I would check the throttle position switch on the throttle body. It's pretty simple on the M103 cars. But it basically indicates to the ECU whether you are at idle or WOT. If it's stuck in the idle position, that could be causing your issues.

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1991 300E - 212K and rising fast...

Thanks.
I'll take a look at it tomorrow.

I installed a new Bosch # 00086 ignition coil today and it certainly seems to have eliminated the sputtering and backfiring upon hard acceleration. I tested the car for probably 20 miles today after the coil was installed. I drove it HARD and was unable to get it to sputter or backfire. It really responds to the demand for power now.

I will post an update hereon in a few days. I want to be absolutely sure the problem has been solved with the new coil before stating the same.

After the coil replacement what is the new position of the economy gauge needle ? Pegged to the left or a little off ?
regards

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mark

I'll have to take a look later and report back. I didn't think to check the economy gauge after the coil install. Are the two related? After having read so many threads I was thinking that I had two unrelated issues.

Thank you.

Well, I went back and re-read my original post which started this thread. I started this thread because I had noticed the economy gauge in my 1990 300SE had moved from normally being pegged to the left during idle in park to being about 1/8" to 3/16" from the left under the same circumstances.

I had read a number of posts regarding the economy gauge and vacuum loss, so when the gauge changed from its normal position of pegged left during idle in park I figured something was not right. I wanted to get ideas of what I should look for in order to resolve the vacuum problem. So, I posted the bit about the sputtering upon hard acceleration hoping that would lead to a quicker resolution of the problem. At the time I thought the sputtering may have been related to the vacuum loss.

It turns out the sputtering was absolutely due to a bad ignition coil. After the coil change I have been unable to reproduce the sputtering and backfiring upon hard acceleration. There is no longer any sputtering or backfiring from my engine.

I was able to isolate the problem and definitely state that it was the ignition coil which caused the sputtering because I tested the vehicle after nearly each new component was installed. I say nearly because I had installed new plug wires, a distributor rotor, distributor cap and inner and outer distributor cap covers and tested the car after all of those items were installed, not after each of them. That would have been some work. The sputtering and backfiring upon hard acceleration remained after those items were installed.

So, the last ignition related item that I installed was the ignition coil. As I stated previously, that took care of the sputtering and backfiring problem.

I installed a new fuel filter two days later because it's on my list of items that I want to change. It made no discernable change in performance. I really hadn't expected it to.

Now I need to track down that vacuum leak which precipitated this thread some 6 months ago.