Need help, engine won't idle, runs rough

**rickyg1** · 08-15-2007, 11:46 PM

1994 GMC C1500 ext cab. 5.7L
I ran out of gas on the way to the station, I put in 1 gal of fresh gas and it started right away but on the way I had to rev it up a bit. 1 mile to the station then I put in 10 gal of gas and STP fuel inj. cleaner, still ran rough and not able to idle. No smoke or excessive fuel.
Next day, Heet water remover, changed fuel filter, and plugs, still runs rough.
I checked EGR last night and it works.
Please help.
Thanks
RG
my_littleitaly@yahoo.com

**TrailLeadr** · 08-16-2007, 12:01 AM

Are you getting a check engine light?

You should check it for codes. Sometimes it stores them even though the light may not have come on, or stayed on.

**rickyg1** · 08-16-2007, 04:08 AM

I'll check it out. Do I need a special device to read it or is this a matter of shorting two pins together? If so, could someone explain where the pins go and which pins get shorted?
Thanks
Rick

**rickyg1** · 08-16-2007, 04:13 AM

I didn't explain very well that when I put in the 1 gal. of gas it ran rough right away. I revved it up a bit to about 4k rpm intermittently to get momentum.
It ran rough the moment I put in the 1 gal. and restarted.
I also took off the air cleaner to observe the fuel being sprayed into the bowls and it was fine.
EGR- I pulled it off, put a vacuum on it and it held for two minutes just fine.
I'd be interested in understanding what happened when I find the bad part.
I'm wondering if I blew something when I revved it up?
Rick

**Crawdaddy** · 08-16-2007, 08:36 AM

If the truck very quickly ran out of fuel and abruptly stopped, instead of petering out, the timing may have gotten thrown off my a tooth or two. On my uncle's Dadge Caravan, he ran over an 18-wheeler driveshaft and it tore the gas tank to shreds. Long story short, the sudden and abrupt stop of the engine caused the timing to get thrown of and he had to get a new belt installed and have it re-timed. Hope this isn't the case for you :|

**TrailLeadr** · 08-16-2007, 09:21 AM

Originally Posted by Crawdaddy

If the truck very quickly ran out of fuel and abruptly stopped, instead of petering out, the timing may have gotten thrown off my a tooth or two. On my uncle's Dadge Caravan, he ran over an 18-wheeler driveshaft and it tore the gas tank to shreds. Long story short, the sudden and abrupt stop of the engine caused the timing to get thrown of and he had to get a new belt installed and have it re-timed. Hope this isn't the case for you :|

It's a possibility, but the 5.7 engine doesn't use belts. The belts are much more pliable, they tend to flex and stretch, easier than a chain will.

As far as checking for the codes, you can stop by a local autozone (if you have one), and they can pull the codes for you for free. If there are no local autozones then you can do it yourself with this:
http://www.troublecodes.net/GM/

**tbplus10** · 08-16-2007, 11:07 AM

Ran out of gas and now runs rough. Check the fuel filter theres a good chance you picked up trash from the tank and now its in the filter or possibly the pump.

**rickyg1** · 08-16-2007, 02:48 PM

Thanks TrailLeadr. I'll try it tonight when I get home.
If I disconnected the battery for approx. 10 secs then reconnected it, would the codes still be stored? And if not, would the code reappear upon first attempt at a failed start or run?
Rick

**84fiero123** · 08-16-2007, 06:53 PM

Could be a clogged injector. Take that air cleaner back off and find an old timing light and hook it up just like you would to check your timing.

Now point the light at the fuel spray coming out of the injectors. It should have a nice cone pattern to it. If it doesn’t you need to have the injectors cleaned professionally or send it out and have it cleaned.

When you disconnect the battery for more than a minute you loose all stored codes. If the problem is still there and the check engine light is still on or flashing then you still have a problem.

And yes you can use the old school paper clip trick on the 94’s. it’s the last year you can do that, now for the newer ones you need an ODII reader, most parts stores have them on loan.

**rickyg1** · 08-16-2007, 10:42 PM

Okay, next idea please.
I checked with jumper and I got the "service engine" light when key turned to on did "flash" pause "on steady"
I checked the cononical form of the jets and they are cones that spray bursts timed exactly out of phase, or opposite timing, i.e. left right left right. The higher the RPM the faster they spray.
Sounds like timing is great! in Park (or Neutral) and when idle is coming down and gets to 900 rpm's it drops off abruptly.
No ability to idle.
The strong spray would sound to me like the fuel filter is fine (new) and the flow is fine.