Hello,

I have a '97 Blazer that I am at my wits end with. For the past several months when Idling in park or in gear it barely stays running and the oil pressure gauge drops to 20. When I am driving whether on road or freeway it hesitates but oil pressure gauge stays around 40 or a bit higher. When I am on road or freeway and give it gas it bogs down like its either starving for fuel or getting too much fuel and I have to let off gas to keep it running then re-engage gas pedal to get going again. The service engine soon light either flashes or stays on steady and repeats.
This past Friday night it died while driving on road and I had it towed to the local Chevy dealer. I knew the gas gauge did not work and like an idiot I ran out of gas but didnt know it at the time. I was going by the tripometer but since Ive been running a lot of 4wd due to weather conditions here in Michigan I must have sucked down quit a bit more gas. My Blazer sat in the lot of the dealership until Monday, 02/11/08. The service advisor called me Monday afternoon and said it ran out of gas and the service engine soon light never came on after they restarted it. They said the mechanic put gas in it and it started right up. They said the mechanic drove it for 10 miles and could not get it to duplicate what I described at all. The service advisor said there were NO codes set, which I can't believe since the service engine light was flashing and steady on for 2 months! I don't understand that but Im wondering because it sat for 3 days before being looked at if that had something to do with it? I picked it up last night from the dealer. Sure enough the service engine soon light did not come on until I drove about 12 miles from dealership. I stopped at a red light and once again the service engine soon light started to flash and came on and stayed on steady.
It was too late in the day to take back to the same dealership to show them. It ran horrible once again all the way home. (approximately 50 miles from dealership). I got it home and put in park and it idled horribly but would never stall out.
The mechanic checked the fuel pressure at the fuel pump and at the motor and both were within specs as well as voltage.

To give a history of the parts / service I had done in the past month was I just had the upper intake gasket replaced, (head gaskets are believed to be ok due to pressure check), new plugs, wires, cap & rotor, EGR valve, new O2 sensors (all of them), oil & filter change, radiator flush and thermostat, pcv, air filter and trans fluid replaced. The fuel filter has about 15000 miles on it.

I checked the other threads and could not find anything that matched my situation exactly. I was hoping someone could help me out before I drop another $110.00 at a different dealership just to be told nothing is wrong with it again!! Thanks in advance!

Bryan

When the Service Engine Light flashes, it means that the problem is affecting the Catalytic Converter. When the light comes on next, take it to the closest AutoZone. They will check the code no charge.
In any case, before you throw more money at this, at least have the code checked and go from there.

Quite the saga. The lack of SES light and no codes in memory is interesting. DTC's, (Diagnostic Trouble Codes) are stored in the PCM and are kept in a memory file within the PCM, they should have been able to retrieve them.

1997 has a unique ignition switch, (only found on 1997). Certain failures within the switch can cause all kinds of seemingly unrelated problems to appear. Rather than "chase a ghost", it might be worthwhile replacing it. There are numerous threads in the "How To" section of the Blazer forum that explain replacing it, some have pictures! Also, fuel pressure is not monitored by OBDII and cannot set a DTC or illuminate the SES. I realize the dealer said they tested fuel pressure, but checking it yourself may give some peace of mind and eliminate or confirm a possible problem. Key on, engine off, pump running, pressure must be 60 to 66psi. Pressure must remain above 55psi for 3 to 5 minutes after the pump shuts off. Post your results.

Thank you for your response. I will do that asap!

One thing is that giant list I didn't see getting replaced...

Mass Air Flow Sensor? The MAF could be your entire problem though
you have some strange symptoms I didn't get having just gone through
the same ordeal.

Easy way to check that came straight from the Forums - unplug it!
Go to the air filter box, follow the hose back and you'll see a grey
piece inserted between the large air intake hoses with a plastic box
on the ring that has a plug. Remove that plug, just let it hang, and
see if the condition goes away. If yes - MAF! If no, well at least
we've eliminated that before you drop $100+ on one. If it is the MAF
thankfully I determined that about 85 models from 9 manufacturers,
not just GM, use the same one so boneyards have tons - I found one
for just $30 off a 2005 Impala with virtually no miles on it so it should
run for 50K+ easily.

Was easy to replace with a little tugging as it fits very snug into
the hoses (on purpose) but boom, boom, plugged it back in and
our lack of accelleration problem evaporated with it's codes.

Like I said, since I didn't see that in the list of new parts but I
did note the O2's replaced it could be this simple and stupid!

Thanks about MAF info. I was thinking that myself but I never realized if I unplug it that I would be able to see if that is the problem or not. My Blazer has 147000 miles and never had a problem with anything in the past. The fuel pump is the original one so I may just go ahead and change that anyway since the gas gauge doesnt work. Ill try it tonight when I get home from work.

Yep, didn't occur to me either but thankfully a series of codes popped and there was the big clue - MAF. And in my case I picked this up used and thought the MAF should be the factory original, but to my surprise I determined someone else had replaced it with a reman'ed unit! So that explained why it failed. Luckily as well it's an easy part to replace and source without buying new, though the big parts places easily carry new and remans but finding the right boneyard with one from a newer compatible vehicle can save big bucks.

Hopefully this did the trick for ya!

Another posibility here ( and this happened to me) is that with the intake being off , perhaps a loose chunk of carbon is blocking the pintle on your EGR valve....its an easy thing to check

Thanks for suggestion...the problem has been going on before I had intake gasket changed. I ordered new catalytic converter, ignition switch and MAP sensor today. MAF sensor seems to be working ok.

Sound just like what mine is doing i have a 97 with 103K on it mine is very intermittent. It like to try to die in gear sitting at a light the comes back to life with a surge. When the weather warms up a little i will work on it i know it likes to set O2 codes alot but i just changed then.otherwise no other codes.peopel have talked about cleaning the MAF how good does that work even if for trouble shooting.and you drive with the MAF unplugged?

:runaround:

Well sadly the MAF turned out not to be the only problem...

We did replace it, the unplug test DOES work. If you remove the plug and the car returns to normal - MAF needs to go. We used CAC's MAF cleaner that's on the shelf at auto parts stores, worked great because it totally evaporates and doesn't leave crud in there that can attract more dirt, etc. So it's highly recommended you use a MAF cleaner - not others which may leave residue!

But, we're back to square 1. Popping codes left and right on lean-run and O2 sensors BUT it's only when it's brutally cold out? Like 15F or lower? And with wind chills - worse. Now if we run at 45MPH or less, it won't trip and it'll run perfect. But at freeway speeds or 50MPH + now on surface streets - sucker pops a code and bogs out. Never stalls, bogs out.

The weird part being now the MAF test shows it's not that? We unplug it and there could be a slight difference but it'll still bog out now. Which should mean the MAF's not the cause anymore but it was something that needed to be replaced.

Ran it today, 50+ - boom pops codes and bogs. Let it warm up going thru a bank, still acting up. Stopped a mile up the road at a station for breakfast, etc. with it totally turned off for 10 minutes and when restarted it's fine? No codes, no idiot light, I know it'll bog over 50 but I was able to reasonably drive it on surface streets for the rest of the trip.

So is there an area where the O2's could get frozen up in cold like that? Wires that could be exposed and shorting out, causing the ECM to think fuel isn't needed when it is? We can't find anything anywhere along the pathways and the MAF wiring goes over the block. I'm told the O2's are underneath, the code indicates a failure BUT it's the same one we just had replaced with a quality Bosch! And the inspection when it was replaced found nothing unusual going on under there, but it was house-shop in 5 minutes without a freeway trip that'd pop codes & trouble.

Any thoughts?

:grinyes: ******PROBLEM(S) SOLVED*******:grinyes:

I wanted to thank everyone for their responses to my problems. First of all the MAF sensor tests ok. (Tested at dealer after I cleaned it out with MAF cleaner.) It definitely needed it. The MAP sensor was partially blocked and needed to be replaced which I did that myself.

Since I'm obviously not a mechanic I am unable to go into great details of what caused the main two problems but Ill do my best to explain in general terms what was explained to me. I basically needed a new fuel pressure regulator and fuel injection kit other wise known as "spyder injection kit" since the complete kit together with the injectors; looks like a spyder. I also needed a new catalytic converter.

On my '97 Blazer the fuel injection system that I have is called Central Sequential Fuel Injection (CSFI). The fuel injectors, fuel pressure regulator and main body of the fuel injection system is housed inside the intake manifold. The main housing was leaking, the fuel pressure regulator failed and two of the injectors were staying open and dumping a large amount of extra fuel into two of the cylinders causing misfire and excess fuel being put through into the cat. The problems with the excess fuel as well as my dumb a** driving it longer than I should have caused the cat to fail we believe. I should have noticed the O2 sensors color of rich fuel burn when I replaced them several months ago.

I still am not sure why the FIRST dealership could not find any codes of misfire or cat failure to show up originally. Once I had the vehicle home I ran it again and as soon as the service engine soon light came back on again (which only took a short time) and started to flash off and on I took it directly to another chevy dealer and this time the codes of misfire and cat failure showed up. I dont know exactly all the codes that showed but there were several. Word to the wise whenever the service engine soon (SES) light starts to flash DO NOT DRIVE the vehicle! This was a costly mistake on my part. I believe I drove it with the SES flashing for almost 3 months.

I was able to purchase an a/c delco spyder assembly and Magnaflow high flow cat on Ebay motors for a good price. The dealership's cost on parts and labor was well over $1000. My brother-in-law is a Ford (shhhh) mechanic and came from out of town to help me replace the new injector assembly and cat. I also purchased a new fuel pump since it is still the original one. I have been told it is rare for the original fuel pump to last 150K miles but it is still working. There really isnt a good reason to replace it but since the fuel gauge doesn't work I figured I would replace the entire unit anyway. This will be installed in the next few weeks. The original one tests good still with good pressure at pump and motor.

Everything was installed with no problems and now it runs like new again! My next project is replacing the oil cooler lines near the oil filter that are leaking. The other set was already replaced and is still doing well.

I hope my information might help some people with similar problems.

:grinyes: ******PROBLEM(S) SOLVED*******:grinyes:

I also purchased a new fuel pump since it is still the original one. I have been told it is rare for the original fuel pump to last 150K miles but it is still working. There really isnt a good reason to replace it but since the fuel gauge doesn't work I figured I would replace the entire unit anyway. This will be installed in the next few weeks. The original one tests good still with good pressure at pump and motor.

Everything was installed with no problems and now it runs like new again! My next project is replacing the oil cooler lines near the oil filter that are leaking. The other set was already replaced and is still doing well.

I hope my information might help some people with similar problems.
I had my fuel pump replaced last summer after I ran out of gas. I was thinking like you, since the pump worked and the sending unit level gage did not I would just keep track of the mileage and fill up between 300 to 350 miles on a tank of gas. Then one day it bit me in the butt and I miscalculated and ran out of gas. I quickly had the pump changed after that since I did not want to be stranded again. I had 148k miles on the original pump. So what I am saying is there probably is good reason to change the pump if you are keeping the truck for a while longer.:2cents: Good luck