Interesting issue I have been having

My 1991 Previa LE has begun a bit of a rough idle, and had a code for the EGR as well as a lean O2 code. I cleaned the EGR, cleared that up, but the lean code and rough idle returned. However I was making a trip from LA to Dallas, then Austin. In Dallas, suddenly, my van would not start.

A quick look determined that my front fuse box was corroded, right where it connects to the positive cable, a common problem on these. I cleaned that up, and it started, but it was a hard start. After shutting it off it would not restart. Checked for fuel, and I had none. So I dropped the tank to check the pump, it works fine, it's not getting power. Instinctively I went looking for an issue with the fuel pump relay, but unlike most vehicles, it is important to know this van uses a switch in the MAF to close the Circuit Opening relay after started, and the ignition switch closes this relay while cranking. So the van, if you just turn the key on, will not be running the pump like most vehicles do for a few seconds. You gotta jump the fuel pump test connector, located under the driver seat by the computer and diagnostic port, to get fuel pressure. Another post on this forum has pics. So I spent a bit of time chasing a fuel pump wiring issue before realizing this, but after knowing how it works I was able to determine it was fine.

So next I checked spark from the coil, located underneath the car about where the front passenger and sliding door meet, on the frame rail. It has a shield over it, but the coil wire is about 6" long and goes to the distributor. I pulled it off there, and checked, and had a very white spark. I checked by putting a small screwdriver into the wire and, holding the screwdriver with insulated pliers, got the metal shaft about 1/8" away from the metal frame. Then I had a friend crank the engine for just a second.
The spark was a very white/yellow color, not good. Ideally you want to see a blue/white spark, so I determined I must have a weak coil, and bought another for $96 after tax.

Well, this is where the real problem finally revealed itself: When I took the old coil out, the coil wire that runs to the distributor had corroded all the way through at the end connected to the coil! The wires are about 1.5 years old, so still under warranty, but they came from Autozone. Duralast brand. I put the new coil on, because forcing it to fire under bad circumstances can cause it to become weak and I don't want future problems. Then I warrantied the wire, and all is great! Van runs perfect.

So, what I learned, if your van does not start and you want to do a fuel pressure test you HAVE to jump the fuel pump connector or you will waste your time trying to figure out why the relay is not getting the power signal when the key is turned on. Also, don't buy the Duralast wireset. I plan to replace them all in the future with some higher quality ones. When it rains, sometimes I have a misfire; I think that problem is gone for now. Anyways, hopefully this helps someone out there pulling their hair out over a simple fix.

Thanks for posting. I got my 93 Previa for cheap because it ran rough (had a miss). While troubleshooting I noticed it had an aftermarket spark plug wire set, I couldn't see anything wrong with them, I just didn't like the fact they were aftermarket. I replaced with genuine Toyota wires and this completely solved the problem. I know Toyota has ridiculous prices, but sometimes it's better to just pony it up. When it comes to certain parts, rather than experiment & waste time, it just makes more sense to insist on genuine Toyota. For me, spark plug wires fall into this category. Tim

autozone spark plug wires are just crap, get rid of them ASAP! I don't care if it's lifetime warranty if it's going to kill coils and strand you
get the toyota genuine wires or at the very least NGK aftermarket... the good thing about the toyota wires is, it has the year of manufacture printed on it, so you can quickly determine when it was approximately put in rather than going purely on mileage

Yeah, good advice on the wires, I was unaware that they could be so problematic! I am gonna be seeing the dealer next week for some new ones!

Any advice on a specific alternator brand for my spaceship (91 Previa LE)? Mine works normally, but one day recently the battery light came on, and I measured no output from the alternator. But a few minutes later it began working again. So, gonna replace it as maintenance. For most of my cars I have put the CarQuest one on, never had problems, but I don't wanna waste money like I did with the freakin plug wires.

With most manufacturers it probably doesn't matter, but when it comes to alternators made by Denso, Denso does the best job rebuilding. So if you want to replace the whole thing, I'd go with a Denso (actually rebuilt by Denso). Before replacing I'd recommend taking the old one apart. You might just have some worn out brushes or something obvious. You can get a brush set in a holder for dirt cheap on www.rockauto.com. Even the genuine OEM brushes are affordable. I made a couple posts on alternators and how to disassemble. The 1st one is more detailed but is for a van. These are pretty similar and all the same stuff applies for the Previa alternators. Tim

http://www.toyotavantech.com/forum/s...lternator-woes

http://www.toyotavantech.com/forum/s...em-with-Previa

Cool! Tuesdays are my day off, so it looks like I will be doing some alternator rebuilding! Thanks for all the info Tim, you are definitely the Toyota Van Man! My friend has a 89 van, and we put an alternator on it, it already had to be warrantied out after about a year! It's a Denso rebuilt one, too. Maybe just a fluke issue though, rebuilt on a Friday.

I have discovered lately a common problem with the TPS harness on the Previa's, I keep finding they set a TPS code, and a new sensor is not the solution. There is a TSB on the wire harness, but I find, every time, about 1/2 inch from the sensor connector, the black ground wire is broken inside the harness. I cut out a few inches, solder and heat shrink a new wire in, and they are always back on the road without having to replace that whole harness.

Yes, before I was aware of that TSB I went through that as well. I ended up isolating a bad wire between the TPS & the ECU. Since the ECU was so close I just pulled a new wire between the 2.

good alternators don't die without a reason
typically it's due to an undercharged or bad battery