I know I asked this before. I am going to be a little bit more detailed.
When in park, neutral it shakes When in reverse it shakes worse. When in drive it shakes under 30 mph. When going above 30 it shakes a lot less or does not shake at all. Shakes at stops.
From Reading Spark plugs & wires seem to be the most cause even if they look new. Wouldn't a compression test tell if it is bad spark plugs?
Greg Rozelle wrote in news:fUpNi.4254$oA2.1319 @nlpi068.nbdc.sbc.com:
Compression test will only show worn Piston rings or bad valve/valve seats.
Test your plug wires with an ohm meter doesn't really matter what reading you get just as long as all the wires are close I can't remember what resistance plug wires have per foot, but like I said if one is bad you will see a very large difference. Also look at the plugs and see if any are fouled (oil) or are also burnt white (which could indicate a lean running condition). like the wires all the plugs should look like each other of one is differnet then you know you have an issue in that cylnder which is causing the rough idle.
Take the time and mark you plug wires before you take them off.
Good practice to change your fuel/air filters when ever you do a tune up. You should be able to blow through the fuel filter fairly easely (be carefull of gas) If it is acting like your trying to blow up a balloon your filter is plugged.
When measuring with an ohm meter, the total from the coil to the plug, on any lead, should not be more than about 15,000 ohms. If over, replace them all.
You might have fuel injectors that are getting plugged. It is really CHEAP to put some injector cleaner into your gas tank. You can even buy it at Wall;yu-Mart for maybe a buck. I had one injector changed on a 97 P.U. 2.4 liter and it made a Big Difference. The mechanic had said my problem
*wasn't* that #4 injector - but the check engine alarm said #4 cylinder was misfiring. The mechanic/technician stated that because he could NOT hear the injector making any noise he felt "sure" that wasn't my problem - - - Wrong. This truck had far better power and smoothness after that injector got changed. That mechanic told me the Nissan fuel injectors are well known as being prone to getting plugged up.
Then we were using some bad "grocery store" cheap gas for a while and BOTH my truck and wife's car started running rough as a cob. I began using some injector cleaner and both our vehicles started running okay after that. Probably the best injector cleaner I've used was some I believe was from an anti-freeze company like maybe (?) Prestone I bought in a Pep Boys. It was in a tall silver or gray plastic bottle and it probably cost more than most clearers. It worked great! The accumulated carbon that then got burned out of the truck combustion chambers caused that truck to overheat quite a bit for the first several miles after the injector cleaner was poured in! IMPRESSIVE!
Another problem this '97 XE pickup (4 cylinder) has had is the original distributer cap gets dirty (why????) INSIDE and it can cause the engine to be hard to start - especially in wet weather. ROUGH running and hard starting also can be caused when the high tension wires to the spark plugs get dirty. I once met an electrical engineer who told me about that. He would take a rag and carefully clean off his high voltage wires to the spark plugs. With a dirty distributer or spark plug wires, the dirt will attract moisture and that allows the spark plug voltege & current to leak off ("short circuit") though the 'dirt' to the vehicle ground = chassis. What works REAL nice to heal your electrical leakage probelm (short circuit of high voltage to ground) is to buy a can of silicone spray & coat the plug wires & distributer with that stuff. After the silicone gets soaked-into the plug wires, the wires tend to repel water a lot better, - - - a can of silicone spray is cheap insurance.
The reason why you won't have a vibration problem at higher engine speeds is the flywheel effect. With the engine turning a couple thousand RPMs the weight of the rotating mass means it's virtually impossible to the motor to exhibit any momentary slowing down or speeding up - the "inertia" of all that rotating steel is too much to allow you to notice any slow-down taking in such a short taime frame. Then your engine will seem to "run smoothly" at highway speeds (or even maybe at 40 MPH) but will be noticably rough at an idle.
It's the easiest thing in the world to dump a can of injector clearer into your gas tank and it only costs $5 to $7 for the best cleaners. I've been using "Sea Foam" injector cleaner lately which was highly recommended around here, and it seems to work okay & costs $5 per can. Be sure to put a can of that in the tank when the tank is near empty - and then fill your tank with gas so it can mix with the cleaner. DON'T put a whole can in unless you are gonna put a lot of gas in on top of the cleaner.
Around here we usually need to special order Nissan parts like injectors from the largest dealer who is also a big representative for Nissan. But there are now auto parts dealers online who may give you a better price. Injectors should be quite common - but a lot of manufacturers are trying to get rich by selling high priced parts.
It seems possible your car mechanic may be trying to "rook" you. He ought to be able to read the computer error code (I'd guess) that almost assuredly IS an available diagnostic aid for your vehicle. That was how I knew my 97 p.u. truck had an injector problem & the error code even said it was with the #4 cylinder injector.
Later I bought a neat little computer diagnostic tool that's even BETTER than trying to "read" the flashing Check-Engine light as it puts out the error code. This diagnosis tool is the "Scan Tool" (or ScanTool) and is available from the "ScanTool.net" web site. This gizmo's input connects to your vehicle's computer plug-in socket and the other side will plug into a port (serial port) on your computer or laptop. With this ScanTool little circuit board and a cable you also get the computer program you need to READ those errors. This is absolutely great!!!!! there are a couple different models for vaious manufacturers, and mine (most foreign cars) is the OBD-2 type. This stands for "On Board Diagnostices vers. 2".
***BAD MANIFOLD AIR FLOW METER*** I'd forgot about this - but 3 years ago a problem developed that my Nissan truck Manifold Air Flow Meter went bad. This made my 97 p.u run very rough. I was NOT able to *read* what that problem was by reading the flashing Check Engine light as is usually possible. But when I plugged-in the ScanTool and did that test with a computer it told the M.A.F. meter was BAD. (This was a bummer!!) I finally got a replacement MAF which had to come from a Nissan dealer = costly. I'd looked at numerous used parts dealers online but could not find an exact replacement model MAF meter to replace mine. In the end I had to pay about $432 plus tax for a new one at the authorized Nissan dealer. HINT: you *can't* (always) simply replace the plug-in electronic module portion of the MAF Meter and expect the engine to run right. Each electronic module (less than the size of a pack of Luck Strike) is specifically adjusted for the airflow charactoristics of the "throat" of the precisely machined aluminum flow meter body.
By taking my old electronic module apart, I found that water had entered it and there was corrosion and "gook" on the circuit board. When installing the new unit a bunch of silicone bathtub caulk was applied on it to keep out any water.
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