96 OBD II engine misfire codes and rough idle

[Ecomike]

No its not dual fuel.

By the way the 2 year old battery went south, and was going bad before, during and after the radiator hose took a leak. We replaced the battery about 2 to 4 days after the radiator leak when I realized it was bad and not something else. The check engine light came on when the radiator hose took a leak. The DTC code after the radiator leak was misfire Cyl 1 & 2, but considering the coolant was, had leaked, I was not surprized to see misfire codes. He said the engine died and the car coasted almost as soon as the check engine light came on the temperature gauge showed it overheating.
From his story it sounds lkie it shut down with in seconmds of the coolant leak. It was a big, fast leak. Can head gasket go that fast?

you don't have remove the intake to change the plugs, but you do to replace the injectors.........is this car a dual fuel setup? it will have a green leaf badge on the side or trunk......had a ranger 3.0 that had problems with missfire's. it turned out that the sensor that tells the pcm what kind of fuel it was running on wasn't working, it was telling the pcm it was on reg fuel and the customer was running on E-85

 

[Ecomike]

I did some more work on it today. The wires to #1 and #2 were toast at the plug ends. Don't know if I damaged the spark plug insulators myself, but I think the insulator on #1 was busted before I got to it, and #2 has hairline cracks in it too. I changed all the plugs and wires, had high hopes, but no joy, still rough idle, and still getting Cyl #1 misfire code.

old Plugs looked OK except the busted insulators on #1 and #2. #1 looked a little rich, with some black carbon, but other than that it looked about the same as the others on the tips (combustion side). No signs of oil or antifreeze leaks on any of the plugs. The gaps were all worn out to .055 already. I gapped the new ons at .044, and I used Motorcraft platinum, OEM plugs, which is what it had before.

So I am guessing it is a leaking, or burned out (never opens), or clogged fuel injector on Cyl #1. Such fun ahead. Anyone changed the rear side injectors before? What do I need to do to pull the IM on this beast? Do I need to drain antifreeze first? Or will the IM come off with out loosing antifreeze? Maybe its easier than it looks. Yah right!!!!

OK any recommendations on fuel injectors? Im think Five-O motorsports where I buy my Jeep injectors.

Almost forgot, I did a vacuum test. Vacuum says the valves and pistons are all like brand new. In other words the engine vacuum readings at low, medium and high rpm are right on spec as well as rapid accel and decel readings, so no burned valves or blown head gasket! But there is 1" of continuous vacuum present at all engine operating ranges including idle on/at the EGR valve, exactly 1" all the time!!! Correct me if I am wrong, but that is not the way it should be, and could be part of the rough idle problem, right?

Removing and capping the vacuum line to the EGR valve did not seem to help the rough idle, but that does not rule a stuck leaking EGR valve itself. Not sure how good the OBD-II EGR diagnostics are??

 

[Ecomike]

I have discovered some problems with the EGR DFFE circuit (clogged orifice and possibly partly stuck open EGR pintle/seat) so its next for some repairs, but I am also going to swap the rear #4 fuel injector from the rear bank ( to the front bank #4 injector position). If the problem misfire moves to #4 it will be easy to replace #4. The rear bank injectors require removal of the intake manifold to reach them. The front bank injectors are much easier to reach.

 

[Ecomike]

First off I have pulled and tested and replaced parts as needed, new plugs and wires, serviced and cleaned the fuel injectors, swapped FI banks or sides, I have fuel and spark to all 6 cylinders now. Got Cyl #1 misfire 20 times in a row after clearing code each time, 20 times. No other codes, no other cyl misfires now, just #1, and it is much more frequent now. EGR system is all good. Idle is much better, but gets rough when the computer shuts of FI #1 after posting a misfire code on cyl #1.

Ok I need some final opinions please!

Firing sequence is 1-4-2-5-3-6 then back to 1

Compression listed in firing order is:

81 PSI (Cyl 1)
125/120 PSI (Cyl 4)
145/155 PSI (Cyl 2)
150 PSI (Cyl 5)
155 PSI (Cyl 3)
115 PSI (Cyl 6)

Compression difference in firing order is:

+41 psi ( 1 to 4)
+20 psi (4 to 2)
+/-5 psi (2 to 5)
+5 psi (5 to 3)
-40 psi (3 to 6)
-34 psi (6 to 1)

What is curious here is that only Cyl #1 is showing up as misfire now, and cyl 1 to cyl 4 has the largest + pressure difference value, +41 psi difference in cylinder compression. The Haynes says 100 PSI minimum and says no more than 15 psi difference between the highest and lowest cylinders. The highest is Cyl #3 and lowest is Cyl #1, 155 - 81 = 74 psi difference.

Wet and dry compression for 4, 5 & 6 were the same. Compression tests were on a cold engine, after it sat overnight.

The very first OBD-II codes thrown were Cyl #'s 1,2 and 6 before I replaced the plugs and wires. Cyl 1 & 2 had bad boots on the end of the plug wires, cyl 1 & 6 have low compression, but are not dead. I think I had a single Cyl #5 misfire before replacing the wires and plugs, and after replacing the plug wires the only misfire I got, about 20 in row was, is now Cyl #1.

So here is my question(s). Since I have no antifreeze leaks yet, and thus no antifreeze signs of a head gasket leak, the oil and antifreeze are normal, and no gas bubbles in the coolant overflow bottle, etc, and I still have 81 PSI in cyl #1, what if I pull the valve covers and re-torque the head bolts, then run some heavy duty block sealer through the coolant system to reseal any "trace" head gasket leaks, then just in case I have some cylinder/piston ring wear in the low compression cylinders I could add some Restore to the oil to bring the cylinder compression back up some. Any one think this has a chance in hell of working, if so how long might it last? I realize if it's a tiny valve leak non of these would work, but what are the chances of the valve resealing itself within a few hours of run time on the freeway with the new plugs and wires and repeated resetting of the OBD-II code? In other words how bad is 81 PSI? I could run it and retest it after an hour or two run time?

At this pint, I have no way of knowing for sure if the low compression on #1, 81 PSI is due to head warpage, head gasket begining to leak, cylinder or piston ring wear, or even more insideous something like piston rings lining up temporarily, a temporary or permanent valve sealing problem.

Since it is an overhead valve engine , should I pull the valve covers next and inspect the rockers and valve springs?

The last note of data is that the cleanest new spark plug was in Cyl #1, still looked brand new, but since the computer keeps turning off the injector and spark for #1, not sure that means anything. The highest compression cylinders showed just a trace of carbon just below the threads on the steel area.

 

[Slo-Sho]

You say the wet/dry compression tests on 4,5,6 are the same. What about 1,2, and 3? You also do not state how you did the wet comp test.

 

[Ecomike]

You say the wet/dry compression tests on 4,5,6 are the same. What about 1,2, and 3? You also do not state how you did the wet comp test.

I saw no reason to test 2 and 3, they both were at 150 psi, and they are harder to get at to add oil. I just skipped the wet test on 1 when it did not help 4 or 6. Guess I should try a wet test on 1!

I added 1/2 ml of straight 40 oil with a 6 inch long lab style plastic eyedropper into the spark plug port, way down inside for the wet test, is that what you were asking for?

 

[Ecomike]

Thought I would kinda update this thread. I started a new thread called something like snake oil ..... where I described a test I am still running on this engine. I added Restore to the engine oil, and 4 dry brown pellets of coolant sealer, plus 1 bottle of Bars Leaks head gasket sealer, medium duty, compatible with antifreeze, no need to drain the system to us it, it is black in color with fiber pellets in the bottom.

After a short time, like 4 hours of engine run time the 3 low compression cylinders came back up some. #1 was up from 81 to about 110-115, and 4 & 6 were back up by about an additional 15-20 psi, #6 to 130 psi, #4 to 135 psi.

After about 700 miles now #4 is now at factory new spec of 150 psi, and #1 is down again at about 85 psi, but this was a cold engine test. I will be running a hot engine test hopefully on Tuesday or Wed.

The engine runs fine except in gear, idling for more than a minute at a stop light, where it keeps throwing the #1 misfire. We just clear the code and it stays cleared until the next extended stop at a stop light. Oil and antifreeze coolant are still normal, no leaks.

 

[CharlesS]

While a blown head gasket could cause low cylinder pressure; there are other things to cause this problem.
A leaking head gasket can be checked by looking for bubbles in the coolant or with a CO sniffer at the radiator cap after the vehicle has run for awhile.
Since adding RESTORE to the engine oil and driving the vehicle for a while raised the cylinder pressure across the line; tends to make me think that either the piston rings are sticking or the cylinder walls are worn or scored.

 

[Ecomike]

That is one of the reasons I tried the additives first. The head gasket sealer additives also might have shored up a weakend head gasket before it completely failed on certain cylinders.

I just retested the cylinders 1 and 6 with the engine still warm from a 30 mile trip. I tested it 30 minutes after parking it and got:

#1 = 110 psi
#6 = 140 psi (was 115 psi at the begining, before puting in the additives)

I saw no reason to retest #4 since it was back to factory spec even cold during the prior test.

I suspect cylinder 1 is a poor valve seal that is sensitive to engine temperature. Hoping to run more frequent tests to see if the hot/cold pressures change on #1. I am thinking cylinder 4 and 6 might have been a weakening head gasket, but it could have been some cylinder wear. No way to know for sure which it was for now. Theoretically if #1 and # 6 are within 20 psi of each other the misfire should stop even at idle in gear.

Is there anything in the valve seat, valve seal, valve spring, etc., that could be sealing better under load, and not sealing as well at idle on number 1?

OH, and just a reminder that the earlier engine vacuum diagnostics I ran indicated no valve, or head gasket leaks, in fact the vacuum tests indicated a like new engine condition.

 

[Ecomike]

This beast has been on the road daily, heavy use, since my last post. No changes since the last post (that I know of). He just shifts to neutral at all stops to keeping it from throwing the misfire code. It will still throw a misfire code at extended idles in drive, only.

We plan on pulling the head, possibly swapping the rear head by June, before the next local gestapo E inspection, since we can not be sure it won't throw a code during an inspection.

 

[Ecomike]

Got an update on this. After several long, back to back highway runs totaling about 800 miles, 4 weeks ago, the engine stopping throwing the code even at idle, while in gear for the last 3 to 4 weeks, this was something new!

It finally started throwing the old code again a few days ago, but he has not changed the oil since December, or about 5000 miles ago , so that may be an issue. He says it's about 1 quart low now, not bad considering its near 200,000 on the ODO. Planning to top it off with 10W30, drive it about 30 minutes, then drain it and put in 15W40 summer oil. Will try to check compression again then, time and other roundtoits permitting.

It has had no other issues or problems since december, 2007.

Still tentatively planning to swap the head in June at this point.

 

[Ecomike]

Well the last 4 weeks of December 2008, the rough idle came back, worse than before, and the CEL misfire Cyl 1 came back and stayed. So we pulled the heads over the Christmas holidays. Machine shop found hairline cracks in both heads. So we replaced the heads. Found some pitted spots here and there in the cylinder walls of the #3 cylinder near the top, suspect there may have been more lower down in other cylinders which might explain why the Restore helped out. Head gasket was OK. The rockers and tappets looked brand new, so someone had done a prior engine job before he bought the beast.

The worst head crack was at the valve seat area. The oil seal and valve guide on Cyl #1 finally gave out and fouled the #1 spark plug and cylinder. In summary, he got 20,000 miles out of it before we finally changed the heads.

It now has a misfire code for #5, which seems to be a plugged Fuel injector from the recent tear down.

 

[Ecomike]

Final update to this story. After replacing the heads last week, and getting the most unpleasant and persistent # 5 cyl missfire code, trying a different fuel injector, checking for spark, checking compression, ....then finally in one last desperate cheap attempt I replaced the spark plug. Bingo! No more more worries. I was just about to pull the heads, or at least dig into the rockers and lifters again.

The old Spark plug looked great, it was a Motorcraft single platinum tip, so were the rest as well as the new one. Must be something internally out of whack with the bad plug.

Long story short, it's a 200,000 miles and back on the road.