My firebird has been running extremely rich so I took it to a professional engine builder/tuner that my next door neighbor hooked me up with for $60 per hour. He hooked it up to his scanner, did fuel pressure test, checked sensors etc. and came up with this.

He said both of the O2's are not reading right, I dont know why because they are brand new.

He said optispark is on its way out, it misses at mid-range and top-end. It will be fine for now though.

And he said he needs to put the injectors on a flow bench. He said he thought some cylinders were running very rich and some lean, so he needs to make sure all injectors are flowing the same.

What could be the cause of this. Both O2's just replaced and both not reading correctly? I'm stumped.

 

ooh, make sure the wires to the sensors arent fried

 

u might have aftermarket injectors which will make your car run rich

 

More info. List your mods and what brand O2s are you using. I had problems with aftermarket not lasting long so I always get them from GM now.

Vacuun or exhast leaks will also give the EMC fits, likewise a failing opti.

Again, without knowing your mods. I say replace the opti ( I think you posted before you had a code that did point to the opti? ), if the wires are a few years old replace them, also maybe upgrade the coil.

 

What readings for the 02's was he seeing? What were the LT adaptives at? What mods do you have? There isn't enough information to even venture a guess. but injector flow is HIGHLY unlikely.

 

Injectors are stock and O2's are bosch. Only 3 days old! I dont know how I could have gotten 2 bad sensors, maybe it is the wiring that is messed up. I am bringing it back to the guy tonight so hopefully I will find out some more information. He said that some cylinders were running rich and some lean so that is why he wants to flow test/clean the injectors, so we know they are all flowing the same. The car has 113000 miles with stock injectors so they are probably dirty. And the only mod is slp loudmouth. I just bought the car so I dont know much info about how it was maintained etc.

 

it wont hurt to have the injectors cleaned and flow matched. How much is he charging for this?

 

$200 for the cleaning, plus $60 per hour. Not bad at all.

 

Ok I took it back to the guy tonight and he cleaned the injectors to flow within 3% of each other. He said that they were really bad. The problem with the 02 sensor was an exhaust manifold leak. That makes sense and I cant believe I never thought of that.

 

as I said.


With teh correct info I coud have told you that. Exhaust leaks before the 02 cause the sebsor to read excessive amounts of air. It belives that the motor is running lean. To combat this the adaptives are allowed to add more fuel. However the 02's will continue to read lean so it will add more and more fuel untill you reach teh adaptive limits. Generaly what you see is an 02 sensor that will tend to stick below Bias voltage and a fuel trim that sugests full enrichment.

Also as I said, "injector flow" is just something that someone says. Any good tech should understand that having that sort of issue happen is highly unlikely. A cloged injector will result in a missfire. A leaking injector will result in a fuel pressure drop that is easy to spot. Injector flow testing runs along the same lines as him saying "I think your PCM is bad"

Last note. Don't trust Bosch 02 sensors. If you have to replace these from being fouled get some new AC delcos. You will not be dissapointed.

 

Well Im just glad they all flow within 3% of each other now. Thanks for thoroughly explaining it though. Do you think the O2s are fouled from only about 1 hour total of driving?

 

it depends on the amount of the fuel. The bosch do not take well at all to fuel fouling. I would keep a good eye on it. It's possible that once everything is fixed that the extra heat of a correct fuel mixture can burn off the contamination. But you just never know.

Just be on the look out next time that he sugests some snake oil fix again like injector flow. Along with what I had said already, unless he has an injector blueprinting set up (very expensive) then there is no way that he could have flow tested them anyway. generaly onlt top speed shops and engine biulders will have one.

 

You should have just bought new injectors, for what he charged to clean the with labor, you could have saved a few bucks.

 

Well the cheapest I found injectors was on a website for $280 already flow matched, who knows how long it would take to get to my house though. I didnt want to wait a week or two to fix this problem, also testing and cleaning was only $200. He sent the injectors to the shop that he works at (since he did all of this in a storage garage after he got off of work) to have them flow tested then cleaned to flow within 3% of each other. I am guessing they had the necessary equipment to do this. Also he only charged me $75 for 3 hours of labor and diagnostics!