Can an O2 sensor be bad without throwing a CEL?

[horizontalkev]

Is that possible? I have bad gas mileage, puffs of light black smoke (rich), on cold startup (40F) crappy narrowband is solid lean for a minute then once warm does the normal bouncing around, random shaky idle mostly when not warmed up (rpms don't jump much), sometimes jumpy on heavy acceleration, and feels low on power. Only CEL I have is P1105, fuel pressure solenoid malfunction.
Thanks

 

[blakkat]

If it only has bad gas mileage at cruising speed that would lead me toward o2 sensor.

If it's worse than normal under accel I would start looking at things like cleaning your maf, making sure fuel pressure is good, cleaning injectors. Etc.

The reason for this is that, on cold start, wot runs, deceleration the ecu ignores the o2 sensor input like it's not even there.

 

[horizontalkev]

Well now today under acceleration the car is jerking in lower rpms until boost starts kicking in. Fuel pressure is good. Ordered new plug wires and NGK BPR7ES spark plugs my plug wires have chew marks on it. Long story.

 

[blakkat]

Clean your maf too and boost leak test the car. A bad boost leak/ vacuum leak can cause lack of power and reduced fuel Econ

 

[horizontalkev]

I started a boost leak test last week but failed because my cheap cigarette lighter air pump couldn't keep up, I was able to get my test to 5PSI before the pump fell flat on its ass. At 5PSI I had a couple minor leaks that I fixed and one bigger one. At a little more than 3 times that amount Im sure ill have a nice leak somewhere. When I get my air tank filled ill retest it. Only thing I don't understand is how to prevent valve overlap

 

[GeneralEclipse]

Hey my friends. I'm curious to how your making out? As it turns out I'm what sounds like in the same boat. I've recently taken my 97 gsx out of storage to only have issues. I've done a million tests and tons of forum research and stumbled on yours. My conditions are very similar: loopy idle after warm up, jerky accel on start up until I hit boost- then life's all good. Once it warms only problem I have is rough/bouncing idle. Smells like fuel. I've only had one cel - p1105. I've scanned two other codes witch never made it to cel...yet. P0300 and p0433(I think it's that - evap anyway) ill be doing boost test tmr. I'm leaning towards o2 aswel but we'll see. Good luck, let me/us know if you've got it straightened out. I'll do the same. Cheers.

 

[horizontalkev]

How long was your car in storage for? I had water in my fuel that was the main problem.

Your engine code P0300 is a misfire, check your plugs and plug wires I can almost bet that's where your problem is, p0433 is evap.

 

[GeneralEclipse]

I've done all the basic tune ups. 2 years she was sitting its been through a tank of fuel already. tested coil's. Cleaned TB and checked all parts related. Im betting Throttle Body shaft seals along with many other leaks and probably o2 are the culprits. I just wonder if it relates to the random misfire. its never actually came up on the cel. One question is; its the front o2 i should have focus on correct? its would be the one giving me issues as described? How did you make out?

 

[horizontalkev]

I've done all the basic tune ups. 2 years she was sitting its been through a tank of fuel already. tested coil's. Cleaned TB and checked all parts related. Im betting Throttle Body shaft seals along with many other leaks and probably o2 are the culprits. I just wonder if it relates to the random misfire. its never actually came up on the cel. One question is; its the front o2 i should have focus on correct? its would be the one giving me issues as described? How did you make out?

Yeah it could be your o2 sensor and correct its the front one, the rear one monitors the catalytic system.. And the misfire I wouldn't think would really be caused by leaks but instead ignition related. You drained the old fuel out and put in fresh fuel correct? First check your spark plug wires (sitting for a long time is an invitation for rodents and they love chewing on those thick wires) and second be sure your spark plugs physically look okay and that they are gapped correctly. Be sure your fuel filter is clean. I also had a misfire, caused by one of my spark plug gaps being nearly closed

 

[GeneralEclipse]

Yes I had replaced and gapped new plugs. But just an update for whom ever reads this. It's turn out I under estimated my vacuum leaks. Never thought it would make my engine run so rough at idle, the low end rpm studded/hesitation. I did a proper boost leak test(which in every post I read recommended to do - figured my problem was a combination of different things) which showed me multiple leaks. Turbo outlet, holes in lines, bov gasket/screws,throttle body shaft seal&gasket, couple vacuum lines. Once I fixed those ran much better. But still rough idle. Did another boost leak - now it's the fuel injectors. Also got a couple other issues but its getting better. I also tested my o2 for the voltage range and they are both good. Anyways thanks for the input. KCCO

 

[talontorque]

did you monitor your o2 to see if it is cycling

 

[GeneralEclipse]

did you monitor your o2 to see if it is cycling

Yes I think so. I tapped into the o2 wire and watch it cycle from .20-.80v. After warm up. I did that with the rear o2 too. I still have a stuttering idle but I'm contributing that to the fuel injector leaks. Hopefully. which is only two of them. Plus my fuel pressure solenoid is done but that shouldn't be an issue unless its cold.