Rough Start and Idling, Engine shakes violently in 1k-3k. KA24E 1990 Nissan 240

[Acedem]

I have a 1990 Nissan 240SX. It was running fine until i hit a big dip in the road. The only thing I had done before that is an Oil change, New Plugs, and wires about 2 weeks before the dip incident.I have a tough time starting the car, but it starts with some throttle. I have cleaned the TB checked my plugs for correct firing order. Car runs but sounds like an old pickup truck. The idle is set at 2k because if i have it any lower it has a tendency to die.I have not had any major problems with the car in the past. Took it to an ASE cert. mechanic who fixed my timing but the car still runs the same.When I'm driving the car and I hit the clutch to stop and go to N the RPM drops below 2k idle then goes back up to the 2k that I had manually adjusted it to. I really need to get my car fixed because it a daily commuter. With out the car I really cant pay the bills. If any body has any suggestions based on the info above please help.If you need any further questions that I missed answered please post as well. I'm counting on all nico members to help me out. I know somebody here has a solution for this or some type of similar experience. Thanks for the help.

[Acedem]

Also does any body think an EGR valve or an injector could be the problem? one of these is the only gut feeling I have about the problem.

[rogoman]

Yes, it definitely could be a sticking EGR valve. Jiggle the EGR valve by hand with the motor shut off; there may be some carbon particles lodged.

One or more fuel injectors may not be working; pull off one injector harness connector at a time to see if it affects the motor operation.

[Acedem]

Yes the #4 has no effect , im guessing i need to replace it. but how will i know its the injector itself and not the wire harness itself that connects to it? All the other injectors have an effect on the motor it bogs down a bit then comes to life when I connect it.

[rogoman]

Before you condemn the injector, make sure that it's not an ignition problem; insure that the spark plug is getting spark.

You can swap the #4 injector with another one and see if the problem follows; make sure to use new O-rings.

[Acedem]

Yea I will do it on thursday. I will let you know what the result is on friday or sat. thanks for you help. I appreciate it.

[Acedem]

Bought a new injector. Mech. said they were all fine. Cleaned them and flow tested them. Replaced them all. Car runs a little better. EGR valve was open according to mech and all he did was close it. The car runs significantly better, but it still sound like an old truck. The engine seems to run smooth. but the noise comes from around the cat-converter and underneath the car. I just want my car to sound and run like it used to. My car has never sounded so ugly in its life. I have already had my cat checked its nice and honeycombed , looks brand new not melted or disorted at all. Maybe some holes in the Exhaust system???

[clinthicum]

Save your time and money on all the new parts that folks are recommending. You've likely got a faulty ground wire connection in the wiring harness near the MAF. Reground them and all the erratic and annoying idling will do away. My mechanic in Annapolis showed me this fix years ago on my S13 '90 and my worries went away.

[hapaboi39]

Mine did the same thing last year and i ended up bighting the bullet and paying a mechanic to diagnose me. The culprit was a bad MAF and a tiny crack in tha plugwire....Up until that point i put a bunch of $$$ into plugs, fuel pr reg, fuel filter, adjusting the timing, and cleaning the aiv.

With that said it woulda saved me hella time and $$$ if i woulda jus payed to get a diagnosis. My mechanic gives me the option to either pay him to do it or to jus diagnose and tell me the problem and then i do it myself. His diagnoses R always right on tha money.

Either way it sounds like a bad MAF.

[Acedem]

I know this might sound stupid but how do I ground my wires near the MAF. I know what the MAF is but as far as how to go about regrounding them I don't know. If you can tell me how to do it or if you would recommend paying somebody to do it. Thanks for all the help. I just need my car to run with some dignity , a 240 should be something that I should be proud to drive not embarrased to turn it on it on it sound like my grandpa's truck.

[Acedem]

I finally found out what it was, something was wrong with the spark plug. it wasn't in all the way or something like that , it was full of gas and with was all black at the tip. sound kinda weird but thats always the problem with my car. something simple . never had any major problems. and nobody is able to find out what it is because its so damn simple . well at least my car runs nice and smooth , just like it used to. Another happy 240 owner .

[hapaboi39]

That's awesome man!Im glad it was an easy fix.My 240 had the same problem but it was my MAF a bad plug wire, and a set of garbage bosch plugs that were fouled.I replaced my MAF, upgraded to tha NGK blue wires, and NGK platinums and now my car runs like a top!Glad your fix was easier than mine though.Good luck!