Drain some fuel from the disconnected fuel return line into a cup and check for water contamination.

STAR TekInfo

 

Thanx, I'll get on that in the AM.

 

Disconnected return hose, ran fuel into clean glass jar. Got about 4 small water bubbles in a pint of fuel. Then disconnected fuel pump from filter, and ran a pint into clean glass jar. No water, just clean fuel. So probably not fuel contamination.
Runs fine at idle, even when up to operating temp. But put it under load at operating temp, and gets the "hiccups". When cold runs fine. No codes, Not sure what to look for as far as live data, or FF data.

 

You could look at long term fuel trims.

With the warm engine, if you increase the rpms to 2500- 3000 and experience hiccups , it is probably a fuel delivery issue. Things like kinked fuel lines, fuel regulator, old and tired fuel pump, etc.

Do you have a fuel pressure gauge?

 

As to LTFTs what am I looking for? LTFT bank 1- 12.5, bank 2- 10.9 Yes I have an FP gauge, but it's at work, not here. I've inspected fuel plumbing, it all appears to be in good shape. Fuel pump is relatively new, as is the filter, (new yesterday) . Pump fills a pint jar in about 5 seconds or less.
No "hiccups" untill driving, then only when up to operating temp, not before. Sitting still in park no hiccups. Sitting still at idle, in gear, no hiccups. Sitting still, in gear, accelerating as much as the brakes will hold, no hiccups.
ECT 79*C
I'm at a loss here.

 

I would check the air intake components. This includes air filter (being dirty or restrictive), MAF sensor not reporting correct airflow rate, throttle plate issues, etc.

The car runs fine when cold, because the ECU is in "open loop", ignoring the MAF sensor and oxygen sensor readings. When the engine gets hot (closed loop), the O2 sensors report reading that are translated to "too rich" fuel mixtures, which causes the ECU to trim the fuel supply to the cylinders (by reducing the duty cycles for the fuel injectors). This may cause hiccups as the fuel to run the engine under load is reduced.

There are of course other possible causes that may be related to a specific bank, but your negative high fuel trims are reported from both banks, so the problem is something common to both banks.

Also check the fuel regulator operation (make sure that the vacuum line is connected and not leaking), and the regulator diaphragm itself is not leaking.

 

What should the LTFT be? What is the range? Also, the MAF shows (live data) to be working properly, but I also don't know what the normal parameters for that are. Nor do I know where to look to find out. Thanx for your help thus far. I'll probably drive it to work on Monday and hook it to diagnostic equipment that I don't have here at home.

 

Typically the MAF sensor reading for airflow at idle and at operating temperature should be close to the engine displacement in liters. So if you have a 4.2 liter engine, one would expect about 4 to 5 grams/ second of airflow. However, this does not mean the MAF sensor is OK, as it needs to rapidly respond increased airflows under heavy load and rpms accurately.

You can try disconnecting the MAF sensor temporarily with key out. In this case, the ECU will use a look-up table to calculate the air to fuel ratio without the information from the O2 sensors and the MAF sensor. It uses the throttle plate angle, and possibly the MAP sensor. This way the car will run in open loop mode.

The Long Term Fuel trims ideally should be zero, but with the engine and other component ages are considered, within +/- 5 percent is reasonable. You do not have fuel trim codes yet, because the fuel trims are still below the threshold levels (I think it is 25 percent).

 

Normal air flow at idle is about 1.3 g/s per liter of displacement.
At WOT (wide open throttle) about 75% of advertised HP.

 

This is just a ballpark figure. The actual specs are below for the M119 in 210.72

STAR TekInfo

The 4,000 rpm figure is between 150 to 177 grams/second.

 

Yes, of course those are just approximate values. Engine mechanical condition, air filters, catalytic converter condition, fuel quality will affect those values.
What is important is very smooth transition from idle to WOT with no dips in MAF readings.

 

Drove it to work Mon. On the way in a new symptom popped up. Came to a stop light, and engine went way bad rough, trying to die, and got message- "ACC SKID CONTROL" , just for a moment, then engine smoothed out, message went away, and I drove on to work. Lunch time I hooked it up and ran it. MAF appears to be doing as it should, with flow of .7lbs at idle, and increase smoothly on acceleration, Fuel pressure at 50psi on initial key on, and at idle 48psi, acceleration and under load increase to about 65 psi, What really stands out to me is Alternator charging at only12.75V, should be between 13.8-14.2v. And no change with RPM (which I didn't really expect anyway). I checked connections at battery, and all the grounds that I could redilly get to, and all seemed to be in good order. Could a low voltage condition be causing this trouble? Driving home, I left the voltmeter hooked up, and with headlights on (it was dark) it held steady at 12.7, and would take "hiccup fits" pretty regular.

 

, and all the grounds that I could redilly get to, and all seemed to be in good order

What grounds have you checked?

Have you checked negative battery to chassis connection behind the rectangular lid on the rear seat wall?

 

Yes, That was the second one I checked. First being the cable to battery connection. I checked all that I could get to without jacking it up, or major disassembly.

 

I would have the battery and charging system checked.

12.75V is low, when the car is running, but should not cause the modules to drop out. The ASR/ESP module needs minimum of 11V before it lights up on the instrument panel.

 

Thanx for the help so far, I'll be digging deeper this weekend. I'm kinda stumped at the moment. Due to the issues, and no CEL, or codes. Last time I had this kind of trouble (several years ago) it was the K40, but it would throw codes, and stuff.

 

What I did today: check all electrical connections, primarily grounds and connections at engine sensors, and actuators. For the life of me, I can't understand why there would be a ground connection stud under the carpet, under the seats. What a PITA. cleaned all ground connections, and made sure they are secure. Made sure battery connections are clean and secure. Charged battery to 100%, checked voltage 12.35v. Fired it up, and voltage changed to 12.75. Put a "load" on the system by turning on everything that I could, headlights on high, fog lights, HVAC blower on high, rear defrost, radio etc. voltage jumped to 12.8, then settled in at 12.7 and stayed there. (checked at the battery) Then I thought about live data. hooked up my cheap OBD tool, and no codes, or FF, Live data as follows:
Fuel sys 1 - CL-Fault
Fuel sys 2 - CL-fault
ECT - 158F
STFT B1 - -1.6% - -3.1%
LTFT B1 - 0
STFT B2 - -2.3% - 3.9% (did drop to 1.6% for a bit)
LTFT B2 - 0
MAP - 10" hg
RPM - 664
Spark ADV - -10 (I assume degrees BTDC, I would think it should be closer to 16-20)
IAT - 84.2F
MAF - 0.7 lb/min (~23.3 @ about 4000 rpm)
AIR - off
O2 B1 S1 - .785v 2.3%
O2 B1 S2 - .755v 99.2%
O2 B2 S1 - .085v 4.7%
O2 B2 S2 - .750v 99.2%
For some reason while I was copying the data, a P0410 code popped up as pending, no hard set, or FF data. Shortly after the AIR pump kicked in. Running it in the shop, and no exhaust hose, I didn't want to run it too long, and shut it down with ECT at about 168F. I guess I'm gonna have to spring for a scan tool that will hook to the 38 pin DLC.

 

Measure the voltage at the charge point under the hood and the chassis ground with the car running.

The alternator is connected to X12/3 terminal block, then to X4 block which is where it is connected to the battery. You may have some corrosion at the X4 terminal block which is located at the driver's side footwell under the carpet (along with the ground terminal).

 

Checked both and they are clean as a pin. Here's pic of the X4. Also, what should the voltage on X22 pin5 be KOEO?

 

Make sure that the connections are tight (not only clean). You get the battery voltage with KOEO. What is more important is the voltage with KOER. You are just testing is there is a voltage drop from the alternator to X12, to X4, to battery terminal.

 

No voltage drop between Alt, X4, X12, Bat. same reading. Connections tight, and clean.
Back to X22 Pin 5 KOEO is 0.9v, didn't check KOER. I would think KOER should be near 0, lest it trigger the warning display.
And fogot to load the pic for the previous post.

 

No voltage drop between Alt, X4, X12, Bat. same reading. Connections tight, and clean.
Back to X22 Pin 5 KOEO is 0.9v, didn't check KOER. I would think KOER should be near 0, lest it trigger the warning display.
And fogot to load the pic for the previous post. View attachment 2809508

0V when engine not running, 12V when engine running or whatever the charging voltage is.

 

OK, that checks out alright.
Now, I finally got my Autel in the mail, and connected the 38 pin connector. Here's the read out in PDF:

 

All Stored. You can safely clear them out as a whole, and drive around to see if there is any fault coming back or a new fault code.

 

Backed out, and when I stopped to put in Drive, "ACC SKID CONTROL" shows up, and engine dies. Starts right up, and I head out. No CEL, Notification went away. Ran like crap. Drove around for a bit, until I got tired of being bucked around with the "hiccups". Made it back, and went to find my tranny dipstick. Checked fluid level, and all is well. While doing that CEL came on. Plugged in, and only code was the EVAP gross leak code, (P0455 I think) which comes up once in a long while, usually when fuel is just under 1/4 tank. No FF data. No other codes set, or pending

 

Any other warning lights on the dash?

Start the engine with your foot on the brake, and check if the BAS light goes out then come back when you release the brake pedal, it is possibly related to your stop light switch.

 

No other lights. Had BAS problem on my ML so I'm familiar with the symptoms. I'd thought about that on this one, but no BAS light, and cruise control still works.