My 2000 chevy blazer has been "cutting out" whenever it reaches 3k RPM's and wont stop cutting out until it either passes 3k RPM's or sometimes it will stick there and you will have to let off of the gas pedal or turn off the cruise to stop it from "cutting out". Its like it momentarily loses all power to the drivetrain then quickly regains it over and over again. It makes a distinct "electrical arching" type sound as well as a clacking sound when its doing it. Those sounds sound like they are coming somewhere from in front of the firewall on the drivers side. We have also discovered its temperature sensitive: when the engine is cold, it doesn't do it. Also temperature sensitive in the sense that when it is cold outside, it does it worse than when its hot outside.

Here is what has been done to it and checked out so far to fix the problem:
fuel pressure checked and its fine
fuel pump replaced
new fuel filter
distributor has been checked and its ok
new cap, rotor, spark plugs, and wires
new camshaft postition sensor
new crankshaft postion sensor
checked all the valves and they all seem to be clean and appear to be fine

The vehicle hasnt thrown any codes or the SES light hasnt came on - sensors included in no codes thrown. One time though, when it was hooked up to the scanner we did find that X number of misfires were detected but still no actual code was given. My dad has been a Mechanic for 25+ years as well as some of his friends and no one can figure out what the problem is. The next thing that we suspect it may be is either injectors or computer problems or maybe a combo of both? Is that completely out of line to think that? ANY HELP AT ALL WILL BE GREATLY APPRECIATED!!!!! So what do you think the problem is or could possibly be?

Thanks in Advance,
Wesley

 

Can you get a code to set by disconnecting a sensor and running the engine?

Why did you replace the fuel pump if the fuel pressure was proper? Did you monitor the pressure during the condition?

Have you monitored all sensors for drop outs during the condition?

 

Well fuel pump sock filter was plugged up pretty bad and the fuel pump wasnt functioning properly. It worked fine until about 1/4 tank or less then would mess up. But with a full tank of fuel, fuel pressure was within range. So we just replaced the pump figured we might as well while we were in there cleaning out the filter. Havent tried disconecting any sensors to get a code no. All sensors have been monitered during the condition and its not giving us anything out of the ordinary.

Anyone else have any ideas???

Sorry I dono how to edit my last post so I can add to it. But does anyone think it could be the EGR possibly? The more I read into it I think thats a viable option. The only thing that has me puzzled is if it is the EGR why is it only cutting out at 3k RPM's?

 

^ I'm thinking his suggestion to disconnect a sensor is to see if it sets a code to rule out ECM failure as a possibility.

 

I am not sure I totally understand what you are saying. If I disconnect a sensor and the ECM gives a code it does tell me the ECM hasnt failed totally, yes but the key word is totally. It could still have partially failed and just say the injection portion of the ECM could be malfunctioning. Am I correct?

My dads friend did come and look at it this morning and we all are in agriance that it is most likely either an electrical issue (short, not good ground, bad connection ect) Or the ECM is bad and it needs re flashed or a completely new one needs to be installed and programed. What are your thoughts on that?

 

My thought is take it somewhere that has a good scanner (Modis, tech 2, etc.) and read the live data. That will show you what the computer is seeing and doing. If anything looks way out of whack you can start to pinpoint from there. It could be injection related. It could be electrical related. Heck it could be some random Sensor that you wouldn't think had anything to do with it confusing the computer into cutting spark or fuel (for example a bad vss causing the computer to think your over the governed limit and cutting fuel) now that doesn't sound like its the problem but it could be something random like that.

 

I'm not sure if I can reply because you evidently didn't like my initial reply and asked "anyone else"...

Diagnosis is a process; you go through the steps and see what happens. If you don't agree with the steps, do them anyway. In the time you've wasted, you could have disconnected any one of the primary sensors (MAF, MAP, EGR, TPS, IAT, etc) and had a result. If it doesn't trigger a code, there is DEFINITELY a problem with the PCM. If it does, you have at least verified that the OBD system is functioning.

Have you been able to narrow down the location of the noise you mentioned? Might have a lot to do with the problem.

As far as the EGR valve goes, if it were bad, it would trigger a code. If it were stuck partially open, it may not trigger a code, but it would cause idle quality problems above pretty much all other problems. You could try removing it, cleaning it, and reinstalling it with a new, screened gasket. We have a tech article that should help in that endeavor.

I'm not here to waste your time so please don't waste mine. There are plenty of other people that need help that will gladly do the requested task rather bicker over it. Don't like it, feel free to tell me to **** into the wind and I'll move along. Thanks and good luck with your problem.

 

No thats not what I meant by that at all and I am sorry if it came off that way. When I put anyone else I just meant anyone else have any ideas because I am trying to get as much info as possible before diving in and working on it. So lets start over I guess....You say that by disconnecting sensor it verifies the computer is not bad correct?...Now I am wondering this, if the computer still gives me codes (it still gives codes just no codes that help with the problem. Last code it gave was crankshaft position sensor fault. I replaced that and it made no difference other than the SES light not coming on) So back to my question if the computer gives me codes like that is it safe to say its still functioning properly or should I still disconnect a sensor? Also I dont believe its the EGR valvle anymore either so I am not even going to go that route.

One thing that has been brought to my attention is it could possibly be the rev limmiter malfunctioning. Is that a possibility? I did put a transmission from a junkyard in it about 5 years ago and it worked fine for the first year then the problem arose and it hasnt been the same ever since? So could it have anything to do with that? I will say that normally when it "cuts out" the engine wont rev above 3k rpm's as well as the drivetrain loses all power. However last night I was making it do it on purpose to try to throw a code and it did its normal cut out thing at 3k rpm's but then the engine reved past 3k rpm's but i still have no power to the drivetrain and still no forward movement power beside coasting. Maybe this will help in diagnoses.

One last thought I have had is it may be just one certain part of the ECM thats not functioning correctly. If thats the case it would be almost impossible to detect. So I have considered getting the computer re flashed at the dealership. How much would the cost of that be exactly? I have heard anything from $80- $300. So what is the average price of that going to cost me?

Update: Went out a few hours ago and purposely made it cut out and I got the SES light to come on and just took it to autozone to have them scan it to see what the code was. Code is saying crankshaft position sensor, again. I have already replaced the crankshaft position sensor once and cleared the code. So whats the reason for this? Any explanation as to why it would throw the code during the condition and then the code is a code I have already adressed and cleared?

Once again thanks for your help in advance,
Wesley