Hey guys this place is awesome for help done lots so far but now I'm at a loss, I'm trying not to spend tons of money to take to a mechanic if I can do it myself so here are the problems I am facing.... I have a 1991 Sierra 350 Z71 has about 250000KM on it
First one is the RPM guage will jump from around 500 (or lower idles low when in operating temp)to 1500 with no change in engine sounds, will do that for a little bit and then will stall out. it will sometimes start up and go for a bit before doing that again but will die and has not started before.
Second, if I am driving for awhile the RPM's (before the first problem) would get really low down to about 200 and then will drop to 0 and stall, the temp will go up and red line and it will not start for 30-40 minutes till it cools down then will start again, not sure why this happens the temp is usually shown around 80 or 100 I have replaced the thermostat but has not worked where it will not overheat.
Third, after all of this my steering column was loose and I was told this may cause the RPM jumps I tighten the column but now it will not start at all, it will turn over and send fuel but will not start, did I screw something up in the steering column. when I did it that day I did take it out and drive and everything worked fine, but it did start to jump in RPM;s again and not its not starting at all... Could it just be the battery which is a couple of years old?
I have just replaced the plugs wires, cap and rotor and will need to get a new rad, it is leaking pretty good, but I have always been putting in lots of colant making sure that it is topped up, not sure if that is a cause of the probs. I have also replaced the fuel filter and oil change about 2.5 months ago.

I got this truck impressed my girlfriend and my buddies but now I'm embarassed to have them around it with their Fords cause thats all I'll hear about for a month... If any of you could help me with some or all of this please let me know cause its a nice truck and I don't want to give it away, dispite the gas bill every week.Thanks

im not an expert on these trucks or any trucks for that matter but it sounds to me like its a bad battery i know vans are different but our van wen the battery was goin it was doin crazy stuff like that it wouldnt do anything properly some times wen you shut it off it would keep runnin the sterio would kinda flick on and off all sorts of crazy things happened. but dont take my word for it let some 1 else clarify this a bit more wish i could b of more help

That '91 would be similar to my '89. That Chevy will be running when your friends Fords are sitting, so don't let them razz you too much. If you've got a bad radiator and you have to add a lot of coolant, then that is one source of overheating. If you've got a closed system then it should operate at a more normal temp.

If you've got a battery problem; make sure all your connections are tight. A loose cable will cause all kind of crazy things, and if that's the problem it's a simple repair. If you've got a bad battery; replace the cables too. If you know how to use a voltmeter, measure at least 12.5V to 12.8V sitting, and over 13V when the engine is running. With the engine off, you can hook up the voltmeter to battery and ground and start wiggling the cables. See if the needle or readout wavers... It's kind of hard to trouble-shoot from a distance, but this is easy stuff to try.

That truck probably needs a little bit of TLC, but I think the problems are solvable.

Thanks Guys I am going to check out the battery, that was one of my brothers thoughts, he had also mentioned that it may not be getting fuel, would that be a cause of it turning over and not starting?

just an update on this problem, the battery seemed fine, just to be sure we hooked up another battery and nothing happened again, Any sugestions where to go now.... It seems like its not getting fuel but the fuel runs to the throttle body.

Well everything is done, I had it towed into the shop and he went over it and it was the ignition module, with that replaced it now runs well,

Good to hear you got it running. Normally if you're getting fuel from the injectors, the best place to go next is the ignition system. And welcome to the board!

The loose steering column and the RPM jumps statement is the one that confused me. As for the FORD BOYS, they were smart enough to give you any advice other than razz you, so they are two times dumb---they bought Fords and they had no clue. Tell them if it weren't for the Fords, then GM would have to sell more S-10s for them to drive.

You can't Piss on what you can't catch GM all the way. I used to drive Ford, then the Eighties came around and Ford died and ugly death ---I saw the light then.