Friend of mine has a '97 perpetually in limp mode because of EGR codes.

I originally got two codes - P0400 egr system malfunction and P0403 egr low flow. I removed and cleaned the EGR, reinstalled it, and eliminated the low flow code but can't keep the 0400 code cleared.

If I start the car and let it idle after about 30 seconds I can see the intake flap close. It stays fully closed for about 2 seconds, then snaps back to full open and the cel / code come on.
If I clear the code, start the engine and immediately start driving it will not throw a code and the car runs great until/unless I let off the accelerator and it drops back to idle for 30 seconds or so.

The CEL was on when he bought the car a year ago and seller told him it was just a glitch in the computer that didn't effect performance. So, he's always thought the car was supposed to be this slow...

Is there any way to do an electrical patch (as I've done on my '98/'99) /or/ have the computer tuned to ignore the EGR altogether?

Just trying to help a friend out. Really annoying to know the performance is in there but not be able to get it out!

Thanks all.

FMB

The flaps are controlled by a transducer (the same as our Wastegate/EGR uses) have you tried swapping them to see if the code moves with the transducer?

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Hi Terry,
Thanks. I'm out of town now but that's what I plan to do when I get back this weekend. I actually swapped the EGR valves first to confirm that the EGR on this car was ok. (The donor car had a near new EGR.).

I saw the connection to the transducer but ran out of time on Sunday. I'm guessing that there's a simple switch in the transducer that might have dirty contacts. It will be amusing if the problem is just in the transducer - which is one heck of a lot cheaper than an ECU.

Will let you know what I find.

Fred

I wonder how long the PO drove that thing in that state of disrepair? Cant be good for the motor or trans. Ouch.....

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1997 E300D Wife's daily driver
1985 300SD my daily driver
1999 Expedition family road trip and material hauler

Big Jim - No clue about the PO but my friend (current owner) has driven it this way since he bought it more than a year ago. He just assumed they were this slow. When I drove it last week I knew something wasn't right since it would max out at 4000 rpm and not shift to top gear with accelerator held to floor. I cleared the codes and it easily ran through the gears, shifting just under the 5,000 rpm redline. Unfortunately, it trips the code and goes to limp as soon as you let it drop to idle.

TM Allison - swapping the transducers (which are identical) is a great idea and I can't believe I didn't think to do that when I had the car again yesterday. The flap is moving - so clearly getting vacuum through its transducer. The EGR valve is NOT getting any vacuum (I teed a gauge in to that one). If I swap the transducers and the EGR operates but the flap doesn't, I will probably get a different code but will know we're on the right track as this will suggest that the circuitry to both transducers is intact.

Thx

Fred,

Check the small vacuum line on the top of the intake driver side. Mine had a split in it and was causing all kinds of weird behavior. Also might help to take a pipe cleaner and clear out the nipple, it can get gunked up in there.

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Dennis
2006 E320 CDI Black/Black Leather. Nav, HTD Seats HK stereo 32000 miles.
2000 VW Passat 1.8t 300,000 miles as of Dec 09, 2009 original owner
1997 E300d Silver 300,000 miles As of Jan 05, 2010
3rd owner SOLD

Also, check the vent lines off the transducers. If they are like the later models they have a small paper filter on the ends which, if they clog even slightly can cause problems - you could always remove them just to test and if it clear the problem replace them.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

It would require pulling the crossover and intake and replacing all vacuum lines, plastic pipes, etc. Also clean all grime etc. from intake, flaps etc. Once this area is in a "known" state, trouble shooting the easy to get to parts ( egr, transducer, etc.) is more effective. Also electrical connectors should all be checked and clean.
For his sake I hope it is something simple but I have some doubts. Best of luck. Jim

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1997 E300D Wife's daily driver
1985 300SD my daily driver
1999 Expedition family road trip and material hauler

Solved it! TM Allison's suggestion that I swap the transducers - duh, why didn't I do that when I was fooling with things the first time?! - got me thinking. Checked and sure enough my '99 uses the exact same transducer to operate the EGR valve. Drove over last night, cleared the codes, swapped my transducer into the '97 and that fixed it. Ordered a new transducer this morning.

The best part was having my friend get in an drive it. He's had it for more than a year and never known how it should run. PO told him the CEL was a problem with the computer that didn't impact performance, so he just thought they were all that slow! Now you can floor it and it winds right up to redline and snaps through all the gears as it should! Not too bad for a non-turbo car (I'm spoiled with my chipped '99.) Of course it's back in limp mode until the new part gets here tomorrow. He's like a kid waiting for Christmas morning.

Simple fix, just took me awhile to get my problem solving sorted out. Thanks all!