Bad TPS causing this issue?
03-17-2016, 08:48 AM
#31
CF Veteran
Plug in an obd2 with live data. Bring the jeep to operating temp, and observe your timing adv. At 3 different rpms. Also look at your stft and ltft. Unplug the downstream. Take a look at your wideband and recheck your timing at the same 3 points and your fuel trims. Install an aem fic. The tap for the upstream o2 sensor allows you to increase or decrease voltage. Tapping of the downstream isn't required although a o22 tap is provided,... It doesn't effect the tuning of this specific vehicle. Possibly newer vehicles using a factory wideband upstream o2.
OP if you want to replace the downstream go for it I don't see the necessity in replacing non failed parts. If it fails a day after your upstream replacement then fix it.
OP if you want to replace the downstream go for it I don't see the necessity in replacing non failed parts. If it fails a day after your upstream replacement then fix it.
03-20-2016, 06:33 PM
#32
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Year: 1998
Model: Cherokee (XJ)
Engine: 4.0
I successfully replaced the upstream O2 sensor today. It came right out with a little heat from the MAP torch and a 22mm flare nut wrench. It runs like a champ now. Thanks for all our help, guys.
03-20-2016, 06:34 PM
#33
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Year: 1998
Model: Cherokee (XJ)
Engine: 4.0
I successfully replaced the upstream O2 sensor today. It came right out with a little heat on the bung from the MAP torch and a 22mm flare nut wrench. It runs like a champ now. Thanks for all our help, guys.
03-22-2016, 10:00 PM
#35
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Year: 1998
Model: Grand Cherokee
Engine: 4.0
Sorry to jump in on this thread but Im having similar issues on my 98 and when I unplug my upstream o2 and let it run it does not throw a code. Is that normal or should I check elsewhere?
03-23-2016, 09:19 AM
#38
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Year: 1998
Model: Cherokee (XJ)
Engine: 4.0
For reference, when I unplugged mine I got a code (O2 sesnsor low voltage or something like that) along with a CEL. It ran fine, as well.
03-23-2016, 09:55 AM
#39
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Year: 1998
Model: Grand Cherokee
Engine: 4.0
No code was thrown from unplugging o2 or tps aand let idle for about 5 min. There was no difference in idle when I started the car with o2 unplugged. The car idles worse if the tps is unplugged though. All other sensors will throw codes if I remove them except these 2
03-23-2016, 10:38 AM
#40
CF Veteran
Open a new thread describe your problem as directly as possible then list what you have done so far. It may be similar to this situation or completely different but should be opened in your own thread.
06-28-2021, 10:18 PM
#41
Newbie
Unplug the upsteam o2 sensor at the connector. Driver side under the motor mount. Without a signal the ecu will run rich in a preset open loop map. You should get a check engine light but if it's the sensor it will run without bucking. No need to mess with the downstream o2 sensor. Test your tps with an analog volt meter, avoid a digital meter if you can. Fuel pressure test will be after these 2 tests simply because it's more testing equipment to buy.
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