Limp mode questions

[Metal Mech]

So question for those more in the know. I’m working on getting the engine running correctly while I wait for the frame to get done. The engine runs smoothly but it cuts into limp mode/esc module error if it idles long enough or if I drive it for a few feet.
Based on the scanner the Crank and Cam sensors need replacement. I replaced the cam, I have the crank but haven’t gotten it in yet. I just ordered VVT sensors because they are a potential issue. Just figured eliminate that as a potential.
The other thing showing on the scanner is oxygen sensors error between first and second sensor. I know I have a leak between those two where the down pipe bolts to the manifold. Would that cause a limp mode error or should the other four sensors take care of the issue?
if I still have this problem after I replace all four what else could be suspect?

 

[Joebob]

What are your DTC codes. I had a lot of limp mode issues and it was not the actual sensors but the wiring either at the plugs being loose or the grounds being incomplete. Check all of those rather than the chasing parts. First thing I would do is unplug and them replug all suspect wiring and remove and reistall cleaned grounds.

Joe

 

[Gtstorey]

What are the actual DTC codes? Quick history of your donor without reading back through your build log and any known mods? Are the codes current and do they return after clearing?
Typically multiple unrelated codes would be a wiring issue but possibly just terrible maintenance.

 

[Metal Mech]

I will try pulling codes again tomorrow. It’s been a while, but what I remember was cam and crank, both VVT and reading error between oxygen sensors.

 

[Gtstorey]

There are multiple codes for most sensors and they all point in a different direction.
For the most part a code for reading different between front and rear o2 sensors would typically be some sort of catalytic converter code.

 

[Metal Mech]

There are multiple codes for most sensors and they all point in a different direction.
For the most part a code for reading different between front and rear o2 sensors would typically be some sort of catalytic converter code.

Yeah I found a saved file of my old codes and the suggested fix for the O2 was replace cat or fix exhaust leak. I know 100% there is a leak. I don’t plan to do anything about it as it will be gone when I bolt on the header and muffler. Just wasn’t sure if that code would cause the car to hit limp mode or not.
It’s been a long time since I really worked on cars beyond upgrades and mods and that was all pre 2000 cars.

 

[Gtstorey]

Cat codes shouldn’t cause any issues with it running but an exhaust leak close to upstream o2 might. Depends on how big and how close.

 

[Metal Mech]

Ok so I got the VVT sensors replaced tonight. Started up the car and let it run until it hit limp mode again. When it does this it kinda acts like it’s gonna stall out, then idles back up.

I scanned the codes and got two trouble codes. Crank sensor which I have yet to change
Too lean code from the exhaust leak.

I am also getting a brake position sensor code.
I doubt that has anything to do with it but guessing I should replace that sensor as well.

 

[Gtstorey]

Just because you have a brake position sensor code doesn’t mean the sensor is bad. You need to look up the code in the service manual for your car and diagnose from there. True for all codes/sensors. Or you can change a sensor and hope that’s it. Probably will be about 50%.

 

[Metal Mech]

Just because you have a brake position sensor code doesn’t mean the sensor is bad. You need to look up the code in the service manual for your car and diagnose from there. True for all codes/sensors. Or you can change a sensor and hope that’s it. Probably will be about 50%.

Gotcha. I was going based on the fact that BlueDriver gives a list of fixes and the only one listed for that one was to replace it.