Jerking and hesitating 96 240sx

[Scirocco16v]

Thanks in advance for any help.

I have a 96 240sx SE, completely stock with 98k miles. There was this one time where I was driving on the freeway at 70mph and felt a struggle and slight jerking on the car. The car was in 5th gear and I saw the stick shift shaking crazy and felt like the car was going to stall. For the next few weeks, the condition got worst where my rolling stops (aka California stops) would stall by jerking, in second gear. Running in 3rd gear for a while and then suddenly flooring it caused it to hesitate, chuckle, and jerking I then decided to change my Fuel Filter and the condition seemed to improve by 15%. I took the old stock fuel filter and shook it over a white bucket and noticed that it came out gray colored, kind of nasty.

I also changed the distributor cap, plugs, and rotor with no noticeable improvement to the drivability of the car. I cleaned the MAF sensor with electric spray and that seemed to help a little. Then I decided to change the fuel pump, Walbro 190lph and discover that it improved the condition by 40%. The car would hesitate or chuckle only if I try to make it happen, but once in a while it would sneak one by me and cause the car to jerk in on rolling stops, but it will not stall like it did before.

The car idles well and the timing is stock. For some reason the “jerking” only happens when the car is warmed up. The car doesn’t lack power nor do I smell gas anywhere (I thought it might be leaking gas).

In another topic, "car hesitating" seems like it is having the same problem as mine. Chris mentions checking the "tps" with a multimeter. How is this done and where is the "tps" located?

One more thing, I have a shop grade fuel injector cleaner, called Flare. It says to hook it up to the pcv valve via vacuum hose. I was reading the FAQ’s and it seems that the pcv valve is very difficult to get to. Is there another way do this? Thank you for any help.

[s13sr20chris]

vacuum hose connections will not clean injectors but only the intake and valves. to clean the inside of the injectors you need to run it through them.

you can check the tps by making sure it has power(5v), ground, and sends a signal to the ecm. there are other functions but you need to know specifics to check the open/closed switches.

check this out too.http://www.nicoclub.com/zerothread?id=81587

[Scirocco16v]

thanks chris!

I found the TPS and did a measurement. It measursed 5.2v. Closed and open seems to be fine and within the parameters. I tried resetting the tps also and didn't notice anything different. I only unplugged the terminal that contained terminals 123. Am I supposed to unplug 456 also to reset the TPS?

I've tighten and retighten the engine ground. The problem seems to worsen when the car is well warmed up and with some mileage. Today, the car was really bad when I went through San Francisco city driving of 40 something miles. There was some jerking when shifted into 2nd gear, from 1st. The car recently passed smog and does not smell rich. Is the idle adjustable? It's at 650 and think its at the min. Thanks for any suggestion

[s13sr20chris]

if you passed smog then its prob not rich or lean. it may be timing. how is your base timing?

[Scirocco16v]

Thanks Chris!!

When I bought the car, the timing was at 26 and was changed to 20 btc to pass smog. I do know that the smog mechanic did the timing without unplugging the tps. Would that have caused the problem, 3 months down the line? The smog was done in end of August 2004, but the problem just started in November. It used to do it in 5th gear which was pretty scary crusing at high speeds, but with some of the changes mentioned above it has gotten a lot better. thanks.

[ddgsxr504]

I HAVE A 95 SE AND I HAD THE SAME PROBLEM ABOUT A YEAR AGO, JERKING FROM TIME TO TIME IN 4TH AND 5TH GEARS, WHEN YOU LET OFF OF THE GAS AND THEN PUSH IT DOWN AGAIN? I DON'T KNOW IF YOU HAVE TESTED THE MAF WITH AN OHM METER BUT JUST BECAUSE YOU SPRAYED THE MAF WITH ELECTRICAL CLEANER DOESN'T MEAN IT'S STILL NOT BAD. I REPLACED MINE AND ALL PROBLEMS CEASED, I HAVE DONE EXTENSIVE RESEARCH ON THE 95-98 240s AND THE ONLY GRIPE THAT IS CONTINUOSLY MENTIONED IS A FAULTY MAF, YOU MIGHT BE LIKE ME AND GET A GOOD ONE THAT WILL LAST YOU TO 115,000 MILES BUT SOME MAY NOT. YOUR BEST BET IS TO REPLACE IT WHICH AT THE DEALER WILL RUN YOU ABOUT $400+. TRY LOOKING ON EBAY ($50-$150) BUT GOOD LUCK AND LET US KNOW WHAT COMES OF THIS.

[s13sr20chris]

setting the timing without pulling the tps usually makes things worse. i would recheck that.

[Scirocco16v]

thanks chris and gsx. I reset the timing with the TPS detached, following the correct procedure in the manual and nothing changed. I will try the tps again, measuring the voltage curve. Also, I will try to monitor the MAF while driving using the "needle" method with a meter in the car. I wonder if the wire in there gets weak when hot or something?

[s13sr20chris]

mafs are funny little boogers. i dont know what causes them to fail but age is certainly a factor.