KE Jetronic problems
05-20-2013, 10:45 PM
#1
Newbie
Thread Starter
Join Date: May 2013
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
1989 300e
KE Jetronic problems
hello, I have an 89 300e that when cold, has full acceleration potential in park. After about 2 minutes of warm up, it wont go past 4500 rpm. Its almost impossible to drive because it has no power and acceleration is very slow. I dont even know where to start. PLEASE ADVISE!
05-21-2013, 07:19 AM
#2
MBWorld Fanatic!
Join Date: May 2005
Location: REHOBOTH BEACH DE
Posts: 2,494
Likes: 0
Received 17 Likes
on
17 Posts
88-300CE TWIN TURBO, 99-C43, 05-G55K, 71-280SL, 94-E320 CAB, 08 CLK63 BLACK SERIES
hello, I have an 89 300e that when cold, has full acceleration potential in park. After about 2 minutes of warm up, it wont go past 4500 rpm. Its almost impossible to drive because it has no power and acceleration is very slow. I dont even know where to start. PLEASE ADVISE!
In park or neutral the RPM is limited by design.
Suggest you start with the basics by removing your spark plugs and "reading" them. This will give a quick indication / diagnosis of individual cylinder fuel and ignition condition.
You may also want to do a compression and leak down test along with a smoke test to check for vacuum leaks.
Waste of time and money if you don't start with the basics.
Remember you have two separate control systems, one for fuel (CIS-E) and the other for ignition (EZL).
05-21-2013, 03:04 PM
#3
MBWorld Fanatic!
Sounds like the Idle Air Control Valve may be stuck wide open. When cold, the extra air causes a super high idle and surging forward. When warm, after the enrichment solenoid duty cycle goes down, the extra air leans the mixture out so the engine won't development proper power. I just went through this on a friend's W201 with Jetronic which exhibited that exact behavior you describe. The IAC valve can be inspected visually - only a small 1mm slit opening should be visible with no power to the valve. Alternatively, you can block off the vacuum line between the IAC and the intake manifold. If the IAC is the source of the extra problem, the engine will not idle, but should run at speed okay.
The IAC uses a galvanometric movement (sometimes referred to a voice coil movement) which is very susceptible to malfunction from foreign debris or wear. My friend's IAC had gotten some grit in it that caused it to stick open.
Good luck,
- FD
The IAC uses a galvanometric movement (sometimes referred to a voice coil movement) which is very susceptible to malfunction from foreign debris or wear. My friend's IAC had gotten some grit in it that caused it to stick open.
Good luck,
- FD
05-25-2013, 09:00 AM
#4
Newbie
Thread Starter
Join Date: May 2013
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
1989 300e
Thanks for the tips guys. I was a little frustrated when I first posted this thread, so I thought I would include a bit of history......
The vehicle was running just great, then all of a sudden I noticed a severe lack of power under load. In WOT it just bogs and falls on its face. I have replaced all the usual tune up components: plugs, cap, rotor, wires, air filter and fuel filter, checked fuel pressure it is fine. The only code that came up was the o2 sensor, so I replaced it, cleared the code, check engine light went off and stays off but still there is no change. I unplugged each of the fuel system electronic components one by one to force a check engine light, with no luck after reconnecting them and clearing the codes. The odd thing is that it will rev past 5000 rpms when it is cold.... but as soon as it warms up it seems to go into limp mode but there is no check engine light. If I pour fuel straight into the air flow sensor at WOT it will accelerate like normal. PLEASE ADVISE!!
The vehicle was running just great, then all of a sudden I noticed a severe lack of power under load. In WOT it just bogs and falls on its face. I have replaced all the usual tune up components: plugs, cap, rotor, wires, air filter and fuel filter, checked fuel pressure it is fine. The only code that came up was the o2 sensor, so I replaced it, cleared the code, check engine light went off and stays off but still there is no change. I unplugged each of the fuel system electronic components one by one to force a check engine light, with no luck after reconnecting them and clearing the codes. The odd thing is that it will rev past 5000 rpms when it is cold.... but as soon as it warms up it seems to go into limp mode but there is no check engine light. If I pour fuel straight into the air flow sensor at WOT it will accelerate like normal. PLEASE ADVISE!!
05-25-2013, 11:21 AM
#5
MBWorld Fanatic!
Steve -
Did you check the IAC as I suggested? There are many causes for low power at speed, but there is only one cause for a super high (5K RPM) idle (cold or hot), and that is excess metered air entering the intake manifold. On this system, there are only two sources of metered air - through the throttle plate or through the IAC loop. Check the throttle plate to make sure it closes and is not stuck open. Then check the IAC system. My preference is to block off the valve on the manifold side temporarily because it is easy and quick. Do not just disconnect the IAC valve (vacuum or electrical) to test this - the complexities of the valve make this test meaningless. Sort the high idle problem first and then see what happens at speed.
- FD
Did you check the IAC as I suggested? There are many causes for low power at speed, but there is only one cause for a super high (5K RPM) idle (cold or hot), and that is excess metered air entering the intake manifold. On this system, there are only two sources of metered air - through the throttle plate or through the IAC loop. Check the throttle plate to make sure it closes and is not stuck open. Then check the IAC system. My preference is to block off the valve on the manifold side temporarily because it is easy and quick. Do not just disconnect the IAC valve (vacuum or electrical) to test this - the complexities of the valve make this test meaningless. Sort the high idle problem first and then see what happens at speed.
- FD
05-25-2013, 12:43 PM
#6
Newbie
Thread Starter
Join Date: May 2013
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
1989 300e
working on the IAC valve
Thanks FD, I'm testing the valve as im typing this. Just for the record, there is no problem with the idle speed, that is fine. Ill post my results as soon as i have them. thanks. 
Trending Topics
05-26-2013, 02:38 PM
#8
MBWorld Fanatic!
Steve -
I think I may have misread your first post. When you said "full acceleration potential in park", I assumed you meant high idle/surging. After you said directly that there was no issue with the idle, I can see where you meant something like the engine has the ability to reach full speed in park.
If adding fuel directly results in normal power, I would suspect the fuel metering assembly. Your system has a separate enrichment valve the supplies extra fuel when cold. It sounds like when that valve shuts down, you have fuel starvation. Is the air sensing vane sticking at any point?
- FD
I think I may have misread your first post. When you said "full acceleration potential in park", I assumed you meant high idle/surging. After you said directly that there was no issue with the idle, I can see where you meant something like the engine has the ability to reach full speed in park.
If adding fuel directly results in normal power, I would suspect the fuel metering assembly. Your system has a separate enrichment valve the supplies extra fuel when cold. It sounds like when that valve shuts down, you have fuel starvation. Is the air sensing vane sticking at any point?
- FD
