[5th Gen : 08+]: Surges on the highway, p1128 code!
#1
03-21-2015, 01:57 PM
Join Date: Mar 2015
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Surges on the highway, p1128 code!
Back story: 2008 GC 3.3l. currently 125k miles on it. Before taking the van on a roadtrip I changed the following: Plugs (champion), wires(napa), air filter (K&N), tranny fluid, oil, coolant, brakes, rotors. Before the trip the van had 105k miles on it. About 800 miles into the drive, doing about 75 on the highway, Cruise Control, the van surges as if it tried to downshift but then changed its mind. It was a good size jerk like hitting a pothole. We drove the van for a total of 19k miles and here are some things that I noticed.
There was no consistent pattern, sometimes it would only surge once, other times there would be 3 or 4 in a row.
Generally the surges happened while accelerating on the highway.
First the surges happened around 75 mph but now are more common around 65
The higher the altitude, the less surges, we had none in the colorado mountains.
The P1128 code is the only code that ever shows up but after clearing, it takes almost a week of driving for it to come back even through the surges are still there.
After searching and searching for someone with the same problem I have come up empty. I have replaced the wires and Crank Shaft Sensor. The surges are not as violent now but are still there.
I am planning on selling this van soon and before I start spending money on parts I was hoping someone knew something that would help.
Thank you in advance!
Also, the van runs fine other than that, no stalling or misfiring, purs like a kitten.
There was no consistent pattern, sometimes it would only surge once, other times there would be 3 or 4 in a row.
Generally the surges happened while accelerating on the highway.
First the surges happened around 75 mph but now are more common around 65
The higher the altitude, the less surges, we had none in the colorado mountains.
The P1128 code is the only code that ever shows up but after clearing, it takes almost a week of driving for it to come back even through the surges are still there.
After searching and searching for someone with the same problem I have come up empty. I have replaced the wires and Crank Shaft Sensor. The surges are not as violent now but are still there.
I am planning on selling this van soon and before I start spending money on parts I was hoping someone knew something that would help.
Thank you in advance!
Also, the van runs fine other than that, no stalling or misfiring, purs like a kitten.
#2
03-23-2015, 01:10 PM
P1128 - Closed Loop Fueling Not Achieved - Bank 1
I've never dealt with it but my first guess would be an engine temp sensor circuit that's telling the PCM the engine isn't up to temp keeping it in open loop mode. That or the thermostat is stuck open. Any indications along those lines such as a lower than normal temp indication or low heater output? Beyond that I would be thinking MAP sensor circuit based on your altitude comment or O2 sensor problems. Might consider having a shop put a scan scope on it to check real-time operation.
Just in case:
In a nutshell, open loop mode is used during engine warm up. Fuel trims etc are controlled by fixed programing in the PCM. The engine switches to closed loop mode once warmed up meaning engine and O2 sensors are heated to spec. Fuel trims are now controlled by O2 and other sensors based on demands you put on the engine.
I've never dealt with it but my first guess would be an engine temp sensor circuit that's telling the PCM the engine isn't up to temp keeping it in open loop mode. That or the thermostat is stuck open. Any indications along those lines such as a lower than normal temp indication or low heater output? Beyond that I would be thinking MAP sensor circuit based on your altitude comment or O2 sensor problems. Might consider having a shop put a scan scope on it to check real-time operation.
Just in case:
In a nutshell, open loop mode is used during engine warm up. Fuel trims etc are controlled by fixed programing in the PCM. The engine switches to closed loop mode once warmed up meaning engine and O2 sensors are heated to spec. Fuel trims are now controlled by O2 and other sensors based on demands you put on the engine.
#3
04-21-2015, 09:36 AM
Professional
I have been chasing a similar problem on my 2008 GC SE for some time now. For me the problem shows up most often when the outside temperature is above 60°F and/or the A/C is on. Here are some selected numbers from my freeze frame data:
Code P1128
Baro 29.5 inHg
MAP 25.7 inHg
Load pct 87.8
ECT 190°F
IAT 88°F
Someone correct me if I'm wrong but I believe that the MAP reading should be much higher than that at that engine load. I pulled the MAP sensor and found the probe end lightly coated with oil which most likely came from my Spectre oiled air filter. I noticed the OP say he installed a K&N, which is Spectre's big competitor. Yesterday I replaced the Spectre filter with a Fram paper filter and wiped off the MAP sensor before reinstalling it. My next step is to clean the intake manifold to get rid of any residual oil, and possibly replace the MAP sensor if necessary.
Code P1128
Baro 29.5 inHg
MAP 25.7 inHg
Load pct 87.8
ECT 190°F
IAT 88°F
Someone correct me if I'm wrong but I believe that the MAP reading should be much higher than that at that engine load. I pulled the MAP sensor and found the probe end lightly coated with oil which most likely came from my Spectre oiled air filter. I noticed the OP say he installed a K&N, which is Spectre's big competitor. Yesterday I replaced the Spectre filter with a Fram paper filter and wiped off the MAP sensor before reinstalling it. My next step is to clean the intake manifold to get rid of any residual oil, and possibly replace the MAP sensor if necessary.
