Bucking and Hesitating in gear
 

86 Trans am with a 350 crate motor, and auto trans. Stumbles and hesitated in gear, fine at idle but as soon as you put load on it, it starts running like crap. Started running crappy, and checked the plugs, one of the wires was burnt. Replaced the plugs, cap, and rotor and it didnt fix it. Checked the firing order and made sure all the plugs were seated, also checked the timing all was good. Noticed that that carb gasket didn't completely cover the base of the carb and that some of the passages were exposed near the mixture screws, replaced the carb gasket, same issue. Replaced the carb with a known good one, same issue. So Im at a loss, Im not good with these older cars, the only thing I could think is the cat is clogged since you can smell the cat burning after WOT so thats my next step. Any suggestions since after that I have no clue what the issue could be. I ordered stock plugs and they were colder then the plugs that were in there idk if that makes a difference, they are also gapped at .040. Also it has good vacuum until you put a load on the motor, also with a load on the motor and the primaries blocked (via shirt over the carb) it kept running and pulled 20in of vacuum, even ran beter.

Sounds like another car that someone was posting about, I think the PCM and lock up function was to blame? Some one hacked in a lock up switch to remove the PCM functions or something

Hows the trans fluid look like?

ecm still running the carb dizzy and trans? if not, start there.

The lockup function was bypassed and is now manually controlled via on off switch. Havnt checked the trans fluid I should probably do that.

ECM has been disconnected, non computer controlled carb, and hei dizzy (which is only about a year old). As far as the trans Im unsure.

As soon as you put the car in gear from park it runs like crap.

What's the timing amount and curve? Any vacuum advance?

what brand distributor?

I think it was like 16* Advanced, but if you turn the distributor either way it runs alot crappier. Curve idk how to read that, it has a vacuum advance on the distributor idk if it works.

I want to say msd because the cap is red but theres no markings on it.

i bet it's an accel, the one they sell as their hei replacement has a red cap - and it is extreme junk. check the connector from the pickup coil to the module and see if it is loose.

^ This, if it's an Accel dizzy be wary.


Just to be clear, it doesn't have any PCM/ECM stuff anymore and it's a standard carb/distributor setup?

Ive had one sitting new in the box for like 5 years and it has a brown/tan cap. Is that the black sensor under the rotor?
This one was installed by a shop that shall remain nameless, and no recite was given for work done at the time so Im unsure of brand.

Edit, it is an accel, I have a gm unit Ill try swapping in.

No pcm/ecm, trans I dont know but motor wise nothing edlebrock (quadrajunk) carb and hei dizzy.

car originally was a computer controlled carb car..when the engine swap was done..the previous owner put a manual carb on it. I was told it was 30 degrees advanced when i got it. It has since been been having charging issues under load..and it seems it starts to lose power..lights dim and such while under load..and the car is idling rather low at about 300-400 rpm. Car ran ok unless i had the ac on..but recently its really running awful, to almost undrive-able condition..

Whose car is this thread about..?

Hers, Im working on it.

The first place to start is the distributor.

Find out exactly how much initial timing is set. Do not forget to disconnect the vacuum advance when you do so. Then rev the motor and find out how much total timing you have, also with the vacuum advance disconnected. Make note of the RPM where full mechanical advance comes in.

You need to figure out where you are at before you can attempt to fix anything. Change one thing at a time.

How many threads does one broken car need?

Theres only one for the current issue?

So one of the old ones can't be updated? When it needs another engine will that be another thread?

That wasnt for this car.

Wow. Didn't realize they were both so full of gremlins

Has either car been professionally diagnosed or looked at? Kind of seems like they are both at a point of diminishing returns and losses should be cut and ge them into a shop just to stop the bleeding of money

I havnt really been throwing any money at them. Cap, rotor, plugs, wires, and carb gasket are all ive put on it. It was about due for a tuneup anyways and had a melted plug wire. The rest of the parts I have laying around the garage.

There is a finite number of things it can be. Have you changed the things so mundane as the fuel filter?

When I used the other carb I removed the fuel filter and ran it, no change.

What was the other carb?

Same thing qudrajet just a gm one not edelbrock