305 deisleing (running after off)

[poordudewhowantcar]

what the can i do to fiz my prob? help out ? better fuel ? timming what ?

[GMMerlin]

Originally Posted by poordudewhowantcar

what the can i do to fiz my prob? help out ? better fuel ? timming what ?

You can start by giving us some information.....sorry my crystal ball is in the shop.

[poordudewhowantcar]

ok you want info????
305 2 bbl low end cam

on long travels (30-50 miles) @ 60 + mph I'll over heat

when i first turn it on (on a good day) it take about 1.5 seconds before it turns over cranks and turns on

On a hot day when the engine is hot i have to turn it over and SLIGHTLY hold the gas so it won turn off
(if i dont hold the gas it WILL turn off)

Ive replaced the antifreeze and so far i have not over heated(but i have still deisled)

I think my timming might be advanced how do i reteard it with out Fackin it up?
also would a thermostat help?
how can i fix the fact that my car turns off after it turns over? by a vacum or something ? help me out

ive told yall everything i know so far.

[poordudewhowantcar]

another thing that i need is new wires and cap and rotor any one got a nice one for sale?

[poordudewhowantcar]

o.............k

[bobss396]

I'll bet your timing is too far advanced. I think stock is like 4-8 degrees BTDC. Put a timing light on it, pull off your vacuum advance and plug the line first. A higher than normal idle will make it run on too. As far as overheating, it usually goes with a retarded timing issue.

Bob

[y2kminuteman]

bobss396 is right. If you address all of what he said it will probably fix your problem or will be a great start...if not spot on.

[comp]

Originally Posted by y2kminuteman

bobss396 is right. If you address all of what he said it will probably fix your problem or will be a great start...if not spot on.

i agree ,also check thermostat,, i have have a few 305's that like to carbon up,, is the EGR still on it and working ??

[silicon212]

First you claim it overheats when operated at freeway speeds. It diesels.

Do you get a Check Engine light? And if so, is the code EGO sensor related (oxygen sensor)?

Dieseling can be caused by a number of factors - including high idle speed, overheating, excessive carbon buildup in the combustion chamber, etc. I'm going to pretty much kill the excessive timing theory here since ignition timing is pretty much out of the equation once the key is turned off. Advanced ignition timing can cause detonation which in turn can cause hot spots in the combustion chamber thus leading to an afterrun problem, but it takes a lot of advanced timing and a car in such a condition will likely have no power on acceleration. You'd know if this was the case.

If the car is idling high, that can cause the problem. Ideally, you don't want your engine idling higher than 900RPM with the transmission in park/neutral, and in the case of an automatic transmission the general rule is 600-700 RPM with the wheels blocked and the transmission in drive (and the vacuum advance or computer interface on the distributor disabled). If its higher than this, that's a place to start. However, there's the problem of the overheating on the freeway. Does the power drop off as well? Look for a plugged catalytic converter, and excessive carbon buildup in the combustion chamber. Chances are you're running rich, and if you have a check engine / service engine soon light, it might be EGO related and would bear out the rich condition. Is the engine carbureted?

You can blast the carbon out of the chambers on a carbureted/TBI engine by SLOWLY pouring 1 cup of water down into the carb/TBI while the engine is running a MINIMUM 2500 RPM. Get a tach if you're going to do this - you don't want the engine running slower than 2500 RPM. By pouring slow, I mean 1 cup of water in about 15-20 seconds. 2500RPM. Remember that. You could hydro-lock the engine if you're not careful here and that would make the dieseling the very least of your problems. Done properly, this will decarbon the upper cylinders. Done improperly and you could have bent connecting rods, broken pistons or at the very least, blown head gaskets and possible bent valves. What remains can be removed by doing a few 20mph-60mph WOT runs.

Adjust your timing by using a Timing Light, and by loosening your distributor hold down bolt SLIGHTLY enough to turn the distributor with a little force. Counterclockwise rotation of the cap will advance the timing, clockwise retards it.

Note - a vacuum leak can cause a dieseling condition as well as off-idle power falloff so you might also want to check for that.

[Stepsider]

A few months ago I began looking through an auto repair manual I bought many years ago.

I began reading this book before I found automotive forum

I was trying to understand how my engine works so that when a problem occured I might better understand what it is.

This article reminded me of something I read in that book

Direct quote
Dieseling could be caused by the thurmal controlled heat valve not operating properly.

I used the direct quote because I could not remember exactly what the book said without reading it.

There is only so much to be learned from one source.

I hope this helps