Hi all,

Im asking on behalf of a friend who's engine isnt running well at all, heres his original message.

The car has NEVER run well. It was ruined by a garage who were trying to get a new engine out of me and that didn't help. It's always had an issue with fouling it's plugs, (stem seals have been done) and generally running poorly. A friend got it running better but found that the exhaust flap had been smashed shut which had caused issues on the engine to be exacerbated significantly. Since then it has deteriorated again and had an issue with stalling and chugging. Carb was adjusted and was better but developed a new issue of overrunning when turning off and puffs of smoke through the carb.

It Over fuels horribly and really stinks. Lacks power and still misfires and pops through the carb."

Can anyone help ?

 

What kind of carb? When was the last tune-up? (plugs, cap, rotor) Have the valves been adjusted? Compression test? Fuel filter? Cat stopped up? Check all the vac lines? Lots of things can cause what you talk about; start with the basic troubleshooting and deferred maintenance type stuff.

 

Yup he needs to check all the basics first. I have said it needs a compression test first because if its all bad results its pointless putting any money into it.

Im not sure what the compression results should be though on each cylinder

 

need engine info!!!!!!!!!!!!!!!!!!!!!!

carb? tuned port? stock? modified?

 

Compression will depend heavily on what cam is in it; stock, should be roughly 160 - 180 on each. Look for consistency: not more than 10% variation or so.

One cyl way low is either a burnt valve or failure of the intake valve train. One cyl way high is failure of the exh valve train. 2 adjacent cyls low is failed head gasket. Might of course have more than one problem.

Make sure the test is done with the 12V to the distributor disconnected, throttle blocked wide open (VERY important), all spark plugs out, GOOD HOT COMPLETELY CHARGED BATTERY at all times.

 

Sounds like the cam has worn lobes

 

its an 83 Trans Am with a 305 carb engine. The engine bay of the car is in quite a state so it doesnt look like its been well looked after through its life.

 

Would a worn cam cause it to smell of fuel and still keep running after turning the key off ?

 

Have you checked the timing?

 

He hasnt no, ive told him to do that though. like all the basics. if it were my car id check for obvious leaks etc then id change the plugs, dizzy cap, rotor arm, leads, check the timing and take it from there.

I still think it needs a compression test

 

I hated the carb on my 83 TA..... It would plug up at the least excuse... It got to the point that I could pull the top off the carb, blow out the jets, and stick it back together, all while sitting on the side of the road. (mainly, because I had to on several occasions.)

Also, that's an electronic carb, with a solenoid in there for mixture control.....

Check all the stuff previously listed, make sure it all up to snuff, and if you still have troubles, rebuild/replace the carb.

 

I would bet that the timing is off, had this experience before.

 

the worrying thing is he said he had the carb rebuilt last year. i think the engine is dying by the sound of it.

stupid as it is i dont really know anything abouts carbs. my car is TPI and thats all ive ever really worked on which is far more complicated lol

 

He should LEAVE THE TIMING ALONE.

For some reason, that's the first thing every n00b thinks ought to be dinked with. Fact of the matter is, with modern electronic distributors, it DOES NOT CHANGE, unless somebody dinks with it.

Back in the day, when cars all had points, it was a different matter. "Received wisdom" (aka Friday night McDonalds parking lot monkey-spank) hasn't caught up with the news.

Check all the mechanical type things before that. Unless you have good reason to suspect it's already been dinked with, don't dink with it.

 

Ouch, I assumed the timing could have been dinked with because head work was done... I guess a pro should have thought it could have been reinstalled out of time and been advanced back by the ecu... wrong?

 

People have the oddest ideas about what the ECM does re.: timing...

The ECM HAS NOT THE VAGUEST FOGGIEST DIMMEST FAINTEST HINT OF A WHIFF OF A GLIMPSE OF AN INKLING OF A CLUE what the timing actually IS. All it knows is, "I got a pulse from the dist just now", "I'ma look up in my table here how long to wait til I tell the coil to spark", "I spark now". That's IT. If you crank on the dist, the ECM just waits however long the table says to wait after that, and sparks. PERIOD. The only feedback it has on that, is the knock sensor; which tells it, too much. It responds by yanking about 50° out to guarantee engine safety. Too little? It'll never be able to tell. It has no eyes in any place that can tell it that.

If you set the dist a little (like, 20°...) too far advanced, the ECM will never know. If you set it an equal amount retarded, it will never know. Just like a mechanical distributor in that regard: all it can create, is AN OFFSET from whatever place you twiddled the distributor to.

"Correct" is when THE ENGINE wants the spark to occur. THE ENGINE does not whup out some "book" published by some holy "authority", whup out its "light", look at its "mark", and decide, "I'm gonna run like crap" or "I'm gonna run great". It cares not the slightest about "mark" and "light". All it knows or cares about, is SPARK. It does not care how the spark comes around to being at the time that IT WANTS; if the spark is at the right time, it likes it. If not, ... you do the math.

The factory's settings, both the static (what you get twiddling the dist body) and the table (chip, program, tune, whatever you call it; or, springs, weights, cans, & cams, back in the day) have to serve MANY masters. Especially in the 80s, the masters were, in order of authority, EMISSIONS, gas mileage, EMISSIONS, grandma doesn't complain her car is "rough" or "harsh", EMISSIONS, warranty, EMISSIONS, wide-range random conditions tolerance (Florida in a thunderstorm, Yellowknife in the winter, Phoenix in the summer, Breckenridge, ...), EMISSIONS, CAFE, EMISSIONS, fuel properties, EMMISIONS, and somewhere WAY down toward the bottom of the list comes power, followed closely by EMISSIONS.

So... yes, in short, wrong.

Ya want your car to run RIGHT, ya find out what THE ENGINE wants the timing to be under all conditions YOU run it under. Worshipping "The Word" of some "book" because you don't understand what the ECM is actually limited to, won't cut it. You do that, I'll beat you every time.

 

I suspect it has been moved because so many people have screwed on with this engine, theres no harm in shining a timing gun at it to see where its at.