I hope someone can help!

My D2a V8 has a rough idling issue which I can't seem to fix. It also throws up a lot of O2 diagnostic trouble codes. Car has around 120,000 km on it.

Confirmed:

• P0130 - O2 sensor circuit malfunction (bank 1, sensor 1) - Front sensor LH bank stoichiometric ratio outside operating band
• P0150 - O2 sensor circuit malfunction (bank 2, sensor 1) - Front sensor RH bank stoichiometric ratio outside operating band
• P0171 - System too lean (bank 1) - Multiplication injector adaptive fuelling - lean limit exceeded LH bank
• P0174 - System too lean (bank 2) - Multiplication injector adaptive fuelling - lean limit exceeded RH bank
• P1171 - System too lean (bank 1) - Additive injector adaptive fuelling - lean limit exceeded LH bank
• P1174 - System too lean (bank 2) - Additive injector adaptive fuelling - lean limit exceeded RH bank
• P0102 - Mass or volume air flow low input - MAF signal < minimum threshold, which is speed dependent

Here's what I've tried in order:

1. Run 98 fuel, sometimes E10 and 95
2. I changed spark plugs (8x NGK)
3. I tried 3x different MAFs (2x brand new Bosch, 1x from a wreck)
4. I changed air filter, and air filter top lid (clamp was broken)
5. Mechanic changed spark plug leads (aftermarket, grey ones)
6. I changed O2 sensors (2x new Bosch)
7. Cleaned the injectors with fuel additive
8. Cleaned idle position sensor's insides with carby spray

What do you suggest that I try next?

Unrelated work done:

• Mechanic: changed rocker cover gaskets (big leak before), thermostat, water pump, coolant flush, throttle body base (big coolant leak).
• Mechanic visually inspected at vacuum hoses, doesn't see any damage or cracks.

Stats I'm getting via OBD2:

0km/h (idle, coolant 26-40C)
980-872 RPM
40-20 kg/h MAF
O2 Bank 1: 0.45-0.54V, 7-19% trim
O2 Bank 2: 0.37-0.75V, 2-11% trim

0km/h (idle, coolant 81-87C)
614-703 RPM
10-16 kg/h MAF
O2 Bank 1: 0.03-0.06V, 25% trim
O2 Bank 2: 0.01-0.06V, 0-25% trim

11km/h (87C)
1639 RPM
108 kg/h MAF
Bank 1: 0.89V 17% trim
Bank 2: 0.74V -6% trim

53km/h (87C)
1286 RPM
29 kg/h MAF
Bank 1: 0.04V 15% trim
Bank 2: 0.04V 17% trim

48km/h (87C)
1684 RPM
91 kg/h MAF
Bank 1: 0.39V 2% trim
Bank 2: 0.53V -3% trim

(Trim and MAF numbers have been rounded.)

 

Monster vacuum leak.

 

You need a better mechanic.

Do a smoke test to find the vacuum leak(s). You can perform a smoke test yourself with a length of tubing, a cigar and a match. I expect there are lots of videos on YouTube showing how to do this.

Vacuum leaks are sometimes caused by deteriorating fuel injector O-rings. There's no way your so-called "mechanic" could've seen that with a visual inspection.

 

Thanks both! Will get a cigar and tubing and try this via YouTube. Will report back on which videos helped for anyone else looking.

Any specific areas I should be testing in the D2 in particular?

Mechanic said they don't have a smoke machine for it.

(Would I also later need to check for leaks after the exhaust manifold?)

 

Not likely you’ll need to check for exhaust leaks, but possible. Intake leaks are way more of a problem. An exhaust leak before the O2 sensors can cause fuelling issues, but not nearly as dramatically as intake leaks.

 

The harbor freight $7 pump works for the smoke test. Put the cigar in one hose and put the other in the intake, post MAF and tape it up. I used one of the protector covers that came with the mat. Just put a hole in it.

 

I wasn't able to get my DIY smoke machine to work. I bought a cigar and a siphon, but it wouldn't pump air the right way (no valve). I tried installing a valve to control the direction of flow, but no luck.

Are there other easy solutions for getting smoke there? Can I put a smoke pellet for bees on a dish, light it, and put it in the air box?

Also, when I'm driving, both ECUs are on closed loop, but at idle, the second ECU goes into open loop:

 

I made a DIY smoke machine and have smoke coming out from somewhere deep in the engine. Would you say it's a big vacuum leak?

But I can't see where exactly?


Questions:

1. What part(s) are easy to remove to get a better look?

2. Should I connect the smoke machine to somewhere else as well to check? Currently fed in from where the MAF would be.3. Is it safe to drive the car while I figure out the source/fix? Or can I damage injectors, O2s, cats, etc.?

tl;dr

- Coming from deep somewhere near the injector area? Gasket? There's also a few smaller hints here and there in my videos.

- None coming from the oil cap when removed.

- A bit coming from brake booster hose. But not much?

Birds eye view from top down:

Here you can see it also comes out a bit up top nearer to the windshield.

Air leak from booster cable:

1 of 2:
2 of 2:

Taking off the oil cap:

 

Likely injector o-rings, or it could be loose lower intake manifold bolts. Tighten the bolts first and if that does not fix it remove the upper intake and pull the injectors and inspect the o-rings. While you have it off you might want to consider this: https://extinctmotorsports.com/land-...elocation-kit/

 

Did you ever identify the location of the leak?