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Cylinder 1& 4 r weak what can I do?

I have a cavalier 96 4 cylinders,automatic 3 speeds and the mechanic told me my scanner says that cylinder 1 and 4 are weak;therefore,I’d like to know what to do? the car in the highway runs excellent, but when I’m waiting to get green lite and I have the brakes applied stars to shake like if it was misfiring.

Did the you tell this to the mechanic and in response you were told that it is because those cylinders were weak? There are a very large number of things that could cause this many of which are very simple. I would take it to some other mechanic (ask around for one you trust), explain the problems as clearly as possible and someone should be able to tell you more than that.

“Weak” could have several meanings. A “weak” cylinder should mean one that is low on compression and in this case a compression test should be run.
I have no idea if they’re using the weak terminology to mean an ignition problem or not.

What codes are being thrown, how many miles on the car, etc.?

It may be misfiring while sitting in DRIVE, with your foot on the BRAKE, engine at idle…
The next time you are sitting at a stop light, let off the foot brake, and apply the Parking brake. Results?

1/4 weak from a scan tool check.NOT. 1/4 do have a common intrest in the fireing process. find a new tech.

yes you’re right I’m gonna take it to a different mechanic and tell me do you think if I replace the head gasket could help?

I’ve been doing that and it turns a little bit smoother, but it’s good apply parking brake as I need it I mean in every stop lite.

Why would you want to replace the head gasket? No one said anything about replacing the head gasket.
If the brake power booster is leaking vacuum, it will affect the way the engine runs when you are sitting at a stop light, the transmission in DRIVE, and your foot on the BRAKE PEDAL. When you use the PARK brake, and release the foot brake, the power brake booster should stop loosing vacuum, IF if has been.

totally agree but if a replace the head gasket what do you think?

Indeed. Where did the idea of replacing the head gasket come from. You likely have a far simpler and far CHEAPER problem.

Mileage on car?? Find a real mechanic with a real compression tester and have him do a real compression test. Post back with the PSI figures for each cylinder.

Modern OBD II PCMs can evaluate the torque contribution of each cylinder. An capable scanner can pull up freeze frame data to see what the computer is reading. The problem of weak cylinders can be anything from a compression problem, a misfire problem, fuel injector clogging, valve cam problem, etc. on and on. This might be happening at road speed but the speed of the engine might be hiding it. Someone is going to have to do a full diagnosis to zero in on the problem.

Does this engine have a distributor or coil packs? If coil packs, then the mechanic could have been referring to a weak spark from the 1/4 coil pack.