I own a 4wd 96 Nissan with the 2.4 KA24E Engine. It has a cold air intake, header, cat back exhaust with a Flowmaster muffler. Lately, when cold, the engine will start to buck and heave at times. A local shop owner stated that the one time they could get the truck to do this they had a fault code for the O2 sensor. I was able to ground the sensor better (the header is ceramic coated) and the truck runs a million times better but it will still buck once in a while when cold. Any ideas? The TPS and manifold 02 sensor were replaced this spring, the 02 sensor after the cat is stock. The truck has 80,000 miles.
Gotta go for now, if you guys have any tips or need more info let me know.
my truck didnt have a preheat intake, just a sensor stickin in it.
doe sit seem to buck in a ceertiangear/speed combo? my truck used to do when i would try to go 30mph in 4th. would stumble and buck. turns out the EGR was either cloged or it wasnt working. blocked it off and runs and drives wonderfully. try pulling the vaccum line off the egr and plugging it then try driving. it might throw a code but it wont hurt anything
hmmm cold air intake, no intake preheat anymore, bucks when cold sometimes... nope, i have no idea.
It wouldn't matter if it had a super duper hot intake. There is no preheat on a 96 ka d21. Temps under the hood will be ambient. I put a 100k on one of these. I suggest ngk plugs, resistance check the plug wires. Run some injector cleaner though it. How does the distributer cap and button look? Are the plug wires getting roasted by the header?
What cold air intake do you have? Does it have the air divertor that goes under the intake hat to keep the maf reading correctly.
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Thanks for the input guys. The plugs were replaced at the shop, the wires all tested good and the cap and rotor are in good shape. I took care with leading the wires, none of them are too close to the header.
There is no diverter in the airbox. Checking the EGR might be a good place to start. I can't fault the shop on this one because it had the same bucking problem and a miss, they worked on it for an hour or so and fixed the miss and couldn't get it to buck again. Heck, they didn't even charge me for a full hour of labor and they physically worked on the truck for close to two.
My 92 240SX has the same engine and uses a mass air flow sensor to calculate the A/F ratio. I've heard that the tiny wires in these air flow meters can become "contaminated" and sometimes need to be cleaned with a special solvent. I've never had any problems with my air flow sensor though (250,000 miles on the car).
As was already suggested, you should double check the vacuum hoses and also that the air snorkel has no cracks in it between the intake and the air flow sensor. Any cracks/leaks would cause an overly lean mixture.