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Rough idle, poor uphill power
04-28-2014, 10:04 AM
Post: #1
Rough idle, poor uphill power
2000 Kia Sportage, 2.0, AT, 170 kmiles, Gulf Coast.
Bad crack in radiator, ran hot, very hot, more than once that afternoon, 50 miles up the interstate. Replaced radiator, started hard, but within minutes water in the exhaust. Removed head and just the top timing belt cover, so after reassembly with the new head gasket I couldn't see the bottom of the belt or crankshaft gear timing mark so I brought #1 to TDC and slid the belt over the cam gears, marks aligned. Started right up, not missing. I run around town all the time, everything ok. BUT stopped in traffic, sitting, foot on brake, rough idle, vibrating. I slip it into neutral, it runs slightly smoother. Dry compression #1,2,3,4; 90,70,100,170. Oil pressure 70 & 80 psi cold, hot at 2500 rpms or so about 20 psi, idling in traffic, in gear, foot on brake, about 10 psi or maybe even less. I'm not a mechanic. I'm somewhat familiar with this engine and it's sensors because I've owned it for 12 years. This engine is not running smooth enough. HOW SHOULD I PROCEED? Very appreciative. Tinkernition on the Gulf Coast.
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04-28-2014, 05:24 PM
Post: #2
RE: Rough idle, poor uphill power
Well, for starters that compression tells me something isn't right. Possibly a few valves got nicked? I'd have to research it to see if that engine has issues with a timing belt being off a few teeth, which would be the first thing to confirm. I'd also want to compare the oil pressure readings with a known good shop gauge. If that pans out then it's possible some of the rings are stuck from the overheating, which would explain bad comp on 3 cyls but not the 4th.

Sounds like you are handy enough to either overhaul the engine or do a replacement if it comes down to it.

Keep us posted as you move forward. I'll be away on vacation for a few days but I will try to check in from time to time.
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04-29-2014, 10:48 AM (This post was last modified: 04-29-2014 10:51 AM by Rupe.)
Post: #3
RE: Rough idle, poor uphill power
Sorry for the delay.

My scan of resources says the 1994-2002 with 2 liter DOHC was not an interference style engine so good chance you don't have any bent valves. Here's my take on the situation.... if all the cyls had low compression then my first shot would be to double check the cam timing BUT you have one cyl that reads about normal. This leads me to believe that either the thing needed a valve job before the over heating or the extreme heat cause the rings to stick. I have seen this before and while a ring job is a pain (requires a tear down) you might be amazed at how quickly you can move along, especially if the oil pan can be taken off in the car to gain access to the rod bearings. I have done a few of these "quicky overhauls" on Nissans and with the right tools it could be a finished job in two days, if you send the head out to a machine shop, and if the pistons are in fairly good shape. (no metal transfer)

BTW, you can confirm the ring problem with a wet / dry compression test. Using a normal shop oil can use 3-4 squirts of light lubricant (engine oil or ATF) in each cyl and do the compression test again. If it goes up say 20 - 30 psi (not much change) then you have a valve problem. If the low cyls come up to almost normal (150 - 175) and the high one only goes up around 20 psi then you have a ring problem on those low cyls. You'll have to decide if you want to tackle an overhaul or a used engine replacement.

Again, keep us posted.
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05-07-2014, 01:02 PM
Post: #4
RE: Rough idle, poor uphill power
Keeping you posted as I move forward:
My new timing light reads 8 degrees BTDC. Under hood label states 6 degrees (+ or - 6). I will do wet compression soon. I am having a problem seeing the low end of my recently installed very small, 0-100 psi, oil pressure gauge so I've ordered, it's on the way, a nice, cheap, 2 1/2" face, 0-30 psi. I believe I've been running 25 psi @ 2500 rpms and 10 or 12 psi @ idle, foot on brake, in gear, about 750 rpms?. I'm hoping at cold oil starts and for the first few minutes of running that the 60 or 70 psi, pegging the gauge to 30, doesn't damage it? It will be awhile before I tackle the wet compression test.
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05-07-2014, 08:10 PM (This post was last modified: 05-07-2014 09:06 PM by Rupe.)
Post: #5
RE: Rough idle, poor uphill power
If you really have around 70 psi cold you will probably damage the the 30 psi gauge.

If you want to see the gauge better buy a $5 flex hose for a grease gun. They are 1/8" pipe thread on both ends. You can get a few more fittings to adapt other things and keep it in your tool collection for the future.

Edited to add: I have several gauges for mine... 30, 100, and 200 PSI plus fittings to adapt from 1/8" - 1/4" and a few male / female elbows. Recently I made one to handle 14 mm spark plug thread so I can check exhaust pack pressure via the O2 sensor hole. The 200 PSI gauge was when I worked on truck air brakes. I also bought the 18" hose and using two of them you can place the gauge almost anywhere easy to see. Duct tape it to the windshield if needed for a test drive!
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