Gee....the bad thing about this form of communication is it lacks expression. The last post was a stab at humor!!!!!!!!! Something to break the monotany of reading through about a thousand posts trying to find an answer to my problems. Look man I know you are busy....you have probably taken more time and helped more folks on this forum than anyone and you definately know your stuff....but don't read negativity or stupidity in everything man.....sometimes things are meant to be taken on the lighter side.

Thanks for the help if you care to offer it.....and if you don't thanks anyway.

 

You have not taken my advice yet, but you jovially talk of speaking to yourself... Restarting the engine puts the PCM back into open loop operation. If the problem is with a sensor not feeding the proper signal to the PCM, it would happen once the PCM transitions to closed loop. If you do not have the capability to look at the inputs and outputs of the PCM, then you may not be able to solve this problem.

And we have these things called smilies. Helps with expression... I do wish you luck with your problem though.

 

No codes indicates a fuel issue. Puter reads just about everyting else.

Could be fuel pressure regulator valve. Does it idle all day long? Does it idle at higher rpms forever?

Is your tank on teh side or in the back of the truck?
It could be a vacuum problem, or your air filter is plugged?

Check your charcoal canister and the vent lines for hte gas tank. Aslo verify your gas cap is on tightly.

PS.
I likes the post about speaking to yourself. I wonder that sometimes too.

 

Kyle, I am trying to take your advice, looking at an Auto X-ray machine now, but in the meantime I trying to find one to use. I think I may have it this evening. So hopefully that will be fruitful. I have a theory I would like to ask some advice on. I have checked the fuel pressure, it is in the norm, I have done the leak down test on the fuel system and no leak indication. Holds pressure with no drop well over 40 minutes. We have eliminated the fuel pump, regulator, the spider and nut kit. (checked them last night) At your prompt I believe my problem is at rpm...and probably when the PCM goes into closed loop operation. Now given that I don't yet have a way to check the I/O's on the PCM yet, I began trying to eliminate all the probable causes I could. I thought perhaps the knock sensor was sending a bad signal to the PCM causing it to retard the timing so bad that it wouldn't run under a load, but shouldn't that show a SES light immediately? So in my neverending quest for research I discovered that the MTV on the pre 96CPI models doesn't have a diagnostic circuit so to speak. It is possible to monitor it during operation, but if it is malfunctioning it won't show a code. Now if I understand correctly....the MTV's job is to tune the plenum at about 36% signal from the TPS. So....I did a little test last night......I let the blazer sit and idle for about 45 minutes and the trouble never started. But the MTV wasn't in operation at idle right? Next I took it out for a drive and low and behold after just a few minutes of backroad out in the country drive time I started having trouble again. So in those conditions the MTV is operating. Could it be breaking down and not opening when it should causing my problem?Even though I don't have a scanner and no guarantee that I can get one that will monitor the I/O signals, I still need to fix this problem. So I am going to try in the meantime to use logic and elimination to point me in the right direction. I can' t afford to just throw parts at it randomly so I have to make a somewhat educated guess. I think I may be going in the right direction, hell yesterday I was talking to myself and didn't even know how to monitor the I/O's on a CPI engine with an OBD1 PCM!

BTW....thanks for the wish for luck......I think I am gonna need it! And there was a smiley in my earlier post....I didn't edit it in there.

 

Hanr3,

That is what I thought too. However I think I may be on to something, hopefully if I can get my hands on a quality scanner this evening I will find out. Fuel Pressure Regulator checks out ok for no leaks, and it will idle forever or at least as long as I have let it sit idling. Tanks is in the back of the truck, vacuum seems ok, no leakdowns indicated there either. Air filter is fairly new and free breathing. Charcoal Canister, never thought about that.....you are saying if it is plugged it could be causing a vacuum in the tank? But the Fuel pressure doesn't drop when the problem starts. Please elaborate. Cap is on tightly.

 

A good multimeter can do more than a scan tool. I never said anything about a scan tool.

BTW, please use the edit feature to add more information to your post. Consecutive posting is prohibited by the rules of the forum. Thank others for double/tripple/etc posting just to raise their post count.

 

I am not positive how the gas fume system works, charcoal canister and hoses.
Are you positive that the excess fuel is freely flowing back to teh gas tank?
My thoughts. Teh fuel system is a closed system, if it has a vacuum leak you may not be able to maintain fuel pressure and the higher the rpms the worse theproblem. Something along those lines.

On the flip side, have you tested teh TPS, the IAC, and on some models there is asecond fuel injector for ideling/low rpms. When you hit higher rpms the other fuel injector kicks in. Mymind is getting a little rusty on teh year specifics and I may be thinking of the old TPI/TBI systems. However it could be a fuel injector problem as well. Where is all this leading? Basically your starving the engine for fuel. Its not getting enough to feed the engine. The problem becomes more noticeable when you place higher fuel demands onit. Teh puter doesn't monitor fuel pressure or fuel delivery, it assumesthe engine gets all the fuel it needs. Hence it will idle all day long with no problems.

Next time you take iffor a test drive watch your rpms instead of your speed. If you don't have a tach, leave it insecond gear.Listen to the engine rpm's.Watch your speed obviaously so you dont get a ticket, however the goal is to see if the higher rpms is the problem as opposed todriving distance.

My gut reaction is that distance/time is only a function of how much fuel your starving the engine for. Driving at lower speeds and higher rpms (2nd gear) for constantlywill eliminate any change the fuel system is playing catch up when you slow down for curves, stop signs, etc. Comprenda?

 

Have checked the TPS .71V@idle and 4.76V@WOT. I actually got it fixed tonight and the solution blows my mind. The NEW fuel pump was bad! I started noticing the thing getting louder. On my way home from work this evening my problem started again, this time I managed to make it into the garage before it got bad enough it wouldn't take any throttle what so ever. I checked my voltages at my sensors to see if maybe I was getting a voltage drop from the PCM as Kyle mentioned. I actually expected to find low voltage at the MTV. But it was working just as it should....energized @3100RPMs and de-energizedat about 4200. This problem didn't start until I changed the pump. But the pump I put in shows the same pressure readings as the one I just took out. The thing that was throwing me was the recovery time in which you could shut it off and then take back off again. A failing pump in my mind would just keep getting worse the longer you run it, not get better after just a seconds rest. But....just because it was getting louder, I decided to take it back and get another. Put it in, unhooked all my jumper wires from my multi-meter, hooked the pressure guage back up and went for a ride. Drove about 30 miles and no problems what so ever, as a matter of fact it has more pickup and harder acceleration than it has since I've owned it.So....can a fuel pump lose volume and keep pressure?? Beats me.....I was 100% sure it was an ECM problem like Kylesaid. Theconsistant timing in which it presented, the quick recovery, and the repetitiveness of it had me convinced. I dunno.

Sorry about the consecutive posts too. Never thought of it from a statistics point of view. Stats never ment that much to me though...I would rather bedefined for who I am and how I conduct myself than how many times I post a note on the puter. But I guess folks look for fame any way they can get it.So to all you 30 second stars looking to boost your rep by racking up posts......Thanks a lot!

Anyways.....thank you all for your help. I really appreciateit. It has been a tremendously crappy week and when the blazer started giving me problems after problems I was about to blow a gasket.

Momma said they was gonna be days like this....but she didn't say they was comin this many in a row!

 

Glad you got it fixed...this is what I suspected from the beginning.

 

Glad you got it fixed. I am curious as to the brand of pump you installed though. Hopefully you did not stay with the same brand the second time around. It is fairly consistent with any non-ACDelco pump that you will have problems sooner rather than later.