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#1
11-01-2016, 07:19 PM
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1995 M104 EGR question
Hi Everyone- I have been struggling with a hunting idle issue for a long time. I seemingly got a little closer to fixing the problem.
The car is in perfect working order. It has a rebuilt harness & throttle body and nearly everything under the sun that would normally make a difference with this issue has been replaced. I plugged the vacuum line leading to the EGR and the car idles normally. I figured it was the switchover valve on the front of the engine. My buddy gave me a number of spare to try out. None of them made any difference at all. Once I applied the vacuum hose to the EGR valve at the back of the engine it started stumbling again. Is there supposed to be vacuum at idle to the EGR? There is a strong amount of vacuum coming from the metal line that routes to the side of the valve cover. I am wondering if this is normal?? I am not sure if there is supposed to be the vacuum at idle and if there is does that mean the EGR valve itself is faulty? Thanks in advance Last edited by ccrelan; 11-01-2016 at 07:30 PM. 
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#2
11-01-2016, 07:31 PM
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There should not be any EGR action at idle.
I'd put a volt meter across the switchover valve and see if the controller is calling for the EGR to operate. The system might modulate the valve by applying a variable voltage / variable pulse width but I don't know for sure. If you don't see any voltage at the switch over valve and it is flowing vacuum, the valve is sticking.
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#3
11-01-2016, 08:22 PM
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It's just an off/on valve and shouldn't be on at idle.
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 90 300TE 4-M Turbo 103, T3/T04E 50 trim T04B cover .60 AR Stage 3 turbine .63 AR A2W I/C, 40 LB/HR MS2E, 60-2 Direct Coil Control 3" Exh, AEM W/B O2 Underdrive Alt. and P/S Pulleys, Vented Rear Discs, .034 Booster. 3.07 diffs 1st Gear Start 90 300CE 104.980 Milled & ported head, 10.3:1 compression 197° intake cam w/20° advancer Tuned CIS ECU 4° ignition advance PCS TCM2000, built 722.6 600W networked suction fan Sportline sway bars V8 rear subframe, Quaife ATB 3.06 diff
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#5
11-01-2016, 08:40 PM
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If the valve passes vacuum when its unplugged, its bad. If it only passes vacuum plugged in then either the module is bad or the harness has a short circuit somewhere.
This is assuming that its connected properly. Source vacuum to the top, load connects to side port, bottom port is a vent, electrical connector facing down.
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90 300TE 4-M Turbo 103, T3/T04E 50 trim T04B cover .60 AR Stage 3 turbine .63 AR A2W I/C, 40 LB/HR MS2E, 60-2 Direct Coil Control 3" Exh, AEM W/B O2 Underdrive Alt. and P/S Pulleys, Vented Rear Discs, .034 Booster. 3.07 diffs 1st Gear Start 90 300CE 104.980 Milled & ported head, 10.3:1 compression 197° intake cam w/20° advancer Tuned CIS ECU 4° ignition advance PCS TCM2000, built 722.6 600W networked suction fan Sportline sway bars V8 rear subframe, Quaife ATB 3.06 diff
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#6
11-13-2016, 12:29 PM
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With the main engine harness & throttle body replaced, I doubt you're having any electrical issues. Was the "B" harness replaced?
Use hand pump, EGR must hold 12" of vac, if not then diaphragm is leaking. Use hand pump to check ALL vac lines in eng mgt system. There is a plastic vac line routed under the battery that can develop pin holes. Ensure rubber holes fit tightly at their connectors. Clean egr metal tube to engine Are you getting any codes?
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