Why does my 99 Ply Voy SE 3.3 ltr eng. spark knock constantly?

Question

I have taken in my 99 Ply Voy SE to dealership for spark knocking. They replaced two vaccuum hoses and told me I need to have fuel injectors and throttle body cleaned for a grand total of about $320. I had them replace the hoses. I feel it may be the timing and they are just trying to get more money out of me. It spark knocks under light acceleration constantly. It only goes aways when I let completely off the gas or accelerate quickly. I have put two bottles of fuel systems cleaner in my gas tank in two separate fill ups. This has not helped. The van has 95,000 miles on it and runs fine otherwise.

Answer 1

Either your knock sensor is bad, or you have carbon build-up on the crowns of your pistons. Use a timing light on your engine with it running, and knock the engine block with a solid object. You should see the timing mark jump around each time you knock it. If not, the sensor is bad. If so, try running your gas tank down to nearly empty, and filling it a quarter way or so with 93-95 octane, and see if it goes away, or diminishes. If so, you probably have carbon build-up, and it increased your compression ratio. You dont' have many miles on your engine, so I don't think this is the case. Don't give in to the fuel injector and throttle body cleaning...they just want your easy money! Clean the throttle body yourself: buy a can of carb. cleaner and spray into the throttle body while using your free hand to throttle the motor. Make sure you clean around the butterfly valve if possible. Check that timing, and good luck!

Answer 2

The timing on these vans is controled by the computer, there is no external adjustment to do. Unless you had the timing belt replaced and they installed it incorectly then you could have a timing issue. The spark knock could caused by a carbon build up in the cylinders, thats why the dealer is recomending doing those services. The injector cleaner you put in the gas tank wont clean that up, its to diluted in the gas. The cleaning they would do, uses a concentrated cleaning product that the car would run on solely causeing it to be far more effective. Id call some local repair shops for some better pricing, the system we use in my shop is called terra-clean and used it on my own cars works great and costs around $160. Hope this helps

Answer 3

Unless your vehicle has been modified the ignition timing is controlled by the ECM and is not adjustable. At 95K miles a stretched or improperly installed timing belt or engine carbon build up could be a cause. A visual verification of engine timing mark positions on cam gear, crank gear, etc and an engine compression test would diagnose both problems respectively. Your question mentions nothing about a check of or replacement of the engine knock sensor which is alot easier to service and would be the first place I would look for a problem.

Answer 4

The Engine can get carbon buildup in the heads and top of the pistons. This carbon when it is hot ignites the fuel in the cylinders.There are top cylinder cleaners that help break up the deposits. and stop your knock. Check around as there are machines that inject cleaners into the fuel system. The other way is pull the heads and clean them out

Answer 5

put some 93 octane gas with a bottle of octane booster this will clean the motor out and useally stop the knocking.if this dont work the try new plug wires. it has nutting to do with your vaccuum lines or your injectors.if none of this works then its your timeing. get a timeing light make sure u read the directions.