'99 S10 Blazer Bogs @ Take-Off
 

Well, I'm not really sure of the best place to start with my troubleshooting. So, I'll give some history.

When I got my Blazer, the air box had been replaced with one of the large, cylindrical air filters and the MAF sensor was gone altogether. The lack of a MAF sensor obviously threw a Check Engine light, but the Blazer seemed to run fine otherwise. Then, about a year ago, the engine started to bog down and die at take-off. I replaced the plugs, plug wires, distributor cap, and rotor button. The problem went away and the Blazer ran fine until a few months ago.

I started noticing a miss at acceleration, so I decided that the lack of a MAF sensor may cause the air/fuel mixture to be off enough to prematurely foul the plugs, so I tracked down a MAF sensor and air box in a junk yard and returned my Blazer to the factory setup. I had the error codes cleared, and the Check Engine light went away. The Blazer seemed to shift a little smoother (I guess the system improved how much gas was sent to the engine based on load), and it seemed to run fine. Then, about two months ago the miss came back.

In the past week, the Blazer started to idle really rough after warming up and when holding it in place at a stop sign. There wasn't any noticeable loss of power; it just idled rough and missed occasionally during acceleration. I thought running the year-old plugs without the MAF sensor for a few months had fouled them again, so a couple of days ago I replaced the plugs again.

Now that I have brand new plugs again, the idle has smoothed out and the miss is gone. However, when I take off from a full stop the engine bogs way down and hesitates likes its going to die before it finally moves. It hasn't died on me yet, but it sounds close at times. I only have trouble at take-off; it runs fine going down the road. Also, it only seems to start doing this after the engine has had time to warm up.

It recently threw another code: P1133 "Heated oxygen sensor - Bank 1 Sensor 1 (H02S11) insufficient switching"

The most obvious answer would be a defective O2 sensor, but I don't want to dump a bunch of money into sensors ($54 per) and not be able to fix it. So, my questions are:

1) Are there any other common problems that could cause these symptoms I should check first? Or, is it most definitely the O2 sensor?

2) I've heard that all O2 sensors have to be replaced at the same time, but the guy at the auto parts store said that its not actually necessary. Would it be alright to just change the one sensor throwing a code?

3) Here's a dumb question, but at least its a simple one for you more seasoned mechanics. I know bank 1, sensor 1 is on the side of the motor with the odd-numbered cylinders. Is that the driver side or the passenger side? I can't remember how the cylinder count works.

I appreciate any tips!

I also want to add that I'm pretty sure its not a transmission issue; loss of power at take-off can also be caused by a transmission failing to shift down to first gear. My Blazer bogs down at take-off in both forward and reverse.

Im having the same issue with the rough idle/miss after warm up. on my 96'
I've only had my blazer for a week, It doesnt seem like it has the power it should,
It also has the very bad bogging and almost dieing, then the rpms fly up n goes,
Pretty sure we have the same problem, I read your description and said to myself thats exactly what my blazer is doing,
Except i dont have a check engine light yet..

So ill be doing some things this week and i'll let you know if i find anything.
But any tips from anyone else would help too!! lol

Once engine warms, disconnect the MAF connector and see if it drives better, if so, clean it.
Use MAF cleaner. dont touch the sensor elements
That is often the cause of bogs and hesitation.

#1 cyl is always the frontmost. Bank 1 is always the side with #1 in it.. not the 'odd number side'.

So, yeah.. the driver side.

'insufficient crossing' could be because the fuel trim is at it's maximum, or because the sensor is contaminated and slow responding. Given the long history of running without full data, the sensor may well be bad.

You can also try to clean the egr valve.

This was the first thing I tried and it made no difference. Its not the MAF sensor.

@Empire932:
I have a strong feeling this is the O2 sensor. If it was a fuel or air supply problem, to me it seems logical that both sensor banks should be throwing a code. Since its just the one sensor, I'm hoping that narrows it down to the sensor or one injector. I didn't have a CEL code until yesterday, but you might want to have yours scanned anyway. Since you just got it, there's always the chance that the bulb is just burned out (or removed; I've seen that too).

Well, I just changed the O2 sensor and drove it until it warmed up. Absolutely no change, and now I'm out $50.

I'm about ready to just push it off a cliff.

sorry, I wasnt trying to be obtuse. I saw where you got one from the yard and installed it, not checked it again after other fixes.

Only thing I can thing of now is MAP {can your scantool check it engine off against local barometer?}
TPS
Or timing

What happens when you accelerate from cruise speed?

I don't have any trouble accelerating from cruise speed. If I'm rolling it runs fine, accelerates fine, and travels smooth. It only bogs down when I take off from a complete stop.

So far I've had AutoZone scan for my codes, but I ordered an OBDII cable for my laptop last week so I can get some more in-depth diagnostics. Hopefully it arrives soon and I can get a little more info on it.

Its alright, I forgot to include I've already sprayed down the sensor with MAF cleaner and tried driving it with the sensor disconnected.

Have you checked your PCV and Vacuum lines?

I really hope its not a vacuum leak. They can be a pain to track down.

What really gets me is that it only does this after it warms up, but I guess a lot of things could act differently when heated. The next thing I'm going to try is a new fuel filter. I've not checked the fuel pressure yet, but its probably due a new filter anyway.

If I figure this thing out, I'll post my solution. It looks like several other people are having similar problems.

I believe I found the problem.

Today I received my OBDII to USB cable, and hooked my laptop up to the Blazer. After clearing all the codes, I drove around town for a while. The Blazer threw another "Lean Fuel Trim" code, but no more O2 codes. I cleared it again, started it back up, and started the hunt for vacuum leaks. As I was looking I happened to notice that the hose running from the valve cover to the intake air piping was disconnected (I must have knocked it off when I took it apart to install the MAF sensor). After reconnecting it I drove it around town again, and it never seemed to hesitate again. When I got home I checked the codes, and it hasn't yet thrown a code for lean fuel.

I'm hoping this fixed the problem. If it does, then my protip to those with similar problems is to check your airflow piping from the air box to the intake carefully; this engine seems to be very picky about its airflow. If you have a leak in the hose coming off of the intake to the valve cover, that could be a problem as well.

That will definitely do it. The reason isn't because the truck is picky per-say, it is because you have introduced a source of outside air that is not being detected by the MAF sensor. When you think about it, it makes complete sense. The MAF sensor is one of the most important sensors in your engine when it comes to responsiveness.

It was just strange that it had no driveability issues with the MAF sensor removed when the previous owner replaced the air box with one of those large, conical filters. Of course, the person who did the mod also cut the hose from the air piping to the valve cover and placed tiny air filters on the exposed ends, so it wasn't exactly sucking straight air with that setup at the time.

Either way, I'm happy to say I have yet to have another problem with it. Those mods may have been trying to circumvent another problem, and in the process of restoring it to the factory setup I have may solved the problem.

mmhhmmm, i disconnected my MAF, it runs better, my problem is when coming to a stop, the idle dips low, then can bog before acceleration, none of that happens with the MAF disconnected, I allready cleaned the MAF correctly, no change.
Vacuum is moderate about 18 at idle, also with the MAF connected the idle seems to fluctuate after warm up.
so tomorrow i will clean the egr valve and see what happens. any other suggestions would be great!!