car hugger

iTrader: (1)

I've been searching reading info on O2 sensors. I have a Defi A/F D-guage I plan on installing next week and want to have the proper sensor to accurately read the A/F Ratio. Planned on getting an AEM but the Defi kinda fell into my lap.

I have a 94 Fed Manual. K&N filter, Down pipe, midpipe, Racing beat dual tip. Stock ECU

Now based on my reading these mods should cause a lean situation however when warming up, car pops alot, very sensitive to throttle being let off. Once warmed up popping decreases, only popping occasionally when letting off the throttle coming to a stop. When accelerating will pop during shift change. Careful driving with brief spirited moments of acceleration is normal driver behavior.

Purchased 3 months ago. Sparks plugs, Fuel filter, oil 20w50 all changed. Possible leak at the Down pipe gasket. New plugs lessened popping. Experimented between Hess and Shell fuels and found less popping using the Shell brand. Gas mileage is close to 200 miles every 16 gallons.

My reading gave me mixed answers to the rich/lean question and also no defintive answer as to what oxygen sensor to buy.

Like I said I read for several hours trying to find my answer and it's possible I just over looked the thread, so apologies in advance.

Thanks.

kraked

I posted a similar thread because I have a similar problem. A member referred to the popping as afterburn. My popping is a very subtle, it sounds like a small bass note from a subwoofer. If you are seeing the same thing as I, then I dont think its a lean problem, but rather rich.

I have a PFC with the base map that includes intake and exhaust (which I dont have yet).. that may be why im running a little rich.

rynberg

First of all, running a full open exhaust on a stock ecu car with no boost controller is a BIG NO-NO.

Secondly, that Defi A/F gauge won't tell you anything other than if your o2 sensor is working during cruise conditions. That gauge relies on the stock narrowband o2 sensor and won't tell you anything under heavy throttle.

Just get a new stock o2 sensor -- www.oxygensensors.net

car hugger

iTrader: (1)

I should add that the turbos are running non-sequential. I've read that a heated O2 sensor is better and also that there are 3wire or more O2 sensors that give a more accurate measurement.

CronoMasamune

Dont people search before they mod their cars? As rynberg said, running full exhaust on the stock ECU is a very bad idea. Get a new ecu before you blow your engine.

nopistons94

I don't even run an o2 sensor with my PFC

POS7

The stock ecu is a POS. It tends to cause rich conditions at idle. An aftermarket ecu like the pfc runs leaner and has an idle learning feature that smooths out the oscillations.

Those mods will cause your car to run lean. However, lean conditions will occur under boost, not vacuum. Therefore you can be running those mods and be rich at idle, boost your car causing it to run lean & blow your motor.

You should put the stock cat back on, or if that isn't possible, even running the stock exhaust will be safer than running straight 3" pipes engine back.

The o2 sensor probably has little to do with the problem you are describing. If anything it will give you better gas mileage.

rynberg

Running rich at idle can be a lot of things -- water or air thermosensor, bad FPR/FPR solenoid, leaking injectors, bad o2 sensor, etc. Get your factory service manual out and start troubleshooting -- Section F is your friend (and worst enemy!).

And if anyone else says you'll run LEAN with those mods on the stock ecu, I'll club them upside the head. The problem is overboosting, NOT running lean. You can run all the bolt-ons and a streetport and still be in the mid-11s AFR wise with the stock ecu.....

POS7

^ I guess I was using the wrong terminology & not expressing myself clearly. I was assuming he'd be overboosting (spiking/creeping) with his mods, and therefore running lean. If he can hold his boost at stock levels, then he'd be alright. I just didn't communicate that as well as I should have

iron4jones

Pretty much all of your questions have been answered. Either get a boost controller or an aftermarket ecu. Having the midpipe will cause you to overboost, becoming dangerously lean and may cause you to blow your engine. I didnt see you mention anything about having a boost gage. If you dont have one you should, so you can properly monitor boost and actually see how much you are creeping. Good Luck.

POS7

Hey, I guess that 4th of July FD cruise fell through huh

iron4jones

If by fell through you mean a total organization fiasco then yes. Didnt happen. Pretty much no one had a flexible schedule that weekend.

car hugger

iTrader: (1)

Thanks for the warnings and info. These mods were on the car at time of purchase. I'm looking at a boost cut controller right now. The boost gauge will be here Wednesday.

Still not reading what O2 sensor I should buy to get a more accurate A/F ratio. Is the single wire fine? I checked oxygensensors.com they only list single wire replacements. I've decided that if what rynberg says is true about the Defi Dgauge then its pretty much useless and I'm getting the AEM wideband. Possibly just spend the extra over the AEM and get a PFC.

Rynberg and all who responded, Thankyou. And if anyone knows of a good wideband O2 please respond. Thanks.

TwinTurbo_SE7EN

Any narrowband O2 sensor will not give you a useable reading for what you want to do. A wideband is the only way to go. With the stock ecu and a wideband you will only be able to see what is going on. You will not be able to change anything to correct any rich or lean conditions.

I have the Innovate Motorsports LC-1 wideband. It was fairly easy to install and the unit without the XD-1 gauge was $200. You can get the LC-1 with the XD-1 gauge for ~$400. There are some other widebands that are also good. You can search for 'wideband' and read more about them to make your decision.

If I were in your situation, I would get a boost controller first. Then I would get a Power FC and look into a wideband.