Deib
New Member
- Joined
- October 10, 2013
- Messages
- 2
- Reaction score
- 0
- City, State
- midwest
- Year, Model & Trim Level
- 1998 explorer
Okay guys, I have a tough one.
2003 explorer 4.0 SOHC 157k miles.
Bought the truck with bad timing chains.
had the heads surfaced, new headgaskets, timing chains and all back together running.
Runs great, idles rough.
Did all the basics. cleaned maf a couple times. tested coil, pcm output, plugs, wires. Harmonic balancer and crank sensor. Injectors pulled, cleaned and tested. no vac leaks.
Checking with scan tool ect, intake air, fuel trims, tps, O2s they all look great and function properly.
Ran compression check. It looked fine. Leak down test passed.
runs great, idles rough. After a couple weeks of driving it would throw a P0300 and P0301. Clear them, same codes come back in a week or two.
So cylinder number one right?
Found a TSB referring to those codes, but that described the problem as only happening over 4800 rpm which this engine rarely if ever sees.
When it idles there is some surge or lope to it. Not a consistent or certain miss, more like a weak fire.
I finally decided to pull the valve covers. Thinking maybe I have a busted valve spring.
Pulled valve covers, cannot find anything wrong.
I hooked up the compression gauge again.
timing is still right on.
Now this is where it gets interesting. While cranking the engine I see the needle bounce, then it stops, like it skips a pulse or two then starts bouncing up again. Some times it will miss 1 pulse sometimes it will miss like 5.
Sometimes if I clear the gauge and immediately re run the test it may not have any compression. Then stop and try again and it will have good compression.
So I did cylinder number 2. Pulsed every time. I did all of the cylinders, repeatedly watching for the pulses.
It looked like 1, 3, 4, 6 would pulse, then randomly stop pulsing, then start again. completely unpredictable. doesn't happen at a certain pressure and doesn't consistently do it.
My first thought, lifters because this engine had a lot of dirty, sludge and garbage go through it before I got it.
So I pull all of the lifters. Compressed the old oil out, cleaned them with solvent. they all seem to move freely.
Put them back in. ran my compression check again. After the oil started flowing, no change. Same missed or skipped pulses. Same cylinders. I moved lifters around from cylinder one to cylinder 2 and no change. same readings.
Curiosity got to me. So I loosened the cam caps a couple of turns so the cam is not seated tight in the head.
Compression was much higher. like 160 instead of 130 psi and no skipped or missed pulses.
I ran it repeatedly. Thinking the lifters are just not pumped up to compensate for the height change.
But nope all cylinders on that head. 1,2,3 have higher compression and no missed pulses on the compression gauge. Compression came up faster and went higher.
So I played around with tightening and torquing the bearing caps differently and every time, as soon as the cam was seated back down my compression problem came back.
I started looking at the followers or rocker arms. thinking they are not allowing the lifter to bleed down. I did a quick google search for replacements and saw some had oiler holes in them. Mine do not. Upon further investigation, the explorer should not have oil holes. So I kind of ruled that out.
Now I am again at a loss. So you die hards will make fun of me, but I took the die grinder to the valve stems on number one and took a little off. Knowing the lifters will take up the slack.
My thinking was over time the valve stems have become just a little taller.
torqued the cam back down. number one now looks perfect.
So I went and took a little off number 3. I did not see the same results. Still showing missed or skipping pulses during a compression test with the cam torqued properly.
So what am I missing?
Weak valve springs could do this but wouldn't I have symptoms at higher rpms ?
Is it just bad lifters?
I thought about drilling holes in the followers to allow the lifters to bleed down easier but I shouldn't have to right?
If the cam was bad the lobes would be smaller and loosening the caps would create less compression.
Oil flows like crazy, I know the passages are clear. I even cranked the engine over with the lifters out and visually checked the oil flow in each lifter hole.
this truck has been a nightmare. Cursed. It has had a trans put int, the convertors were plugged so that is all new. The amount of time and money I have dumped in this is too much to give up.
I see the problem, I can re create the problem, but I have no idea how to fix it or what caused it.
2003 explorer 4.0 SOHC 157k miles.
Bought the truck with bad timing chains.
had the heads surfaced, new headgaskets, timing chains and all back together running.
Runs great, idles rough.
Did all the basics. cleaned maf a couple times. tested coil, pcm output, plugs, wires. Harmonic balancer and crank sensor. Injectors pulled, cleaned and tested. no vac leaks.
Checking with scan tool ect, intake air, fuel trims, tps, O2s they all look great and function properly.
Ran compression check. It looked fine. Leak down test passed.
runs great, idles rough. After a couple weeks of driving it would throw a P0300 and P0301. Clear them, same codes come back in a week or two.
So cylinder number one right?
Found a TSB referring to those codes, but that described the problem as only happening over 4800 rpm which this engine rarely if ever sees.
When it idles there is some surge or lope to it. Not a consistent or certain miss, more like a weak fire.
I finally decided to pull the valve covers. Thinking maybe I have a busted valve spring.
Pulled valve covers, cannot find anything wrong.
I hooked up the compression gauge again.
timing is still right on.
Now this is where it gets interesting. While cranking the engine I see the needle bounce, then it stops, like it skips a pulse or two then starts bouncing up again. Some times it will miss 1 pulse sometimes it will miss like 5.
Sometimes if I clear the gauge and immediately re run the test it may not have any compression. Then stop and try again and it will have good compression.
So I did cylinder number 2. Pulsed every time. I did all of the cylinders, repeatedly watching for the pulses.
It looked like 1, 3, 4, 6 would pulse, then randomly stop pulsing, then start again. completely unpredictable. doesn't happen at a certain pressure and doesn't consistently do it.
My first thought, lifters because this engine had a lot of dirty, sludge and garbage go through it before I got it.
So I pull all of the lifters. Compressed the old oil out, cleaned them with solvent. they all seem to move freely.
Put them back in. ran my compression check again. After the oil started flowing, no change. Same missed or skipped pulses. Same cylinders. I moved lifters around from cylinder one to cylinder 2 and no change. same readings.
Curiosity got to me. So I loosened the cam caps a couple of turns so the cam is not seated tight in the head.
Compression was much higher. like 160 instead of 130 psi and no skipped or missed pulses.
I ran it repeatedly. Thinking the lifters are just not pumped up to compensate for the height change.
But nope all cylinders on that head. 1,2,3 have higher compression and no missed pulses on the compression gauge. Compression came up faster and went higher.
So I played around with tightening and torquing the bearing caps differently and every time, as soon as the cam was seated back down my compression problem came back.
I started looking at the followers or rocker arms. thinking they are not allowing the lifter to bleed down. I did a quick google search for replacements and saw some had oiler holes in them. Mine do not. Upon further investigation, the explorer should not have oil holes. So I kind of ruled that out.
Now I am again at a loss. So you die hards will make fun of me, but I took the die grinder to the valve stems on number one and took a little off. Knowing the lifters will take up the slack.
My thinking was over time the valve stems have become just a little taller.
torqued the cam back down. number one now looks perfect.
So I went and took a little off number 3. I did not see the same results. Still showing missed or skipping pulses during a compression test with the cam torqued properly.
So what am I missing?
Weak valve springs could do this but wouldn't I have symptoms at higher rpms ?
Is it just bad lifters?
I thought about drilling holes in the followers to allow the lifters to bleed down easier but I shouldn't have to right?
If the cam was bad the lobes would be smaller and loosening the caps would create less compression.
Oil flows like crazy, I know the passages are clear. I even cranked the engine over with the lifters out and visually checked the oil flow in each lifter hole.
this truck has been a nightmare. Cursed. It has had a trans put int, the convertors were plugged so that is all new. The amount of time and money I have dumped in this is too much to give up.
I see the problem, I can re create the problem, but I have no idea how to fix it or what caused it.
