348 stumbles at 5500 rpm

Here ya go.

Quite a bit harder to see when the motor's in the car.
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I wonder if perhaps the 5500 rpm symptom is significant, as according to the Shop Manual that is the cutoff speed for the intake compensation solenoid valve (see page C18-19). Maybe you have a vacuum hose off, or a problem with the linkage to the butterfly valve in the intake plenum?

 

Replace the crank shaft sensors, the Kia ones work perfect and are dirt cheap.
There are several of us using them now.

 

Kia ... I didn't know, thanks for the info, if I ever need, I know what to buy !

 

Roberto,

Here is a pic of the part number. The old, crumbling Bosch sensor is on the left, new Kia sensor on the right. You will need two of them, and they are around $20/each from online sources, $35/each from the dealer. Despite all the heckling and naysayers, I've been running them for 8,000 miles without issue.
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I had a similar problem recently but only when it was hot. Before I could diagnose it I spilled oil all over the o2 connectors and then had some issues there. I had figured the missfire to be a crank sensor so I replaced both (with Kia sensors ) and both o2 sensors (Walker $70 each). I don't know what fixed the hesitation but the car runs like a champ now.

The crank sensor swap on the t takes 10 minutes with a lift. I imagine the 348 is similar.

I remember another FChatter with a Mondial t describing a similar problem and it turned out to be a connector under the dash having something to do with the ECU. How he found that I don't know.

Good luck,
Dave

 

Brain dump:

I think the battery/alt light is red? If so, maybe a loose engine ground strap? Slipping alternator belt and dead/dying battery?

I think the low fuel warning is yellow? Perhaps you caught a glimpse of that when the fuel sloshed around / the engine stuttered?

Another sensor to check while you are looking is the throttle position sensor. We've had several people (myself included) see improvement in high RPM issues by simply cleaning this poteniometer with lubricant/cleaner from Radio Shack.


Keep at it. I'm sure you'll find it!

 

Well, what are the odds....

This started happening to my car today! Gotta dose of religion when my car shuddered at about 6000 RPM. Shook like hitting the rev limiter.

No check engine lights, so I revved the motor a few times. No stutter. Got on it again and it stutttered again. Odd.

Made my way home, then pulled over, restarted engine and tried it again. No stutter.

Came home and sat in my driveway and slowly wound up the motor to 6.5k in neutral and it finally stuttered again once, and I saw a CEL blink. Yes, they are orange/yellow, not red. SUCCESS!

I immediately pulled the codes on both sides:

4121: on both sides.. yeah yeah yeah, cats. My slow down lights seem to work though and weren't on, so I'm not gonna sweat this one yet.

4114: TDC / Crank sensor-- That's what I wanted to see. Loose connection on the crank sensor I bet, further aggravated by inertia when accelerating... I suggest you do what the others said and check your cam and crank sensors. My cam sensor already flaked out a few years back and needed replacement, so this isn't really a shock.

In any case, wanted to pass this along. Will keep you posted when I fix it.

 

Eric,

How do you wire these things? Is it only two wires with no polarity (i.e. an induction sensor) I assume?

 

No wiring required - the Kia's use 3-pin amp connectors, same as the Bosch units. Just remove the old ones and plug in the new ones. Each sensor is held by a 5mm allen bolt, and a metal bracket with one 8mm nut holds both connector ends for the sensors.

Edit: Here are a couple of pics of the connectors.
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Nice! As much as I like giving Daniel money, gonna hit the Kia dealer. At this price, might as well change them if I'm gonna jack the car up and check em.

 

I'm no expert on the Motronic, but I'd wager a guess that the sensor is failiing only at certain speeds, which results in the ECU failing over to some preset map quickly, causing a stutter. If it failed completely, we'd probably see the CEL lit.

My thinking is that a bad connection/vibration/water intrustion/corrosion is causing too little current to flow through the inductive sensor, which although damaged may generate enough current at low RPMs for the ECU to read, but then subsuquently faills at higher RPMs. If there is too much resistance, the voltage may be falling below an acceptable signal voltage and causing an error condition. Makes sense, and seems to fall in line with similar things I've seen.

I have my parts coming in tomorrow so I'll let you know what I find.

 

Got the parts in today. Two KIA Sensors, and they are an exact fit. In fact, they seem to be an improvement on the original design.

Here was my repair process:

1. Jack the rear of the car on both sides, use jack stands and chock the front wheels.

2. Shimmy under with metric ratchet set, short 5mm allen wrench, and phillips screwdriver.

3. Remove the louvered shield under the front of the engine. Has 2 bolts on either side and a handful of screws.

4. Once that is out, grab your SHORT 5mm allen wrench.

5. You can see both sensors. The bottom one is easy to get too, the side one is not. You will need a short allen key to remove it, and a lot of patience. Alternatively, you will need a person with tiny hands who is also a contortionist.

6. The two sensor plugs meet in a bracket, where they are attached to the wiring harness. Both sensors snap into the bracket. Make a note of which goes to which sensor, then remove the nut holding the bracket.

7. Remove both sensors and replace. Make sure to get the tiny metal gasket aligned properly.

8. Clip the sensor ends back into the metal bracket. They are a bit of a pain to get in, but they will fit. Make sure the keyed side of the plug is facing the engine on both plugs when you snap them in, otherwise one of the clips won't seat easily. Also, make sure there is no residue from your old clip on in the plugs.

As suspected, one of my sensor plugs was completely disintegrated! All of the insulation was gone, and even the plug itself was shattered in the plug housing. I had to pick the broken plug parts out with a screwdriver and needle nose pliers.

After warming the car up, I took it out and did a few high RPM runs. The only stuttering I heard tonight was my rev limiter! In fact, I feel a noticable power improvement, so I suspect this had been causing sub par performance for a while as well.

Overall, another win for the Brotherhood!

BONUS: I made a horrible iPhone video so you can see what a bad sensor looks like. I'll add it to the thread when it finished uploading.

VIDEO HERE: http://www.youtube.com/watch?v=S-08jnIkGLQ