Help with diagnosis for an '84 Trans Am

[shelivedhere]

My '84 Trans Am has been idling rough and stalling out, even when the engine is warm.  Basically, it wants to stall when I hit the brakes.  I've been told that this is most likely a carburetor issue, but the last shop I took the car to doesn't do carburetor work and I don't think they investigated this all that well.  So, I'm not so sure yet that the carb needs to be pulled out and rebuilt.  My thought was to start by cleaning it. I am just looking for another opinion on what the problem might be based on the symptoms.  As I said it stalls all the time at stoplights, etc. One other thing I noticed was that when I take the key out of the ignition the "Choke" light comes on briefly. 

Any help here is greatly appreciated.  Thanks!


Tracey

[jameskuzman]

Hi Tracey -

I'm a relative newbie to the forum, so I defer to those with more experience of course, but a couple of things come to mind.

You mention that the engine wants to stall when you hit the brakes.  I'm thinking this could be a float level problem, perhaps, if it's gotten heavy and isn't keeping a sufficient amount of fuel in the carb as the weight transfers forward under deceleration.

How many miles are on the car, and have you ever had the carb rebuilt? 

Jim

[shelivedhere]

Hi Jim,

Thanks for the response!  The car only has about 85K on it and I don't believe its ever had carburetor work done.  I am the third owner and have not had the car for very long. 

I don't know if this means anything, but if the car is running in park it doesn't idle as roughly and won't stall.  Its only when I'm hitting the brakes that it will stall out. 

Thanks again!

[Toronado]

If you do not know the condition of the carb.,
I would suggest buying Cliffs book and a
SR carb. kit.

The reason why i say this is because lets say you find
the problem that causes bad idle & fix it, its most
likely dirty and under performing. A carb. in
a unknown state is waiting to start running
bad or cause the vehicle to no start on a cold rainy night.
Save yourself future headaches and rebuild it right.
(by the way rebuilding a carb. is very easy if your patient)

My car had a similar issue, and its the vent tube is just to short
so hit the brakes fuel comes out and floods it, it acts like its going
to die but doesnt, a fuel hose extension fixed it, after I rebuilt it.

[jameskuzman]

No problem, Tracey.

I must say I agree with Toronado that a carb rebuild is probably in order. 

Even though your car doesn't have a ton of miles on her, time takes its toll, particularly by way of ethanol-blended fuels on rubber and plastic components not meant to stand up to it.

I recently (and succesfully) rebuilt the E4MC Quadrajet on my 1985 Buick LeSabre.  It was my first carburetor rebuild.

I have no interest (outside of gratitude!) in Cliff's business personally, and say this unsolicited:  Buy the better kit from Cliff.  The over-the-counter kits vary wildly in quality, probably aren't as specific to your carb and vehicle as you think, and are only a few dollars cheaper.  Cliff's kit was incredibly thorough and very specific to my carb.  He also assembles the kits with ethanol-friendly components.  Well worth the small premium, plus you get fantastic support should you need it.

I also suggest buying Cliff's book, and if you want to be really thorough, Doug Roe's book on Rochester carbs.  Each is different in its presentation, and I believe they compliment one another well.  If you only get one, get Cliff's. 

I also STRONGLY recommend LOTS of good, clear, close-up digital pictures all through the rebuild process.  You have no idea how valuable those were to me during reassembly, or when some tiny spring or lever would suddenly fall off or tip out.  I referred to them more than once.

Mark each of the vacuum hoses attached to the carb as you remove them.  I used masking tape and numbered them, with corresponding numbers on a drawing of the carb.  There were 11 of the things on my car, and some appear interchangeable but they're not. 

Keep a clean, organized work area with good light.  I used zip-lock baggies to store the parts by section as I took them off so as not to get them mixed up.  Overkill, perhaps, but it worked well for me.

Your car should have the E4MC or E4ME, I believe - the CCC (electronic) carb.  Some people say these are difficult to work on, but I wouldn't be intimidated.  (I think those people just don't understand how the things work, personally).

If you get into the project, e-mail or PM me and I'll share some details of things I learned along the way, particularly as it relates to the CCC carb :-)

Jim

[qjetsrule]

check to make sure the choke is opening fully, if not make sure you are getting 12 volts to the choke coil and the connection is good. on the other end of the spectrum you might have and open vacuum source somewhere, a friend of mine uses a small propane torch ( not lit ) to locate vacuum leaks, works good and no mess. good luck

[jamesF]

Is it anytime you apply the brakes or only as you are driving at speed then come to a stop?
Could be flooding due to fuel sloshing?

TO see if you have a vacuum leak like qjetsrule mentioned you can use one of those handheld Propane torches. Open the valve a little bit DONT LIGHT IT OF COURSE, then move it around the carb base as you are idling. The propane acts like fuel and if there is a leak that is sucking in air, the car will speed up. If that happens look and see what the deal is in that area.

Now if the air cleaner is off sometimes you can get false readings if the fumes get pulled in the top inadvertently. So hold it down near the base as you move it around. This is where the leaks would likely be anyhow. You can also spray carb cleaner (I think its still made out of flammable solutions) sometimes the little red straw will help you be more precise... It also cleans the engine!! 

[jamesF]

check to make sure the choke is opening fully, if not make sure you are getting 12 volts to the choke coil and the connection is good.

Amen.

Funny thing happened to me a few months back, I have my electric choke getting power from a splice in the wiper motor power. I was doing some work in the interior during my final "resto repairs" work, putting my wiring back together in the car, and shorted something and blew a fuse. Stuff stopped working, etc.. I looked and didnt have any fuses, got my keys and went to start my car to go buy some fuses and it idled REALLY BADLY... This was  shortly after putting my newly rebuilt 455 I had built in the car that had been very consistent in sound and idle and running quality..... I started to sweat thinking bad things...
Realized my choke was not getting power due to the blown fuse....
Whew.....

[shelivedhere]

Thanks so much for all the responses.  There's a ton of good info here. I'm also wondering if using something like Seafoam in my gas tank might help things. Is it possible that the carb just needs a good cleaning?  I've been noticing that the idle has been a little smoother and the stalling hasn't been happening as frequently since I had the O2 sensor replaced two weeks ago.  I've been driving the car more often and been taking it on longer trips.  My immediate concern is that I need to get it to pass CA Smog Testing in the next few weeks and I don't know how all this is going to impact my chances of passing.

I also just found out that the shop I take my Honda to handles this type of thing so I think I may have their mechanics take a look at it given my time constraints. But I will make sure they check all the things you guys mentioned. Thanks again for the guidance! I will keep you posted on the progress.