Low power problem with my 2.6L 190e-Problem Solved
I have posted several posts and emailed several people trying to figure the low power problem in my 1993 2.6L 190e.
I rebuilt the cylinderhead with guides, stems and springs 3K miles ago due to excessive oil consumption. The oil level is holding prefectly at the full mark after 3K miles and the oil color is still about 75% clear. Spark plugs are still looking normal. The igntion wires are 1 week old. Cap and rotor have less than 15K and look good. All six injectors were replaced about 40K miles ago apperently for no reason as it did not solve the low power problem.
The car starts fine cold and hot and idles at about 750 rpm. The idle fluctuates with +/- 20-25 rpm and I can feel that. This issue did not exist before the cylinderhead rebuild.
Just before I start posting this problem, I did some extra tests.
1. Attaching a vacum gage to the intake manifold gives a reading of 14-15 psi fluctuating according to the idle issue.
2. When raising the rpm to 2000 rpm and holding there, the vacuum needle goes up to about 17 psi then down to 15 psi and holds there.
3. Turning the A/C on brings the vacuum to 10-11 psi and the car feels slugish when driving off a start or trying to pass a car.
4. An engine compression test has shown an exact reading of 185 psi for all 6 cylinders. Test was repeated several times with the same reading no less or more. Specification I believe is 170 psi.
5. I have checked just about all the vaccum lines in the engine compartment and all still fine. I have disconnected a few lines when I rebuilt the head as I kept the intake manifold in the car during R&R of head.
Other tests I did in the past month.
EHA current and duty cycle were +1-1.2 amps and 61-69%. I adjusted to about -2 Amps and 45% duty cycle. Thanks to Steve B. A slight improvement in power (The O2 sensor works as it should)
Ignition coil passed the resistance test per the MB manual.
I adjsuted the control pressure cable several times and still shifts hard and doesn't accelerate as it should. I beleive the hard shift is due to low vacuum.
OVP was replaced with new 2 fuses unit apparently for no reason as it did not help. I just had to clear that thought.
I don't have a check engine light in this car nor an O2 sensor light at the dash. Is this normal? or PO has removed it?
I don't know what else to do? Any recommendations before I take it to the dealer or an inde shop
I must say after the cylinderhead job, when I start the car and the engine fires, it make a sound like an exhust manifold gasket leak sound then disappear immediately and I don't hear it anymore. I can't tell where it's coming from. Again, only when the engine fires hot or cold.
I haven't changed the fuel filter yet and I have one ready for this coming weekend.
1993 190E 2.6
Advanced Diesel Systems Test and Research Engineer
Last edited by Meza; 09-01-2003 at 09:51 PM.