2lte engine surging (1 Viewer)

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May 10, 2020
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Location
Victoria, BC
Hi everyone. I'm having an issue with my 2lte and would appreciate some input.

My RPMs have been surging. Not always, but frequency seems to be increasing. It happens driving, stopped or parked.

Here's a video of the tach while idling. The manual control for the idle is turned down completely...



Here's one with the manual control turned up. This is the most erratic I've seen it as the idle is typically set low...



And one while driving...

2lte surge while driving - https://m.youtube.com/watch?v=QmFzn-avjpg

My initial reaction was to replace the throttle sensor, it's now new. The engine does have an EGR delete, plates and vacuum lines removed. In checking for fuel leaks I found a weeping line, it's been replaced. Before I continue to throw more parts at this I'd love to hear some thoughts.

Cheers

Curtis
 
Have you pulled the ECU check engine codes? Might give you some hints of something doesn't seem right to the ECU.

Does your A/C work? Almost seems like an intermittenant A/C idle up. Not normal for it to turn on/off so quick tho.

Bad connection at one of the compensation resistors on the injection pump maybe?

Does the boost sensor work ok? Hooked up through the OEM hose with little filter?

Was wiring to your injection pump damaged at all when you did your engine work?
 
Have you pulled the ECU check engine codes? Might give you some hints of something doesn't seem right to the ECU.

Does your A/C work? Almost seems like an intermittenant A/C idle up. Not normal for it to turn on/off so quick tho.

Bad connection at one of the compensation resistors on the injection pump maybe?

Does the boost sensor work ok? Hooked up through the OEM hose with little filter?

Was wiring to your injection pump damaged at all when you did your engine work?
Between all the time spent parked and my indifference towards A/C I don't recall checking to see if it worked. I seldom use it. So I removed the A/C belt yesterday before heading out and had zero surging. I also idled it this morning (fast and slow) for a bit before work, still no surge. I'll see how it does going forward but I'm optimistic. Thanks.

You mentioned my boost sensor. Possibly unrelated, but after I posted this my boost sensor started giving me grief. Out for a drive and have been losing the turbo light and getting the excess boost/engine light. This is on rural roads, doing 50km with the engine at 2000rpm. Highways and hills I don't want to try. This has happened the past two drives. Could this be my actuator sticking?

I pulled codes and got 5 and 12. From what I could find, 5 can mean knock sensor or manifold absolute pressure. The second one makes sense. As for 12, I found multiple meanings for that.

-Engine revolution signal missing

-Memory to controller has been cleared within 50-100 engine starts.

-Diagnostic mode

-Battery or computer recently disconnected

-Idle control fault

-Air flow sensor fault

I unhook my battery frequently. Diagnostic mode also fits too.
 
Between all the time spent parked and my indifference towards A/C I don't recall checking to see if it worked. I seldom use it. So I removed the A/C belt yesterday before heading out and had zero surging. I also idled it this morning (fast and slow) for a bit before work, still no surge. I'll see how it does going forward but I'm optimistic. Thanks.

You mentioned my boost sensor. Possibly unrelated, but after I posted this my boost sensor started giving me grief. Out for a drive and have been losing the turbo light and getting the excess boost/engine light. This is on rural roads, doing 50km with the engine at 2000rpm. Highways and hills I don't want to try. This has happened the past two drives. Could this be my actuator sticking?

I pulled codes and got 5 and 12. From what I could find, 5 can mean knock sensor or manifold absolute pressure. The second one makes sense. As for 12, I found multiple meanings for that.

-Engine revolution signal missing

-Memory to controller has been cleared within 50-100 engine starts.

-Diagnostic mode

-Battery or computer recently disconnected

-Idle control fault

-Air flow sensor fault

I unhook my battery frequently. Diagnostic mode also fits too.

Removing the A/C belt alone won't stop the A/C idle up from happening. Basically when you turn your A/C switch on, the ECU knows it, and automatically idles up in anticipation of the compressor load. So make sure the switch is off is all. It's a weird rheostat behind your fan switch.

If the boost hose from your turbo to the waste gate is leaking or missing, you'll get the overboost issue you're seeing. Or if the wastegate is leaking. Or maybe someone installed a boost controller there? Anyhow, check it out closely.

Here are the ECU codes specific to the 2LTE (table below). Your code 5 is absolutely what could be causing your surge problems. That is why I mentioned correction resistors in my first post above. A bad connection to one of them would do exactly what you're seeing.

Code 12 comes up whenever the ECU doesn't see the timing it's expecting. It compares crank timing to injection pump timing. It's constantly adjusting timing (by way of the timing control valve) as the demands of the engine change. Lots of things can produce this code including timing sensor issues, timing control valve issues, timing belt or injection pump timing issues, etc. It could be a left over code from previous work you've done. It could also be related to your intermittent resistor issue for that matter.

I'd look for bad wiring to those two resistors. If it's un-repairable, just measure the resistance of your calibration resistors, and solder a new identical resistor directly to the wires. On my truck I actually cut the wires at the ECU, and ran them to a couple of potentiometers in my truck. I have subtly adjusted my fuel and timing with these.

page-1-jpg.206868

page-2-jpg.206869
 
Removing the A/C belt alone won't stop the A/C idle up from happening. Basically when you turn your A/C switch on, the ECU knows it, and automatically idles up in anticipation of the compressor load. So make sure the switch is off is all. It's a weird rheostat behind your fan switch.

If the boost hose from your turbo to the waste gate is leaking or missing, you'll get the overboost issue you're seeing. Or if the wastegate is leaking. Or maybe someone installed a boost controller there? Anyhow, check it out closely.

Here are the ECU codes specific to the 2LTE (table below). Your code 5 is absolutely what could be causing your surge problems. That is why I mentioned correction resistors in my first post above. A bad connection to one of them would do exactly what you're seeing.

Code 12 comes up whenever the ECU doesn't see the timing it's expecting. It compares crank timing to injection pump timing. It's constantly adjusting timing (by way of the timing control valve) as the demands of the engine change. Lots of things can produce this code including timing sensor issues, timing control valve issues, timing belt or injection pump timing issues, etc. It could be a left over code from previous work you've done. It could also be related to your intermittent resistor issue for that matter.

I'd look for bad wiring to those two resistors. If it's un-repairable, just measure the resistance of your calibration resistors, and solder a new identical resistor directly to the wires. On my truck I actually cut the wires at the ECU, and ran them to a couple of potentiometers in my truck. I have subtly adjusted my fuel and timing with these.

page-1-jpg.206868

page-2-jpg.206869
Of course it wouldn't be as simple as removing a belt. Wishful thinking on my part. For the sake of it I played around with the A/C switch to feel the idle up. Feels quite similar.

Thanks for sharing that table, saved to my files. Of all the sites I checked Toyota ECU codes on, none had anything 2lte specific. I remember you mentioned posting something about diagnostics on here somewhat recently but I could not find it.

I'll definitely be pulling those resistors off and checking them. I played around with the connections a bit. One of the connectors doesn't grab so great, the locking tab is there but doesn't really lock. Possibly vibrating loose? On the subject of code 5 and resistors, here's an article about repairing them. Literally these exact ones from what it looks. I do recall reading about your potentiometer set-up at some point.


After solving code 5 I'll move on to 12.

The boost hose on the turbo is in good condition. I replaced the hose clamps today, one of the existing ones looked a little tired. Definitely no boost controller. I can't see anything amiss about the wastegate. But I'm not really loaded with turbo experience either.

Tonight's drive had the surge return, but not much. Ran pretty good actually, up until the overboost light came back. Then I limped home. In about a weeks time I'll have a boost gauge installed. Should help.

Will report back my findings on this. Thanks again @GTSSportCoupe for sharing the knowledge.
 
Finally got to checking out the resistors. Using the link above as a reference, they do have the correct value.

Grey - 010 - 0.532kohm
Beige - 008 - 0.316kohm

I'm guessing it must be the wiring or connector. Nothing stands out visually about the wiring. I'm leaning away from the idea of vibration loosening the connector. The ECU will show code 5 after being reset before the trucks been started. Whereas code 12 returns after it runs.

I think my best option is to buy new resistors and relocate them near the ECU. I'll probably set up a small terminal block so they can be replaced or changed without soldering.
 
Update on the surging, specifically the resistors.

I couldn't find anything with the same value as those on the pump locally so I had to order them in. Got around to installing them today. The wires off the ECU had push connections on them I doubt were factory. No surprise, the PO liked to cut into things. They weren't connected well, but just the same I couldn't read the resistors at the pump from there.

Here's the new setup.
20210526_154444.jpg

20210526_155504.jpg


This cleared the ECU code 5. I went out for a fairly long drive tonight and had no surging at all. Before, even on the good days, I would get a slight variation when idling at a light. Nothing tonight though. Hopefully this is a fix and not simply an uneventful drive.

ECU code 12 is still there and will need figuring out. But with the truck running smoothly I'm not too stressed about it. Thanks again @GTSSportCoupe for the advice.
 
Update on the surging, specifically the resistors.

I couldn't find anything with the same value as those on the pump locally so I had to order them in. Got around to installing them today. The wires off the ECU had push connections on them I doubt were factory. No surprise, the PO liked to cut into things. They weren't connected well, but just the same I couldn't read the resistors at the pump from there.

Here's the new setup.
View attachment 2685771
View attachment 2685772

This cleared the ECU code 5. I went out for a fairly long drive tonight and had no surging at all. Before, even on the good days, I would get a slight variation when idling at a light. Nothing tonight though. Hopefully this is a fix and not simply an uneventful drive.

ECU code 12 is still there and will need figuring out. But with the truck running smoothly I'm not too stressed about it. Thanks again @GTSSportCoupe for the advice.


Nice work!! I'm glad that sorted your problem.
 

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