Crazy o2s

[10-29GN]

I just got a scanmaster today and plugged it in to see what is causing my irradic idle problem. O2s were wildly fluctuating with engine surges. Car came with a heated o2 sensor. Does this mean the sensor is fried or is it supposer to do this or should the numbers be steady?

 

[ijames]

The O2's are supposed to be constantly changing between about 0.1 and 0.9 volts while idling and cruising, after the engine is warmed up. The ecm constantly bounces between rich and lean, trying to average the exactly stoichiometric air fuel ratio, to keep the catalytic converter working best. The surges are a different matter. What are your tps and iac readings at idle, in park, well warmed up?

 

[10-29GN]

OK here is what I got :
o2-402/808/156 etc...
Af-05
L8-43/37/30/29
bat-14/13.6
int-148/152
BL-160
clt-100-101-162
ats-73/79
r-850/800
tps-.40/.42
iac-40/39/21
cc-03/05/19/33/134
nal-00

No directions with scanmaster and can't consult the holy site (gnttype) . Any help is sure appreciated!Thanks!

 

[TurboDave]

OK here is what I got :
o2-402/808/156 etc...
Af-05
L8-43/37/30/29
bat-14/13.6
int-148/152
BL-160
clt-100-101-162
ats-73/79
r-850/800
tps-.40/.42
iac-40/39/21
cc-03/05/19/33/134
nal-00

No directions with scanmaster and can't consult the holy site (gnttype) . Any help is sure appreciated!Thanks!

Everything looks good except your BL (BLM) and int (INT). Those are your long term and short term fuel modifiers. BLM being pegged at it's max like that tells me you've probably got a significant vacuum leak, and/or a good sized pre turbo exhaust leak. It must be pretty bad because the INT is up in the 150 area which means it's still trying to drive the BLM even higher (which is already maxed).

 

[87geeinn]

Agree with TurboDave. Everything looks good except for your BLMs. You're running really lean. Look for any vacuum leaks after the MAF sensor that air might be getting in. Also, you might want to adjust the TPS sensor just a smidge to get at to read at least .42 to .46 consistently at idle and anything over 4.5 at WOT. Also, what chip/injectors/combo do you have? Be careful if you go WOT as you may be running head-gasket-poppingly lean. Try a short WOT run and see what 02s and knock you get. Also, switch to the "cc" screen and try another brief WOT run. The number that is on the screen just as you go WOT should lock and not change. If it does, let off...quickly.

 

[10-29GN]

Thanks guys. I have a reds 93 chip and stock injectors, I think. They look pretty old! I'm using 93 octane pumpgas. I also have a K&N filter with a cold air kit. There is what seems to be some type of sensor that was shoved in the neck of the filter by the previous owner?? Could a loose clamp cause the blm's to be so high or is it likely to be something more complex? What else should I look for? I hate to do a WOT run and risk further damage. :redface:

 

[87geeinn]

It could definitely be a loose clamp but there are several places vacuum leaks can occur. Thus, you could have multiple small leaks. If it is indeed a vacuum leak, it's gonna be a big one if the BLMs are that high. For example, the vacuum block on top of the plenum is plastic and may be leaking (gasket too). Throttle blade seals, intercooler hoses, any vacuum lines, charcoal canister solenoid, PVC valve, MAF hose, EGR valve, etc.

The sensor in the neck of the K&N is more than likely the MAT sensor (aka-the air temp sensor). That sensor gives you the "ATS" on the Scanmaster. It's basically a thermometer. That is a common place to thread the sensor on aftermarket intakes.

I've never run a Red's chip, but you might want to try a new chip from Eric @ TurboTweak in conjunction with fresh injectors if you still have stockers. Make sure you have a new GM PCV valve and not a Autozone brand one. If you still have a flexible/stock MAF hose (hose from air filter to turbo), check and see if there are any holes in it, particularly where it rests close to the alternator bracket. With engine running, pull vacuum hose off of EGR valve, hold your finger over the vacuum port on it, reach under it with your other hand and push the diaphragm up. The engine should stumble and the diaphragm should stay where you pushed it.

Check your headers too. Often times, they crack especially between cylinder #3 and #5 on the driver's side. That could be the problem to, but let's hope not.

What mods/combo are you running. That would be very helpful. Do you have a fuel pressure gauge hooked up? Be patient, you'll figure it out.

 

[turbojd]

Thats your MAT sensor thats in your K&N air filter neck, it's supposed to be there.

 

[10-29GN]

I have a pertty much stock set up with a few basic mods. Stock turbo and injectors (for now). The vacuum block on top of the plennum is the aftermarket billet aluminum one with a new gasket. All of the tubes from the K&N to the I/C and turbo are after market crome. When I was driving the car home after I got her I punched it a few times to see what she could do :biggrin: . About the fourth time I heard a pop and lost all power . I pulled over and checked under the hood I saw that the hose going to the T/B had popped off (had a conquest that did the same thing once). I checked all of the other hoses and found most were only finger tight.
I have a fuel guage mounted on the rail it bounces between 25 and 35 with the engine surges. I bought a fuel pump and am waiting for a hot wire kit and sending unit. Digital guage is wrong, runs out of gas when reading 3 gals left, I found out the hard way! Thank the GN Gods for the State Police Motorist Assistance guy (who was impressed by my ride and a GN fan himself).
I know I need an adjustable F/P regulator but need to wait for more funds. The one I have looks new but I'm not sure. It has a 3inch down pipe and a new catilitic converter.
The gas mileage is awful and she doesn't want to shift into overdrive. Rpm's were at 3K while cruising on the highway. I know this might be tranny but haven't had time to pull the pan yet.
Hope you all don't get sick of my rookie questions! Thanks for your help and please keep it comming. Hopefully I'll get some free time this week to get under the hood :biggrin:

 

[87geeinn]

That fuel pressure seems fairly low assuming you are taking those readings with the vacuum line on the fuel regulator. Most chips call for a static (vacuum line off) pressure of around 43psi at idle. Get that new pump, hotwire, and adjustable regulator and you should see a noticeable improvement. Also, you should throw in a new fuel filter if you haven't done so.

 

[10-29GN]

Finally got some free time. Sprayed carb cleaner around vac block and got a reaction. Some of the hoses had cracks underneath. Took them off and replaced them. Sprayed carb cleaner and got no reaction. BLM STILL at 160! I thought I had it fixed :frown: . Now what

 

[87geeinn]

Did you check ALL of the things I recommended in post #7? I'm leaning more toward a fuel delivery problem and/or a cracked header. Also, try unhooking the orange wire from the positive side of the battery for about thirty seconds and then plug it back in. This is wire to your ECM. It will reset your BLMs to 128. Drive it around a bit and see where they settle.

Did you tighten all of those loose intercooler hoses? Undo your air filter and check to make sure there is at least one screen in the MAF sensor. Check hoses that run to and from the solenoid on the charcoal canister. Also be patient and get that new pump and hotwire kit done. I also strongly recommend new injectors and chip. Injectors are pretty easy to swap out.

Use a mechanic's stethescope or alternatively a piece of vacuum hose and check the injectors with the car running. You should hear all of them ticking.

 

[10-29GN]

Do you think that a fuel delivery problem would cause the car to "run out of gas " even when the digital guage shows 3 gals? I think I'm going to replace the float in the tank since I'll have to get in there to change the pump anyway. I saw one for sale that seemed t be the right one 90ohms. Do I need a specific one for the digital dash or is the wiring the same in the tank.
I did re-tighten all of the hose clamps. I have not checked the injectors or the MAF yet. What kind of injectors do you reccomend? I'm not trying to set a land speed record but would like to kill a few mustangs or whatever rolls up As far as patience goes I could use some of that too. I checked the for sale forum here and ebay but still can't find any . I can't help it the weather here is beautiful and I want to go for a cruise with the T-tops off :wink:

 

[87geeinn]

Actually, if the stock fuel pump is in there you can have problems with even a full tank. When I recently pulled my old stocker out you should have seen the strainer sock. It looked like a piece of beef jerky. No kidding! After replacing the pump, the difference was tremendous. Yours could be clogged and is probably collapsed as well leading to fuel starvation. That coupled with low voltage to the pump will undoubtedly give you problems.

The gauge in the dash isn't going to change the fuel delivery of the car. My gauge is pretty screwy too. I don't think the float is the problem on the sending unit unless it is binding up for some reason. You can check this when you pull it all out. Usually, it is bad/corroded connections on the sending unit. There is a guy on here that created an entire page on how to fix a sending unit. I suggest post a message in the "Fuel" area on the forums and see if someone has the link. A new sending unit is impossible to find and if you do find one it is going to cost you. If you need further info, contact someone at www.casperselectronics.com. They have everything electrically related to our cars and they specialize in digital dash stuff. I'm not sure about the wiring.

Oh yeah, most people (including myself) will tell you it is a good idea to get into the habit of NOT running the tank that low to begin with. I never go lower than 1/4 tank. There is a slight chance of the pump being starved of fuel during heavy acceleration due to fuel being pulled to the rear of the tank.

A very common upgrade is what is referred to as the 009's. These are rated at 42-43#. However, recently a lot of people go to the 60# Motoron injectors which are pretty big and allow for a lot of "growing room." Plus I hear they are very tuner friendly and do not require an ECM upgrade. I personally have 009's and they work fine for me. The stock injectors are rated at 28# and stock replacement injectors are 30#. You will need to have a new chip for anything above 30# injectors for the car to run correctly.

Your best bet is to try www.racetronix.com for injectors. You'll find the best deals on injectors there, especially the 009's.

I did the same thing that you did by blowing an intercooler hose off one time too. I about **** my pants and thought my engine was gone.

I know it sucks money wise, but you need to have that adjustable regulator soon. It's a necessity. I really think with new injectors, pump + hotwire, adjustable regulator you'll find a world of a difference. Plus all of those things can be done in one day provided you have someone help you raise and lower the fuel tank.

 

[10-29GN]

I'm going to order the regulator and hot wire kit this week. I'm going to have to wait on the injectors. I'll let you know how I make out when I do the install. I've changed out a fuel pump on a 1500 Chevy pickup so I think it should be about the same. I'll get a new fuel sock too, I overlooked that so thanks for mentioning it. Thanks for all the good info and sources, I really appreciate it! Now if you could give me a hand lowering the gas tank....... :biggrin:

 

[87geeinn]

Depending on what pump you got, it probably comes with a sock. The Walbro's do anyway.