M20 stroker hesitation

[NC325iC]

Sorry if this gets long.

Was driving to the beach with my wife today in my e30 when I had a bit of hesitation in the m20.

Quick rundown on the relevant equipment:

3.0L stroker
Miller PSIK
War chip
Wideband o2 sensor with g gauge in cab

Alright, so, driving down the highway at about 80mph about 60miles down the road. Felt a bit of hesitation and saw the o2 lean out. It corrected after a bit of pedal play, but of course it happened again. It did it a few times, and I found that going wot pretty much cured it. After stopping at the gas station I found that some suggested that it could be the o2 sensor or maybe the tps.

I noticed that it ran alright just after startup before the o2 sensor warmed up.

Unhooking the o2 sensor didn't help anything. Unhooking the tps seemed to have solved it.

It was running pretty well with the tps unhooked apart from the same issue coming in every 30 miles or so. When it happened without the tps hooked up the o2 would drop lean while on throttle but would stoich if I let off the pedal, seeming like it switched to idle mode.

Recently changed the crank sensor and both fuel pumps.

Any ideas? New tps for sure but why did it keep doing it?

[NC325iC]

Bump

[NC325iC]

I replaced the tps, didn't really fix anything.

I also cleaned out all my fuel lines with some air, including the pass through tube from one side of the tank to the other. All were clear, no improvement noticed. The problem seems to present at a higher frequency when the gas is below half tank.
Both fuel pumps are new as of a couple months ago.

I have a bit of a tight bend from the pressure pump that I will try to open up to prevent kinking. Other than that I'm stumped. I'm gonna have a peak at the in tank pump again to see if its getting clogged up.

[Sykohtic]

Unless you set it up differently, at wot the computer ignores the O2 sensor entirely. Its only gonna be important at less that wot, especially in the rev range thats gonna probably be around 80 mph (I'm assuming you have a 3.73 diff, but idk). I would guess you checked the fuel filter when you checked the lines.

Definitely take another through look at your intake parts. If the cars leaning out, there's a possibility its not properly getting the air it wants, so its cutting back on fuel.

I really don't know. This is kinda just me thinking, so a more experienced member will know better. I'm really wanting this knowledge as well so hat I know when I build my 3.0 M20.

[NC325iC]

Update.

I went through the vac system and checked all of the points I could think of to find what would be a massive vacuum leak, but never found it. I replaced the IAC hose section at the tb because it was cracked some.

I jumpered the fuel pump and reset my afpr to stock settings, it was set at 4bar for some reason, way too high.

Some research showed that a complete lean reading like that is just as likely, or more likely, to come from an ignition problem. O2 sensors don't read unburnt fuel.

I pulled the plugs and found them all to be a little dark and smelling like gas, but not toooo terrible, apart from #5. I cleaned them up and reinstalled them and started the car up. It died quickly, I needed to reset the computer after pulling 1bar of FP out. After the comp rest it fired up and idled just fine, ran a little rich at first but I drove it some and it was OK. I will need to run a tank of gas through it before I officially declare the problem solved. But I need to replace the cheap autolite spark plugs with some bosch copper cores.

[NC325iC]

Solved, it was the crank position sensor. I didn't think it was because I had just replaced it, but the new one measured 300ohms high. Borrowed one from a friend who's mid m52 swap and it runs much better.

[Lugnuts]

Did your new CPS have a plastic sensor housing, and was it made by Vemo/FAE?

[NC325iC]

Yes I believe it did

[barry]

CPS plastic sensors suck...

[Hooffenstein HD]

CPS plastic sensors suck...

Vemo suck in general.