way!
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Hey Gordon, I think he's completely stock. Also, when in neutral the secondary turbo will not come on at all, and when in gear it needs at least 7psi to switchover. It would be a very good idea to just go ahead and put some new plugs in, just to start with.
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06-23-02, 10:30 PM
#8
Originally posted by gmonsen
first, do you have any intake or exhaust related mods? like an intake or downpipe or even a very high flow catback that would change the air flow a lot?
second, have you done anything to the ecu or any other control related mods?
thanks, gordon
first, do you have any intake or exhaust related mods? like an intake or downpipe or even a very high flow catback that would change the air flow a lot?
second, have you done anything to the ecu or any other control related mods?
thanks, gordon
I re-tested the voltage at the Pressure sender per the Factory manual page F-33 (since originally there was a code for this).
I think the manual is mislabeled. It says to check the continuity between pressure sensor and terminal (BR/B) and ECU terminal 4D. Well there is no BR/B wire (brown/black) wire on the pressure sender but wire 4D at the ECU is BR/B. One wire on the pressure sender connector (BR/W) gives a reading of 800 ohms measured against 4D (BR/B).
Tested another known good FD on the same connection and I get 451 ohms. Almost 2X.
Jeff
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