Wompa164

iTrader: (4)

So yo.

I've got a '79 with 5 speed manual. We had the engine replaced at 80k, in 1994.

Recently, when I drive it, my RPMs sometimes jump wildly. Like, sometimes from 2k to 3.5k, making the car lurch and such.

I'm fearing the worst, but are there some simple things I can try and check / replace before I get it looked at?

My dad says it could have been bad gasoline, which makes sense, like bad combustion, but this has happened atleast 5 times since it started a few months ago. Last night was particularly bad.

Also, it feels like I lose power after I hit about 5000 rpms.. like.. after I reach 5k in first, I gain much more speed by switching to second than continuing on. Is that.. normal? I was under the impression that more RPMs = more power.. but then again.. I don't know much.

Thank you!

Wompa164

iTrader: (4)

Bump. Need advice, please.

JEC-31

Throttle linkage binding, maybe? I'm just guessing.
Doesn't sound like you need to be fearing The Worst, but it is definitely a problem.

C'mon guys, help this dude out.

marshp

i dont quite have all the same problems..
but in the morning when i warm up my rex my tach never seems to work, which is annoying.
and as well as you, i dont seem to have any power after 5000 rpm in first, im not sure why but id like to fix it.

LongDuck

You might try changing out the fuel filter. What you're describing may be due to several things, most notably that a clogged fuel filter will only supply so much pressure from the fuel pump to fill the float bowls in the carb. If the filter is clogged, the pressure is reduced, and the more gas you use out of the bowls, the longer it takes to fill them up. A carb relies on a smooth and even fuel level in the bowls to supply the jets in the carb.

Could be that by the time you hit 5000RPM in 1st, you've already exhausted the fuel supply in the bowls, and shifting to 2nd will; 1) give a second or two for the bowls to fill up again, and 2) bring engine RPM (and vacuum) down enough that not as much fuel is being drawn through the jets.

I would expect that if you drive at high engine RPM for very long, the bowls will dry out and you'll lose speed/power. I had this problem in my 80LS a long time ago and fixed it with a carb rebuild.

You might also check your fuel pressue pump, as a bad pump may not be moving enough fuel to generate pressure at the float valves, resulting in problems similar to those described above. This is where an in-line fuel pressure gauge is valuable.

Ever notice how the 60's muscle cars almost always have a glass, fuel filled fuel pressure gauge in-line to the carb - this is why. HTH,

Rx7carl

Hmmm, possible weak fuel pump and/or clogged fuel filter. Good description of when the car drops off above 5k but I dont understand what your saying about the rpm jumping, can you describe it in more detail?

Wompa164

iTrader: (4)

Alright, thanks to the advice of everyone, I'm going to check the fuel filter with my Dad this weekend. Is it hard to get to? Neither of us is very car savvy..

The RPM jumping.. ok, I'll have my foot on the accelerator at a constant rate, right? I should be moving smoothly. Instead, the needle jumps as if I were jamming on the gas, and letting off again and again, in rapid succession, but the needle jumps faster than it could go. Say I was just driving, then it goes.. 2000.. 3500.. 2500... 3300... 2000.. your car lurches. So annoying, and really bad.

Keep it coming!