04 Quest engine cutting out

[Mattwhite503]

So the engine idles just fine. And runs ok until it warms up and then starts having issues. It doesn’t die, it just hesitates and cuts out when you are trying to accelerate or keep speed. I just replaced the coils and plugs. I just had the codes checked and I’m throwing codes for the TPS P0123 and P0223. Could this be my issue seeing how the car idles just fine?
Other codes are:

P1574 vehicle speed sensor
P0113 intake air temp sensor
P0462 fuel level sensor
P0507 idle air control system

Before I drop the money on a throttle body I’d like to make sure I’m doing the right thing. Since I have to buy the whole throttle body with TPS included.

[far raf]

I would start by opening the TPPS body and re-soldering the resistor leads. It costs nothing, but has a potential to solve all TPPS codes. If it does not, investigate further.
Did you do IACV bypass yet? Read up on IACV frying itself and the ECU. Scary s***.

[Mattwhite503]

Ok I’ll look into both of those things. Thanks for the tips. I’ll report back when I’ve gotten somewhere.

[Mattwhite503]

I’m not seeing anything on an IACV bypass for the Quest. It’s possible I got the hoses for the iacv installed backwards after Doing the plugs and coils so I’ll check that.

[far raf]

The bypass is for all VQ35DE engines regardless if in an Infinity, Maxima, Murano or Quest. The engine, IACV and ECU are all the same. I doubt you got hoses backwards, and I doubt that would throw any codes, but doing a bypass if you can may save you from the frustration of having to replace both IACV and ECU if IACV decides to leak coolant into the electric circuits and fry itself and take the ECU with it.

[Mattwhite503]

So just to be clear to access the tpps I would need to drill out the rivet fasteners?!?

[far raf]

Can you post pictures of what you mean?
Mine looked like this:

All I had to do was melting those dimples you can see along the perimeter of the plastic case, and pry the lid with a thin flat screwdriver.
As screws hold the lid tight, I did not even bother restoring those dimples.

[Mattwhite503]

I guess melting would work just as good as drilling. I’ll give that a shot today.

[Mattwhite503]

https://ibb.co/krWoiw

Here Is what mine look like. DOESnt look like it needs any work.

[far raf]

Mine looked exactly like that but stopped cutting off once re-soldered. You never know where those microscopic cracks are hiding under RoHS compliant lead free solder.
I would re-solder anyway. Again, it costs nothing, but may save you hundred bucks.

Just wanted to add, that I reversed the 3 long screws to access them easier when assembling, and trimmed about 1/2" off of the far one which is closer to the firewall as it would not fit the power pedal assembly. When they were in their original position, I found it very hard to turn the nuts with the ratchet while holding the screw heads with the wrench while crouching on the ground near the van.

[Mattwhite503]

Alright I re soldered the connections on the tpps and my new throttle body is arriving today so after the relearn process I’m hoping my Quest will be running good again. Then onto my list of other repairs.

[far raf]

I would hold off installing the throttle body. Hopefully, if re-soldered TPPS sensor fixes the issue, you can return it and get a few $$ back.
Slap the TPPS sensor on, see if you can rev the engine again and go from there.

[Mattwhite503]

Well I went ahead and installed it anyways. Tpps and TB and the van drives better but still has the issue. I went and cleared the codes and the only one that came back so far was P0507 for idle speed system. Which I don’t think will cause my engine to cut out when accelerating.

What are the chances that I have clogged catalytic converters?

[far raf]

Now you don't know which fixed the issue - TPPS or TB. Hoping you did not spend tons of $$ on TB.

How high is your idle (which the code P0507 means)? High idle can be a large vacuum leak. Check the air filter housing, air duct and vacuum hoses and connections around it for leaks - cracks, loose clamps, hoses pulled and not reinstalled. Your IACV can be stuck open as well. This will be a perfect time to perform IACV coolant bypass.

Clogged cats do not cause high idle, they cause poor MPG. Did you get lower than expected MPG for the last year or so?

[Mattwhite503]

My idle was high for a few after the tb install however has since returned to around 650 ish. The car idles fine. The problem is when you try to accelerate sometimes it just doesn’t. It will bog down and you have to feather the accelerator to get it to go. It has a serious power loss issue once the car is warm. It drives completely fine until it is fully at operation temperature. And mpg is hard for me to guess seeing how I only got a gauge cluster up and working about 3 days ago.

[far raf]

There should be a code then.

[Mattwhite503]

No code yet but using IR gun we’ve determined the cat is faulty. I unplugged one of the bungs and while it’s hissing like crazy it drives a lot better. Going to have it replaced. It’s neither of the banked cats, it’s my downstream one. Thankful for that.

[far raf]

If main one is plugged, you may be running rich for a long time due to failed O2 sensors. Did you ever get 1st stage O2 sensor codes (for those before the pre cats)?
On my Honda Pilot they just replaced the main cat due to the rotted rear flange and I noticed increase in MPG. It's 110k on the original cat, so it was somewhat plugged. My fuel trims are slightly on the higher side, so O2 sensors are due for a replacement soon, I am hoping to get another 6+ months out of them.

[Mattwhite503]

I never got codes for o2 sensors. All the codes I ever got I listed on these threads. Drives a 1000 times better now.

[far raf]

It almost does not matter anymore for an 04 Quest, but if you want to keep the van for another few years, read fuel trims and see if they are higher than normal, as if that is the case, they are killing your pre-cats and the new main cat. Manufacturers are not stupid, they will let the engine kill parts first, then throw a code. It's a war on consumer, if you did not notice yet.

[Mattwhite503]

HOW does one begin to check fuel trims? Also, I’ve noticed now that my valvetrain tends to get noisy when I keep rpms steady under load. Could this be due to a fatigued timing chain?

[far raf]

Depends on the OBD scanner program you use. I use Scanmaster and it will be in the real time data tab, in the table. Some programs show +-percent, others show a ratio, i.e. 0.98 (low, OK) or 1.12 (high, should investigate).