beauphus

I am going to describe my issues to the best of my ability. I find it hard to believe I am the only person who has had these issues, especially considering the amount of mods done to the 55k platform.

When I start my car it has a rougher idle then most because of the cams which is fine. When I put the car into gear all is generally well with the car too. After I have given the car some gas and created boost once the car drops back down to idle range or low throttle I get an EXTREMELY rough idle (sometimes to the point of engine shutoff) and once I come to a stop te car surges and jumps back and forth as though I am at a traffic light enticing someone to race me. It is completely uncontrollable and if I give it gas it sputters and sometimes pulls out of this behavior at higher rpms and other times it stays rough and unresponsive. If I cycle the key off and then on it generally goes away and operates fine.

I have replaced the MAP sensor to no avail and am scratching my head as to what could be casing this. some have said my cams are too aggressive - but if that were the case other with the VRP/PTE cams would have similar symptoms I assume. Others have mentioned that I could have a faulty throttle body or idle air control valve. There has been tons of speculation. Funny thing is when the car is in this weird possessed mode it is amazingly powerful and fast as hell.

Has anyone experienced symptoms like I have described? Thanks for the help!!

bassn_07

I have very similar conditions with my car right now due to a faulty 02. I used my datalogger to check the current conditions of my 02 sensor. From what I understand the voltage of a healthy reading 02 sensor should cycle between .02-.8 several times a second. My sensor 1 bank 1 does this exact thing but my sensor 1 bank 2 is stuck at .045, at least the last time I looked at it. This causes my car to run extremely rich with a very bad idle. All your symptoms seem similar except I have a rough idle from start up.

Hopes this helps.

Tech-Tune

Similar issues here too.
I've gotten used to the rough idle but would like to remedy the issue.

Alan, have you resloved this with a new o2 sensor?

bassn_07

Not yet but the car will going under the knife very shortly. To be honest I feel a little reluctant due to the fact that Aaron is having idling issues. This has always been my biggest fear but Pat assured me that with a bump in idle I will be just fine. He's a well respected member here on MBW and I trust his word.

Alex if you have time give me a ring.

Worth the wait

If it was an issue with the A/F ratio wouldn't the car throw codes (or at least show issues when connected to Star) for the abnormal fuel trims? I am not saying this is gospel, just going by what some trusted techs I have spoken with have said.

What about a cam position sensor? Aren't those magnetized...maybe some residual metal from the rebuild founds its way on there.
I dunno, just throwing stuff out there trying to help...lol.
Good luck man, I know what a ***** it can be to spend all this time and a truck load of money only to be faced with a car that runs less than perfect.

bassn_07

I forgot to mention that I did get a P0155 CEl, something about the heater circuit.

I haven't received any codes in regards to fuel trims. I did get misfiring codes with multiple cylinders. I have been getting that P0155 off and on for a while now and I think the 0@'s finally took a dump. My tech also believes the same thing with the description I provided.

sneakyneon

Is this been the case since you put it together or a new issue? What is the afr when its acting up? what is the vacume as well? My car acts this way when I have a vacume leak. I have made a boost leak checker that has come in handy. If you want some idea of how to build one or a pic of mine let me know.

AMGPilot

Do a compression and leakdown test. I don't think your going to like the results

O-55

look for a hose behind the driver side valve cover (pic below). it can come loose and cause rough idle, engine shutoff, and delayed throttle response.

ahmad0658

Check all hoses on TB or TB housing for any air leak, if you TB is not stock, I had same problem when I installed the 82mm TB. If you have spacer, I would recommend you check them too.

chiromikey

i'm a firm believe that this is tb/vacuum related and am quite positive it's not a motor problem. our ecu's just don't seem to have perfect control over idle with these larger tb's.

beauphus

i have checked for leaks with no luck. i have gotten a few different codes (air pressure implausible, idle air control valve, etc). i have eliminated my spacers. even judging by this thread could be be one of many culprits. i guess its just gonna mean tackling each one - one at a time. i wish i understood a fraction of the way it works.

beauphus

to be honest the rebuild and initial tuning of this car was done almost 3 months ago. at that time i drove the car approx 100 miles with no issues to speak of. i then removed my SC to be sent out for rebuild, porting, and polishing and upgraded to the 190 pulley. this was completed maybe 2 weeks ago. the problem has been occurring since then. the only difference between then and now is the p&p SC and bigger pulley.

i will dbl check but when i hooked up a mechanical boost gauge to the plenum and monitored vacuum while these symptoms were present i didnt see any erratic behvior on the gauge and under full load my car is only making 14 to 14.5 lbs boost.

attached is my cel codes from a cpl weeks ago. though MAP sensor replacement would fix the issue. wrong.

aleksandar1099

In regards to the rough idle. I worked on my friends e55 with similar mods to yours plus top mount inter coolers and the car also had an idling issue. It would stall out and turn off at low rpms in drive and reverse. The car did not throw any codes like yours did, but it was very annoying!! It was solved with a new tune. The previous tune on the car was terrible and caused it to run extremely rough after hard runs, it no longer has the issue....

Something to look at if you exhausted all other possible solutions. What kind of tune are you running now if you don't mind me asking?

Thanks
Aleks

beauphus

just got tuned this weekend. didnt solve anything. tuned by Jeremy himself

PTE

Alan Is on to something , I think if he goes to obd-II port with a scanner and looks at the short term & long Term fuel trim numbers He will see them out of wack They show (-) minus numbers & (+) positive numbers of correction IE;
-8 & +8 appear to be normal. But a -8 & +14 something out of wack. The ecu is struggling to compensate. If you have a slow O2 sensor or one that is Stuck ( So to speak) it will show up , you may it with no voltage movement. If you notice ,the Factory position of the o2 sensor , it is usually mounted vertical. and close to the manifold. this helps keeps it clean & moisture free, so it can proper heat up quicker & perform it duties. Innovate Mtrsports LM-1 suggest that there wide band sensor be mounted close to the same fashion , as so water or moisture will not damage the o2 sensor. Can we say water & age could damage the sensor. Lots of o2 sensors go faulty , If you do not have cats & the tuner did the
2nd o2 sensor delete so you don't get a CEL.I do not believe that causes any fuel trim issues, But What does the ecu see for idle & low speed fuel trims. Look alittle farther. Understand these cams are not that aggressive in the BIG world. Do you know ,what the manifold vaccum is at idle in gear?on this modded engine . Do we know what the vaccum is on a stock , non modded motor. We could still have a very small air leak. or a o2 sensor issue. Look at Splitsec.com they have a cam tuner . Nice instruction & a Q & A section on low speed & idle fuel trims. But it will not repair a slow or non responsive sensor, A tuner can 'nt also correct a funny reading sensor. And generally assumes the motor is is a healthy state. Jeremy did a great job on my car and I'm please with his workmanship.
Read up ! Thanks for your eyes & ears. _PTEngineering

hooleyboy

P0155 code is directly related to the extensions of the 02 sensors. To run the setup you have, your o2 wires were extended. When I say extended, I mean the o2 sensor/wire was cut and butt connected back together. Then wrapped in electrical tape?

I've seen this 4 times now. Replacing the o2 sensors might not fix the problem. Its my understanding the butt connecting the o2 sensor wire, causes 1 of 2 things to happen. 1) a bigtime resistance issue. 2) a short circuit some place between the ECU and extended 02 sensor.

After some folks stopping by the shop, who are running similar o2 extension setups as you. The first move would be to replace both o2 sensors. Then extend the wiring harness side rather then physically cutting/splicing an o2 sensor.

As far as I know, the correct way to extend the o2's is not 100% fixing the issue. That lead me to believe a short has occurred with the old setup. Where that short is is unknown to me at this point. So with that said the heater code will come back even after replacing the old o2's.

Just know that your not the only one who is having this issue. I am just about 100% sure it has to do with your placement of your o2's in your exhaust system.

if you are going to replace the front o2's. I would try extending the harness side rather than cutting the o2's. If that doesnt work, I would look at the PCM connectors or all the way up to the ECU. Hope this helps you out a bit.

hooleyboy

So you recently put cams in? I would look at the connections to the coil packs. The clips that hold the power supply to the coils are very flimsy. They break off all the time. If one is loose, it could cause a very rough idle, major shaking when you are driving, stalling, On the list that others have mentioned, I would add this one to it.

Marcus Frost

This thread really puts in perspective just how hard a rough idle can be to diagnose. There are so many things that can trigger a rough idle it can drive you mad. Idle control in ECUs is incredibly complex and doing a "dyno tune" is not necessarily going to give you a good idle. Being on the dyno at WOT is not your problem, it's after you go WOT, it's on cold starts, etc., etc., where most tuners are not paying attention to. With your setup, you've got a lot of things going on that need to be looked at.

It may be something physical (leak, etc), something electrical, or something in software. I'm guessing software is probably a good place to start... you cannot just have a good dyno tune and think your car is going to idle well. The maps used for WOT are not the same that control idle.

-m

Jakpro1

Okay on the redlight jumping, surging and stalls, here is what was wrong with my car. There is a hose that connects to the TB I believe...NO not the one that everyone talks about (the air box hose on the right) but one deep in there that connects to the TB. Upon inspection, mine looked connected and fine and we were really stumped. It was when my tech started tugging on hoses that we noticed that it was just butted up against the TB. Once he connected the hose snug, car was fine.

You probably know more about the hoses then I do after reading about you ripping off the blower etc. Not sure where to tell you to look and tug around the TB, but was hoping you would know the hoses I was talking about.

Also another thing that helped my car a LOT at red lights is cranking up that idle speed. Once it was at about 700rpms, it calmed down a lot.

Whats your car idling at right now?

When my idle drops too low, car starts rocking and rolling at redlights. Must be a trip to watch a 4 door luxury car rocking back and forth...literally rocking under engine torque. I know it's not a Comp Cams radical cam but it's a blast.

Sometimes I gotta pop it in neutral. I am a weirdo though...I friggin love it.

Thanks Pat for the great cams!

Hope you get er worked out brotha!

PTE

Marcus : I was hoping you would chime in. Your insight is always welcomed in my book.

Hooley you may be on to something. The extensions I build for my rear 02 sensors was with the exact some wire make up & I used the MB couplers & Pins & sockets .

Jim : you would not believe how many hose connects , that bleed off manifold vacuum. I used special Tie wraps & Oetiker with 360* compression then check for leaks with carb cleaner , in a spray can. Thanks for your vote of confidence. We will keep on helping Beauphus. His Car make a ton of Power. Cheers _PTEngineerng

MB_Forever

From what I've seen in the past, the idle air control valve has caused similar symptoms on stock-cams cars, so it would be a good place to check as well. When you put the car in drive and hold the brakes, is it still rough or is it stable?

hooleyboy

I have only seen this with people running the FF/VRP headers and exhaust system. First off it has nothing to do with the headers or exhaust, but the way the o2 sensors are extended. If this system did not require an o2 sensor extension (placement of the o2 bungs). There would be no such issue with a o2 heater code/CEL.

When random people stroll in to the shop to see if a o2 heater code can be fixed. It gets you thinking. All of them had the FF/VRP headers. The first time I seen this, we where scratching our heads. The second time, with the same exact exhaust/header setup. Got the noodle in my head working. Then a 3rd time. and now a 4th, All having the same exact exhaust & header set up.

It wouldn't even surprise me if this style of extending the o2 directly messes up the ECU. If this is causing a short... That short might be happening inside the ECU itself (not good). Again the short (If it is) could be happening any place in between the o2 and the ECU.

This might explain why just replacing the o2's doesnt fix the issue. Extending the o2's on the harness side, wont fix it.

It kind of opens the door to "who know??"
Maybe these cars dont like to have their o2 extended by cutting the o2 wire or by extending them harness side. Lets hope thats the case, and its not a permanent ECU issue.

IMO, avoid all all cost extended o2 sensors on these cars, This o2 wire might be a calibrated length. So messing with that could open up a huge can or worms.

I would also advise getting a can or card or brake parts cleaner. While the car is running spray that stuff directly on suspect areas. like throttle body housing, vacuum line/connections. just to name a few. You will know when you find the leak. I the car will 1 of 2 things... spike in RPM's or stall out. if that happens, you have found your problem... Thats if its and vacuum leak.

beauphus

i appreciate everyone chiming in. its very humbling not knowing how to resolve this kind of stuff and everyones collaborated input is helpful. i am going to try and isolate the problem from what you guys have mentioned. here is the list of possible problems. i plan on checking each one to the best of my ability:

1. short term fuel trim tabs - ECU idle map
2. vacuum leak - TB hose connection
3. o2 sensor wire (doubtful - mine are not extended or spliced at all)
4. bad o2 sensor
5. throttle body malfunction
6. idle air control valve

any other suggestions? thanks again for the help!!

hooleyboy

You dont have an o2 heater issue at all.

You should definitely check your short term fuel trims. they should generally be a 0% at idle. You may know this, but I'll say it any way... If you are +/- and number of %. That means your ECU is adding (+) or subtracting (-) at idle.

My Vacuum leak on my old C55, was caused by a slightly warped throttle body housing from rapid cooling after welding in some bypass valves. At Idle the short term fuel trims were at 16% (kind of a big leak). I knew I was getting unmetered air in from some place. We found the issue, fixed it, problem solved...

What I cant remember is if I reset the ECU after fixing. However my short term fuel trims went back to the correct spot. So.... Checking those first could be a good place to start. However I would check the coil pack power wires to each coil too. Just to make sure they are not loose.