88 300TE hot misfire help needed. - PeachParts Mercedes-Benz Forum

Merkey · #1 07-14-2006, 10:30 AM

My sons 1988 300TE has a misfire, but only when really hot.
Once the car is moving and above 2000 rpm, I cant feel it... but it maybe there. It only seems to happen at 85/90C reading on the gauge... and only afer that temp is sustained for a while.

Changed the OVP and that cured a stalling issue.
Changed the sparkplugs yesterday, leads, rotor and cap are all recent.
Duty cycle I have varied from about 50% to about 75% without change.
Plan to replace all of the intake vacum hoses soon, and Fuel filter.

Couple of questions....
This car does not have an Air Temp sensor on the intake hose... there is a hole for it but no sensor... is that right?
It also only has one fuel pump, that I can see, There is supposed to be a fuel cooler inline. I read that there was an issue with fuel vaporisation in the line near the engine, that uses the A/C line to cool, but the A/C is not working, at this time.
I also read that the that the twin pump setup was added and cured this.
Anyone have any ideas?

david s poole · #2 07-14-2006, 11:55 AM

on the wagon only the fuel pumps are not mounted together.one of the pumps is mounted further back follow the input line to the pump[ you can see under the cover where the filter is] back towards the rear bumper. david poole e. p. dallas tx.

BENZ-LGB · #3 07-14-2006, 02:10 PM

Quote:

Originally Posted by Merkey

Couple of questions....
This car does not have an Air Temp sensor on the intake hose... there is a hole for it but no sensor... is that right?

It also only has one fuel pump, that I can see, There is supposed to be a fuel cooler inline. I read that there was an issue with fuel vaporisation in the line near the engine, that uses the A/C line to cool, but the A/C is not working, at this time.
I also read that the that the twin pump setup was added and cured this.
Anyone have any ideas?

Merk...are you referrring to an air sensor that attaches to the plastic air intake "snorkel" that goes from the air filter houseing to the front of the car, by the left headlight assembly?

If yes, then no...

What I mean is that the air intake sensor was not used in the W124 until 1990 and on (even though there is a perfectly good "hole" to attach it).

Follow the link below...I once had the same question.

Misssing sensor help

I think that your car has two fuel pumps.

Like the other writer stated, just follow the lines...

Follow the link below...

http://www.performanceproducts4benz.com/Drawings.aspx?bmid=70

Or check these links...

http://mb.braingears.com/124_DISC1/Program/Engine/LHIS/47-0005.pdf

http://mb.braingears.com/124_DISC1/Program/Engine/103/Prog_Repairs/comb1.pdf

http://mb.braingears.com/124_DISC1/Program/Engine/103/Prog_Repairs/comb4.pdf

This lastlink should be particularly helpful in answering your fuel pumpquestion. Read the NOTE on page 5 of 6.

http://mb.braingears.com/124_DISC1/Program/Engine/103/07.3-0266.pdf

Have a good weekend. I am leaving early today to go kayaking with my son. I hope I don't drown...or become a snack for a hungry shark...from a distance, a myopic shark may confuse me with a tasty, chubby seal...

Merkey · #4 07-15-2006, 07:32 PM

I see from your other post you were not Sharksnaks...

I will look for the other pump...
I read your post about the air temp sensor and it was funny cos I read that too before posting!
More later!

BENZ-LGB · #5 07-15-2006, 10:45 PM

Kayaking is fun, when the waters are not too rough. We are planning an excursion to the Channel islands...but I have to improve on my "in-and-out" technique before I go out on more ambitious treks.

No sharks...but a few dolphins.

Merkey · #6 07-22-2006, 11:00 PM

We have the A/C working....
We changed the fuel filter... listened to the two pumps... sounded OK.
We also changed the 2 large vacuum hoses from the Idle Control Valve and the hoses from the inlet manifold to valve cover.

No change... its still runs rough and misfires when hot... the hotter it gets the worse it gets...

What is next?
Check fuel pressure?
Check Spark Coil?
Ideas please!

dave_rose69 · #7 07-25-2006, 09:17 PM

If your ignition coil, has a metal stamped laminated center section, try a new coil. The newer version has a solid cast centerbody. Try swapping with a known good coil if you can, otherwise for 70 bucks, its another thing that wont go south when you least expect it.

gmercoleza · #8 09-13-2006, 10:15 AM

See post #5:

300E Apparent Misfiring, Hesitation

Just one more thing to check...

Merkey · #9 11-04-2006, 12:57 PM

We found out that the engine needs valve oil seals.
See this thread:
Spark Plug Horror! Look!