I have a 1997 Blazer 4.3 L 4 wheel drive Vin W.
Bought it from a Chevy Dealership about 6 years ago.
It had 70,000 mile on it and it now has 150,000.
I have changed many items on it. Fuel pump, injectors and fuel tank
about 2 years ago to name a few..
I have a problem with the engine losing power and almost cutting out.
It will not get above 1200-1400 rpms.
And that is in Park or Neutral.

I had a tuneup about 4 months a go.
Rotor, Cap, Plugs, Wires, PVC Valve Fuel Filter. I only use Ac Delco Parts.
I also had a gasket changed on the front of the converter. There was good
size leak coming from that area.
I have a scanner and after 4 months of driving I never
have had a code come up. I did notice that after I got the
Tuneup and gasket replaced that the vehicle seemed to have
a hard time when it first was accelerating. It seemed like something
was holding it back like it was under a heavy load, but as long as I took
it slow and easy accelerating it would act properly. I could go 0 to 60 with
no problems. Recently it started to surge slightly. It was most noticeable
at speeds around 45-65. It seemed to have a hard time holding speed
with my foot on the accelerator. If I used the Cruise Control I never
noticed any problem. The other day It started to surge when I was going
around 45. The rpm's went up to 3000 and this time instead
of backing off I floored it. It immediately lost about 90 per cent
of it's power. It will not go over 10mph. It starts normally and will stay on
but I cannot get to stay at a constant rpm above 1400 rpm's. It will start
to stutter and go down to idle speed 600 rpm's. I have watched it with my
scanner and the only thing that comes to my attention is the*Ignition* Advance
Degrees. When it starts to act screwy the*Ignition* Advance Degrees starts jumping around.
At Idle 600 rpm's the*Ignition* Advance Degree is 20.0 Degrees. As long as I don't
touch the throttle it will stay like that until it ran out of fuel. The*Ignition* Advance
starts jumping. Any ideas what would cause this. I don't get any codes.
Thanks for any help in Advance. This is my first post. I feel like I have written
a book here.

 

I am new to this. Can you change anything I said about Engine Advance Degrees to IGNITION Advance Degrees.
Thanks.

 

Done, per your request. To edit your own post, just use the 'edit' feature.

 

Thanks rriddle3 for the help with the editing.

I have some ideas of what this might be. It would be a guess.
I have looked thru a lot of posts. I have come up with
a Bad Ignition Coil or Bad Distributor Gear. I will wait to see
what others come up with. People helping people.
Great WebSite. I love my Blazer.
I can see that a lot of other people do also.

Thanks Mark

 

I would recommend you clean the EGR valve and MAF sensor just to be sure that they are not causing some of these symptoms. It is a good routine maintenance.

I would also see what the output from your TPS (throttle position sensor) is through the continuous range of throttle positions. This can cause some pretty severe drive-ability concerns.

 

I had cleaned the MAF sensor with a recommended spray(CRC) about 2 months ago.
It did not look like it was dirty then but when I get the chance I will give it another cleaning.
I live in the Midwest(Illinois)-no garage. I have a friend who is a mechanic who has a garage
about 40 miles away. AAA is not towing farther than 10 miles this past week so it will
probably be another few days before I can get it inside for a real good analysis with
a true mechanic. Just so you know I am not a mechanic by no means. I try to fix
things by myself thru good research and rely on my friend to treat my pocket book gently.
The Blazer Forum has given me a lot of insight/opportunity to do just that.

The scanner that I have takes a reading every 4 tenths of a second. The TPS readings
look to be good. I am using an Actron CP9180. It gives me readings for the TPS
sensor in Percentages. The scanner gave me 70 frames. At idle Frame 1 shows the TPS
Sensor at 0.3%. The scanner reads the MAF Flow in GR/SE. At Idle Frame 1 reads 8.27.
The Engine Speed is read in Rpms. Frame 1 at Idle is 662. Ignition Advance(IGN) is in Degrees.
On Frame 1 the reading was 18.0


I will jump around and give you a sample of each at different frames.
This is Frame 5 info(2.2 seconds)
TPS 15.2%
MAF 20.38
Rpm 1266
IGN 5.5

Frame 10(4.2 seconds)
TPS 10.1
MAF 11.59
Rpm 1291
IGN 20.1


Frame 15-Back to Idle(6.2 Seconds)
TPS 0.0
MAF 7.91
Rpm 647
IGN 19.5


Frame 20(8.2 Seconds)
TPS 5.4
MAF 11.87
Rpm 928
IGN 22.1


Frame 30(12.2 Seconds)
TPS 15.6
MAF 16.46
Rpm 944
IGN 2.0


Frame 40(16.2 Seconds)
TPS 6.2
MAF 16.21
Rpm 889
IGN 18.0

Frame 50(20.7Seconds)
TPS 14.1
MAF 19.38
Rpm 974
IGN 7.5


Frame 60(24.3 Seconds)
TPS 17.6
MAF 17.33
Rpm 908
IGN 2.0

Frame 70(28.3 seconds)
TPS 20.7
MAF 15.58
Rpm 775
IGN 1.5

Hope this helps in your analysis. If need be I can just run these 4 only
and get a probably a 120 seconds of readings. Thanks for your help Kyle.

Mark

 

Try checking your EGR valve on the front of the intake manifold. It is the coke can like device with wires coming out of it by the thermostat housing. If you remove this you can see the Pintle that is to move in and out letting exhaust gases into the manifold and if this is stuck or not functioning it can cause some issues like you talk of. If you can find some Seafoam or other decarbonizing spray then spray it into the manifold side and then if you have a 3/4 inch round brush you could run it into the passage to make sure that any carbon is clogging the intake... You could spray into the area and then make sure that nobody is in the area and just start the engine and let the exhaust gases just blow out the carbon that was knocked off of the passage walls... It will be noisy but it is just one quick way to "blow" out the carbon from the passage. Also spray the area of the EGR valve with the spray solvent and let it sit and then find a small wire brush or pipe cleaner and then carefully clean the inside passages...

This is a simple cleaning to do there are just two bolts and a gasket to replace in the process. If you can find it there is a gasket out there with a metal screen to make sure the large chunks of carbon do not get into the EGR valve itself...

 

I'm willing to bet that its your TPS. That thing is jumping all around when just at idle! It shouldnt read anymore than 5 volts. Probably like .75 volts +/- .05 volts at idle. Get a Haynes manual and check the parameters of the TPS.

 

Thanks for everybody's input. I will try to take the EGR valve tomorrow if the weather
holds up. I will change the gasket no matter to a screened version.
I have a Haynes Manual and will also check the specs on the TPS.

Mark

 

Well I was going to try to change the EGR Valve to
check it out, but decided to fire the old girl up
one more time. I just noticed /heard a hissing noise.

I have a small 1-2millimeter hole in the Y-Pipe.

Could this be stealing my power. It is on the passenger side
right where the y comes together. It sounds like a t-kettle
going off. I am surprised that I am not getting any codes.
The exhaust looks normal. Can this hole just be welded closed
or should I just replaced the entire y-pipe. Would anybody have
a quick fix to close it up to see if this would restore my power.
I am wondering if some kind of back pressure thing is happening
or just a fluke that it happened at the same time as the loss of power.

Mark

Mark