Saturday, May 15, 2010

Possible cause for code p0440 or p0441 on a Dodge Intrepid with a 2.7 liter V-6

This is an update from an earlier post concerning a problem with the evaporative emissions on my Dodge Intrepid with the 2.7 liter v-6 engine installed. While I imagine this could apply in some way, shape, or form to the 3.2 or 3.5 liter engines, this is unlikely unless the engine is very high-mileage or has been used and abused. There's one fundamental difference between the 3.2/3.5 and the 2.7 liter that I'll go over later in this post.

These are facts, and nothing but facts. I am not writing to bad mouth Chrysler or one product over another, but to help someone save some time and money. I am not a car mechanic, but gifted with better than average problem solving skills. The processes described should be a very low risk of messing anything up (unless of course, you're all thumbs). However, since I have no control over your work you assume the risks.

The evaporative emissions control is a necessary evil to prevent pollution and I do not advocate disconnecting or tampering with any emissions control device. This also means removing the "check engine" light. I've been around long enough to know neglecting maintenance can mean taking the shoe leather express at some point in time.

The EVAP system uses the engine to suck gasoline vapors from the carbon canister into the intake manifold to be burned in the combustion chamber. An electronic valve shuts off when the engine is off to prevent the uncontrolled flow of vapors into the atmosphere. In the case of the Intrepid, a NVLD, or Natural Vacuum Leak Detection switch, measures the flow and gives the computer a play by play. Leaks in the hoses, parts or a problem with the canister purge valve (solenoid) will set a trouble code and turn on the MIL or Malfunction indicator Light (check engine light). Because the NVLD on the Dodge is failure prone, the natural (pun intended) reaction is to replace the part. This is about $200 and if not the right part, this is a costly mistake. No, I did not replace mine.

The 2.7 liter V-6 in the Dodge Intrepid, Stratus, Concorde, etc is not known for their long-term durability. Like anything else with lots of parts it will have a propensity to break down more frequently. Added to this is Chrysler's tendency (along with any other automaker) to get their parts from the lowest bidder. The result is an engine that seldom lasts more than two or three years even rebuilt. Two weeks ago, mine started to make noise that got progressively worse. Then it misfired so badly I couldn't get the car to crack 35 miles an hour on I496, where speeds easily double that. I limped the car to my parents, let it sit, started it up and it drove relatively normal (save for the noise).

My checks included running the engine and disconnecting each coil, one-by-one, to see if the engine idle would change. It did markedly on each one; so the coils, plugs and computer were fine. The ticking noise was about the same. My engine has less than 34,000 miles on a rebuild which is now out of warranty. The check engine light came on over a year ago at 72,000 miles and the car has 84,000 as it stands now. On a hunch, realizing that the engine is a vacuum pump manufactured to close tolerances (and the fact there was a lot of oil in the air cleaner), I removed the right-side valve cover. This is going to mean removing the upper intake manifold as well. There are 10 bolts on top and one or two under the throttle body, but the object is to move the manifold aside to access the screws holding the valve cover on. Just remove those screws and leave them in place. The coils and plug wires can stay on the cover, but put it aside.

There's three timing chains in this engine and you'll be able to see two of them. The primary chain drives the sprockets and water pump and the other two drive the camshafts in sync. The primary timing chain is held taut with no less than four plastic guides and a plunger filled with oil to hold it together as the chain stretches. If each link stretches a tiny amount, this is amplified by the number of links on the chain, which by my reckoning could exceed several inches. I found a fair amount of slack and the plunger that lives in the right cylinder head extended past its body 1 3/8 inches. This is about the maximum wear limit for the chain and it will cause the engine to have blow by (remember the oil), affect the pumping and sealing of the engine. In my humble opinion, this could be affecting the performance of the EVAP system to the point the "check engine" light is on.

But there is another, more disastrous consequence associated with this that you need to know about. The 2.7 liter is what's called an interference engine. This means the valves extend into the potential path of the pistons when they open. This is very common to raise the compression ratio and allow the engine to "breathe" better. The most famous of these was the 1981 Ford Escort with the timing belts failing at 70,000 miles. It resulted in a lot of ruined engines and possibly a few consumer complaints for Ford.

The difference is that a timing belt is about $30 to $50 dollars and a water pump about $50. Tack on an hour labor that any backyard mechanic can do and this is small potatoes to save your motor. The timing chain on the Intrepid's 2.7 liter, at least on mine, by my reckoning, lasted about 25,000 miles (on a rebuilt engine) before it stretched enough to cause the engine light to come on. This is not small potatoes to fix. A timing set with gears, chains and guides is going to be about $500. A tensioner is $60 and a water pump (driven off the timing chain) is about $90. Gaskets will run upwards of $100 and in my case the balancer is also distorted (probably another $100 to replace). A mechanic bills 10 hours to get this done, so at $80 an hour, this is $800 for labor.

Before even fixing the engine cradle and transmission mount, this is going to cost $1450.00, but the price of a used engine is about $3500 and a new one is upwards of $6000 without the 17 hours of labor to install it. A 3.5 liter is an option, but that will require more mods to accomplish, all on a car worth about $2000 in pristine condition. The main feature of a 3.5 or 3.2 is that they use a belt that's much less costly and isn't prone to stretch the way a chain does.

This isn't to make any ones mind up for them, but to help you understand that things are not what they seem in the auto repair world. This is an expensive engine to work on and one not known for its durability. I've driven GM and Ford cars thousands of miles without even replacing a timing chain. Belts were a no brainer, I've done these in less than an hour, even on a V-6. But this is a different animal and I know it. God never meant us to try and figure out a dual overhead cam V-6 with three timing chains.

Right now, I've got a paperweight that mercifully, we're making our last payment on in June. It has 84,000 miles and on its second engine. This is going to cost over $3000 to fix, but because it's still poorly engineered means the replacement parts won't be much better. We're not in the market for another car, but the Lord provides. Regardless of what happens, He's still in control.

1 comment:

Walter Grace said...

The valves and pistons did collide, so the engine is ruined. Because of the durability problems associated with the 2.7 liter, it wouldn't be advisable to replace the engine even if I did win the powerball. Obviously, I have not (thank the Lord for that). So this means asking for help. I need a car or minivan. I'm not picky, but four doors would be nice and something larger would be great. I'm unemployed and looking for work, plus taking care of of two little ones. If you have something serviceable and want to help someone out, this would be most appreciated.