420 sel 1991 - PeachParts Mercedes-Benz Forum

marinos90209 · #1 01-13-2007, 02:55 AM

Hello ,during The Warm Up The Car Idles Rough And Sometimes Misfired As Well,once The Normal Engine Temperature Is Reach Everithing Goes Back To Normal,
Any Help..

Thanks

Marino

just-n-time · #2 01-15-2007, 05:35 PM

Quote:

Originally Posted by marinos90209

Hello ,during The Warm Up The Car Idles Rough And Sometimes Misfired As Well,once The Normal Engine Temperature Is Reach Everithing Goes Back To Normal,
Any Help..

Thanks

Marino

First tell us what you have done,plugs looked at? wires checked? Have you looked at the x11 pin3 readings? get the #'s so we can atempt to help.j-n-t

1988 benze · #3 01-15-2007, 08:03 PM

please excuse me, but i also have tha same problem. I have changed spark plugs and wires,rotor pin,replaced air filter with a K&N. My o2 sens comes on only untill i start moveing and then the light gose off. I have 178000ml on my 1987 420 SEL. I used BOSH wires and plugs (not the best) from what i have been reading on this site, but i'm still learning about these cars. Any insight would be very helpful and no, i have not had the timeing chain done yet!

david s poole · #4 01-16-2007, 10:24 AM

vacuum leaks on the intake manifold,i know i sound like a broken record but all this old rubber is getting petrified.a good start is to replace all the injector seals and the plastic cups with o rings that the injectors fit into and also the long rubber tubes that join the injector cups together on each side.

London380sl · #5 01-16-2007, 11:57 AM

Quote:

Originally Posted by david s poole

vacuum leaks on the intake manifold,i know i sound like a broken record but all this old rubber is getting petrified.

Any idea how much it is to fix this problem. I took my car in for emission testing and my mechanic says I have a vacum leak there. It passed but its something that should be addressed down the road.

david s poole · #6 01-16-2007, 12:17 PM

maybe 50 bucks of parts.and lots of careful allen bolt removal[for the injectors].

BENZ-LGB · #7 01-16-2007, 12:46 PM

Quote:

Originally Posted by marinos90209

Hello ,during The Warm Up The Car Idles Rough And Sometimes Misfired As Well,once The Normal Engine Temperature Is Reach Everithing Goes Back To Normal,
Any Help..

Thanks

Marino

Have you tried a cold engine leakdown test?

If the problem occurs only while the engine is cold, you may have a problem with the lifters not properly causing the valves to seal off. Once the engine warms up, and the metal inside expands, then the valves seal better and your idle returns to smooth.

It is a simple test and it can give you lots of info about your engine's condition.

Good luck and let us know how you eventually solve the problem.

Mistress · #8 01-16-2007, 01:11 PM

Hi- I have a 1990 420 SEl with the same problem. This is what I've done so far and it seems to have helped trememdously. First i replaced the ignition, distrib cap, plugs and wires. It got better but the best thing I did was put BG fuel system cleaner in it- I ran it through two tanks of gas and boy has it helped. PM "Johnhef" and he can explain it further, he's the one who put the magic elixer in the tank.