O2/boosting problem Options

[90GSX]

Ok my car has been throwing a C/E light for some time, well it comes on for a few days, goes off for a few days, and so on. Well for a while now i have felt a powerloss from when i bought the car it seems. My factory boost guage only is reading 4-5 PSi and never any higher. Well after playing with my pocketlogger, the light says its code 11 O2 sensor. Does that mean its bad or is something else making it read wrong? I logged a run and the front o2 reads 2.5v all the time, never changes. the rear o2 read 0.00v-0.13v peak on a run. I get about 43 counts of knock about 6500-7k RPM, it reads ~0 till i hit 3k-3500 rpm. My car is totally stock, and i checked the piping and dont see any visible leaks and my question is will a bad o2 make you loose boost and is the o2 sensor itself bad? They are 118 bucks for a new one so i wanted to cover all other options before i got a new one. I have 176k miles, and i know at one point the previous owner replaced it already, but i dont remember when, i will have to check the paperwork. any help will be appreciated. Oh and another thought of a boost leak would be it might possibly be leaking into the crankcase, the dipstick pops out sometimes and also the "breather" completely comes out also. My oil pressure reads about a quarter inch from the 2nd line on the guage when i get on it, i have a feeling that probably isnt accurate considering the miliage. Anyone got any ideas? thanks

[turbohcar]

First of all, if you've got a first generation car, you only have ONE O2 sensor. That's the one on the O2 housing coming off of the exhaust side of the turbo. Autozone carries O2 sensors for less than 118. I believe they're around 70 bucks but you have to splice the wires because it comes without a connector so you have to use your wiring harness and connector. Boost leaks wouldn't leak into the crank case they only deal with the intake and therefore are confined to intake related items. You may have positive crankcase pressure because of worn rings and the air mixture is now getting past the piston and making crankcase pressure. Take your dipstick out, spray it down with brake cleaner and also spray a small amount down into your dipstick tube. Wipe them both off and it shouldn't pop out for awhile. From the sounds of it your oil pressure is normal you've just got an older car that needs a little work.

[KOU In3]

I'm assuming this is on your '90 AWD? If so, I'm not sure how you're gettting a reading for a rear O2. It does sound like the O2 sensor is bad. This should make you run rich and will hurt your gas mileage, might make the engine stutter or bog, but shouldn't induce knock.

The 43 counts of knock makes me suspect the knock sensor is bad. That or the cold weather is giving you enough air to make you run short of fuel. Doubtful at stock boost levels though.

You really can't use your stock boost gauge to judge that 4-5 psi though.

Personally, I'd swap O2 sensors (stay away from the universals, the crimp connectors don't last well IMHO). Then see if your knock sensor needs refreshing as well (use the logger). Also, invest in a boost gauge. You can normally find used ones for ~$20 if you shop.

[90GSX]

yeah is for the 90 gsx. I was assuming it was possible to leak boost through the turbo into the crankcase though the oil return line. Maybe i was wrong. The oil pressure i assume would be good if its close to that second line, but surprising with the miles i do have. The 2 other DSMs i had never got that good. my laser barely gets above the first line. I went to advance auto to price the o2, they have been the cheapest i have found on stuff for my car, i havent priced autozone yet. I thought i only had 1 o2, i dont know why my logger is getting a reading for an o2-r . im using MMcd logging software with a palm m/105 . the o2-f reads 2.50v and never moves. As for the 43 counts of knock, if thats the case, doesnt the ECU pull the boost back if it reads that much knock? Im a big newbie here. Ive been trying to follow posts here for almost 2 years before i finally got my turbo car. Ive been made aware not to trust the factory boost gauge, and i am on the lookout for an aftermarket gauge and pod (dual or tripple) if anyone has one for sale. I would just buy new, but im still paying on it so money is alittle tight at the moment, and i need a new exhaust anyways. Stock definatly sounds horrible. Gas miliage wise, im running about 24 mpg with a fair share of highway driving and in town driving and (getting on it to hear the turbo) hehe. So i dont know if im really running that rich or not, but imo the car doesnt feel as spunky (i guess i can put it like that) as it did when i bought it a couple months back, so thats kinda how im guessing my boost isnt where its supposed to be, even for stock.

[JMoushon]

1. Replace o2 sensor
2. Replace knock sensor (better safe than sorry)
3. Figure out your logger and why it even has a reading for a non-existent rear o2
4. The ECU doesn't pull boost when it sees knock, it retards the timing. This, assuming you have bypassed the boost restrictor.
5. The stock boost guage is not a guage of anything. Pay no attention to it, it is useless. It is an airflow-based inferrence on the part of the ecu. It is wrong.
6. I assume you run 93 octane premium. If not, start now.

If you have any questions, ask. People on here are great at answering questions. If you think you know something, it is always better to double-check than to blow up.

[90GSX]

hopefully someone on here with the same software might know, mine didnt come with any info. Probably wasnt the best idea to go cheap ebay stuff.

My plans are to just go for a total engine rebuild and a evo 3 16g turbo, im not looking for an obscene amount of power, just a nice and perky DD, 250-350hp range max.

But i guess i will try o2 sensor
knock sensor
then a boost gauge and see what that does for me.

Im running 92 octane cause 93 is hard to come by around here, travis told me when i bought it that it wouldnt be a problem and i have ran 93 and it doesnt feel like any difference to me.

As for the Boost control solinoid (assuming thats the boost restrictor your talking about) , i have no idea if its even there or not, i havent personally done any mods to it, but visually the only mod i have seen was the hacked aircan mod.

EDIT: just a thought, but "if" there was engine vibration due to worn motor mount or ticking lifters, would that read as knock?

[ncgalant]

That's how MMCD has been on every first gen I've logged. The front O2 sensor is O2-r and the O2-f is nothing. Your O2 sensor sounds pretty trashed though.

[JMoushon]

Have you done a compression test? 250-300 hp is an easily attainable goal, especially 250.
When I was on a 14b at 22 psi, Shell Vpower 93 made 7-10 more counts of knock than Amoco Ult 93. Not just a 1 time thing, every time I switched I logged it.
I would have to look at your engine to really know any more.

[90GSX]

Well when i bought the car travis had done a compression test car i bought it about 3 months ago and it had ~155 across the board and i trust what he says. Well now i guess i know what to go by on my logger, i wonder why its set up as the front o2 as being o2-r. Its kinda wierd then that the o2-f reads 2.5v all the time and its not even reading anything. well i guess the o2 will be replaced then and see what happens. thanks

[natedogg]

It is very possible to pressurize your crankcase through a seal in turbo. I don't think you are losing that much boost into the crankcase, so you may want to test for leaks yet, but that is a very real possiblity for high crankcase pressure.

[KOU In3]

the dipstick pops out sometimes

This is a bit of a band-aid fix in light of the other issues, but the dipstick popping is not that uncommon even on otherwise healthy cars. The rubber seals around the dipstick can harden over time (15 years in this case) and make it seal less perfectly.

You can crimp the top of the dipstick tube with a pair of vicegrips to make it hold the dipstick in a bit better as well as replace the dipstick itself (cheap part) in order to fix the aging rubber seal problem.

Again, not a fix to everything above but might help eliminate one of the smaller symptoms you're encountering.

[90GSX]

well it only does it on occasion, but also i forgot to mention the "breather can" on coming out of the head also pops out and i will find it occasionally sitting in the engine bay, and i just pop it back in.

[KOU In3]

Hose clamp that badboy on there.