Hey Guys. Mine's an 85 Trans Am with LG4 / 5-speed.

When i'm accellerating, usually when i'm up around 3 grand or so, my car inconsistantly acts as if it's out of gas... it doesn't die, but it begins to accelerate, then acts as if i got off the gas completely, and kinda stumbles right back up.

In addition, the first time i go to start up my car after it's sat for 6+ hours, i have to pump the gas rather excessively. Like 5-15 times. Furthermore-- i'm in FL, and it is not a temperature dependent problem. (it never gets that cold here!)

I've been living with the 2nd symptom for about 6 months, the 1st symptom has only become an issue in the last month or so. I'm thinking accelerator pump... What about you more educated people?

Thanks

 

"Cold" is a relative term. To the engine, 80 degrees is "cold", and some choke is better to get it started. If fully warm, then it shouldn't need the choke. The other possibility is the fuel bowl is leaking dry while the car sits. That can either be a syphon effect back through the fuel pump (fuel filter with a built-in check valve prevents this), or leaking core plugs on the bottom of the fuel bowl (a common q-jet problem).

Your other problem is fuel delivery, either a clogged fuel filter or weak fuel pump, or both. Or, a weak ignition (very possible).

 

I went through and replaced the fuel filter (with one with a check-valve) after the hard-to-start problem first started.

As far as the ignition system goes... I replaced the coil cap & rotor, plugs & plug wires a few months ago. (not to discount it, but to bring you(s) up to speed on what i've done.

Recommended diagnostic courses of action for ignition system & or leaking core plugs??

 

The leaking core plugs are going to require removal of the carburetor. The "fix" is to clean, re-pein the metal over the plugs, then seal with an epoxy compound like JB Weld or something similar.

As for the lean/no power at upper RPMs, when is the last time you checked the TPS voltage (0.48VDC at idle) and set the mixture control (MC) solenoid? You could be at the lean end of mixture control under part throttle, causing hesitation to open throttle. Of course, you'll want to eliminate all the usual suspects first, like the ignition and any vacuum leaks.

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Later,
Vader
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All my life I've been searching for something. Something never comes - never leads to nothing...

 

I have a TPS error code comming up right now-- I posted about it here 2 months ago when it started, i was told not to worry about it.... SO i bet that's what the problem is there.

I'm planning on doing a carb rebuild in december... is this something that would typically be covered in a rebuild kit?

thanks

 

nope the rebuild kits don't cover the tps. it could just be out of adjustment or it may need replaced. back in august i took my carb apart to find that the plunger of the tps was broken off
then probably about a month and a half ago started doing almost the same as yours. took me while to figure out but it turns out that somehow the timing got messed up, set it back to where its supposed to be and problem sloved!

 

Righton. Does anyone (vader) have any diagrams regarding the TPS? Looking @ the carb from the front of the car, is it the electronic unit on the left front top? (one of my friends in his infinite intellegence managed to break the clip on that plug off, so it's being held together with electrical tape right now...)

By the "is that included in the rebuild kit" i was wondering about the (potentially) leaking core plugs.

thanks again

 

I've replaced a few TPS in the old E4MEs, and it's no picnic. Actually, it isn't that difficult, just time-consuming.

This might give you an idea:



Item 71 is the TPS, and item 63 is the mixture control solenoid.

 

no the core plugs are not included in the kit either, you'll have to clean them up and use JB weld or something like vader said.
if you don't already have it buying the haynes carb manual ($15 autozone, advance, ect...) it's very helpful especially if this is your first rebuild.