I have a 1995 blazer 4x4 (CPFI)that started out running rough and surging; especially at lower speeds. It would sometimes die at idle and was sometimes hard to start again.

Next day - The Blazer is VERY hard to get started today. I have to crank it several times before it fires up. After it starts, it still surges at low RPMs, but stays running.

And the next day - The blazer died and would not start again. Last night I checked the fuel pressure and the temp sensor located on the drivers side between the back two cylinders. I has good fuel pressure and the temp sensor is within parameters.

And the next day - The Blazer will not start at all now no matter what the temperature.

The EGR valve was replaced about 1 1/2 years ago. The fuel pump and filter were replaced less than a year ago. The whole spider injector assembly, O2 sensor, distributor cap, rotor, coil, spark plugs, plug wires, and exhaust system from the catalytic converter back (including the catalytic converter) were replaced about 4 months ago. It ran great after that. I have a code reader and there are no codes.

Any ideas would be appreciated.

 

Numbers, numbers! What was the fuel pressure? What happened to the fuel pressure after you turned the key off?

 

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.

 

will it start with either?

 

First, I don't have any ether; I need to get some. Secondly, I went out this morning andthe Blazerfired right up. If I hold it around 1200 RPM it tends to surge slightly (to like 1800RPM)every once in a while. While doing this, it coded a P0131 O2 Sensor Circuit Low Voltage (Bank I Sensor I). I checked the O2 sensor and confirmed it is still plugged in. I got this same code a week ago, cleared it, and this is the first I have seen of it since then. Just to throw this out there, but the ignition control module was about the only thing in thefiring side of the process that wasn't replaced (see first post). Do they go intermittant? Could it be causing this? Or, I also wonder if the spider injector assembly is being intermittant since it is the only part of the fuel system that I can not 100% confirm. I have started and shut off the Blazer five times now.

 

ICMs typically heat up causing problems after driving the truck for a while. Then they will start to drop out randomly or just refuse to send the spark signal to the coil.

As far as the O2 sensor code goes, I would swap the upstream sensors side to side and see if the code follows. If you do end up replacing the sensor, get an AC Delco sensor.

 

I replaced the O2 sensor that is forward for the catalytic converter before. I did not replace the other one (rear of the converter). Those are the only two. Which one is bank 1 sensor 1? This thing is starting every time today. Hard to troubleshoot when it wont break. I know the trouble is not gone. It was parked on a slant when it wouldnt start yesterday and the outside temperature was 65, but I dont see how that has anything to do with it. When it first started messing up, it was worse when to outside temperature was45F or below.

 

You are correct, sorry, I saw 2nd gen section and thought of the 96+ trucks. B1S1 is the upstream or pre-converter sensor.

 

Heres the latest. The Blazer will start every time now. Heres the good part. As long as it is sitting in the driveway, it can run it up and down the RPM spectrum and it barely misses. However, once I put it in drive and head down the road, it has symptoms ranging from surging and lurching to acting like it is starved for gas. There are times I have to have it almost to the floor to get it to go 30MPH and during that it will intermittently just take off. As long as it is at idle, it runs great. And, like I said, runs ok in driveway when not in drive. If I put it in drive and hold the brake it runs badly. Could that spider injector assembly I replaced have gone bad? Almost acts like a fuel filter, but they supposedly replaced it when they replaced the fuel pump (I farmed out that work).

I just read on another post on here that sounds similar. ( https://blazerforum.com/archive/thre...-117690-1.html) It suggests the MAF (althoughthe95 Blazers have a MAP). Could the MAP be causing my problem without throwing anycodes?

 

There are a lot of things which just ran through my head. When in park, the fuel, intake flow, and exhaust flow requirements to run up through the RPM range is drastically reduced.

I doubt that intake flow is the problem, but a bad catalytic converter could cause these symptoms. A competent exhaust shop should have an exhaust pressure analyzer which they would remove the pre- and post- cat sensors to install their pressure sensors in and determine if the catalytic converter is causing a restriction in the exhaust flow.

Now, with that said, if fuel supply is the problem, then a fuel pressure gauge would show you that and is something that you can do yourself. You just need to somehow get the fuel pressure gauge where you can see it while you drive down the road.

None of this rules out an electrical problem though...