legacycentral bbs

I have a problem. When I bought this car it hesitated. So I fixed a few loose vacuum lines and thought that would fix the problem. Nope it didn't. I installed new plugs and wires. So I then decided to install a narrow band Auto meter air/fuel gauge. It tells me when I floor it i go to rich then to lean real fast. But if I gently ease on the throttle it can get it into rich but when I go all the way down on the throttle it goes into lean. STOCK BOOST, and a tdo4 turbo with a engine that has about 15k miles. I am running STOCK boost right now. with a tdo4 turbo. Could this be a throttle position sensor? or a Mass airflow meter?

I am at my wits end because I cant play with this car cause every time I go into boost I start to run lean.....please help

What you are experiencing is normal.

First off, using a narrow band to measure AFR's is not going to give you a true indication of what you're running outside of stiochiometric.

Secondly, what you are describing about going lean when you let off the throttle is a desired effect and called overrun or deceleration fuel cut. There's no reason to keep injecting fuel when the engine is decelerating and has viturally no load on it. As soon as you get back into the throttle, AFR's should come back to normal.

Regarding going lean when going into boost. You need to have a wide band to correctly determine this. A narrow band O2 is not going to be able to provide you with it.

x2 that narrowband gauge is useless.

Ok, when I floor it, the car hesitates and acts like it don't want to go and the narrow-band is telling me that it is running lean. I put a narrow band in to just measure if im running lean or rich, no more, no less. I dont need a accurate reading. I just need to know if im running lean or rich. If i ease into the throttle i can get it run rich. if i just floor it it does NOT run rich, instead it runs LEAN (red). The narrow band is just wired in to the signal wire which is the same wire that tells the ECU what is happing so again i just wanted to know what is happing when i go into boost.


Thanks though guys. I am just very frustrated

Legacy777 wrote:What you are experiencing is normal.

First off, using a narrow band to measure AFR's is not going to give you a true indication of what you're running outside of stiochiometric.

Secondly, what you are describing about going lean when you let off the throttle is a desired effect and called overrun or deceleration fuel cut. There's no reason to keep injecting fuel when the engine is decelerating and has viturally no load on it. As soon as you get back into the throttle, AFR's should come back to normal.

Regarding going lean when going into boost. You need to have a wide band to correctly determine this. A narrow band O2 is not going to be able to provide you with it.

No I run lean when I floor it. If i ease into it I can run rich. If I mash it I run lean.. Its never normal to run lean under boost. Could this be a throttle position sensor?

What mods are on the car? I'm specifically interested in the intake track/air box/etc.

Also, is it MT or AT?

Legacy777 wrote:What mods are on the car? I'm specifically interested in the intake track/air box/etc.

Also, is it MT or AT?

stock airbox, coffee cup mod, k&n, wrx tdo4, Manual Transmission. I cant think of anything else. I can take some pictures if you want

Is the snorkel in the fender still there?

Have you checked the MAF to see if it looks dirty or has any other damage? When's the last time you've cleaned the K&N?

I'd suggest cleaning the MAF to start out with, and possibly resetting the ECU. However, I'd only do one thing at a time. Clean the MAF, see how the car runs, and then reset the ECU.

Legacy777 wrote:Is the snorkel in the fender still there?

Have you checked the MAF to see if it looks dirty or has any other damage? When's the last time you've cleaned the K&N?

I'd suggest cleaning the MAF to start out with, and possibly resetting the ECU. However, I'd only do one thing at a time. Clean the MAF, see how the car runs, and then reset the ECU.

Awesome. How do I clean the maf? Just some break clean? Im not sure if the snorkle is still there. I will find out tonight. And How do I reset the ECU?

Thank you very much for your help.

So I took apart the whole intake track, K&n was dirty, the silicone 90 that was attached to the TDO4 was loose, I cleaned the maf with maf cleaner. STILL DOING THE SAME THING. I havent reset the ecu yet. I will do that at lunch. I am thinking it could be a faulty O2 sensor.

I am going to do this stuff in order

1. Check fuel filter (replace)

2. Check fuel pump pressure

3. Check o2 senser.

Anybody else have any ideas?

Paul, I'm going to copy & paste the email I sent to you so others can follow the conversation/troubleshooting.


The MAF sensor is the primary device to tell the ECU how much fuel is needed. The ECU also looks at the TPS signal to determine how much fuel enrichment is necessary during acceleration. There may also be an additional enrichment based upon how quickly the throttle is opened. Typically, more fuel enrichment is given when accelerating from low rpms and low load compared to when the engine is at higher rpms and higher loads. Also, there is more enrichment when the engine is cold.

Have you tested the TPS per the instructions in the FSM?

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I’d start with the TPS or MAF assuming the readings from your narrow band are even in the ballpark.

I got it figured out. I was the fuel pump, thanks guys

i remember i had the same problem in my car (minus knowing lean or rich) but the car would fall on its ass when i floored it but if i eased in on throttle it'd do fine. then one day my fuel pump just died. replaced it and it ran like a champ

cj91legss wrote:i remember i had the same problem in my car (minus knowing lean or rich) but the car would fall on its ass when i floored it but if i eased in on throttle it'd do fine. then one day my fuel pump just died. replaced it and it ran like a champ

That was what my car was doing and I just thought I would install a narrow band to see if I was runnning lean and I was. A lot of people say not to use a narrow band but if you just want to make sure your not running lean its a great tool. Its a lot more fun to drive now that I got that fixed.