Engine rocking, car shaking problems

[Matty_V]

Hey,

I am new to the NICO network, even though I have been using 240sx.org for quite some time for help on my 1990 240SX SE. Thought I might ask a question, as I have not found it on the 240 site.

I have an intermittent 'rocking' or 'shaking' of my engine and exhaust system upon startup, which then relays the shaking to the shifter and the entire rest of the car. It only happens at certain startup times, and does not always occur. But when it does, it remains that way for the entire ride. Also, seems like it happens more frequently after it has been run for a while and/or if it is warm (hot) out.

After recent replacement of the air filter, spark plugs and wires, I think that it may have something to do with the mass air flow sensor or the O2 sensor, as a friend of mine has had a similar problem that was linked to a faulty sensor. Thought I might take it into Auto Zone or Advance and have them hook it up to their computer to see if they can diagnose the problem. Any ideas?

Matt Vanden Eynden1990 240SX SE 116.7 K
Modified by Matty_V at 5:36 AM 8/2/2006

[Axel Grungy]

sounds like one of your injectors is getting clogged. Next time this happens, try to locate which injector isnt working. Easiest way i found, just start unplugging injectors, whichever one doesnt make the engine sound worse is the one that isnt working.

[ricebike]

you can also stick a long screwdriver to the injector & the handle to your ear...

clicking? good

not clicking? wiggle the electrical plug to see if it does kick on... then presume it's bad

doing a resistance check @ the injector's plug would only test to see if there's continuity, not to test if it's working right or clogged

once you isolate the injector, you can either swap it w/ another one from the other cylinder & check again...

or just get a noid light to test the harness side of the injector system



PS: u know you can access the ecu on the passenger side kick panel & get the trouble codes yourself?

goto http://www.240sx.org FAQs section...

[OldmanPurdy]

You had this same post in 240 general? like I said there its most likely a mafs problem or as others mentioned injectors, did you try the procedure i mentioned? what was the result? NICO can fix all sorts of car problems but we need you to try things and post the results so we can help fix the problem.

[vvaffle]

I had a similar problem until one of the injectors just stopped working and the car shook ALL the time. As others said, when it happens just unplug one injector at a time and the one that doesn't change anything is at fault. If you don't quite feel like doing that, wait until it starts shaking and then put a piece of paper up to your exhaust. If it gets sucked towards the exhaust, there is a good chance that it's an injector problem. I think this can also be a sign of many other problems though.

[Matty_V]

Thanks for everyone's input. I put this post on two different 240 forums hoping to get more responses (which I did). I've also been short on time lately and haven't been able to work on it out in the blistering 100 degree heat.

Anyway, there are new injectors (2 years) on the car, but that doesn't mean that they aren't the culprit. Now that I have new exhaust on the thing, I can most likely find some more time to get this under control. Thanks.

Matt Vanden Eynden1990 240SX SE 116.7K

[OldmanPurdy]

I hear ya, working under blistering heat in an engine bay sucks, but ya if your injectors check out fine look at your mafs. Mine messed up again yesterday due to the wires getting hot ( I had them running along my injen intake and they got very hot ), heat can cause some unexpected problems in older cars.