Fuel Pump Surging? Goes away in limp mode
 

Hi all, I'm looking for some help. I tried searching, but maybe I didn't use the correct terms because i didn't get any applicable previous posts.

My 1994 E320 has an occasional issue with a power surging. When this happens, it feels like a bad fuel pump or clogged filter or cat. When it happens, the car will idle perfectly and run smoothly up to 1500rpm, then it bucks like a bronco! If you turn the car off and restart it runs just fine. Codes ( I don't remember which ones it threw and I don't have the car with me just now) point to the TA (CC/ISC module) and that the car is in limp home mode. The wiring harness is pristine, but I haven't checked the wires to the TA yet. If I clear the codes the problem will return, go into limp mode and run okay until I clear the codes again. The car does not have ASR. I am planning to pull the TA this weekend and rewire if necessary, but any ideas as to other avenues to look at would be appreciated./

Thanks
Greg

WAG (wild assed guess) - Crank position sensor.....

I changed the fuel filter, Cleaned the TA and tightened up a loose clamp at the MAF. I then cleared the codes. After ~100mi, mostly with the CEL off (it came just as my son turned onto our road).

These are the codes that came back

Pin 3

6 - Idle Speed Control Faulty

26 - Upshift Delay Faulty ( this has been a problem and for the most part I ignore it, I did change the switchover valve with no effect and can't seem to find a vacuum leak)

Pin 14

2 - Cruise control / Idle speed control module

3 - Cruise control / Idle speed control actuator

11 - Fuel safety shut-off to LH-SFI control module

I have no codes from any of the other pins.

I pulled the crossover tube on the intake and the air resonance valve from the intake so I could get to the TA wires. I cut a slit through the cover about 3" long and and peeled it back to take a look at the insulation and it is perfect, no cracks or flakes. The same is true for the engine harness. This is leading me to believe that the TA is bad. If you have any other suggestions as to other items to look at me and my wallet would be very grateful.

Thanks
Greg

ABS lamp come on when condition presents??????????/

Arthur

No, only the CEL. I forgot to mention that the surge seems to have gone away when I changed the fuel filter. Now it is just the annoying CEL and loss of cruise control.

Greg

OK

Clear DTC and then turn key Off for 10 sec, On for 90 sec and start car.
That resets the EA ..see if codes come back [ codes 2/3]

Also, make sure cable has 1/4" slack and cable is not sticking. [ 11]

26 is you have a bad actuator element on tranny cable for shift delay.
BB the line and forget about it. [ or warm up the car before you take off if it's cold out. Most guys just hold it in lower range for first mile.

Arthur

I reset the computer per your instructions. I will see what codes pop up over the next couple of days.

Thanks
Greg

These are the codes that came back after resetting the computer per Arthur's instructions:

Pin 3

Code 6 - Idle speed control faulty

Pin 8

Code 8 - Idle speed control at upper or lower control stop or CC or EA indicates Limp Home mode

Pin 14

Code 2 - Cruise control / Idle speed control module

From these codes, I'm thinking that I either have a bad TA or a bad CC/ISC module or both. Where is the CC/ISC module located on this car? Is it in the TA?

Please advise

No ideas?

Code 8 list Limp mode for EA/CC , with possible cause as vac intake leak.
Code 2 list Limp and remedy to be Re-adapt EA..[ which you have done]
It then states if codes return, EA actuator is suspect
The problem w/actuator is there are subcodes for the offending part of actuator, but the Flash codes do not get to those... A Benz HHT scanner does.
Those address CTP and possible Resistor Pot codes.
Check everywhere for vac leak, as that jives with the limit code, and take another look at the short harness for EA actuator.

I would also put a BB in that line to the SOV that you replaced [ or unplug the SOV] for the tranny delat shift..you have a bad vac element down at the shift cable and that will go back to intake whan DS is called for [ but I do not think that is the problem]

Alright

Foolish question time. Does the BB go upstream or downstream of the SOV? I will check for vac leaks again and do a more thorough check of the EA by actually pulling it off and checking nearer to the connector.

Thanks for the help.
Greg

Makes no difference..

The idea is to block the vac line so that when the delay shift is activated by the ECU, the leaking element at the trany does not allow air to be sucked into the engine intake while the shift SOV is OPEN..that's all.
That could be your vac leak..by plugging that line anywhere before the trans cable element , you have eliminated that possibility.
I am fairly confident from what you have posted that your vac line from the SOV down to the tranny will not hold a vac..[you can test that with a hand pump..] If it doesn't , then you know the VERY common problem of a leaking/split shift actuator elment is the problem for code 26.
You went and changed the shift SOV, when you should have tested the green line going from the SOV to the trans actuator for vac holding.

But that may/may not not be what is causing your limit stop @ idle .
So, the simple test is to get rid of that possible w/BB

Thanks

I'm heading out to do it just now.

I put the bb in the line, cleared the codes and reset the computer. My wife said we needed milk so I took it about 5 miles to the store and back. no codes just yet, but I realized that my '93 300E (M104) EA goes through some sort of POST test (you can hear it cycle) if you leave put the car in diagnostic mode (turn the key to run without starting) but the '94 E320 doesn't do this. I'm beginning to think that the EA is the culprit. I will definitely pull it and verify the wiring in more detail.

I bought a low mile (!03K) EA from a salvage yard and rewired it. I'm keeping my fingers crossed.