turboguard

So my car has a strange bogging problem that eventually gets better if I drive the car around enough after a cold start. It doesn't just bog when in gear and accelerating, it also bogs while in park/neutral! Here is what it does at a cold start, car had been sitting 9 hours while I was at work, started it and let the electronic choke fully open:


And this is how it is after my 30 min highway drive home:


Any input on what I should start checking first in order to solve this problem? Thanks!

turboguard

Could this possibly be a fuel delivery issue? Maybe a bad mechanical pump since it seems to improve over time as it warms up?

redneckjoe

i'd try a new fuel filter.

zed-028

ill chime in with fuel deliver too

check the entire system, fuel pump, line filter, carb filter.

Biledriver

Sounds like the accelerator pump in the carb. You can check if it's squirting with the engine off looking down the carb and rocking the throttle.

turboguard

Thanks for all the replies, guys!

I'll probably go ahead and just replace the fuel pump since its super cheap and my current one looks pretty worn anyway. I did a quick n dirty rebuild of the carb not too long ago and the fuel pump *seemed* okay at the time (I replaced the oring and spring thingie) but it did look kind of corroded so a new one wouldnt hurt.

For filters, as far as I'm aware the only one for my LG4 is in the carb, I don't think I have a line filter. Also, is there any easy way to check the fuel lines running from the pump to the gas tank without dropping the tank? I think that's a project that's a little too much for someone without a paved driveway or garage, lol.

zed-028

there can be up to 3 pumping devices and 2 fuel filters on one of these cars.

Could be any combo of these
1. In Tank Electric pump + in line filter (rear of the car) + mechanical block pump + carb filter + accellerator pump (springy thing in carb)
2. In tank electric pump + mechanical block pump + carb filter + accellerator pump (springy thing in carb)
3. In line filter (rear of the car) + mechanical block pump + carb filter + accellerator pump (springy thing in carb)

i could be wrong but the accellerator pump doesnt shouldnt really change that much performance wise with heating up/time as its just a pump cup assembly.

warming up issues tell me its more an inline filter as once the carb one blocks up (being so small) the flow just dies.

fuel pumps are a strong possibility, if its an in tank one, its a pain in the a$$. block one isnt so bad.

Biledriver

Looking down the carb seems easier to check first. Cold engines can need the pump to start and rev in park. Q-jets can pump half *** and run **** pore. Even if the pump is weak the carb should fill up at idle and rev good once or twice.

turboguard

Could a bad throttle position sensor also cause this issue? I tried to test it with my multimeter but I kept getting weird readings so I'm not sure I was doing it right, lol

turboguard

So I decided to go ahead and replace my fuel pump, and boy I can already tell a difference in overall responsiveness! I actually discovered someone had plugged the smaller fuel return line with a screw and just put the rubber hose over it! I made sure both lines from the tank were flowing good and free from obstructions as well.

I replaced the fuel filter in the carb too, and it was pretty dirty (I actually already replaced it once several months ago). That being said, how often should those fuel filters be replaced? Could the need to replace them frequently be indicative of a problem with the fuel tank plumping? I would really love to drop the tank and see whats going on in there (especially since when I originally bought the car it had a new fuel tank installed), but that seems like it would be a real chore.

zed-028

I've never been a huge fan of the in carp filter, everyone will have an opinion on this as per usual however i removed mine and put a decent inline between the mech pump and the carb. I've found its much easier to inspect, change and the replacements here in australia are a dime a dozen.

I found when i put a bottle of fuel system cleaner in my car that i changed a filter every couple of days for about a week and a half. after that there hasnt been a shred of anything come through.

beware though, that stuff will lower the octane of your fuel so far that you will probably start dieseling. im glad i did it though.