Rough idling ...

i have a 87 Astro van with a 94 Vortex engine 4.3L V6 sitting nicely in my puppy. for this past month i have been experiencing a rough idle once i start her up in the morning and stalls when i back up, occasionally the engine will rattle like hell until i step on the gas. would any of you would know what could cause this?

i have recently done the timing, the heads, ignition, vaccum lines have been inspected and no cracks so far, but my Cylinder number 4 is pumpimg oil like crazy. she use to pump it before doing the heads, but the scenario is getting worse. Starting to do some back firing when i step on the gas. i could maybe think that some sensors are slowly going.

Also need to mention that she is on Propane and had the engine serviced this week and did the heads about 4 months ago. Also forgot to mention that the engine has over 550,000,00 KM on it as i work as a delivery driver.

i do take good care of the van and the tranny went on me 6 months ago and that has been rebuild and updated. my diff is also going and going to be replaced pretty soon as i have a spare one on my lot.

Correct me if i am wrong, but if one cylinder is going or pumping oil, would any other cyl would show sign of weakness? like a small residue of oil?

i am thinking that the mechanic didn't do a good job on the heads as she is worse now than ever before. I am going to 2 liters of oil "20W 50" every week or 2. are the seal gone now and giving the cyl # 4 a bad compression?

Any feed back would be nice so that i know where i stand and get another mechanic to do the right job this time or is it time for a rebuild engine.

If you are getting oil in the cylinders, that's the fundamental problem. The side effect is that it cruds up the spark plugs to the point where they don't spark the fuel/air mixture.
Are you getting visible smoke out of the tail pipe?
Assuming the job on the head gaskets was good to begin with, I'd pose the question to the group: Could this be bad rings on the piston?

I can't really tell if i can see smoke, actually i don't. the fact that i am running on propane and using a Synthetic 20w-50 oil. synthetic doesn't show smoke when pumped, regular would, but i do notice some smell. some people say it is the ring, but wouldn't the others cylinders shows some weaknesses?

either way, the engine is going for a rebuild. anything that i should watch for?

the guy told me that he was going to remove the balancer for an extra 20 hp.

let me know what i should watch for so i don't get scammed.

thanks

I have this identical problem with my 89 4.3 on petro - Just redid the head gaskets and all was doing well. Inspected the engine very thoroughly before rebuild, no warping or cracks.

Tonnes of power, no back fires, a little black smoke, but not much. Good pressure, and not going through oil, however:

Found a small leak, dropping a couple drops of oil a day. Can't find where it's coming from. Checking oil regularly and it smells burnt/funny?

SES light comes on after about 20 minutes on the road.

Rough idle and stalls during reverse.

Aside from that, once moving it flies although idle is getting worse.

I thought timing was just a bit off and burning rich, but burnt oil? Hmmmm....

Also, in park sits nicely, only in D while stopped is it problematic.

something just caught my attention while i was driving. Could the ignition module could cause this kind of behaviour to my van? most people say thatit could. i fnot, try the map sensor or try your rotor and cap.

Problem Solved

i found out what it was for the idle problem. ever since that thing has been fixed? the van started the first time and no more bad idling.

2 vacuum lines coming out of the firewall on the driver side where you can see a bunch of wire coming out behind the battery? 2 lines broke at 5 different places. those lines has now been replaced and the idle is now way better and the van starts at first time in Cold start. propane usually takes several seconds before it actually starts. LOL no more.

more has been done to the van today as i finally got my steering column installed, more lights installed and more will be done tomorrow. "ignition related. :lol2:

Groundwar,
I've got an '89 too. I've been having idle problems as well. I just rebuilt my throttle body today. What I found was a huge amount of carbon build up in the PCV port. The port was nearly closed off, the gaskets were mush, the throttle body bolts were under torqued. Basically the trottle body was a huge vacuum leak. I'll post again tomorrow after I finish up the clearance mods to complete my power plate install.
I've done all the tune stuff and all the sensors, catalytic covertor too. I think the tbi cleanup is the silver bullet.