Low and rough idle

[Biotex]

Got a super deal on a 99 runner with 225k miles. It has the 4 cylinder (2.7L) engine and is 2wd. I think I got it so cheap because it is hard to start and when it finally does start, the idle is low and the engine shakes. I figured I could fix whatever the issue is, so here goes.

First off I replaced the wires and plugs. No change.
Because I knew the car sat for a time of over a year, I dropped the tank to inspect. Absolutely perfect inside, but I changed the fuel filter anyway because it was an unknown. No change.

I cleaned the MAF, no change.
I cleaned the throttle body and IAC, slightly better, but still harde to start and still idle is too low.

At this point I threw a misfire #3 code. I tested the ohm of the first three injectors and they are all good. The stethoscope test was also pointing to good injectors.

I changed out the Temperature sensor on the back of the head, no change. (I was taking it out to test it, and dropped it, so had to replace it.)

So today I did a compression test.
#1 = 125
#2 = 110
#3 = 70
#4 = 150

Since my misfire was on #3, I would say this is my problem.
I pulled the valve cover and am waiting for the engine to cool down so I can check the valve clearances.

Would like to hear your thoughts as to what I'm getting into. Probably going to have to pull the head huh? I don't have a leak down tester, but am wondering if it sounds like the valves. Could it be just an adjustment?

 

[Raintrees]

long shot but the cylinder compression seems low all 2 if not 3 of those cylinders. does it smoke when it runs?

 

[Biotex]

long shot but the cylinder compression seems low all 2 if not 3 of those cylinders. does it smoke when it runs?

Yes, I agree 3 of the four are low. There is no smoke at all. Car runs clean so I'm guessing it is valves.

What is my next step?

 

[Raintrees]

leak down? idk i dont think there going to be a quick fix to this.
low compression could be what bad rings, head gasket going, leaking valves.

 

[Biotex]

Here's the followup:
So I turned over the engine with all four plugs removed. I watched the cam lobe on the two intake & exhaust valves for cylinder #3. Got the lobes so they are pointing up away from the lifters, thus all valves closed. I measured the clearances and my thinnest gauge of .001 would not slide through on the exhaust valves, but the intakes were fine.
Not good!

I pressurized the cylinder and could easily hear the air escaping. Verified it was coming out the exhaust valves. I'm pretty confident I have burned valves, so am going to have to pull the head. Looks to be a sucky job, but needs done.

Now I know why I got the car so cheap...

 

[Raintrees]

Here's the followup:
So I turned over the engine with all four plugs removed. I watched the cam lobe on the two intake & exhaust valves for cylinder #3. Got the lobes so they are pointing up away from the lifters, thus all valves closed. I measured the clearances and my thinnest gauge of .001 would not slide through on the exhaust valves, but the intakes were fine.
Not good!

I pressurized the cylinder and could easily hear the air escaping. Verified it was coming out the exhaust valves. I'm pretty confident I have burned valves, so am going to have to pull the head. Looks to be a sucky job, but needs done.

Now I know why I got the car so cheap...

Well yea, it all pointed to the head being removed. XD Glade you foind your problem.

 

[Biotex]

Update:
I removed the head and found one of the exhaust valves in cylinder #3 was setting lower into the seat than any of the others. Here are a couple of photos of the work.

This shows cylinder number three, and you can see the exhaust valve (lower left) is sitting lower than it should.
Not sure what caused that, but it doesn't appear burnt to my untrained eye. What do you think caused this?

 

[Biotex]

Another update:

I removed the exhaust valves and the one is burnt bad enough you can see it with the eye. A couple of others are burnt also, but barely. The seats are ok. I am going to replace all the exhaust valves with new and do a valve job myself. I looked and only tool I'm missing is the correct size arbor, so will have to purchase that.
Should save me around $300.

Also, the head is not warped. Amazing how well these engines are built!

 

[Biotex]

Final Followup:
I replaced all the exhaust valves with new and touched up the seats. Reassembled the engine using DNJ gasket set. The engine fired up way faster than I was expecting and had a perfect idle. Only squawk was a leaking injector o-ring which I addressed in another recent thread and fixed.

I have test driven the car for a couple of days and she runs perfectly and starts right up. I can conclusively say that my hard start and low idle issue was indeed due to the loss of compression due to burnt exhaust valves. Hope this helps someone else with a high mileage engine who has the same symptoms.

Don't throw money at it. Run the very simple compression test first thing.