P0402

Ok, yet another post about the CEL code P0402.
I have a 2.7l 03 Taco. I have changed the egr, temp sensor, and the vsv. I have a small exhaust leak I am getting fixed in the morning, but that to me sounds like it would be a 401 issue.
When the engine is cold, the motor sputters and cuts out. After it idles a while or it gets up to temp it stops. Any other suggestions?
I’ve done a vacuum test on most of what I can understand.
The one area I am unsure about is the one of three vacuum lines coming from the throttle to the vsv has no vacuum (when revved or not)? But the two that run to the modulator (P&R) do when revved.
I think I typed all of that correctly.

 

I would check the orifices in the throttle body, sounds like one or more of them is clogged. Make sure you can blow air through them.

 

That’s the thing, I tried to push air into the unknown throttle vacuum line and it didn’t seem to build pressure.

 

Would it be safe to blow air into it with an air compressor? Or would I jack up a diaphragm or sensor?

 

I cleaned out the throttle body side with an air compressor, so far so good.

 

Is this back into the throttle body? I wouldn’t expect it to build pressure if it was clear

 

Yes. R and E on the diagram below have vacuum when revved. The other unmarked port does not move the gauge when revved.

 

Ok, so this one was a doozy.
I chased this one for a couple of days as you can see by the time stamps on my posts. A few different things were happening all at once and I think I may have spent a little money where I didn’t need to but oh well. Now I don’t have to worry.

First things first I had the P0402 code. I initially thought this was a faulty EGR and without the tools to check it was my initial go to. This didn’t help the issue sadly.

Second I checked the VSV and it looked kind of new so I didn’t mess with it and the previous owner said they had changed it.

Third I moved on to the egr temp switch. I did a bad job a testing and thought it was bad so I bought one and no luck there.

After that I looked at the exhaust. Turned out I had some major leaks there. I had my cat checked and the leak repaired. Man did that open a can of worms. This caused the truck to run even worse, even when warmed up. The sputtering would eventually stop after a warm engine start after running about 5 miles.

so I went back to the VSV hoping that what had happened to another member was also my issue. NO LUCK.
New EGR, New temp sensor, new VSV, repaired exhaust…. I’m thinking major vacuum issues. I’m about to replace all hoses.

4:30 this morning I’m on my way to the gym and I have to go up this big hill each morning almost exactly 1 mile from my house. I try to let it warm up a little but I’m late already and it’s cold out 30F. My truck starts it’s usual cold stutter but doesn’t stop. (Usually about 3 seconds of stutter every time I’m below 2,000 rpm in the cold while driving)
This time it doesn’t stop. Hmmm that seems like a bad coil.
Checked and had a misfire on #4. That’s new.
Went to replace all plugs and coils. 3 of the 4 plugs are almost hand tight. Cylinder 4 is a little snug but not even close to spec.

Change plugs and coils. Purring like a kitten!!! I cold started and drove it after work. And it seems to be running better. Fingers crossed. I’ll try to keep updates coming.


TLDR: P0402 code possibly could have been a low compression issue?

 

IIRC, P0402 is too much EGR flow in the intake. I am thinking that the VSV for the EGR valve should not be allowing any vacuum to the valve until the engine is at operating temp. The VSV could be “leaking” vacuum. You could put a golf tee in the line that’s goes to the EGV valve and see if the stuttering when cold ceases.

 

Actually it seems to be running great since the spark plug change and coil change. No check engine as of yet in about 20 miles. The only issue I am seeing now is a slight power loss on the low rpms? It almost feels like when it hits 2700 rpm a power band kicks in. it’s hard to tell f I am just imagining things at this point. But I’m going to keep monitoring it. Probably gonna run a bunch of octane booster. And see if it’s the injectors.

 

Update:
After resolving this issue I have moved across the US. Drove my little 2.7 fully loaded all the way from PA to ND (almost MT) which was about 30hrs after a little detour to MO. From there I have had multiple 2hr+ drives. And even another little trip down to MO. I have had zero issues.