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-   -   98 ML 320 low engine power ?? (

osmosis 02-02-2004 10:42 PM

98 ML 320 low engine power ??
Thanks all for the great info here

I have a 98 320 with 91K miles.

It's had all the warantee work that everyone else has described +some. From the balancer to the fuel pump to the window switches, dash that fell apart, dash swtches that just fell out. Turn signal / high beam switch fell out of column. Computer "forgot" all the keys. Sunroof stuck etc.

And the brake job after brake job, after brake job.

The brakes amaze me just because I have never had a vehicle that got less than 90k miles on brakes ( including 3 corvettes ) so I'm not a "brake diver" but the ML sure eats em.

OK now the problem. I have had some CEL issues. I tested and got the "fuel bank 2 mis -. I replaced the plugs, and cleaned the MAF sensor inside and out with high quality electronics cleaner and cleaned the EGR valve tube and throttle plate with a spray fuel injector intake cleaner. All is well in the CEL world. ( at this minute ) ( 1000 miles, and 3 fillups later)

However the vehicle seems to lack power from about 30 MPH to 60+. It just seems to take forever to accelerate. Under no load the engine will only rev to 4200 then it appears that a rev limiter kicks in and the engine will not rev any higher. I slowly bring up the rpm till it gets to 4200 and then it "misses" and stays at 4200. (valve float ??) or a rev limiter?? I'm OK with that if the engine does have a rev limiter.

Now under load from a dead stop , smash the gas and the engine will go to about 5500 in drive and then shift up through the gears. Shifting seems normal, however from about 55, "kick down" to accelerate doesn't seem to work correctly. It just seems to have a poor power curve. Our 2001 Isuzu trooper with the v6 has MUCH better acceleration from both a stop and for "passing"

None of the CEL codes have indicated the O2 sensors.

Does anyone have any 0-60 times that I can compare to, as this would tell me immediatly if i'm in the ballpark proformance wise, of driving a slug in need of repair.

I get 22.9 MPG on the highway as averaged by the onboard computer, so it appears to be running fine, and doesn't seem to miss at an idle.

I am installing the front Monroe Reflex shocks ($41.00 ea) to improve the ride a little when hitting road expansion joints. And installing drilled rotors ( I drive through tons of standing water ) and the new Wagner Thermo Quiet pads. I figure with how I go through stock pads and rotors, how could these possibly perform worse ?? and for less than $200.00 per axle, I can burn through a lot of these brakes before I touch the dealer parts cost.

Anyone use the valvoline Dot 4+ Synthetic break fluid. ??

Sorry , big post. Again thanks for all the good info.

98 ML 320
2001 Isuzu Trooper
2003 Vette zo6

itb76 02-07-2004 09:00 AM

0-60 should be in the 9 second range. I'd definitely rule out the oxygen sensors; if they were that far off they would set a code. Your gas mileage is good; I do well to get 20 highway but then I never ran a set of brake pads for 90K on anything. The rev limiter should be somewhat over 6,000 rpm; my ML sees 6 grand every week (118K and going strong). My hunch is that it's the MAF sensor, but there's got to be a way to prove it. Replacing parts on a hunch is very expensive. Seems to me if it's that low on power it should have set a code.

The stock rotors and Pagid pads work fine for me in all kinds of weather. I have never had the brakes hydroplane on the ML.

Last one's easy. I use Valvoline DOT 4 on the street and Wilwood DOT 3 on the track. Reason being, on the street you want the highest wet boiling point you can get, on the track dry boiling point is more important because you change the fluid every couple of weeks.

osmosis 02-07-2004 07:22 PM

Shocks. brakes and a MAS oh MY
Thanks for the 0-60 time.

Looks like I'm driving a slug.

Mine is ~17 seconds +or -. I checked the OBD and although the CEL is not on I have the "fuel trim" codes that others have described as a MAS, I will be replacing it this week.

As for the Brakes. I installed the Wagner Thermoquiet and they are just that QUIET and appear to be very nice and smooth coming to a stop and and do not "grab" like the the pads I had on.

I also replaced the front shocks with the Monroe Reflex and WOW what a difference. I have only driven ~100 miles since installation, but the clunk that I used to get leaving my development road to the highway is now gone. the brake "dive" is almost nill and you can feel a definate reduction in body sway when cornering.

Total time for the job was about 2 hours. Including cleanup. A hint for the shocks, spray the top nuts with a little WD 40 before doing anything else. To hold the top shock stud, I used a pair of needle nose vice grips, locked it on the top stud, then accesed the nut with an open end wrench by just pushing the fenderwell up to gain access, worked great, since the wheel was already off for the brake job.

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