HELP: Fuel cut out between 1500-3000 rpm but not when TPS is disconnected.
08-23-2005, 03:36 AM
#1
Burning Brakes
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HELP: Fuel cut out between 1500-3000 rpm but not when TPS is disconnected.
Sorry in advance for being long winded, but I could really use some help.
My car is having the weirdest problem and I hope someone can help. Basically there is no fuel between 1500 and 3000 rpm. Below 1500 and above 3000 everything is perfectly fine. But as you might imagine it is VERY difficult to drive without any use of the 1500-3000 rpm band.
The strangest part is that if I disconnect the TPS connector then none of these problems are experienced at all. The car actually drive 90% fine like this. However the Air Fuel Ratio’s are not quite right as can be imagined as the DME does not know what the throttle position is.
There are basically two different symptoms:
1) When driving in any gear the car drives fine from idle to 1500 rpm no matter what the throttle position. As soon as the car hits 1500 rpm while driving it feels like all fuel is cut and the WB02 shows full lean. Once the car goes below 1500 rpm fuel comes back and the car runs fine until it goes above 1500 rpm at which time fuel is cut again. It basically feels like the overboost protection is kicking in but of course it is not because there is no boost at 1500 rpm.
It gets stranger though. If I force the car to go above 3000 rpm by coasting down a hill with the clutch in or by revving above 3000rpm with the clutch in(which can be done as describe in symptom 2) and then dropping the clutch and letting the tires spin then the car is FINE as long as I keep it above 3000 rpm. I can get full boost and run through all the gears but if I let the rpm’s get below 3000 rpm then all fuel is cut until I drop below 1500 rpm at which time fuel comes back.
2) While idling in neutral I can rev the car fine through all rpms so long as my throttle position does not go above 56 as indicated by my WB02. If I try to use a throttle above 56 below 3000rpm the engine revs to 2300ish rpm and then cuts fuel to 1500rpm then revs back to 2300ish and continues to cycle but will not go above 2300ish rpm. If I use a lower throttle position such as 40 and rev the engine above 3000 rpm then I can use above 56 no problem as long as I don’t let it fall below 3000 rpm.
As listed in my Signature I do have a Link MAP kit and everything was running just fine for the past week or so. Yesterday I started having this problem intermittently and now it happening constantly.
Sorry for being so long winded but I have been troubleshooting this for the past 8 hours and I am completely out of ideas. Any help is much appreciated.
Thanks a million,
John
My car is having the weirdest problem and I hope someone can help. Basically there is no fuel between 1500 and 3000 rpm. Below 1500 and above 3000 everything is perfectly fine. But as you might imagine it is VERY difficult to drive without any use of the 1500-3000 rpm band.
The strangest part is that if I disconnect the TPS connector then none of these problems are experienced at all. The car actually drive 90% fine like this. However the Air Fuel Ratio’s are not quite right as can be imagined as the DME does not know what the throttle position is.
There are basically two different symptoms:
1) When driving in any gear the car drives fine from idle to 1500 rpm no matter what the throttle position. As soon as the car hits 1500 rpm while driving it feels like all fuel is cut and the WB02 shows full lean. Once the car goes below 1500 rpm fuel comes back and the car runs fine until it goes above 1500 rpm at which time fuel is cut again. It basically feels like the overboost protection is kicking in but of course it is not because there is no boost at 1500 rpm.
It gets stranger though. If I force the car to go above 3000 rpm by coasting down a hill with the clutch in or by revving above 3000rpm with the clutch in(which can be done as describe in symptom 2) and then dropping the clutch and letting the tires spin then the car is FINE as long as I keep it above 3000 rpm. I can get full boost and run through all the gears but if I let the rpm’s get below 3000 rpm then all fuel is cut until I drop below 1500 rpm at which time fuel comes back.
2) While idling in neutral I can rev the car fine through all rpms so long as my throttle position does not go above 56 as indicated by my WB02. If I try to use a throttle above 56 below 3000rpm the engine revs to 2300ish rpm and then cuts fuel to 1500rpm then revs back to 2300ish and continues to cycle but will not go above 2300ish rpm. If I use a lower throttle position such as 40 and rev the engine above 3000 rpm then I can use above 56 no problem as long as I don’t let it fall below 3000 rpm.
As listed in my Signature I do have a Link MAP kit and everything was running just fine for the past week or so. Yesterday I started having this problem intermittently and now it happening constantly.
Sorry for being so long winded but I have been troubleshooting this for the past 8 hours and I am completely out of ideas. Any help is much appreciated.
Thanks a million,
John
08-23-2005, 04:24 AM
#3
Burning Brakes
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Well first of all thanks for the reply, and yes sir, you are correct that I had pretty much ruled out the TPS. The reason I think that it is ok, is that I am datalogging the TPS signal from the KLR's harness with my WB02. As I move the throttle up and down I can see that the TPS reading is still accurate with respect to the pedals movement. You do have me thinking though. I know that the TPS has like 5 or so wires that come out of it, so maybe it does some other things than just the signal the KLR receives. Hmmmmmm. Any ideas?
Or any other ideas, my brains all used up.
Thanks,
John
Or any other ideas, my brains all used up.
Thanks,
John
Last edited by johne; 08-23-2005 at 04:46 AM.
08-23-2005, 07:39 AM
#4
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It's the TPS. You are logging the throttle angle part of the TPS but not the idle contacts. The TPS idle contacts are shorted and telling the DME you are idling and will only supply enough fuel for that condition.
08-23-2005, 01:49 PM
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When the DME receives an idle signal from the TPS it will activate fuel cut above 1200 rpm. Edit, I think the correct number is 1560 rpm instead and it will be higher than that when the engine is cold.
Check the TPS idle switch.
Check the TPS idle switch.
Last edited by Tomas L; 08-23-2005 at 02:39 PM.
08-23-2005, 09:35 PM
#6
Burning Brakes
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Well thank you all very much. A new TPS is on the way from Paragon Products. I love you rennlisters. 
Well maybe not loooove but you get the idea
-John
Well maybe not loooove but you get the idea
-John
08-23-2005, 11:04 PM
#7
Race Car
Yup, that's how it sounds so far. I suppose if you were determined enough, you could datalog the idle contacts in the TPS as well to help you pin it down, but that is how it sounds.
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08-23-2005, 11:26 PM
#8
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Sure sound like the TPS idle switch. The only part of your story that confuses me is why the motor seems fine above 3000 rpms? I always thought that fuel was cut above 1600 (or so) rpms when the idle switch closes -- so I'm not sure why your fuel delivers above 3000?
