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Chrysler diagnostics and misfire in 3, 5-liter engines

Chrysler diagnostics and misfire in 3, 5-liter engines 1

Chrysler diagnostics and misfires in 3.5-liter engines

Malfunctions such as misfire in the cylinders, uneven idling, poor performance, increased fuel consumption, for Pacifica models (CS platform) 2004-2006, Chrysler 300 2005-2006, Magnum and Charger (LX platform) with a 3.5 liter V 6 engine, may be associated with carbon deposits on valves. This problem is observed in models on the CS platform built after February 1, 2004 (MDH 0201 XX) equipped with a 3.5-liter engine (sales code: EGN).

According to Chrysler Maintenance Bulletin 09-010-06, valve rotation mechanisms do not work fast enough to prevent deposits from depositing on valves, especially if engine speeds rarely increase to 3500 rpm or higher. The reason for the increased deposition of soot can be short trips, driving around the city with frequent stops, light pressing the gas pedal. Carbon deposits form in the combustion chamber and on the valves, which may interfere with their complete closure. This causes a loss of compression, which leads to misfire in the cylinders, uneven idling, poor performance and increased fuel consumption.

Chrysler experts say that if you occasionally increase the engine speed to 5,000 rpm (sharp acceleration), the valves will rotate fast enough to prevent carbon deposits. But with slow city driving, the engine does not accelerate enough to rotate the valves and knock carbon deposits off the valve stems.

Low-quality gasoline, with little or no detergent, also exacerbates the problem. The use of high-grade gasoline with a high content of detergents will keep valves clean.

diagnostic check

If the “Check Engine” indicator lights up, connect a scanner or code reader to check for misfire codes. If misfire codes appear in one or more cylinders (P 0301, P 0302, P 0303, P 0304, P 0305 or P 0306), there may be a problem in the deposits on the exhaust valves..

To eliminate the misfire problem, check the spark plugs – they may be wet, dirty or worn out. Replace worn or contaminated candles as needed. Ensure that the gaps between the spark plug electrodes are within specifications (from .048 to .053 inches). Original spark plugs for such engines have a platinum coating on both electrodes (Double Platinum); if replacement is required, replace them with durable platinum or iridium candles, which require replacement every 100,000 miles.

Other possible causes of misfire in the cylinders are dirty or faulty fuel injectors, vacuum leaks, a leak in the exhaust gas recirculation valve, or weak or faulty ignition coils..

The 3.5-liter V 6 engines are equipped with an ignition system with an individual coil on each candle. To replace the spark plugs, you will need to remove the coils. The coils are held in place by Torx screws (with a star head). After removing the coil, check the protective cap that is put on the shank of the spark plug for cracks, carbon traces or moisture. Clean or replace the coil, if necessary, so that a spark forms on the candle and does not go “to ground”, causing misfire.

Simple solution to the problem

The easiest and cheapest solution to the problem is to purchase a bottle of engine cleaner or a solution for removing carbon deposits, and, following the instructions on the product packaging, soften and remove the carbon layer from the combustion chambers and from the valves. For professional cleaning, a concentrated solvent is usually used, which is poured directly into the fuel injector pipe when the engine is idling. Household cleaning products can be fed into the intake manifold via a vacuum hose, into the fuel rail, or sprayed into the throttle body.

You can also add a bottle of fuel system cleaner to the fuel tank. Techron cleaning products do an excellent job cleaning fuel nozzles, combustion chambers, and valves. Follow the directions on the product packaging and repeat the procedure if necessary if once is not enough. Take the highway and step on the gas. Accelerate the engine at least five times to 5,000 rpm or more. This acceleration helps to rotate the valves and knock carbon deposits off the valve stems..

Chrysler Repair or Correct Solution

To solve the problem on Chrysler vehicles, it is necessary to replace the valve spring disc locks (part number 53022277 AA). New valve spring disc locks better handle valve rotation at lower speeds. Replacing all locks is a laborious job that takes about 4 hours. Firstly, valve caps and rocker axles must be removed from the cylinder heads. Then you need to manually spin the engine so that the piston of each cylinder reaches the top dead center. After that, production compressed air is supplied to the cylinder through the spark plug hole to keep the valves closed. You can use a special valve spring compression device (MD 998772 A or equivalent) to remove the original valve spring plate locks and replace them with new ones. As advised by Chrysler, each valve should be rotated 90 degrees to make sure they rotate freely..

It is also recommended to replace manifold absolute pressure sensors (MAP, Manifold Absolute pressure sensors). The MAP sensor detects the vacuum at the inlet and tells the computer when the engine is under load so that the fuel mixture and the ignition timing can be adjusted properly. On models on the LX platform and on the CS platform, MAP sensors No. 05033310 AC and No. 04896003 AB, respectively, are used. On CS models, the sensor hole should face down during installation. Use only one fastener.

After replacing the locks of the valve spring plates and the collector absolute pressure sensors, the engine must be cleaned of carbon deposits using a fuel cleaning agent or resort to professional engine cleaning using special equipment.


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