Stumbling Off Idle

[Maroon]

My car has been "stumbling" and running rough. It is most pronounced under load: ie starting from a stop, or just off idle while revving in neutral. It runs smooth if I hold it at 2-3000 rpm in neutral at a stop.

For the record, I have always had the low/bouncing idle issue. This is not the issue I am talking about. So it is not the EGR, a vacuum leak, or exhaust leak. It's something else.

I had the codes read and there is no code that would cause this issue.

I bought a replacement coil pack (store only had one in stock) and swapped it around. It made no difference.

Any input? Thanks.

 

[hotcracker69]

if you have already change the spark plugs with the correct gap, cable.
clean the idle control valve and the maf.

 

[Maroon]

I checked all the plugs. The plugs and wires have less than 20,000 on them.

I tried cleaning the MAF and will try the IAC. Does anyone know what happens when you unplug these sensors? On some vehicles you can unplug sensors to determine what is bad. I don't know if that works with these.

 

[kms1990]

Do not i repeat do not unplug a mass airflow sensor while the car is running 99% of all obd 2 cars (1996 and newer) can have the computer fried if this happens.

 

[kms1990]

We need more information. what codes did you have? any other issues with the car?

 

[Maroon]

The codes were for bank 1 oxygen sensor 2 (the one in the J Pipe after the precat) and the neutral switch for the transmission. But these have been on for thousands of miles so they are not the problem.

There are no other known issues with the car.

It's getting progressively worse. I can hold the throttle at 2,500 rpm in neutral, and it runs smooth, but at a lower rpm or under any load it runs rough. I have to slip the clutch much more when starting from a stop because it's so under powered. But it has its moments when it "snaps" back to normal power. I'll be accelerating, it will be running rough, then for a brief 2 seconds it will smooth out and run like normal until I upshift.

1 week ago, I would just get an occasional hardly noticeable "blip" or cut off when accelerating.

 

[pcb]

Seafoam !!
In the gas and in the brake booster.

(clean the IAC too)

Your car may be stuck in limp mode if its got that code for the o2 sensor it may have been running rich for a long time.

 

[Maroon]

The thought of fixing it with a can of stuff is tempting, but I feel that Seafoam is an $8 can of snake oil.

It went downhill pretty fast. It wasn't a gradual build up of carbon that Seafoam claims to fix.

 

[hotcracker69]

so your oxygen sensor is broken and you dont wanna to fix it? what if you were told that neglect of replacing the o2 sensor is what caused your issue today?
some say that 02 sensor does nothing, I dont believe so, what if that sensor is what mixes fuel and air correctly for proper combustion? and now you have carbon build up cause of it?

 

[Maroon]

Again, it went downhill fast. Carbon build up occurs over a long time, and there are gradual impacts on performance.

Why play "what if" with the O2 sensor, and instead just know what it does? The O2 sensor that is broken is after the precat. The one before the precat that controls air fuel is not throwing a code. Unplugging either sensor makes no difference to this issue. It's common to replace the precat with a header while putting a non fouler on the sensor to render it useless anyway.

I could spend hundreds of dollars replacing parts on a what if basis, but I'd rather have a logical reason.

 

[pcb]

I'm willing to bet you've got a fouled up fuel system including the IAC valve that can happen quickly with a bad tank of gas. Your injectors might be fouled as well.

Do the non fouler trick and clear the code that will take your car out of limp mode. You're wasting gas losing horsepower and fouling up your engine with all that extra gas.

It's about $10 for the two non-foulers.

That $8 can of seafoam may very well fix your problem it's worth a gamble.

 

[Maroon]

I'm pretty sure it's my #1 fuel injector. I pulled the connectors individually, and the only one that had no effect was #1. I haven't put a new injector in yet. These ******* things are ridiculously overpriced (why did I buy an import?).