DonnieD

No codes. I also have the problem at times while driving at 60-70. The car will buck, the afr will be in the 16 range. If i try to accelerate, it will go to 18 and full lean. Fells like the fuel pump is failing. I cant figure out why it only does it when driving at light loads for over 5 miles. It is like it goes into an economy mode. Others on this forum have had exactly the same problem. I have not seen a cure.

ctravis595

if the issue was the s/c not disengaging, wouldn't you notice it continually running even at idle with the hood popped though?

Hulk

What's your boost gauge telling you?

PACougar

You would, and he should pull over and check to see if it is after it happens.

bstudey01

I have this exact smae issue, being caused by the same thing of light throttle application at hwy speeds for an extended period of time. Gotta be something in the tune. Never did it before the 82mm. I have also heard others having the issue to. I am tripping a Map sensor code though P0105. I feel the buck at hwy speeds and my stft's max out at +25%. the ecu will find 14.7 but you can tell its struggling. If I pull over and restart it all goes back to normal. Going to be getting it checked out sometime next week, will see if Speedriven knows anything about raising Map Sensor voltage in the tune. I have been told by a few people this is the problem

Alps

Dont rule out the fuel pumps, mine would only show a problem after 5500 rpm, if they are on the way out then they could be intermittently be inturrupting the fuel supply.

bstudey01

Mine was done 23K miles ago, so don't think it should be an issue. This is actually happening at low RPMS, My WOT is perfect AFR's all the way up to 6500

E55Greasemonkey

Have you replaced your front O2 sensors?

bstudey01

No, but wouldn't they throw a code? I'm only getting the Map sensor code, and only throws it at hwy speeds

E55Greasemonkey

Just a theory, but the ECU may have a cruise/economy table when it detects what would be your highway driving. The throttle position sensor voltage also playing a part, and now with a larger TB there is more air coming in vs the stock TB at the same voltage or throttle position-meaning a leaner mixture, and possibly the ECU not able to or confused as to how to compensate. If it throws a code for the MAP sensor it may then go to a fixed default value based on the throttle position. Again though, this throttle position is technically not correct with the larger TB. Hard to explain. And a slow or bad O2 sensor will not always set a code.

bstudey01

Absolutely makes sense. Would also describe why so many others are having the same exact problem. I will see what Speedriven can do to the tune. He's busy right now but should be able to get me in next week

DonnieD

I am driving my car every day from now on with a star tester connected. I think it is in the tune or TB.

I used to tune Mercedes with Kleemann. What i learned is that there are batches of control units. Each has a different checksum value for the hex code written and changed in the ecu for the tune.

With this said, i wonder if some batches have a different base tune which, even when modified doesn't compensate enough.

DonnieD

Please let me know if anyone figures this out before me!

DonnieD

Quick update. I have been dataloging with star tester. So far the engine will not act up with star connected.

THIS MAKES ME WONDER! Does the controller go into a special mode when connected to star, or is it eating some of the can data that could cause the problem...

I wonder if the trans controller could tell the engine controller to lean out because it thinks it is about to shift? Just thinking out loud.

ctravis595

that is odd indeed. if i were you i would just run the car in "dyno mode" all the time. i bet you wouldn't have any issues

PACougar

You know, unless he wanted to stop in the rain.

ctravis595

i'm sure he'd be aware of that. if you weren't aware of the fact you don't have esp then he has no business tuning his car in the first place...

PACougar

It's not the esp that's the problem it's the complete loss of ABS and the braking system acts funny.

Denroll

I am also having the hiccup issue. I'll rule out the fuel pump as I had a brand new one installed a few thousand miles ago thanks to the infamous leak.

I'm about to try a 90mm and see if it continues. For me, the problem is easily repeatable as it happens in almost the same place in my morning commute, I get on the highway, after a few minutes, cruising constant 75-80, I go down a hill, and then up another one. If I keep the speed constant, about 1/3 of the way up the hill, once the load gets high enough on the engine, it does the hiccup. I have tried it in 4th and 3rd gear and it will still do it despite the increased rpm. If I am going 80, let off the gas until 75, 1/2 throttle it back up to 80, coast to 75 and keep doing that until I am at the top of the hill, I can avoid the hiccup.

I am bumping up the idle tomorrow with star and I will see what happens.

DonnieD

Yes. I have confirmed that some of our contol units do this...now i have to figure out why.

It is not the engine or equipment... It is in some our ECUs.

Denroll

My issue is fixed!!! Super happy and it was an easy fix. I don't know how it got by so many sets of eyes, but driver's side way back by the throttle body, there was a hose disconnected and that rigid hose that is part of the evap system. I found the leak using brake cleaner and my mechanic found the hose when I pointed out where the leak was. If you are having these symptoms, pull off the driver's side airbox and follow that rigid black hose on back. Removing the Y-pipe will aid in finding any hose problems back there.

TPS is now at a steady 2.0% at idle in gear when before it was hunting around at 0.7%. I cleared the codes and the P0505 and P0507 codes have not come back. I am also free from that damn gas cap warning. She idles and drives smoother and with the pulley reshimmed, s/c engagement is much better.

Last thing I have to fix is a P0141 and then I'm good to go.

DonnieD

Good to hear! I have no leaks and NO check engine light or codes.

I have adapted to the higher idle which has cured all codes. I have driven almost 10k miles since the mods and the only problem is as described.

Denroll

Just so you know, I have replaced the fuel pump (due to the infamous leak/smell) and gas cap (due to dash warning) within the last year. I have the TTM fuel rail and injectors.
Being a master tech, I'm sure you've done the brake or carb cleaner vacuum leak test. I found mine by spraying down between the TB and surge tank on the driver's side, kinda deep down in there.