I'm getting to the end of my rope with my 1995 Kia Sportage. I love the car and I would say it works trouble free for 2-3 months at a time, however since the first week I purchased it, I have experienced a major stalling issue with some minor hiccups in between.
The minor issue - sometimes as I'm driving, there is a brief but noticeable drop in power as the car is running steadily or accelerating. It feels as though I just took my foot off the accelerator for 1/2 a second. Sometimes I wonder if I did. Or it feels like I hit a small dip in the road. I believe this is related to the major issue but I don't know.
The major issue - every few months as I am driving along or accelerating, the car bucks pretty violently as if the engine just shut off and then restarted or dropped in rpm and then picked up again. This may happen a few times in a few seconds. Usually, the car stalls out completely or within a few seconds of this happening. If I start it up right away, it will sputter and barely have enough power to pull to the side of the road. Sometimes the check engine light comes on, sometimes not. In every case when this has happened, I let the car sit for 10 minutes before starting it back up and babying it home. Then for three months or so it will run like a clock. I'm neither rough nor gentle on the sportage, and though initially I thought this issue might have something to do with a loose connection or failing part that was somehow aggravated by bumps in the road, I don't think this is the case - at least with bumps or rough rough being the cause.
I'm a very amateur mechanic without much ability to effectively test parts. I have a multimeter and some specs from the manual, but nothing ever seems to line up like it should anyway. So yes, I've thrown lots of parts at it based on the trouble codes I've gotten and repair forums.
Here's what I've done:
New spark plugs
New spark plug wires
Fuel Filter - replaced
Fuel Pump - Initially I thought it might be the fuel pump, so I replaced it.
I've tried to clean up all the grounds in the vehicle. I believe I did all of them.
Replaced my battery at the recommendation of a shop test.
The trouble codes I got after one stall indicated the MAF (cleaned old one first), Upstream O2, IAC valve and Vehicle Speed Sensor. I replaced each of these. The IAC I got used.
I noticed the EGR valve was done, so I replaced that.
I replaced the PCV valve.
I installed new hoses on anything that looked questionable. The hose clamp holding the air intake to the throttle bottle was very loose. I removed this, cleaned the throttle body and reattached the air intake and all the hoses.
I checked for vacuum leaks and did not find any. Used your cigar method : ) But it kinda made me dizzy too.
My air filter is in good shape.
The last thing I replaced is the Throttle position sensor. I thought I had it figured out, but four months later, same issue.
I had the valves adjusted recently and the car passed it's emissions test immediately afterward.
After a major stall today, I tried wiggling the connector to the TPS, but it made no noticeable difference while the car was idling. I also wiggled the attached injector wires a bit. Nothing. Tapped on the relay box a bit just in case. Nothing.
Any thoughts in the next steps? Thank you!