This may be a little ridiculous - a $2018 challenge oddessey

So, sat and stared at the car after dinner tonight.

The next big thing to do is to sort the running issues.

Im using this to check my thinking. 

Its running poorly in transitional state. 

It wont run out with maf connected, but wont idle disconnected.

No known vacuum leaks confirmed with multiple smoke tests.

No oxygen sensor signal, with cel for such despite confirmed continuity of wiring and correct pcm pinout and new sensor x3.. 

Feels like its not as powerful as it should be.

Feels like rev limiter came earlier than it should 

This is on a "tuned" ecm. 04 rondevous sensors and such. 01 impala pcm.

My thoughts, in order of cost/effort to fix/swap out

1. Fuel pressure is wrong. Either too high or too low, possibly a bad regulator.

2. Bad maf, causing drivability issues and oxygen sensor code being somehow related.

3. Faultu ecm or tune.

4. The berkeley if i know, burn it to the ground.

Other ideas and checks and solutions are welcome! At this point if i could find a 99 dollar microsquirt and canned 3400 tune, id do it in a skinny damn minute. But the likelihood of that is about the same as me becoming the pope.....

Have you scanned for codes yet?

In reply to wvumtnbkr :

Yrs. Only one is oxygen sensor related. Dont remember the specific cose off top of my head.

So if it throws a code for 02 sensor, it could be that the o2 sensor really is seeing a lean or rich condition.

If it is, that could mean that either there is a different amount of air going into the engine than it thinks there is, or a different amount of fuel.

I would be looking strongly at the maf, and oar.

Stupid question....  is your maf in fairly straight flow?  Is it going the correct direction (they have a flow indicator on them)?

Ill have to confirm the maf orientation. Its set up with a giant freaking cone air filter attached directly to the maf, and the factory gm maf to throttle body elbow behind it.

The oxygen sensor codes are for no signal, not rich/lean. According to the live data, voltage never changes. And i have voltage on 3 out of 4 legs of the plug, which cant be right. But the wiring and pinouts are correct.

Fuel pressure and regulator are the first checks because theyre free, and relatively simple (have to pull the throttle body for clearance). 

What is oar? Other than a late 90s jam band?

Honestly sounds like a bad O2 sensor to me. I had very similar problems on my old LT1 after I built the exhaust. I tried to save the sensors, because Challenge budget, but one of them was rusted to the bung. So I cut that bank's bung out, sensor and all, and welded it to my new exhaust. I think the heat ruined the sensor and I was getting flat/constant signal from that bank, which was doing weird things to injector PW. IIRC, in my case the constant voltage from that bank's O2 sensor was causing a fake rich condition, so it was basically over-leaning half the injectors. It was also intermittent and unpredictable. I was able to read all this through a phone app and OBD1 cable. A new O2 sensor 100% completely fixed the issue.

I've put 3 different sensors in so far with same results. 

In reply to Dusterbd13-michael :

Dang. 

In reply to maschinenbau :

Yup. I hoped it wad two defective ones in row. So i tried a known good, same result. Which makes my brain go: cooked ecm, or maf issue? Probably cooked ecm.....

In reply to Dusterbd13-michael :

I feel your pain. Pretty sure I cooked and ECU on the drift car somehow. Not really sure how though.

How hard is it to find a Rendezvous ECM and MAF and try those out? I'd be ready to fire the parts cannon at this point. My local pull-a-part has like 20 Rendezvouses on the lot right now. At least for the sake of narrowing down what's wrong.

I think I cooked the ECM by welding on it with it still hooked up. The current plan, is to grab another ECM and vats module and mass air flow sensor. Test one at a time until I find the solution. The ECM and MAF would both be covered under the maintenance Clause because they were known good parts before I broke them somehow.

Man, have you had a big "sensor, ECM related kick in the balls" kind of year or what?  I can probably get Kenny to MS2 your car cheap/off the books as a team member but that would involve being in Montgomery, Alabama and skirt the "dont be a dick" rule a tad.  Considering you've done a GM v6 swap on a fully seam welded Miata I personally would allow it.

intake and maf per request. And it IS i. The correct direction according to the arrow. 

Nice chunk of tie down.  "Because Challenge!"

Nice chunk of tie down.  "Because Challenge!"

In reply to Justjim75 :

Finding a more elegant solution to that is on my to-do list before the challenge. Same with the radiator overflow bottle.

Do you have the 02 in the upstream or downstream position?

Also, is 1 bank o2 sensor shut off in the pcm?  Mine only has the 1 upstream o2 for 1 bank enabled.

Its in the upstream wiring position. Its located in my y pipe. However, when i went to pull codes today, the code for 02 has disappeared leaving me with only a maf code.

No downstream o2 enabled in the pcm.

Ziptie or bailing wire upgrade? Both would cover less air filter, lol

Have you checked your 5v reference at all the sensors? 

Here is a longshot...

We just had a problem with our swap.  It ran poorly at idle and didnt really wanna rev.

Yep, we had the cam sensor and 24x crank sensor plugs switched...

In reply to wvumtnbkr :

That is a distinct possibility! Ill have to look and see if its the case!

Since it IS resurrection sunday, i have the car outside and warmed up.

To do list: 

Figure out drivability issues (o2 and maf)

Find intermittent fault with ecm powering up (first time its happened, possibly related?)

Redo intake tract for smoother flow to maf and better looks

Make different overflow bottle

Paint and body

Swap upper radiator hose to the free one

Add gas

Reattach door panels properly

Make hardtop 

Scrub every inch of the interior 

Fix trunk lock

More testing

Tidy and clean engine bay

Aero

Thats a long list before October......