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  #1  
Old 09-09-2017, 03:48 PM
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Om602 sluggishness

My 92 300d has a lack of responsiveness when you give it throttle. The turbo works great, i replaced all the vacuum lines and the turbo spools at like 1600-2k. But i drive it with my foot in it all the way before kickdown. If you floor it, there's a general lack of responsiveness. The car won't move, it will just keep going at the same pace. At wot from a deadstop, it does have power but not otherwise.

The fuel filters ok and the vacuum system is functioning. It also has a good vacuum pump.

I was thinking of checking the alda and taking it off for a test drive but looks like you have to take the manifold off. Not what I'm trying to do at the moment till i have a gasket and glow plugs to replace the broken ones.

Also, how hard is it to check the intank filter? Can that cause a lack of responsiveness in throttle? It just seems like the engine doesn't want to raise in rpm when you give it gas

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  #2  
Old 09-09-2017, 04:20 PM
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Check your ALDA. If it is good, it should be able to hold vacuum. If it doesn't, you probably need a reseal. My SDL was behaving this way before I tuned the IP and resealed the ALDA. Post-tuneup the difference is incredible. I wound up making the IP leaner, but with the now-functional ALDA the power pickup is very smooth and the power delivery is more or less "effortless" when driving around in town.

Prior to the tuning and ALDA fixing, it was DOG until the turbo spooled up, then had decent power. The problem came in city traffic where it was in a high gear and the turbo just wasn't spooling. GUTLESS.
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  #3  
Old 09-09-2017, 04:38 PM
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Also check the 27mm over-pressure switch on the in-take manifold, just in front of the cruise control actuator in this picture here: http://www.peachparts.com/shopforum/groups/w124-300d-2-5-turbo-picture2068-dsc00027.html

Too much pressure grounds the lead, which then opens the vacuum tube switch to the alda.
If the pressure switch is stuck, i.e. constantly grounding, then your alda will not boost your fuel during turbo time and, ergo, no turbo benefit. Disconnect the lead and check for ground continuity on the switch connector (with the engine off). You should not have any. The switch can get gummed up inside with egr goop. Try cleaning before replacing. Also check that the lead between the over-pressure switch and the vacuum tube switch is not shorting to ground itself.
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  #4  
Old 09-09-2017, 05:29 PM
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You shouldn't have to take the manifold out to get to the ALDA. It's tight but you can do it.
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  #5  
Old 09-09-2017, 06:08 PM
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Quote:
Originally Posted by pwogaman View Post
Also check the 27mm over-pressure switch on the in-take manifold, just in front of the cruise control actuator in this picture here: http://www.peachparts.com/shopforum/groups/w124-300d-2-5-turbo-picture2068-dsc00027.html

Too much pressure grounds the lead, which then opens the vacuum tube switch to the alda.
If the pressure switch is stuck, i.e. constantly grounding, then your alda will not boost your fuel during turbo time and, ergo, no turbo benefit. Disconnect the lead and check for ground continuity on the switch connector (with the engine off). You should not have any. The switch can get gummed up inside with egr goop. Try cleaning before replacing. Also check that the lead between the over-pressure switch and the vacuum tube switch is not shorting to ground itself.
Are you talking about the overboost protection circuit? The '92 doesn't have that. If you're talking about something else, well, I didn't recognize the thing in your pic, so maybe the '92 doesn't have that either, lol.
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Last edited by Bimmer-Bob; 09-09-2017 at 10:48 PM.
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  #6  
Old 09-09-2017, 06:49 PM
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Yeah I'm confused too. Could you elaborate a little more ]wogaman? Mine doesnt have the blue saucer setup. Ill check the alda too.. can the tank filter cause a low power issue
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  #7  
Old 09-09-2017, 09:15 PM
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If you're getting enough diesel to have good power off the line with WOT, then no, the strainer in the tank probably isn't the issue. If it was, you'd be choking then too.

If you have the vacuum operated wastegate you likely don't have the overboost protection circuit. The earlier cars with the mechanical wastegate had a sensor in the intake plenum and a switchover valve on the firewall which killed the ALDA signal to prevent the turbo from spooling if the wastegate stuck closed.
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Old 09-10-2017, 12:08 AM
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Bump

GPS

'Got I.M. for '90 AND '92 and whatever's in the picture is on Neither (?)

But,I'll delve into it...
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Old 09-12-2017, 08:29 AM
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Have you tried disconnecting the MAF? That restored all the power to mine when I was having over boost protection kick in from the ECU. The ECU looks at changes in MAF when exhaust gases are recirculated into the intake and limits boost. Unplugging the MAF seems to bypass that part of the ECU's logic.
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  #10  
Old 09-12-2017, 02:26 PM
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Originally Posted by dieselbenz1 View Post
Have you tried disconnecting the MAF? That restored all the power to mine when I was having over boost protection kick in from the ECU. The ECU looks at changes in MAF when exhaust gases are recirculated into the intake and limits boost. Unplugging the MAF seems to bypass that part of the ECU's logic.
nah i didn't thanks i'll check that too.

thanks for all the suggestions will update as time proceeds for me to look at the car
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  #11  
Old 09-21-2017, 02:39 PM
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I just went through all this stuff on semi-project car. Started and ran great, zero power, no boost.

Cleaned intake manifold + new gaskets
Fuel filters
Wastegate upgrade
Connected manifold pressure straight to the alda
EGR and flapper delete
2.5 inch straight pipe

14 peak PSI, spins the tires off the line.

The one thing the really helped was the bypassing of all the stuff controlling the ALDA. It came alive. I'm still going to adjust it and get some more off the line responsiveness, but for now, it's actually fun to drive.
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  #12  
Old 09-21-2017, 03:01 PM
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Originally Posted by Russhole View Post
I just went through all this stuff on semi-project car. Started and ran great, zero power, no boost.

Cleaned intake manifold + new gaskets
Fuel filters
Wastegate upgrade
Connected manifold pressure straight to the alda
EGR and flapper delete
2.5 inch straight pipe

14 peak PSI, spins the tires off the line.

The one thing the really helped was the bypassing of all the stuff controlling the ALDA. It came alive. I'm still going to adjust it and get some more off the line responsiveness, but for now, it's actually fun to drive.
I since sold this car, but I will take that advice into consideration. I plan to do that, I just picked up a 93 300d that won't do over 50mph off a member off here. Once I get it home and work on it I will investigate.

I'm surprised your car spins tires. Mine wouldn't even do a burnout power braking it
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Old 09-21-2017, 03:35 PM
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On loose gravel my SDL will spin the tires off the line. Otherwise you can forget about it. That said, I'm pretty sure a Yaris will spin the tires off the line on loose gravel too. With good tires on one of these cars, I don't buy a burnout on takeoff.
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  #14  
Old 09-21-2017, 04:55 PM
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Quote:
Originally Posted by Diseasel300 View Post
On loose gravel my SDL will spin the tires off the line. Otherwise you can forget about it. That said, I'm pretty sure a Yaris will spin the tires off the line on loose gravel too. With good tires on one of these cars, I don't buy a burnout on takeoff.
I'm thinking the same thing
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  #15  
Old 09-21-2017, 06:39 PM
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I'll take a video when I leave work this evening. I have a pair of crappy tires (lots of tread) that offer zero traction under any circumstance.

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