envious2016

Ok may I be the one of many to post this issue on here again. lol
First and foremost i bid everyone on this forum a good evening. Now I hope my fellow Mercedes owners can take time to put down the brandy and fine cigar and give me some feedback please.

I own a 1997 E320 with 230,000 miles on it. After the car has warmed up about 15 minutes from driving, at red lights and stops it will begin to chug terribly close to stalling out (stalled once, started back up though) On acceleration it will then on occassion lug down like it does not want to go then with slowly accelerate and run fine. But always chugs at red lights.

Brought to a mercedes /trusted friend. of course he had car to 3 days found nothing, no codes, drove it idled it NOTHING!!! On my way home from his shop it started to act up. he said bring it back but thought I would look into it a bit myself to save money. This morning i changed the oil, replaced air filter, and pulled MAF sensor and cleaned it thoroughly. NO IMPROVEMENT . Although it may still need to be changed just wanted to see if cleaning would help a little bit. We also thought maybe bad gas? I filled with supreme chevron with techron and added Fuel injector cleaner to the tank too. We usually never let the car go to low as soon as light turns on we fill up.

Tomorrow I will change spark plugs cause it needs to be done (5 years about 75,00 miles) not that im praying on that to fix issue. Any help will be greatly appreciated but dont wanna be chasing ghosts on this. wanna start out with cheaper things first like possibly Fuel filter? then fuel pump? EGR valve? Im gonna check vacuum lines too. If anyone can help I would greatly appreciate it. And no its not the motor mounts or transmission. Am I at least on the right track on this? THANK YOU!!!

Plutoe

Well bro, you know that the ECU via the throttle valve actuator motor controls the engine idle speed and depending on the coolant temp sensor the valve is set and adjusts with load bla bla------so you can putz around with all sorts of cheap initial non fixes--such as plugs wires, ash trays,transmission connectors, wipers, light bulbs, EGR,AGE, CC,fan blades(see polak johnnies experience at Ben's Wurld),trunk lid---however if you want to start to solve the problem---test you coolant temp sensor and then purchase a rebuilt throttle valve actuator-----then change mechanics as he may not understand the MB system!!

envious2016

Ok well hot do I go about testing this coolant temp sensor? Or since it is only about $20 should I just replace? I appreciate your reply sir. But some more details on how to do this would be great. thank you

Plutoe

You sound like you have loads of free time on your hands--I'll post the test later today!!

envious2016

Yes thank you I would greatly appreciate that . i will be working on it today starting to do spark plugs. Not the handiest guy in the world (brother in law will be helping me) so if you can get it posted today at some point that would be groovy. This way Im sure he can figure out how to follow your directions. thanks you!!!

Plutoe

The coolant temp sensor is tested with an ohm meter--at 20C you should get 3100 ohms + -5%------at 80C you should get 315 ohms + - 5%---

Regarding the actuator,regrettably you need factory software to quickly test----I honestly don't know how you would do it otherwise!!

kajtek1

Coolant temp sensor is #6 on climatronic sensor readouts.
Aren't those I6 engines requiring new plugs every 30K ?

envious2016

Wow Plutoe thanks for telling me in the end I will have to take to my mercedes benz dealership for proper diagnosis as I dont have the software.

fabbrisd1

KJTK is spot on - the correct OE spark plug is Bosch copper F8DC4 or it's Bosch Ytrium replacement 7927 - with about 30K miles before replacement - good news in the E320 not quite as sensitive as the E420 - the plugs are cheap/cheap - correct Bosch copper about $1.50 each.

If coming to a braked stop - the engine RPM drops below normal, feels like the engine is "choking" and will die, then catches itself before stall, RPM notches back up, then drops, "hunt's around" - this direct symptom is normally acknosledged to be the sign of a failing MAF... and has nothing to do with coolant sensor except if in the extreme edge of the solar system.

"Cleaning" may recover a dirty/fouled MAF - but cleaning will not do anything for a failing MAF.

Recommending MAF replacement would be the indicated advise - and replacement with a genuine Bosch ONLY from a reputable internet source - such as AutohausAz.com.

Note on 1997 E320 - the original MAF design was updated as indicated by a different connector and connecting cable.

The other issue on MAF replacement are the # of TDF owners (TDF = Too Damn Frugal) who search the internet for a MAF "deal" - and end up buying a non-Bosch MAF either intentionally or by being duped. MAF's are considered electrical non-returnable items - or oft counterfeit MAF sellers will commit "free replacement" to someone who pays genuine Bosch MAF prices to buy one of their $18-$20 China/India counterfeit MAF's.

It's your choice to cleanup the fuel system - starts with 1/2 bottle of a $9 Stabil Marine (blue bottle) - replacement of the fuel tank screen ($25 part) - and a $30 Bosch fuel filter/can (about $14-$18 more than a China can).

Hope this helps - at 230K miles you want to prudent on expense - at the same time you want advice/diagnostic that will get you running smooth again..

Keep the beat !

envious2016

Thank you fabbrisd for the advice, I greatly appreciate it. Ok so here is the update. I went and bought a new Bosch MAF sensor and unfortunately it still chugging like an MF at idle. Thankfully I have great rapport with my local auto parts store and they took it back with receipt. So now know the car has not had any major codes come up, spark plugs replaced and i dont think its a misfire cause as i drive the car its SMOOOTH as silk great acceleration and shifting, accept in that one instance when it seems it wants to lug down a bit, I ease off gas step on it again and away i go. So the only other thing I think it could be is either the Fuel pump of Fuel filter. (ordered and will arrive on monday) Have owned the car 9 years and never replaced either. If this does not do it I will have to bring back to my mercedes mechanic as anything further may be too complicated for me to do, and dont wanna chase ghosts any further. Any feedback on this will be great !! FABBRISD1 THANK YOU THANK YOU!!!

ml3204me

Before you go changing the Fuel Pump, Fuel Filter etc. You should check the PSI in the fuel rail. Guessing on these things are just going to cost you money and replacing good parts will not fix the problem.

When you changed the MAF sensor did you clear the CEL? This resets the ECU to factory settings and allows it to relearn air intake/fuel ratios etc. Not resetting it will cause your vehicle to continue to run at the other settings.

If it's chugging like a MF at idle and not when you are driving most likely the fuel pump is good and the problem has to do with your air intake manifold could be a broken plastic piece on one of the vacuum actuators or hoses.


Here's how you check the fuel PSI:
Here's how to replace the Air Intake Manifold: