Ben Taylor

My 81 has been having problems going up hills lately. Everything's perfectly fine when I'm diving on level ground or going down hills, but when I get to any steep hills the car will start to sort of surge. There's this hill that I used to be able to go up at 85 without a problem, but now it has problems when I go more than 55.

I haven't done anything to the car lately and this has slowly been getting worse over the last 3 weeks.

Tominator

Do you notice if it's not down shifting to a lower gear? If it's a steep hill it might need to down shift to build up power.

mvftw

What kind of plugs are you using, it's usually a spark issue.

BSeery

My first question is when is the last time you replaced the fuel filter? Low fuel flow from a bad filter or a bad pump can do this.

Second is have you checked the backpressure on the catalytic converter? A plugged exhaust system will give you these problems.
If the converter is plugged it probably can be traced to a faulty O2 sensor letting too much fuel into the system. The un-burned fuel gums up the converter and can lead to a fire if bad enough.

Ben Taylor

It's not downshifting, but it never had to downshift before. I used to be able to go up this hill at the same speed as the level straightaway right before it without having to give it any more throttle.

I thought it might be bad plugs to, so I got some new Accel header plugs, but there wasn't any change. The old plugs were AC Delco plugs, and they were all dry and tan colored.

Tominator

Well at least we're starting to narrow it down some, BSERRY has some good ideas to try.

Ben Taylor

I replaced the fuel filter about a year ago. I just replaced my rubber fuel lines at the pump on saturday because one was leaking if that makes any difference.

How would I go about checking my backpressure? I put a new O2 sensor and catalytic converter in about a year ago also. Should I try taking the cat off and driving around?

BSeery

Did you have problems before changing fuel lines or after. If after, you could have a plugged fuel filter. The best bet would be to get a fuel pressure gage and mount it in a way that you could watch it as you go up the hill. See if it can maintain at least 5-6 psi all the way up.

To test backpressure on the cat. You need to drill a hole before and after the cat in the exhaust pipe. Go out and drive and get it all nice and warmed up. Then while idling put a hose over the hole and check the pressure before and after the cat. Reading should be the same. if you can take it off and have a straight pipe, that's an easier test. Plug the holes with a welder or if made small enough you can use pop-rivets.

Usually problems like this are due to not getting enough fuel in, or not being able to get the exhaust out. I had a car that ran fine at idle, stop and go, downhill -- but it wouldn't climb a hill to save it's life. It was a fuel pump. Just wouldn't give me enough flow to feed the engine.

Matt Gruber

:iagree:
also a lot of c3's don't open fully floored. throttle needs to be adjusted


[Modified by Matt Gruber, 7:05 PM 7/7/2003]

Ben Taylor

The problems started before I changed the fuel lines.

I didn't have a pipe to go in place of the cat, so I just ran it without anything there, and I was able to go a little bit faster up the hill before it started shaking, and the shaking wasn't nearly as bad.

Since this has the original fuel pump, I'll try replacing that tomorrow and see what happens.

Bill 81 F

Ben: I also have an 81, but had a similar problem with a Pontiac Bonneville SSEI (supercharged 3800) a few years ago. I had new plugs in it so I didn't suspect them until I read a little more in the shop manual. It turns out I had a crack in the porcelain in one of the plugs. After replacing it, the problem went away. Also on the list was plug wires and vacume leaks. Let us know how you make out. I'm still on my original fuel pump w/50k.

Trevelisek

I had this exact same problem a couple of weeks ago after replacing the fuel pump on my 78 L-48.

With me, it was because there was a kink in one of the rubber fuel lines I had just installed (it was too long, and was kinking instead of curving).

I shortened the line a bit, and reinstalled it so it curved smoothly without kinking, and I have not had the problem since.

Chinaski

if i were you, i would replace the fuel pump anyways....make sure there are no kinks in the fuel lines you installed :thumbs:

BSeery

Any updates ???

Ben Taylor

While I had the car up in the air I decided to replace some leaking gaskets and things. I finally got it back together tonight and took it for a test drive.

The car is back to normal after the new fuel pump, hills are no longer a problem, thanks for the help guys.