Thank you for the detailed reply. If you look at the first post, you will see all that has been replaced. The entire exhaust system including the catalytic converter were replaced in June.

I have checked the fuel pressure. The fuel pressure read 58-60 lbs just turning the key on through 4 tries. At idle, the fuel pressure is 52lbs. All within specs. After I turned the key off, the fuel presure dropped from 60 to 54 and held for quite a while then after about 45 mins. to an hour it was down to 40.

I checked the MAP last night and it is ok also. There are no OBDII codes except the random P0131 O2 Sensor Circuit Low Voltage (Bank I Sensor I). I have checked the connections going to this sensor (which I replaced in June) and they are ok. Do you suppose this could be the ECM itself?

 

You mention fuel pressure, but are you monitoring the fuel pressure while you are experiencing the problem? Fuel pressure is one thing, pressure under demand is entirely different.

And sorry for "missing" the information in your first post. This still does not rule out that you could have gotten a bad catalytic converter though. All useful information whether you want to use it or not.

 

I suppose it is possible that a bad new catalytic converter got installed when I had Midas do the exhaust system. I hope not. That is the reason I paid the extra money for them to do it.

As for the fuel pressure, I guess I dont understand enough about it. I was under the impression that outside of the fuel pump and the fuel pressure regulator on the injector assembly (and associated lines), that there was not anything else that controlled the fuel pressure. I should be able to use the brake and put it in drive in the driveway to check it under load.

 

Have you done that though? Everything that you have written has stated idle or key-on/engine-off...

While those are the only things that directly control fuel pressure, the checks you have done so far have not assessed the supply side of things (i.e. the ability of the pump to supply the required pressure at higher flow rates).

 

I finally had time to get back to the blazer. I hooked up the fuel pressure gauge, put it in drive, held the brake, and monitored the fuel pressure are I took it up to 2000 RPM. The engine was surging but the fuel pressure was 58 to 60 and steady. If it is fuel, it would have to be the injectors themselves, but I doubt it. Still no useful codes.

 

it's gotta be injectors. but i don't understand why there's no codes. maybe theyre just cutting down the amt of fuel going through rather than cutting off. the same exact thing happened to me but i went through a lake-sized puddle with my jetta vr6(not on purpose, long story) it started surging and then went through a spell where it acted starved and almost immediately my check engine light came on. i mashed the throttle just to keep it running and then it would take off and throw me into my seat. lol. it was my injectors grounding out i found out later, becauswe of the water. that was some scary ****.

 

I know, I keep thinking about those injectors as well. Here is how it ran yesterday. It now surges (most of the time) when I hit the gas pedal quickly to take it to about 2000 rpm. If I ease into the gas it will sometimes run smoothly. If I hit it a little harder, it will backfire occasionally while surging. As long as I hold the gas in that one place it will continue surging. Usually if I increase the gas it will smooth out, but not always. It always smooths out when I let it drop to idle. The only code it has given me during all of this is P0131 - O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1). This code shows up occasionally if I hold the gas andlet it surge for an extended period.

Bottom line I guess is how many people think it is the injectors? I replaced the whole assemblyin June for a similar problem. It is still under warranty from autozone (12 Month). Do these go bad this quickly ever?

 

Here is a follow-up.I replaced the injector assembly again (under warranty), the nut kit (fuel lines to the assembly), and spliced in a new injector assembly connector and wires. I used a shrink seal crimp to splice the wires to seal it from contamination. The replacement plug seals better than the original. The Blazer is running great.

One last thing though. The plastic clip that holds the cruise control cable onto the throttle broke. Since the cruise control cable is threaded through the plastic clip, do I have to replace the whole cable or is there an aftermarket fix for this?