Turbo car running badly/bogging down, blowing black smoke

[BeanBolta]

Hi everyone, I'm hoping someone can shed some light on my situation!

I'll start by saying that after the check engine light came on, I pulled the codes and got 21 (o2 sensor) and 22 (coolant temp sensor).

Seemingly out of nowhere I've been having a problem where the idle is all over the place, going down to 550-600 and up to 1300 or there abouts. When I accelerate (in gear), the car bogs down more the more boost it builds up, beyond about 2 psi. It's also blowing a fair bit of black smoke when boosting.

I replaced the coolant temp sensor a while ago, but regardless, could these two things cause this problem?

Any ideas are greatly appreciated!

*EDIT*
Interesting thing I just noticed, while the car is running on the turbo timer, the idle smooths out almost completely. Hmm!
I also just looked up what the fuel pressure should be, apparently 27-31 psi, on turbo timer it's sitting on 20, and idling normally it goes between 20-24. But that doesn't make sense, because it's running rich! Perhaps it has one or more bad injectors?

[shorod]

Welcome to the forum!

Please provide the details on what Make, Model, and Year of vehicle you have. With the 2-digit codes you list it sounds a bit like an older GM, but I'm not sure. Also, have you checked the vehicle specific forums here for possible common issues that cause these symptoms?

-Rod

[BeanBolta]

Thanks Rod!

Would've been wise to put that info in there! Okay, I've got a 1990 st185 Toyota Celica GT4, so it's about the right age for problems like this to pop up (and believe me, they are)!

I had a look through the Celica forum, found a couple similar things, but there's so many different answers. One says burning oil (I know that's a minor issue in my car, but not the problem here), I've heard O2 sensor, or a leaky (is that the right term?) injector, timing off, low compression (which it has, reasonably anyway) etc.

I'd really like to save some dough by not taking it to a mechanic if it's a relatively easy fix.

Oh, I don't know if this is important but I believe it's not an import and was originally Australian.

[shorod]

Considering the dark exhaust, I'd be inclined to suspect a rich condition as well, possibly due to a fuel injector or two that are not completely shutting (allowing fuel to leak past). But, since you have a code pointing toward the coolant temperature sensor, if that is out of spec it could easily cause a rich condition as well. I'm not sure what the exact code description is for the code 21, but it probably is just stating that the O2 sensor is detecting a rich condition.

Or, if you happen to have an aftermarket performance air filter, there may be a film coating the MAF sensor and screwing up readings leading to a rich condition.

-Rod

[vgames33]

If the turbo timer allows it to run smoothly, I'd start by inspecting the turbo timer wiring. Maybe there is a loose wire where the installer tapped into the ignition switch circuit.

[BeanBolta]

Do Coolant Temp. Sensors always fail in the same way? I've had one fail before, though I can't remember if it made it run like this. I do know that it made the idle go haywire, as in up to 2.7k and back.

I dare say the injectors have been in there since new, but I couldn't confirm that. Too bad they're covered by so much dang piping and wiring and such!

I haven't got a manual but a website with all the codes just lists it as "Detection of oxygen sensor deterioration/Open or short in oxygen sensor heater".

It's interesting that you should mention a coating on the MAF, Rod, I do have an aftermarket filter, and I now must admit to a possible bad move on my part (I actually have no idea), but I cleaned the filter.. With degreaser from a can. It certainly needed it, since it was filled with soot from a bad exhaust manifold gasket. I made sure I washed the heck out of it then dried it VERY thoroughly, but I have no idea whether degreasers leave any residue?

If I take the car to a mechanic I'll mention the wiring of the turbo timer, since I have no idea how they're installed or where the wiring goes to for this one, though I've never had an issue with it before. I wouldn't really be surprised if there were a wiring issue on that point, since I have a standalone tachometer who's needle bounces when I'm coasting in gear. I've been told that could be due to bad wiring - so who knows!

I'm gonna go out and clean the MAF right now to see if it helps!

[redfastbike]

check all the turbo hoses for air leaks

[shorod]

It's not the cleaning and degreaser of the air filter that coats the MAF sensor, but rather the over-oiling of the filter afterwards that coats the MAF. I've been there.

-Rod

[BeanBolta]

I actually hadn't oiled the filter after I cleaned it, didn't have any on hand. The MAF was pretty coated in black (soot I assume), so cleaned that, and while I was there, the MAP and O2 sensors with contact cleaner. If you want an idea on how black the O2 was, have a look between the stars on a moonless night. Haha!

I also ended up redoing the connections for my coolant temp sensor since they were pretty shoddy and looked very old. While on that topic, any idea why there's 2? I had a problem ages ago with the idle going way up and down which turned out to be one of those, but as far as I know if there is 2 one is probably for the gauge, but they're both twin wires (the gauge would be a single wire, right?), and my auto electrician had no idea what the other was for!

So anyway, the car runs well again! This time however, the CEL is on all the time, and even after clearing the old codes I'm still getting the O2 and coolant temp. sensor ones. Odd! I guess it's possible (one of) the coolant temp sensors is/are shorting, since it isn't actually a plug, but two small terminals jammed in there. I might go shrink wrap one of them to see if that changes anything.

P.S. Preparing to oil the filter this time

[haiderk]

Had a 300zx with similar issues. It also had 2 coolant temp sensors - separate for ecu and dash gauge.
That and o2 sensors will be the cause of it, but it'll mess up your spark plugs and o2 sensor while running rich, possibly clog your injectors. So change your plugs and sensors, then pour some fuel cleaner additive in your tank before startup.
Oh don't forget to reset your ecu codes as safety mode will run it rich and kill your plugs too -_-
(Yes I went through 3 sets before fixing this issue)