I was really hoping I wouldn't have to ask this question but after 3 weekends of work and spending money I'm no further along than when I started. 2001 S-Type 4.0 94,000 miles.

New battery, coils, plugs, fuel filter, coil connectors, injector connectors, cam cover gaskets, intake manifold gaskets. Injectors all check good, fuel pressure is 35 psi at idle w/ no increase at full rev, no vacuum leaks and wait for it... No Codes!

Runs very rough at idle, misses at cruise speed (any). Accelerates as if there were no issues what so ever, (pulls like a bear). Did I mention No Codes!

BTW, the symptoms are exactly as when I started, as if I've done nothing. Also, pretty sure fuel is good, I burn the same stuff from the same station in my Harley without any issues.

 

I don't know if 35psi is enough - it's not for my car.

How do you know there are no air leaks?

Is yours the engine with the idle valve? (Most S-Types don't have one but some do.)

Have you got P1111 (pending) and is the car running CL (closed loop) at idle (and say 2500rpm)?

Have you changed the chain tensioners to the metal-bodied ones? Jumped timing may be a possibility.

 

No pending codes either. Checked vacuum lines with TB cleaner. Not sure about the idle valve. I have not changed the chain tensioners. Would the engine pull as strong with jumped time? The acceleration is a strong as ever.

 

There will ALWAYS be a pending code so if you don't have one then you need a new OBD tool.

That's a poor way to check for a leak. OBD is much better.

Tensioners WILL fail, just a matter of when. Maybe already allowed a one tooth jump but hope not.

 

Spend the $120 and get the dealer to diagnose the problem. You've already paid for that 5x over.

 

Billy,

I too have been down the same path as you. I typed a long reply, however I don't think it posted. So, I'll try it aging but shorter. See my posts on the same. I have a new Ford low cost $60 solution. Replaced the Idle Air Speed Control Valve. It is an exact fit and replacement. Plugs into the same plug.
So far, from cold start, smooth, park, R, N, D smooth. AND this is all new from the prior symptoms of an apparent miss, every 45 sec. to 1 minute in drive or park, at an idle. It is now idling smoothly at about 750 rpms. Ford had the same problems with the 3.9L v8 in Ford trucks, Lincoln LS and other vehicles it put the exact same motor in. Yes there are variations: 3.9, 4.0, 4.5. This is all changed by the mfg. spec. for the engine for the application. I'm not going to get into all of that.

John

 

Update: New OBD scanner, still no codes. I pulled the IASV connector prior to start, had no effect other than idle speed, still ran very rough. I unplugged the MAF sensor, no effect. Plugged both back in.

Now when I ran the scan I got P0066 confirmed, and P0102 pending, hence the MIL Status On in the following.

Ran these scans:
MIL STATUS On
ABSLT TPS(%) 14.9
ENG SPEED(RPM) 720
CALC LOAD(%) 34.1
MAF(LB/M) 0.78
COOLANT(°F) 205
IAT(°F) 131
IGN ADV(°) 22.0
ST FTRM1(%) -3.1
ST FTRM2(%) 0.0
LT FTRM1(%) -11.7
LT FTRM2(%) 10.2
VEH SPEED(MPH) 0
FUEL PRES(PSI) 54
FUEL SYS 1 CLSD
FUEL SYS 2 N/A
O2S11(V) 0.465
ST FTRM11(%) -6.3
O2S12(V) 0.900
O2S21(V) 0.045
ST FTRM21(%) 7.8
O2S22(V) 0.060
OBD2 STAT CA/US

and

MIL STATUS On
ABSLT TPS(%) 18.0
ENG SPEED(RPM) 2398
CALC LOAD(%) 20.4
MAF(LB/M) 2.05
COOLANT(°F) 208
IAT(°F) 142
IGN ADV(°) 20.5
ST FTRM1(%) 1.6
ST FTRM2(%) 6.3
LT FTRM1(%) -8.6
LT FTRM2(%) 16.4
VEH SPEED(MPH) 0
FUEL PRES(PSI) 55
FUEL SYS 1 CLSD
FUEL SYS 2 N/A
O2S11(V) 0.775
ST FTRM11(%) -2.3
O2S12(V) 0.885
O2S21(V) 0.790
ST FTRM21(%) 0.0
O2S22(V) 0.085
OBD2 STAT CA/US

What does this mean?

Again, runs very rough at idle, and when I reach desired speed (any) and ease out of acceleration it bucks harshly. If I vary slightly between decel and accell it purrs like a cat, as if nothing were wrong, no miss. And under hard accel, I'm getting full power, no miss.

 

Since you are not finding anything you need to check the tensions. It's too easy not to do it.

Just pull one cam cover and see what it looks like. Orange looking plastic is old and bad.
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Metal Timing Chain Upper Tensioners already installed.

BTW, I bought this car from the original owner whom had all service/repairs done at the dealer. She even had a Jag oil filter when I get `er, FWIW.

 

Those fuel trims are weird but at least you don't look to have an air leak.

Things we've seen that upset trims are blocked cat(s), bad ("lazy") O2 sensor(s).

With such different banks you're looking for things that are not common to both banks (so such as MAF is unlikely to be a cause).

Your OBD tool should always show P1000 or P1111. Worry if it doesn't as it's failing to tell you what's there so must be suspect of other bad behaviour.

 

K. I'm starting to get this Fuel Trim thingy figured out. I will record the data during my drive home this evening and should have the complete picture, Low rpm - low load, high rpm - low load, and high rpm - high load.

But just looking at the numbers above, bank 2 is dumping a lot of fuel over what bank 1 is getting. I'm leaning toward an O2 sensor issue.

Thoughts?

 

Thanks JagV8. I'll check the Cats. In the mean time I'll order the O2 sensors as they are on the list of items know to be problematic at this mileage and age.

 

Were just the secondary tensioners changed?

Several people have done this and it's not a solution and you will have additional problems. Were the chains replaced? They stretch so they do need to be changed.
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I agree with tbird6 as mentioned above. Engines with timing chain issues require replacement of the tensioners, guides and chains. The flopping around does stretch them and there is no quick fix unless you change a part prematurely, preventing it from failing (i.e. when car is very new).


Like the BMW V8 engine that has a similar issue, timing chain rattle. The only solution is new guides and chains. On that engine, oddly enough, the tensioner seems to outlive the car.

 

Billy - Did you run the scanner for real time STFT when you checked the vacuum lines with TB cleaner? If not it is worth doing to rule out air leaks. While watching she STFT's spray the cleaner everywhere - especially around the throttle body, the EGR valve, and the underside of the intake tube. You will know instantly if you have an air leak as the trims will jump even if you are not hearing the idle change

 

I intend to do a complete timing chain replacement in the near future. Right now I've got to get my arms around the current issue before I lose a Cat, if I haven't already.

The O2 sensors will be here by this weekend and I will inspect the cats (both backpressure and visual) during the install. If they're also gone I'll replace those.

As my LTFT issue is on bank 2, and dramatic, it doesn't support a leak, or would make tracing one problematic, especially if the O2s have lost their minds. And so I'm going with O2s all around. Once they're in I will feel more confident doing a thorough leak check.

Hopefully, I will be adding "Resolved" to this thread very soon.

Thanks all!

 

$#!%... 8 days for O2 sensors to deliver. Changed all 4, cats are good.

Ran really weird for a bit at start-up. I let it idle for a few minutes, then road tested it for about 2 miles. It seemed to be getting better (I assume it was re-educating itself). I took it out on the big road and most issues are still there, i.e. rough idle (although not as bad) but the minute you hit cruise it bucks harshly. I ran the scanner during the first road test. I've attached a .pdf of the data.

Still just the P0066 code, (I haven't cleared since I cycled the IASV). JagV8, I checked into my scanner, it doesn't show P1000 or P1111, it shows the exact status of the IM monitors, i.e. ok, inc and n/a.

I noticed the fuel system goes Open Loop at 50 MPH and above, regardless of load.

On a good note, I ordered a complete timing chain set w/ gaskets for $599 (tool kit $189). I'd just like to have the current issue settled before I tackle that job.

 

Good price on the timing kit.
I don't see anything except the fuel trims are too high but do erase the code and try a bit more driving.

So far I can't help but am watching your posts.
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Battery is meant to be disconnected to force relearn. Much quicker and more reliable.

 

Willey,

Your issue sounds very similar to mine. See my posts. Rough idle/stall, changed all cops, plugs, tested for codes (none), tested for vac. leaks. Even tried an independent unsuccessfully.

My solution I posted: In short.
1. Change Idle Air Control valve. I was reluctant to change it at about $250. Best thing I did. I'm also at only 30K miles, could be a problem in itself with little use. Mine did nothing at idle when unplugged! That's the problem. It is supposed to be controlling idle speed. My new one at idle if I unplug it the engine dies, so it is now doing something.
2. Buy another COP. change out each one until you find the "defective" new one. I had a bad one. If you have your old 8 COPs, take one and change it out of each one. A new one would be a better test. I took an old one and traded out my new ones and sure enough one of my new ones was bad, or possibly not seated fully. Don't know, but I'm not going to pull it out now.

I listened to the tail pipes. I could hear a louder miss on the drivers side. I started the cop change out testing there. Got it on 3 one on the drivers side.

3. I also changed the plugs to NGK platinum G. See my post.

4. Also check your cop wiring din connectors for broken lock in clips. If so buy new and or zip tie together temporarily until new ones are installed. I have 3 out of 4 broken clips on the Drivers side.

Good luck keep us posted.

John