1988 300TE - Inconsistant Running - PeachParts Mercedes-Benz Forum

ps2cho · #1 08-04-2007, 09:27 PM

Hi guys,

I have a 1988 300TE with 70,000 miles on it. It runs pretty good, but some days less good....
Some pictures of the car and valve seals, condition of camshaft etc at http://ps2cho.net/?page_id=13

Items done so far:

* Valve Seals
* Spark plugs + leads
* Distributor Cap and rotor
* OVP and Voltage Regulator
* Air Filter
* Idle Air Hoses
* Duty Cycle is set ~50%

It is difficult to describe...the idle is slightly lumpy like there is a mild misfire, and other days it is close to perfect. Some days the acceleration feels very sluggish and other days it feel very responsive/snappy.

Before we did the valve seals it was using a quart every 500 miles, now it has just done 3000 miles and hasn't used a drop. The previous owner looks like he replaced the oxygen sensor, but I'm concerned with the oil consumption that we had before, that the oxygen sensor might be contaminated.

Any ideas or any other items we should check out?

Thanks, Robert

dkveuro · #2 08-04-2007, 09:58 PM

Check under the manifold for cracked and misplaced air hoses.
Check the air flap is not touching the sides of the funnel.

Does the duty frequency change if you apply throttle?

Faulty injectors are rare but not unknown.....run some injector cleaner like Chevron's
Techron....some gasolines have it in already.

Clean up/check the fuse in the OVPR.

Has yours twin fuel pumps ?

.

ps2cho · #3 08-07-2007, 01:43 AM

Quote:

Originally Posted by dkveuro

Check under the manifold for cracked and misplaced air hoses.
Check the air flap is not touching the sides of the funnel.

Does the duty frequency change if you apply throttle?

Faulty injectors are rare but not unknown.....run some injector cleaner like Chevron's
Techron....some gasolines have it in already.

Clean up/check the fuse in the OVPR.

Has yours twin fuel pumps ?

.

Injector + seals were changed about 10,000 miles ago before we got the car. Yes it has twin fuel pumps. We replaced the OVPR and fuel filter. As far as the duty cycle is concerned, we can check that this weekend.

dkveuro · #4 08-07-2007, 10:16 AM

It is possible that one of the pumps is not running.

david s poole · #5 08-07-2007, 10:25 AM

i had a te in here the other day,running inconsistantly.the first of two pumps is inside a black cover back at the fuel tank and on this car although the pump under the cover next to the filter had been changed and the other pump[at the tank] could be felt to be running,the pump at tank was faulty and original.i proved it by running a fuel volume test at the fuel distrib [should be 1 litre in 30 secs] replaced pump and all problems cured.

John Plut · #6 08-07-2007, 01:40 PM

A couple other things that could need replacing on a M103 of your vintage are the EHA valve and the airflow sensor pot.

When the EHA was bad on my car it would hesitate badly while warming up. Once warm, it ran okay. The idle was also erratic with a slight miss. If the EHA is leaking fuel at all, it is probably bad. I just replaced one that was bad but not leaking.

A bad airflow sensor pot usually causes stalls while idling or while driving with you foot off the accelerator.

ps2cho · #7 08-07-2007, 03:49 PM

Quote:

Originally Posted by david s poole

i had a te in here the other day,running inconsistantly.the first of two pumps is inside a black cover back at the fuel tank and on this car although the pump under the cover next to the filter had been changed and the other pump[at the tank] could be felt to be running,the pump at tank was faulty and original.i proved it by running a fuel volume test at the fuel distrib [should be 1 litre in 30 secs] replaced pump and all problems cured.

I have a fuel test kit that I can use to test this so I will for sure test this as you have the same car as me.
How does your TE run these days? (if you still have it) I still have a frequent misfire on it at idle and it differs from day to day. Some days I can only just feel it a little, and others its harsh. Do you think with all the oil leakage it has had for the past ~7k miles from the leaky stem seals, the O2 sensor could be contaminated? It was replaced before we got the car, but we couldn't get round to fixing the seals until ~7k miles later...

david s poole · #8 08-07-2007, 04:12 PM

i had what you described until i changed the fuel distributor.now it starts first twist of key and idles smoothly.

ps2cho · #9 08-08-2007, 07:45 PM

Quote:

Originally Posted by david s poole

i had what you described until i changed the fuel distributor.now it starts first twist of key and idles smoothly.

Mine takes a good 2-4 seconds of holding the key before it starts. If I were to change the fuel distributor, is this the rotor? I couldn't seem to find exactly fuel distributor on the buy parts.

david s poole · #10 08-09-2007, 12:23 PM

you need to go to a web site called "specialtauto.com " and you can look up the one for your car.