spuddering while driving

[nathanmoris]

Im not really sure what this is under when looking. I have a 90 240sx sohc and my car seems to jerk a little while crusing down the road. Im not really sure whats going on. It doesnt happen the entire time but its does happen often any help would be great thanks for the help

[modulation]

When was the last time you changed sparkplugs?

[cbt240sx]

Man, I've been having the same problem on a 90 SOHC.

[kernan240sx]

having similar problem, most noticeable in 1st gear. Been having bad starts as well...if that helps

[nathanmoris]

i just replaced the spark plugs about a month ago with some NGKs and replaced fuel injectors and fuel filter about two weeks ago. thanks for the help Jonathan

[cbt240sx]

Man, I've replaced the injectors, had the engine harness rebuilt, replaced fuel filter!! My issue is mainly noticeable in 4th gear, mostly when up to 70mph, when you give it gas, it seems to 'buck' or loose power......wtf

[rogoman]

1 - The MAF may be marginal. Check the voltages.

2 - You may have a major vacuum leak in the intake system.

To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. A good place to connect to is the charcoal canister. There should be three hoses connecting the carbon canister. Two of the hoses go to a purge valve that's built into the canister. The second larger hose off the purge valve should be your vacuum line. With the motor fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be 21 InHg.

If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.

[nissanpunkrock]

cbt ever find the problem?

[cbt240sx]

Not yet man, I noticed the other day that Ive got an exhaust leak (which Im sure isnt helping things) so I put her up until I can spend some quality time on her. Ive cleaned the MAF and it seemed to help a little. Thanks Rogoman!!