Guys I have a heavy load misfire. While driving car normal its non existant but when romping on it I have gotten check engine light flash and checking error codes it shows multiple engine cylinder misfire. These are the two probable causes told for me to check

1. loosen bolts to pipe that ties cats to system to see if misfire goes away
2. my rear SAM controls my feul pump and seems to not be cummunicating or working right


any ideas or suggestions?

While at the track Saturday adaptations were cleared and on run it happened and even Jerry installed another Tune and it almost made it til the end then misfire happened.

 

What code are you getting?
If a P0300 then that will be hard to find.
I would check to make sure all you ignition wire and coil pack wiring is tight. Might even be time to replace the ignition wires if they have a lot of miles.

 

need the codes vic...

 

Question: What octane are you running Vic?? 87, 89 or 93??? That could cause a CEL code too with your mods. I haven't heard of many problems with the LET Crank pulley causing misfires or CELs so lets look elsewhere?? Plugs??
Fuel issues??? Do you consistently run the 93, if not you should??

 

I would use in the past back maybe 3 weeks ago 89 Octane but 93 since...battery died on Code reader so will buy new Battery in a bit and see if it stored the error codes the adaptations were cleared and another Tune installed and it almost made it down the track and then misfire.


Anyone who don't know in Chicagoland area our Octane grades are 87/89/93.
Also no one is blaming the pullies or Tune.

 

Why would you ever run 89??? That's just above regular here?? Big diff between 89 and 93 as well?

Let me ask you this?? Did you have the problem BEFORE the change from the ASP to the new pulley?? Sounds like a fuel issue to me. Either wrong grade or delivery issues. If it only happens on the top end, then you're not getting enough gas?? 89 can do that too if you're still running through a tank of that?? Come on Vic, 89 is like doing this to your engine and 93 is like this 100 is like this

 

i by no means have any insite on Mercedes issues. however it sounds like either a M.A.P sensor or M.A.F sensor to me. its a cheep test.... just spray some mass air flow cleaner on either sensor.....

or dont lol.... just throwing my 2cents out there

 

Good point!!! Or some 89 Octane gas? That'll do the trick. Victor, I am so very disappointed in you!!!

 

get a compression test or a leak down test to be sure there's nothing mechanically wrong inside your engine.

 

As I recall the C32 has neither a map/maf sensor to worry about

 

Nothing less then 93 Octane from here on...even if its not the cause.

 

How is that test perform?

compression/leak down?

 

I will have to write down code next time it happens...my code reader was completely dead thus no codes saved.

 

I have Magnecor wires and Denso Iridium IK20 plugs just over a year and 4 months used. Jerry on Saturday checked to see that coil pack and wires were snug.

 

hmmmm. is the car speed density? basically im wondering what type of sensor on your car determines how much fuel is delivered. normally cars have a throttle position sensor in adition to another sensor. im not too familiar with Mercedes products... sorry = (

as for peforming a compression test it involves renting a compression tester (basically a psi guage) from autozone or wherever. you take a spark plug out and put the pressure gauge adapter in the hole. unhook your distributer and or efi relay (or fuse depending on the application). crank your motor over for approx 15 seconds and read the gauge it will give you a compression number to check against factory specs. repeat this for every cylander. This test allows you to see weither or not there is low compression with in the cylander wich might indicate a blown head gasket/ broken/ dammage piston rings/ dammaged pistions or dammaged cylander walls.

a leak down test is basically the same thing however it is slightly more complex and should usually only be dont if there seems to be an issure with the compression numbers.

 

Victor,

I would check the following:

MAP sensor
Fuel Filter
Cats

If you were running 89 on a "hot" tune, your car could very well have been dumping fuel and has killed the Cat in the process.

A plugged Fuel Filter can cause similar issues, and a lazy MAP can give incorrect boost readings and consequently the incorrect fueling maps for the actual boost.

Please keep us informed.

 

C32s have MAP sensors

 

I didn't know the C32 has a map sensor...thanks!

Where is the map sensor located? Also how do you check it?
I am checking cats tomorrow by loosening and running car to see if misfire occurs
how can one check a possible clogged feul pump?

 

 

Just found out there is a MAP sensor...sorry.

 

Remove the plenum and check for Intercooler leak.
I have the same problem. Random misfire

/Göran

 

c32used,

To add to your list... you might have a bad ignition coil pack. If the code is "random cyl misfire" and not an identified cyl. misfire, this is less likely... however, I had this problem on my M111K coupe - would be fine driving, but under heavy load would pop a CEL and run very rough - changed the coil packs and it was good as new

GL diagnosing your problem... hope you get it running right soon, I'm sure it's a beast with the new mods

 

Vic,

Bring it over to Fluid Motor Union by us. They are really good guys and are the ones that found jerry's misfire (bad cats) Me and andy will have our cars there this or next week for some additional work as well.

If its a coil pack, swap the pack with another one and see if the error follows the pack.

I have a good feeling though, that it is the cats...

 

Vic - We will figure it out. Drive over to Fluid and have them take a peek at the cats for you.

 

And Code III just introduced the Spearco solution for about $1 K