240 Weird Rich Mixture Issue

I've been having this problem for a while now that I thought was a vacuum leak, but I don't think it is anymore (i've fixed every single vacuum line)

I have a lh2.2/breakerless ign, turbo b21ft with a 15g. I have this weird rich spike when I depress the accelerator pedal again after engine braking or just accelerating in general. Car normally idles around 14.6~14.9 AFR, with the rich spikes upon accel pegging it down to the mid 13s to high 12s. It stays there for around a few seconds, than goes back to 14.6 even under normal accel (no boost, all in vaccuum). It didn't have this problem before, and I'm getting **** gas mileage (though that may be due to me driving like a dick), currently around 16mpg combined, when it was formerly around 18-20 combined.

I think it's the FPR... AMM, and throttle body adjustments are checked out. Could that be a cause? Or is this just a stupid 2.2/breakerless thing?

Thanks!

Check the coolant temperature sensor, the one near the back of the head closest to the firewall. Even better backprobe the wiring at the computer to make sure it's not a wiring issue. You'll have up take the cover off the connector then check the resistance at the pins for the CTS. Check the green books for the correct pins. Volvowiringdiagrams looks to be down maybe someone else can chime in where to look.

Werd. That was poking around in the back of my mind too as a potential issue.

I’ll try checking tomorrow and report back, and prolly swap it out anyways because I don’t know how old it is...

If not that, should I even bother with the fpr?

Also, I have the PDFs saved on my computer... maybe I can upload them to my website?

^
I second what VB242 said!

I addition I just recently cured a rich running condition by renewing all the grounds and then checking the power supply to the ECU and AMM. The signal wires to and from the sensors were just fine. Redoing the grounds only offered incremental improvements as to where a burnt out power wire to the fuel relay was the real problem.





As these old bricks get older I learned to prioritise possible running problems by revisiting any wiring that has been modified/hacked-up and then checking ALL the power related connectors for bad leads. If they're ok, then I go through the tedious task of pinning out the signal wires. More often than not, the components work just fine, it's just the network that causes a 404.

Interesting. That makes total sense though! I'll have to double check the wiring... I've never had a good chance to sort through it. Coincidentally, my temp gauge is reading way higher than the actual engine temp. I think the wirings fine, but I'm only pulling about 9v from the wire, and it even dipped down to 8 for a little bit.. IIRC, shouldn't it be a constant 10v?

let us know when you find it! I have pretty much the same issue but with lh2.4. that initial stumble from a stop and any fast throttle changes cause it on mine

Oddly enough there's no stumbling of the engine... then again it idles like dog**** thanks to the cam in there.

I still need to check the grounds and all that.

when the mixture drops, do you not feel any type of hesitation? when mine drops to a ric mixture when its not supposed to. it hesitates or "stumbles", then recovers quickly.

Whoops, forgot to check this thread...

It accelerates normally, though now I’m getting somewhat of a spark blowout with light accel at 10psi boost. That’s with the throttle halfway from WOT