Engine stumbles under while in low torque

Hey everyone,

First, allow me to apologize. I'm posting this regarding a vehicle other than a Windstar. While my wife/I own two Windstars, my personal commuter is a 2000 Kia. The Kia forum sucks and has cobwebs and ghosts roaming around in it. No one ever responds. The Windstar forum is very active and so I thought I'd post a general question to guys for input.

2000 Kia Sephia (P.O.S) w/ 185,000 miles w/ a 1.8 l inline 4. I've been ecstatic about keeping this ugly beast running for as long as I have, but recently, it's developed a stumble after shifting into a higher gear before you've really reached the power band.

For example, if I shift into 3rd a little early on a normal vehicle, the engine would run fine, but just have very little power. On my car, it bucks and stumbles. Very aggravating. At higher RPMS, the engine seems to smooth out. This problem happens regardless of gear....just when I have very little torque.

Recently, I've had two problems. One was a busted rubber air transport hose from the air filter to the intake manifold. I replaced it thinking that since the MAF was located at the filter, it was getting an incorrect amount of air into the engine for the MAF reading. That didn't really change anything. Next were codes...I briefly got a "misfire on multiple cylinder" code, but cleared it and it hasn't came back. About a week later I got a MAF out of range code. Once again, I cleared it and it hasn't came back.

Here's the heart of my question. Part of me thinks the engine is simply just worn out and possibly suffering a compression issue. But I'd love to simply replace a part and have it run like new again. I haven't ran a compression test yet, because I'm out of town for a few weeks and don't have all my tools. An engine with low compression, do the symptoms get better at higher RPMS?

I'm just trying to grasp at straws right now. The car's ugly and embarrassing to drive, but it's been very reliable and it's my daily driver. Like a man married to a fat woman, I've been with her for so long that I'm somehow proud of my achievement. I consider myself a pretty good mechanic, but this problem has me stumped. No check engine lights, but a constant stumble under low torque situations. I look forward to any insight you folks may have. I realize this is a Kia question, but I value the Windstar forum's dedication to continuing to keep their beast's on the road.

Mark

A few quick thoughts, noting that I have little Kia-specific background...

Yes, I'd check compression. But I doubt that's really the problem. Modern design and manufacturing methods mean engine internals simply don't wear out the way they did in the old days. I suspect a compression test will reveal numbers that are still within spec.

Of course, make sure all basic tune-up stuff is up to date (filters, plugs, ignition components, etc). But I suspect you do that already.

Now: Three areas I've run into that have caused similar symptoms to what you're seeing...

EGR: I've seen leaky EGR valves cause strange idle problems. That said, my experience in this area has been with cars older than your Kia. EGR designs have changed over the years, so this may or may not be a potential concern for your car. Still, it's probably worth investigating.

Fuel Injectors: I had a strange idle problem (again, on an older car) that I finally tracked to a leaky fuel injector. The injector nominally worked - but was dripping enough that idle was rough and lumpy. At higher RPMs, it wasn't noticeable. There are places on-line (start your research by searching eBay for "kia sephia injector") that sell sets of used injectors that have been cleaned and flow-tested for very reasonable prices.

Vacuum leaks: This tends to not be the problem it was on older cars with lots of vacuum lines, but I'd still verify that everything on the engine's intake is tight, clean and leak-free.

Maybe a good strong fuel system cleaner to clean the injectors?

Fuel filter?.....sadly, on some vehicles, they seem to put this inside the fuel tank as a part of the fuel pump assembly (like my 2003 Toyota Sienna).
When they do that, you have to drop the fuel tank and remove the fuel pump assembly to change the fuel filter.
If you have the in-tank fuel filter......keep this in mind, but hopefully you find something simpler to be causing the problem.

Since you found 1 place air was able to leak into the system.....give the system a good looking over for any sign of that......maybe a gasket not seated just right on the air filter, a loose or damaged vaccum line.

Another thing to try is cleaning the MAF with a non-residue electronic cleaner (MAF cleaner).

Make sure that the spark plugs being used match up with what is called for by the manufacturer as the wrong plug can cause strange problems.
Those spark plug wires are now 10 years old, if original.

Ugly it may be, but it should be a great car to get back and forth to work in......and get great fuel economy......that makes it a pretty good looking car in my book.

First of all, thanks for everyone's input. I spent a few minutes today and figured out my problem.

On my Kia, it's a 4 cylinder. The coils are integrated into the spark plug wires on cylinder 2 and 4. (They sit atop the hard plastic spark plug boot that goes into the middle of the engine.)

Many moons ago, when doing maintenance, I noticed that the locking clip that holds the 2-wire clip in coil had broken. Since the wires still made contact, I decided to turn a blind eye. The next time I went to the junkyard, I procured a replacement wire, but didn't install it. (I still have it at the house and just figured I'd install it next time I had the spark plug wire covers off.)

Tonight, when I opened the spark plug wire cover to explore my issue, I noticed that the crimped on connector that actually makes electrical connection had broken. It was laying very close to the connector and so under higher RPM, I believe it was making good connection. Under lower RPMs, my connections were not as good and I was having the hesitation.

I am still currently out of town and since I already have the replacement part at the house, I just refashioned the connector to allow it to get me down the road for a few more days. If it falls off again, I'll probably just go grab some of those cheap little female spade connectors and make my repair a touch more permanent.

Mark

Good news! Finding the source of the problem is usually the biggest part of the job.