Kwijybow

So I'm running an LG4 in my third gen. My engine has been acting oddly lately and Im not sure what the cause is, as I am aware of a few small issues (such as noisy alternater berrings) and im not sure which could be causing my problems. Shortly after the cap / rotor replacement, the engine started idling rougher than usual, especially when idling warm at red lights. If left idling in gear with the brakes on, the engine rpms will fluctuate up and down a bit and then drop down to a stall. I have to push the gas down about 1/8th of the way and hold it there to keep the engine running and it will keep running, however the idle gets really rough (not sure what "knocking" sounds / feels like). Once I start moving again, the engine smooths out noticably...until the next red light. The engine also runs on after turning the ignition off. I will turn the key to off and the engine runs for a good few seconds before finally dying. I'm planning on taking the car to a mechanic in the near future, I just want to know if any of you guys know whats going on, or even have a guess? I don't want to go to the mechanic being totally clueless. I don't want them to fix what doesnt need fixed.

Rob00158

Hi there,

Engine run on is usually caused by excessive heat inside the cylinder igniting the fuel after you switch the ignition off. Did you check the timing after you changed the cap? If the timing is out of whack (which I suspect) it'll cause idle problems / run on and possibly detonation which will resemble on knocking / pinking noise. Check the thiming with a strobe light or ask the garage to do it. 8 degrees advance should be about right.

Hope this helps

sofakingdom

iTrader: (1)

That would be a vacuum leak, pure and simple.

It is NOT the timing!!!! LEAVE THE TIMING ALONE. It doesn't just decide all on its own to up and loosen the bolt and move the dist and change, out of the clear blue for no reason; therefore, there's no reason to dink with it, unless it's already been dinked with. Changing the cap DOES NOT affect it. It is NOT the cause of the issue at hand, so don't compound the REAL issue by letting that big nut that belongs between the steering wheel and the driver's seat, back off and get loose and start rattling around under the hood knocking stuff out of adjustment that then just has to be put back where it came from.

Kwijybow

So I (regretably) had a "backyard mechanic" replace the cap / rotor and when he installed the new cap, he adjusted the distributor position by hand with no timing light, claiming "right about there should do it". I didn't like that one bit but the engine ran better after the work than it did before. So I guess I'll get a REAL mechanic to double check the timing and hopefully that should do it? Also, would an alternator with bad bearings have any effect on idle at all? I know my alternator's bearings are bad, (they make a noticable grinding / rattling noise at idle) but the power levels on my dash gauges show power levels are still right in the middle.

naf

iTrader: (7)

A timing problem is not consistent with your symptom of a rough idle (and smoother operation at higher rpms). The most likely cuprit that fits all of the symptoms is a vac leak.

Before you take it to a mechanic (who does that with a 20+ year old car?) open up the hood, remove the air cleaner and visually inspect all of the rubber hoses that connect to the carburetor and intake manifold. Look for something loose, broken, mangled or just plain not connected. If you see something that puzzles you, post a pic.

Kwijybow

So an interesting development on this problem. After reading this thread, I took all the advice about getting under the hood and looking around. After checking all the hoses, I figured I might aswell re-jet the carb leaner while I had the hood up and air cleaner off, (been meaning to do it for months now, just never bothered / too lazy). I leaned out the secondaries 2 sizes based on the edelbrock carb tuning chart and my idle and run on problems have noticably declined. That got me wondering, could it have just been an overly rich burn condition this whole time? Maybe a combination of too rich and winter gas? I don't actually know for sure if this was the problem so Im curious what you guys think.