Problems with EGR, clogged CAT

[Nuget]

Hey all, a couple of weeks back my 95 previa suffered a sudden loss of power. I took it to two shops and discovered that my CAT is clogged, the EGR system has problems (modulator, valve leak, #1 O2 sensor), and the oil reservoir is empty while the oil level is overfull. So far I've replaced the EGR modulator (which was burnt and missing the tube that connects it to the EGR valve), and replaced all of the tubing that I can. I plan to change the oil and spark plugs and then take it to the muffler shop to replace my two CATs. Is there anything else I should do before replacing the CATs? I have been warned that they will clog again if my EGR system isn't running properly. Really hope I can bring my van back to good health! Thank you in advance.

[John Kaufmann]

Have you cleaned out the EGR line, through to (and including) the throttle body? At ~20 years old (~300K miles), my 91 Previa EGR line to the intake manifold was completely blocked at the cold end (next to throttle body). Before starting that job, make sure you have 2 new line plugs (90331-16001), because you will not be able to reuse the old ones. You will also need a throttle body gasket (22271-76010). [I just checked: ToyoDIY says they used the same parts on all Previas of that vintage (TCR1*,TCR2*).] It looks like the plugs (~$3 each) and TB gasket (~$5) are still widely available - better than many parts of that era.

[Nuget]

Thanks John, I am approaching 300k miles, haven't serviced the EGR line yet. Parts have been ordered

[Jonny]

Much info on this stuff here. Do several different searches and lots of reading. Also check out this page... https://zenseeker.net/Previa/ ... it is very worthwhile browsing and has a lot of common problem information, usually with solutions.

[Nuget]

The gasket and two plugs are arriving tomorrow, I have read other people's write-ups on how to service the EGR line. The only thing I'm confused about is the EGR valve coolant, where does it come from? Where do I refill it after I drain it from the two hoses connected to the EGR valve?

[Jonny]

The coolant lines servicing the EGR valve are part of the main cooling system so you'll just be checking the reservoir level and adding coolant there if necessary. If you plan on disconnecting the coolant lines do the job with the engine cool/cold. Personally I've never had to do anything with the EGR valve, so I don't know whether its best to drain some coolant first from the radiator drain cock, to minimize the mess. Might be worth doing so anyway.

Get a genuine Toyota repair manual from EBAY for your year. It's money well spent. The manual is generally excellent and answers most things you need to know when you're doing your own work.

Regarding your oil level problem, you have a sticking oil level sensor (stuck on the low signal). Read this thread...
https://www.toyotavantech.com/forum/...sor-Best-Fixes
You need to fix this pronto if you haven't already, at a minimum by disconnecting the sensor connector so that the sump doesn't keep overfilling, and do all oil level maintenance the old fashioned way.

[bjk]

Have you cleaned out the EGR line, through to (and including) the throttle body? At ~20 years old (~300K miles), my 91 Previa EGR line to the intake manifold was completely blocked at the cold end (next to throttle body). Before starting that job, make sure you have 2 new line plugs (90331-16001), because you will not be able to reuse the old ones. You will also need a throttle body gasket (22271-76010). [I just checked: ToyoDIY says they used the same parts on all Previas of that vintage (TCR1*,TCR2*).] It looks like the plugs (~$3 each) and TB gasket (~$5) are still widely available - better than many parts of that era.

I have a '95 and have cleaned the EGR before but without removing the plugs. I looked up the plug part numbers and they are available the for the '95 but I am wondering howto remove them. Is it enough to drill a hole then pull them out with a screwdriver? Or is there more or less to it? Will squirting throttle body cleaner in there be enough to clean the area after removing the plugs?

[John Kaufmann]

That's right. I used a couple different sizes of hex head wood screws, which have the kind of coarse threads needed for pulling. You can begin small (say, 1/4") and go up as needed. IIRC I used my right-angle drill (though I'm not sure that is needed), both for punching through the plugs and (with caution) for rough cleaning of the tube after the plugs were removed. Then a rag and throttle body cleaner.