[Denis Mitchell]

Hey everyone,

I hate to make my first post on a forum one asking for help, but I need to get some ideas from the Allpar community.

My family has owned a 2002 Town and Country since new, and it has had minimal problems until recently. In the last month, the mileage dropped from an average of 18.9 MPG to about 14.8 MPG, the car was running extremely rough on start up, and power would not "kick in" until about 4100 RPM.

Naturally, we assumed this was because we had had the same spark plugs in the car since new... for over 215,000 miles. I did the job and replaced all the plugs, and expected a brand new engine. While I was back there, I also noticed that the rear exhaust manifold bolts were almost all lose, and there was soot on the spark plug wire on cylinder no. 1. For about 3 years, the car had an exhaust leak that made it sound like a lawn-mower. It didn't affect mileage or driveability, so we had just ignored it. Discovering THAT problem, I re-tightened the exhaust manifold bolts, attached all the plug wires and started the car up.

The lawnmower was no longer present under the hood, and the car started quickly with 0 roughness after start up. I took it for a spin, but found myself upset when I noticed that the accelerator still appeared to have dead spots - especially at low rpms (up to about 3500). For example, flooring it from a dead stop resulted in less than stellar performance, and the power would still not really "kick in" until about 4100 RPM. Gas mileage is still just as bad, and I notice at low engine speeds and low throttle, such as when accelerating slowly from a stop in a 25 mph zone, the car surges, noticeably. It is as if I am taking my foot off the gas, then putting it on, taking it off... I also notice a lack of power on relatively flat road around 50 MPH, the car needs to shift down a gear to have any real power - I expected more torque from this engine!

We have a '97 T&C with the older 3.8, and it definitely has more balls right now than our '02, so I know something's wrong with the engine. The other thing I have noticed is it seems to be running slightly rough, very subtle but definitely present. You can also see it when the engine is at idle with the hood popped.



This car has never thrown a Check Engine Light in its lifetime. The only issues we have really had were with a sensor for the airbag being bad, and recently our ABS light has come on at highway speeds, but then goes away. No lights are on the dash right now.

My first thought was to clean the MAF sensor, only to discover that, indeed. these engines utilize a MAP sensor. I thought the O2 sensors may be bad, but those are expensive and difficult to access just to throw at the car. We did not change the spark plug wires, but we are going to replace them with a set of Bosch wires from AutoZone tomorrow. The new plugs I put in the car were the correct Champion Double Platinum plugs. The old plugs were almost completely eroded, and yet, I barely noticed a difference in the way the vehicle runs.

Any help would be greatly appreciated! Thanks much for reading this!

- Denis

 

[Denis Mitchell]

check the basics, air flow, spark, and fuel pressure. I'd hook up a fuel pressure gauge and see what the fuel pressure is doing when it wont get out of its own way since you already replaced the plugs.

Sounds good. We'll give that a shot soon if some other methods don't work. I've actually been thinking about changing the fuel filter, it's probably due for it by now...

Check for any fault codes - not all codes trigger the CEL. Advance Auto and AutoZone will read the codes for no charge. That would be the first step. No sense in going any further until you get the codes, if any.

Did you replace the plug wires when you changed out the plugs? After 215K miles I'm sure the plug wires are worn and may indeed be the source of your "miss". Back when I stupidly bought a used '93 Aerostar, I ended up taking back to the dealer as it was running rough. The replaced the plugs and while it was a litte better, I could still feel the miss. Rather than fight with them, I replace the plugs wires and wa la!, the miss was gone.

I dread to think how big the gap was on those plugs after 215K miles. My Hemi-powered Ram has coppers which are suppose to be changed out every 30K. Well, I went over 100K on one set - the gap was huge. Fuel mileage had dropped by 1 mpg, but otherwise was running fine. Not fun changing out 16 plugs.

We did not replace the plug wires, and we're going to do that in the next couple days. Good advice on the fault codes, I'll run down to the local store and have 'em see what comes up. Can you check those with the Key On 3 times trick? Oh, and the gap was monster, the worst plug had probably less than 0.010 inches of material left with a gap more than twice what is prescribed. Amazingly, the car didn't run any better after replacing the plugs.

WOW! 215K on plugs??? Are you sure no one replaced them before??? I would do plug wires, and

do a good inspection on the Throttle body,for gum coking, check the egr valve, and check for codes

in PCM. I would also check the coils for primary and secondary resistence if you even went half that mileage

on plugs! Thats very hard on the coils when gaps open up from lack of maintence. Did you check your fuel PSi

may need a filter.its in he tank but they do clog up after 200K. Do a complete tune up first. With mileage do plug wires.

first foremost then check the ThrottleBody and Check for Codes.

Jake

I am positive no one changed the plugs before, since we've owned it since new! Only in the last few weeks has it started to run poorly. My plan was to take some throttle-body cleaner to the intake manifold and related areas, I've been toying around with sea-foaming in my head but that'll come at a later date. I doubt that sea-foaming would solve a problem that happened so suddenly.

Do you have any information on checking the coil-pack? It is a 2002, so it has the 6-pack coil pack. Also, how bad is it to change the fuel filter on these cars? In-tank sounds like a night-frickin'-mare.

 

[Denis Mitchell]

Well, I changed the plug wires yesterday, and the car started running better. Picked up in power, no more stumble off idle at low throttle openings, still felt a little rough on the road, but gas mileage was back up to 16 city... and then later that day, I started it and it ran rough, felt like a cylinder wasn't firing. My dad had just driven it and confirmed it was running better, and an hour later it feels like a cylinder is missing.

I left it alone last night because I was busy, and this morning checked and re-checked all the plug wires and connections. Still running rough. Last night, when I tried to start it, the Check Engine Light was on, code P1684. I understand this means the TCM was disconnected from battery power. I thought this odd, as I had not disconnected the battery, and no one had touched the car since my dad had driven it, much less popped the hood.

When we were looking at it this morning, my dad revved it up to see if that made any difference it how it ran, and I noticed white smoke pouring out of the exhaust, even at idle speeds. I also tried pulling plug wires while it was running (zap) to see if any cylinder did not make a difference, and when we pulled the No. 4 cylinder, I noticed it didn't make much of a difference, although it did start running worse shortly after. We decided to rent a compression tester, parked the car, and pulled the hood and cowl off to find out what's up.

We began pulling the plugs off. When we pulled the No. 2 spark plug, we noticed it had debris on it, and cleaned it off. It also appeared that it was running lean, as there was white chalkiness on the plug. No. 1, 4, 5, and 6 all just looked like they ran lean. no debris. The No. 3 plug told a different story, however, as it was coated in (and reeked of) gasoline. We cleaned the plug off.

We pulled the fuel pump relay and the fuse for the ignition, and removed all spark plugs and set the wires to the side. We ran our compression tests, starting with cylinder No. 1. We noticed when we cranked the engine over for No. 1, there were puffs of vapor escaping No. 3, which smelled like gas. This leads us to believe that the No. 3 cylinder has an injector that is stuck open, but we have not confirmed yet. After cranking a few times, the vapor diminished. While looking at the back of the engine, we also noticed that there was moisture on the O2 sensor there, immediately behind cylinder No. 3. It did not smell like gas, it looked like condensation, just plain water.

At this point, we ran the remaining cylinders. 1, 2, 3, 5, and 6 all read between 200-215 psi, where as cylinder No. 4 read 180 psi. We added some oil, and the reading jumped up to 210 psi, which we believe indicates (a) bad ring(s). We've also noticed the engine sounds rough when it starts up, possible the result of the rings being the way they are. For years it had run fine, but just recently it's run terribly, and now this.

At this point, we're considering pulling the upper intake manifold off and inspecting the injectors. Also, when we checked the coolant, we did not notice any bubbles which are usually indicative of a head-gasket leak. There was no green tint to the oil and no "milkshake" under the oil cap, but the car has been slowly consuming coolant for the last year.

 

[Denis Mitchell]

Another update!

We pulled both valve covers and the front head off (cylinders 2,4,6) today. It took a little bit of doing, but it was well worth it. The valve-train on both cylinders looks excellent, which is a good sign. The front cylinder head did reveal a bit of information to us. The number 4 cylinder, which had the lower compression, appeared to have valves which were not seating properly. The exhaust valve has a quite obvious gap, and the intake valve a gap that is a little less subtle. We also noticed the cylinder wall was slightly scored, but it did not appear bad, our fingernail did not catch on the scoring. The cross-hatching was gone from all cylinder walls (expected a 217k). The pistons all appeared to be rusty, which we attribute to evidence of the failed head-gasket.

At this point, we're going to pull the other head off and inspect it, and then check the main bearings and rod ends to see if anything there is in bad shape. If everything checks out/only needs minor work, we intend on sending the heads out to be checked/hot-tanked/re-machined if necessary, and then we'll replace the head-gasket and bolt everything back together.

We'll keep you updated as we go!

 

[Denis Mitchell]

Pulled the back cylinder head yesterday. Everything looked okay, except the head-gasket was obviously leaking, which we suspected. Furthermore, we noticed (in the better light) that the cross-hatching actually IS present on all 6 cylinder walls still, so this is great news. The back head seems fine otherwise, and we're probably going to still send both heads out to be checked and re-machined. We've given some thought to doing a rudimentary head job ourselves, as my cousin had done with his 3.8 that he rebuilt the top end on.

We also droppped the oil pan today with little difficulty. nothing looks out of sorts here. We're giving some serious thought to replacing the timing chain, sprockets, and oil pump while we're tearing into the engine. If the bearings check out okay, might as well make this engine run forever!

 

[Denis Mitchell]

Since you've gone that far already, why not just replace the rod bearings and main bearings while the pan is off? I'd put a new oil pump and pickup screen in it too.

That is what we're intending on doing if they aren't out of spec. Heck, even if they're in spec we may replace them. I'm pretty sure we can replace the rod end bearings without dropping the crank-shaft, but I'm not sure about the mains, but we'll see.