1970 Buick Riviera little/no acceleration, engine very roug

LAULEE77

MEMBER
1970 BUICK RIVIERA
6 CYL
FWD
AUTOMATIC
200,000 MILES

My buick riviera quit running about a week ago. We replaced fuel pump, and it ran fine. Now, a week later, it's doing the same thing. Engine runs very rough, when you step on gas it barely accelerates, then dies out. It will restart, and sometimes, after about 30 mins, it will appear fine. We were told that the fuel filter was NOT changed at time new pump was changed. We did change filter, but hasn't helped. In morning, it will drive fine, and once it heats up, it begins to bog, then you can't go over 5 miles per hour.
Any suggestions would really help out!

1 Reply

JDL

MECHANIC
16,098 POSTS

Welcome to the forum, how long since a tune-up? Do you have spark at all the plugs, when it acts-up? An easy way to tell, is to use a digital voltmeter as a quick first test, not conclusive, but, you don't unplug anything. One meter lead you ground, the other you touch to plug wires one at a time, engine running. It's an inductive reading, you don't penetrate the plug insulation, you don't take plug wire loose. The meter may only show 1/2 volt, the reading can differ from one make and model to another, I just look for the reading to be close to the same for each plug wire.

I'd probably make double sure about fuel pressure/ volumn. With some carbs, you can remove the air-horn without removing the carb, if possible remove the air-horn see if there is any fuel in the float-bowl, when the problem occurs. Thanks for the donation.