Hello i have a 86 TA with a 350 swap Mallary distributer ignition and a rochester Quadrajet carb unsure of the size also edelbrock intake. The issue that im having is that the car runs great with no load, but once under a load it starts missing or stuttering not sure which after about 2200 rpm can anyone help me. I was told the bowl could be draining and not refilling or fuel pump is too weak Av flap not opening timing is off distributer worn out and a few others no one can seem to agree on the answer. Thank you

 

The reason no one on line can give you a definatitive diagnosis is that there are several different problems that could cause your problem , and it's impossible to devine which is which without seeing and testing the car in person .

Yes , a weak or mistimed spark most certainly cause the engine to falter as the load on it is increased , Have you set the timing correctly and done a spark intensity test ?

Yes , an improper fuel mixture most certainly could cause the engine to run badly as the load on it is increased , Have you checked all adjustments on the carb and verified exact routing of ALL vacuum hoses/devices ?

I realize it's a "new" (Swap = rebuilt ?) engine , but take nothing for granted till ya verify it for yourself . I've seen a lot of "rebuilt" parts over the years , engines included , that were , , lets just say , , Lacking ....

 

it is a rebuilt 350 and the answers i got before were from relatives not online. checked the spark yes timing not yet doing that today but was just looking to see if there should be other things to check also checked the carb was a little gumed up but everything seemed to be working fine the jet was a little wet yet even after not running.thanks for responding mate

 

Yea , Checking the timing would be an easy great first check to to .

Something I do with any used car I buy , and a good habit for anyone , is to establish a "baseline" of all of the testable parameters that affect engine performance , and write them down on the inside cover of the repair manual .

Things like the cyls compression and the normal manifold vacuum that it runs at can be real handy to know , for when it begins to run badly . If all cyls have acceptable compression , that hasn't changed since the last check , well then you'd know the basic structure of the engine is likely still solid . One weak compression reading in a cyl , with a corresponding bouncing of the vacuum gauge , would send me in deeper looking for the reason . Without knowing the particular engine's normal running conditions it can be harder to pin down whats amiss . Even fuel pressure is a great indicator , if your carb needs 5 PSI of fuel pressure and is only getting 1 , well that right there could cause a failure to run right at higher engine loads .

It takes a few extra tools (the compression testers and vacuum/fuel pressure gauges) to check these things at each tune up , but having the normal running conditions can really save ya diagnostic time when it runs badly . Figure you've already got the plugs out while doing a tuneup anyway , so why not check the compression while ya there . Those kinds of preventative maintenance are what will get you the answers you need for sure .

Oh Yea , I almost forgot , Cleaning the gummed up slime in the carb would be an easy and inexpensive test as well , That right there could cure the bad running at higher rpm , engine loading .

Good luck with it .

 

!st place to start would be a complete tune up, wires , cap, plugs, timing. Do a compression check when the plugs are out. Look your plugs over, for any clues.

If all that checks out, look at your fuel pressure reading when the issue is happening.

Many things can cause the symptoms you have. Eliminate the basic stuff.

 

Ok tune up is done cap rotor fuel filter plugs 8mm wires air filter and still doing it now it has run on after shut off. when plugs were pulled they were black but looked like they were still burning unsure of the gap thats supposed to be at so i gapped the new ones at 35. Carb has enough fuel pressure so ruled that out as well. Any ideas? Thanks.

 

Heres a update turned choke out so the door opens all the way 90% the stutter came out oh yeah after retarding the timing 5 deg. Its almost as it should be still has a little stutter but at least it has some power and i dont feel like im driving a geo metro.