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Car loses power and stumbles uphill going forward only

im having problems with my 1994 hyundai excel 5spd man. trans…when i drive the car it seems fine but if i go up a hill it stumbles and loses power very quickly and cant make it up the hill. it feels like the motor starts jerking and stumbling but if i put it in reverse and reverse up the same hill it has tons of power and doesnt run rough…the car hasnt been driven much in the last 6 months or so and the fuel gauge says 3/4 full…the motor also idles good but takes a long time to warm up (like 20 mins or so even when driving it around in 75-80F weather)

any idea what the problem might be :confused: ? thanks for any suggestions

Try replacing the thermostat to start with.
Are the RPM’s going down when you lose power or are they revving up? If up, your clutch might be slipping, and you would need to have that replaced.

Other thoughts that come to mind: bad gas. If its been sitting around with the same gas that can make it run rough. Although going in reverse fine seems to indicate the gas is ok.

If it were my car Id have the clutch checked out, if thats ok then Id drain the gas out, or let it idle until empty and run a few tanks of high test in it.

Sometimes the plugs can get fouled up too. Try flooring it up to the redline through a gear or two and see if any black smoke comes out the tail pipe in your rear view mirror. Thats burning the junk off of them.

Sounds like it isn’t picking up fuel when pointed up.

The gearing is probably lower in reverse than in the forward gears, so that may be part of the reason it seems to perform better in reverse. I expect the problem will turn out to be related to the car not being driven much in the past 6 months. Various fuel system components may be gummed up or the fuel pump inlet is semi-clogged. I’d probably ask my mechanic to completely drain the tank and refill with new fuel and see if that helped. Before doing any of that tho, have the diagnostic trouble codes read out.

Edit: It’s also probably worth it before assuming the problem is fuel related to pull the spark plugs for a visual inspection of the electrodes and measure the gap.

I’ve had several vehicles that did this and they all turned out to have fuel supply issues. Some had to have the fuel pump replaced. A fuel pressure test will usually point right to the problem.

Cataylitic converter with broken honeycomb, If this is it you can go under the car with a rubbet malett and hit the converter and it will rattle. Second guess, bad fuel fikteror pump.

It works fine in reverse because reverse has a very high gear ratio, so the engine benefits from the gearing.

The first thing I’d do is get the engine maintenance completely up to date including fresh OEM spark plugs and fresh filters. I’d also want to check the compression and the fuel line pressure. And “read” the spark plugs when you remove them, or take photos and post them here. The condition of your spark plugs can be revealing.

Changing the T-stat (and coolant) is a good idea too, but be sure to check your coolant level while you’re working on the system. Excessively lengthy warm up times can be a symptom of low coolant.

I find myself also wondering if you’re an experienced manual transmission driver or new to driving. Are you downshifting to get up the hill? If not, you may be simply lugging the engine. The engine needs the advantage of a lower gear to get up a hill.

Please post back with the answers.

Slipping clutch or worn compression rings. Do a compression check on all your cylinders.

The engine isn’t revving, it’s lugging, so I’d be inclined to dismiss the clutch as a suspect.

sorry i havent posted back in a while been a bit busy…thanks for all the replies! so far i had a bad battery, the positive wire wasnt making a good connection with the terminal either and the water pump was leaking so i replaced that and the thermostat.

the more i drive it the better it seems to get although its still having a bit of trouble getting up hills but so far its gotten a little better (there is a hill down the street that i test it on and the first time i couldnt make it up even half way and now i can all the way up with little problem) when i go up the hill mostly i cant get it into 3rd gear before it starts the lugging…if i ride it up in 1st gear (or reverse) it makes it up no problem lol…ill change out the plugs and wires next cause i have no idea how long its been since they were last changed…thanks guys for all the replies and if you have more ideas post please…also the motor is carb not fuel injection if that helps too

I think you’re on the right track here. Clean up all the small stuff and I’ll bet it’ll run fine.
Oh, and you might want to check for vacuum leaks too. Or, since vacuum line is dirt-cheap, buy a roll and change the lines… one by one, so you don’t cross any up.

If it doesn’t post back and we’ll discuss carburators.

ok thanks! ill be out of town till friday so on saturday ill be changing plugs and wires and ill grab some vac line and change them out as well…the fuel tank is about 1/4 full right now so ill fill up soon with fresh gas too

i drove a bit today and it lugs in second gear up the hills but not in first or third (can get into 3rd pretty easily before the hill starts if the light is green lol) but today i was in 2nd gear and it was spuddering and couldnt get it going fast enough to make it into 3rd