miguelc561

For the last year ive been battling the same problem with my car. 86 sport coupe 305 carbed bone stock. Ive been given the run around with vac lines. Timing. My carb. Vac leaks. All kinds.of things. Ive probably spent 2000 dollars in replacement parts and my car runs the same, ive taken.it.to.multiple.shops and noones got a clue. One told me my head gasket was bad during a.compression test i replaced it. Nothing. Heads are fine. There are no leaks.anywhere and my carb is fine. Ive put 2 of the same carb on my car and it ran the same. My car when.first started idles at 1500. Sometimes i can knock it.out by giving it gas and it.goes to 1000 and.slowly dies.in.neutral. my car drives just fine until i let off the gas. I have to 2 foot it everywhere. Sometimes itll run just fine till i come till a stop sign and it stalls. Sometimes itll idle at 1500. I shut off the car restart it and i have the.rev it.just.to.keep it.on. it has a mind.of its own. Im out of ideas. Fuel pressure is ok. My car wont even.sell.for 1000 bucks so im stuck with it. Only 86,000 miles. Crazy huh. Only think i think.it.could be is my ignition switch but im 99% sure my car ran bad before this. One day it was stuck. I replaced the ignition switch. Still stuck. I got pissed and forced it.forward a.d to this day it starts when i.turn it 180° but like i said pretty sure.it ran vad before that. To.drive.my car its a constant battle of putting.it.in.neutral. reving and shoving it in drive. Feel free to put out ideas. Im.running on all 8 good spark to all. Full tune up. All new lines and.hoses, assume everything is.new cause it.probably is

rusty vango

what do you have the timing set at? have you tested the ICM? how is your fuel filter? is your coil good? have you tested it?

miguelc561

Ive had the ignition tested they said all 8 were getting a good spark. New filters. ICM?

miguelc561

Ive tried it with the tining everywhich way. Thats not it

miguelc561

To me it doesnt sound like it.could be the module

rusty vango

ICMs can and do go all wonky .and since you haven't replaced/tested it .I would do that. while your at it, test your coils output. I think ,from your posts, that you have an ign or fuel problem.sometimes. its the little things that you may have overlooked that make you want to set it on fire

miguelc561

Well my fuel pumps fine. I dont understand why if i had a fuel problem.it would run so hi at first then cut out and whenever it wants runs completely fine whenever it wants. Ill post a video on youtube eventually then send the link

Berlinetta00

One other consideration could be your timing, obviously to include the ignition control module. Easy to check with a timing light, just rev it through where it should have full advance (about 2500 rpm) and ensure it does not skip around at a set engine speed. It should have at least 30* total timing, with about 8* at idle. If it skips or is way off, ensure your module, distributor, and timing chain are all in good repair.

miguelc561

Really think it could be? Cause im running.out if money to just blow in this thing like i said 2000 in parts so far

miguelc561

any ideas. This is when.its warm when its cold it idles at 2000 rpms

ASE doc

I would guess it's a fueling issue. Not fuel supply but rather lean fuel(too much air, too little fuel) at idle. However, I'm not really in the business of guessing. Before I asked you to spend another dime on parts or repairs, I would have you first connect a scan tool and read codes, if the CEL works and lights up when the engine is running sometimes(the CEL should light up at bulb check with the key on then turn off when the engine is started). If the CEL works and doesn't light up when driving, use the scan tool to read O2 sensor voltage as the engine goes to idle. Your car, if it is really all original and complete, uses a computer command control carburetor with an ECM and oxygen sensor to monitor and control fuel mixture. The carb has a mixture control solenoid built into it, along with a throttle position sensor. The solenoid stops are adjustable for base idle mixture. Assuming that your CCC system is functional, you can use a scan tool to monitor O2 voltage and adjust the MCS stops to achieve the correct idle mixture, assuming that there are no unmetered air leaks, poor valve sealing, other causes of low compression, or other issues in general that will cause the engine to run lean in spite of where the carb is set. The scan tool will also let you see manifold pressure(vacuum) and throttle position sensor voltage as either one or both of these could cause your problem.

You were told that your ignition is okay because it fires on all 8. However, what I don't know is if the ignition was actually scope checked to verify KV and normal combustion. A scope trace of the secondary patterns will also reveal lean air fuel mixture or other problems in the combustion process. Weak spark due to a failing old coil, high resistance in wires, or a worn cap and rotor can aggravate a lean condition as it takes more KV to fire the lean mixture. These engines were tuned to run lean from the factory for emissions sake. Anything that causes the engine to draw unmetered air or otherwise affects idle fueling will cause exactly the symptoms you describe.

ASE doc

An inexpensive alternative to a scope check of the ignition, while nothing like a substitute, is a KV tester. I have a cheapo Thexton adjustable tester for quick checks that connects to the plug end of the wire and can be set to various KV. The GM HEI should fire 40K with a loud bright arc. If it won't there is a problem. If you can get 40K at the coil and not at the plug, the problem is the wires, cap and rotor. If you can't get 40K at the coil, replace the coil.

miguelc561

Im just going to take it to the shop for the third time. Noone knows whats wrong with it but i trust this guy. If he cant figure it iut he wont charge me. Ive invested ti much time and gotten nowhere