Hey all,

Just picked up an 85 T/A with the 305ci LG4 (automatic) two weeks ago, it was running fine until just two days ago where it started having this issue where it surges rpms after 2000, mostly in the 2500-300 range. It gets to around 2600 and then drops back down to 1900 then back to 2200 or so with loss of acceleration/power until I back off the gas.

Any ideas what it could be? It idles in D around 500rpm, so maybe the timing?

Is it the distributer, fuel filter? Do you all have recommendations for those parts?

This is my first time with a classic, so any help would be appreciated, thank you!!

 

Fuel delivery

Could easily be the filter. If it still has the original carb, then the filter is in the big nut where the fuel line enters; cryptically enough, labelled "FILTER", with an arrow pointing to it.




To change it, unscrew the fuel line from the nut first. This will require a 5/8" line/tubing/crow's foot wrench. NOT an open-end, NOT a Crescent wrench, NOT pliers, NOT NOT NOT NOT NOT NOT. A line/tubing/crow's foot wrench. Looks something like this: note the extra features that grip extra flats of the nut, to keep from rounding it. Might help to soak it in penetrating oil such as PB Blaster or Kroil for a day or 2 first. Not WD-40; actual penetrating oil.




You MUST hold the big nut still; for that, yerbasic 1" open-end will do fine. Once the line is out, use the 1" to unscrew the big nut. The filter is behind there. Pay attention to which direction the filter goes and to the spring. The filter has a built-in check valve (only allows flow in one direction, specifically INTO the carb; prevents flow the opposite way). If you put the new one in backwards, no fuel will ever get pumped into the carb. Be VERY careful not to cross-thread the big nut in the casting, or overtighten it, which may strip the casting threads. Either condition basically SCRAPS the carb permanently.

When you put it back together, use some thick grease or anti-seize on the threads. NOT sealer. The threads don't seal, the flared end of the line does that.

As far as brand, I prefer New. Will look something like this, although the one for our cars is not actually this long.

https://www.autozone.com/filters-and...471/894602_0_0

 

And I should mention as always, the problem is NOT the "timing". Not sure why that's every n00b's go-to first guess for EVERY driveability problem, but w/e. "Timing" DOES NOT cause fuel delivery problems.

Note that I am NOT saying "your 'timing' is perfect", NOT saying "'timing' doesn't matter", NOT saying "you don't need to make sure your 'timing' is right", NOT NOT NOT NOT NOT NOT NOT NOT NOT NOT NOT. Only, that "timing" CANNOT cause this problem, and therefore, messing with it CANNOT fix it. If you REALLY want to dink with it, wait until AFTER you resolve the fuel delivery problem, so that you're not making it WORSE, and then having 2 THINGS wrong with it at the same time that you have to sort out. Focus on the ACTUAL PROBLEM that you DO have, which is fuel delivery, and don't wander around chasing shiny things that are off the path.

 

Thanks sofakingdom, tried looking for the air filter and everyone was out of stock. NAPA had it but they closed at 4. I will get it tomorrow and report back when I get the time to do it haha

 

Not the air filter. The FUEL filter.

Every parts store will have it. Dpesn't need to be NAPA. Usually hanging on a card along with PCV valves and other somewhat related parts, usually in the filter section somewhere.

 

My bad I meant fuel filter, I will try to get to it this weekend. Thanks for all the help so far!

 

Hey @sofakingdom , I was trying to get it on video for for a friend but wasn't recording when it was happening, I went to get gas and a ton of air escaped when I unscrewed the gas cap for gas and then it drove perfectly back home, I unscrewed the cap again when I was in the garage and a decent amount of vapor got out after like a 15m drive. Could it be vapor locking?

Here's a video of it:
I know you can't hear it over the music, but essentially, it sounds like normal revs and then suddenly drops