Question1998 Voyager SE. When driven the car has a bad shake all the time, no matter what speed or revs.It has been on a diagnostic comp twice and once in a chrysler garage but all electrics seem ok. It has had a new catalytic converter 6mths ago and now it needs a new one. It has had a new cam sensor, throttle sensor and new plugs so any ideas would be welcome.
AnswerHi Geoff,
If the electrics are fine, then the other issues are the fuels supply and of course the mechanical aspects of the engine. I think that you may not have had the vehicle in the hands of a competent engine tune-up/analyst. For example, with the Chrysler type of code reader you might be able to identify which cylinder is not working properly and thus causing a miss and consequent vibration. And the reader should be able to identify which cylinder is involved. Or you could try discnecting the spark plugs while the engine is idling (and ideally roughly if the problem also includes missing at idle),one at a time,to see if there is one which when disconnected does not cause an exacerbation of the problem. Or if necessary you could try doing this one plug at a time test but instead driving the car and see which one causes the condition to not get any worse when you have it disconnected because that will be the one that is not contributing power normally and is the source of the problem. It will run worse with each of the other plugs pulled (may not even run) but there will be one that makes no difference when you pull the spark plug insulated cap off the plug (pull on the outside of the plug cap, not the wire, to remove it). Then once you have the cylinder identified, you could do a compression test on it to see if it has equal compression with anyother cylinder. It it does, then the mechanical is probably not it, but rather the fuel injector (if this is a multiport system with one injector per cylinder).
So far I have focossed on the possibility of one cylinder being faulty. But other possibilites for general missing are:
fuel filter clogged, low fuel pressure (pump or regulator faulty, can measure the pressure), ignition timing (but that is not adjustable, is run by the computer and sensors that have been replaced already), poor or wrongly gapped spark plugs, faulty emission system (particularly check the egr and pcv valve), leak in the vacuum lines or intake manifold gasket.
Most of these items can be checked/measured easily. I think you need to ask around to see if anyone else with a Chrysler product can give you a lead on a good mechanic with Chrysler experience. The different manufacturers are so sophisticated that it really helps to have a person who know your engine try to find the problem.
Let me know if any of this helps and how it is resolved ultimately. And tell me which engine you have if you write back with further questions.
Roland
