My 2007 Forenza suddenly began hesitating between 50 and 60 mph @ roughly 2200 rpms, so I took it to my regular shop and they said the only codes thrown were for the o2 sensors and they couldn't get it to do what I was saying it was doing, but were emphatic that the o2 sensors couldn't be causing that kind of problem. So I took it to autozone, they did a diagnostic and these were the codes thrown: P0133, P0138, P0131, P0124. The check engine light is not coming on BTW. So I took it to a second shop, they also thought that the O2 sensors couldn't be causing it, but they said it was surging, not hesitating, don't know what the difference is. Anyway, they had it a long time and then they said that they checked online and were told that the O2 sensors could in fact be causing the problem. However, they wanted to charge me $500 to replace the O2 sensors and since I've already done research on this I knew I could get the sensors from autozone for $200, so they are wanting to charge me $300 in labor? Anyway, my question is, can the sensors be causing this issue, it feels like the car is hiccuping and it doesn't do it all the time. If so, I will go to shop number one, they have always been fair with their pricing, but they couldn't get it to do it when I had it in initially. Thanks for your help.
Don't have the O2 sensors replaced just yet, as I'm not convinced they are the culprits.
I believe the P0124 code could be responsible for the surging.
P0124 means Throttle Position Sensor/Switch A Circuit Intermittent
Have your mechanic check the TPS plug and associated wiring.
The TPS itself could be failing, but it is most likely a loose connection.
It could be at the TPS plug (3 wire) itself or at a splice pack right above the transmission (S101) that carries the ground wire for the TPS.
This is the wiring diagram for splice pack S101
The second black wire from the top left is the Throttle Position Sensor "1" terminal and gets its ground from the M64 terminal at the ECM. Have them verify this wire is properly grounded.
If that checks out, and the other 2 wires at the TPS (+5V and signal out to ECM) are OK, it MAY be a failing or dirty TPS.
Max, when this issue initially surfaced I took it in, they changed the spark plugs and wires and I had had a valve gasket cover issue that was leaking and they fixed that. I also had the air conditioner fixed because I live in southern florida and it is impossible to live down here in the summer without air. I put some cheap fuel injector cleaner in it, but I will look up seafoam, thank you.
P1nky, I will take your schematic into the shop, I'm a girl and not mechanically knowledgeable, although I'm learning quite a lot recently, LOL. I'm just very frustrated, I've had this car a year and have put more money in it already than the Chrysler T&C that I owned for 10 years and traded it in for. Thanks for your time.
2) Oil consumption
3) Use of "non O2 sensor friendly" sealants.
O2 sensors are maintenance items, they wear out over time and need to be periodically replaced just as you would spark plugs or tires, older sensors had a 50,000 mile life span, newer ones can go triple that distance.
Engines that burn oil (or run rich) contaminate the sensors and can cause reduced life.
RTV silicone sealants give off fumes that can contaminate the sensors and cause reduced life.
98 - 1.8 Mitsubishi Pajero iO
98 - 2.0 Suzuki Grand Vitara - SQ420
05 - 2.0 Suzuki Grand Vitara - JB420
15 - 2.4 Kia Sportage
Hello, my 06 Forenza is doing the same thing. I wondered if you ever found a solution to the issue. Relatively new plugs and wires, if it were a plug or wire issue wouldn't the problem be present regardless of speed or load?
$300-$500 in parts and labor.
If you need a O2 sensor and this is for every one that need one.
If you can turn a wrench you don't need to be a certified mechanic of any kind.
RockAuto.com for the sensor $27.79-$105.79 for upstream and $60.79-$146.79 for downstream.
Then go to Harbor Freight Tools for the 7/8in O2 sensor socket for $7.99 or you can get the O2 and diesel fuel injection socket set for $39.99.
I got the socket set and already used it on mutable vehicles mine and friends and made a couple of bucks doing so.
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