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Discussion Starter #1
3.0 Liter Mitsu 94 Caravan EGR good but Modulator may be bad - Vac Hose between Modulator & Intake was "cooked" - I understand that new one comes as an assembly - Now that I have it all apart please remind me if Vac Hose off Modulator Port marked EGR goes to the "top" / rearmost Port on top of EGR Actuator Diaghram that has the teeny Orifice or does it go to the Port on EGR that is the pipe built onto EGR ? - This of course will tell me where the triangular Vacuum Hose thingy goes onto EGR - WHEN COASTING TO STOP my idle would drop to zero & stall - 94K on original Fuel Pump w/new Filter - Going in to Clean AIS / Cone Valve today.
 

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A cooked rubber EGR hose is probably bad news. The catalytic converter may be plugged and pushing hot exhaust gases into the EGR transducer (modulator) and damaging it.
Check the converter before replacing the EGR/transducer assembly.
You are correct that they are serviced together. The transducer should come marked for proper hookup or you should have an underhood vacuum circuit label to use as a map.
 

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Here's the hookup as it relates to the black cylindrical plastic part that has the electrical connector:

- Nipple below the electrical connector goes to the EGR diaphragm fitting
- Nipple on opposite opposite side goes to intake manifold fitting
- Triangular rubber piece connects small metal pipe coming from the cast base of the EGR assy to the underside of the black plastic tranducer diaphragm.
 

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Discussion Starter #4
Thanx so much guys for the timely expert replies - I sure hope Cat is not Prob... I do have Vacuum at Vac Pipe Cast into EGR until you back off Throttle then you get the expected Exhaust Burps - BTW I broke fragile Throttle Body to intake Gasket - Trying thin coat of Hi Temp RTV on this Sunday... gotta watch the Skins at 430 - TB & Intake was mildly sooty but not too bad, certainly anyone w/EGR probs should clean TB & AIS & Intake mouth - Plugs look nice & Tan still, not lumps of Charcoal like in "terminal" EGR Valve probs - I actually have good EGR Modulator off an old Toyota that I thought about trying but lacks the connector of course - I take it that Electrical Connector on Mitsu Modulator is what disables EGR via Modulator when Engine is Cold ? - On Toyota EGR may have been disabled via Modulator by a Temp Sensitive Vac Valve or something - I have to add that this thing is actually not difficult to work on like virtually everything else I own ~!
 

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Discussion Starter #5
Runs great with a 1981 2TC Toyota Corolla EGR Modulator when Hot ... Gotta love that Toyota quality... Runs a little weird when Cold - Always pretty Temperate here in SC but this our coldest time of year until March when it starts to warm - Son uses car for work so I had to cut it loose w/Toy Modulator until at least next weekend - I take it that Electrical Connector on Mitsu Modulator is where ECM disables EGR via Modulator when Engine is Cold ?
 

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The modulator is actually run by a variable PCM duty-cycle signal. It varies the length of 'on' time depending on the amount of EGR needed. When it is cold, the EGR is kept off easily enough. Demand for EGR is high under warm acceleration.
The PCM also runs an EGR self test at certain times by turning on the EGR and watching the MAP vacuum drop while seeing a lean-shift in the O2 sensor signal.
With the electrical portion on your modulator missing, I imagine that your 'ck eng' light will be on and an EGR fault code stored.
 

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Discussion Starter #7
YUP we have new CEL now sure enuff returning after disconnecting Battery & of course I had CEL at first fault - Will install new Chrysler Modualtor ASAP as I'm sure all this aint great for Cat either, but in a pinch for Sunday Parts this worked fairly well as stopgap.
 
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