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View Full Version : Sudden rough running 92 Previa w/145k mi.



ArtisticJS
04-25-2014, 01:28 AM
I'm the original owner & quite proud of my "silver bullet" as my family calls it. The van is not driven much these days. ( 1-2 times a month) Normally runs very well but just recently runs very rough, doesn't accelerate much even in park let alone try to drive; shudders too. Less than 1,000 mi. ago, I replaced plugs, distributor cap & wires with no problems. I thought perhaps the gas (87 w10% ethanol) degraded as there was about 8 gal sitting in it since last Nov. 2013 before restarting in March '14. I added 1/2 bottle of HEAT to displace any moisture buildup with little change. I added about 8-10 gal of 93 grade to perhaps boost overall octane in tank. I then read all sorts of great things about using Sea Foam to clean out carbon & "gunk." Put appx. 10oz. in 16 gal of fuel and siphoned another 3-4oz directly into engine via Master Brake cylinder vacuum hose with engine slightly above idle. Exhaust pipe now free of any carbon. I also sprayed carb cleaner into air intake (without air filter ) several times to try to clean throttle body without the hassle of disassembly.
All of this helped a little but not yet back to normal. I did check all plug connections in distributor cap & coil for connectivity - seems good w/boots locked in place. I then opened access hatch under driver's seat to observe throttle body connections, cables, look for bad vacuum lines, etc. I started engine, revved as best it could and then noticed
the secondary cable (mech spark advance, yes?) was limp & at no time had any tension on it regardless of throttle position. Am I possibly on a right track that it's stuck on the distributor end? Cure? Comments? Here's a couple of pix... thanks for any & all help. I'm going to need the bullet to pick up my son from college in 3 weeks - yikes!
Jim
15351536

timsrv
04-25-2014, 05:08 AM
The stuck cable is for your transmission kick-down. With it stuck like this it will exhibit problems shifting into the higher gears. Sometimes you can work penetrating oil down into the cable to free it up, but you will likely need to have the cable replaced. It attaches to the valve body inside the transmission and the valve body needs to be removed to access the connection point inside the transmission. A mechanically inclined person with the help of the factory service manual should be able to replace. If you're not that person, then I would suggest taking it into a transmission shop.

The rough running could be any number of things. The Previa is known for oil fouling the inside of the distributor, so I'd pull the cap again just to make sure there's no oil in there. If there is, then that could be the cause of your problem. There is an o-ring that can be replaced to correct this issue. If that's not it, then check the trouble codes. Here's a quote from a recent post:


jump terminals TE1 & E1 of the "check engine connector" (little terminal box) underneath the driver's seat. With these terminals jumped (metal paperclip works fine) and the key in the "Run" position (engine not running), the "check engine light" on the dash will start blinking a repeating code. There will be pauses between each series of blinks, and codes can be read by counting blinks between pauses. All codes for this model year will be 2 digits, but there may be multiple codes stored. A 4.5 second pause is the beginning of the loop. Then you will have one or more blinks with no pauses (this is the 1st digit of the code). Before the 2nd digit is displayed there will be a 1.5 second pause. If there is more than one code stored, there will be a 2.5 second pause before it displays.

If you get a chance to check this, report back with your findings and I'll look up the code for you.

ArtisticJS
04-25-2014, 09:53 AM
OK, thanks Tim. I'll check the distributor. Could the engine oil being 2/3 quart over the full line have anything to do with rough engine? Another clue I did not mention earlier: Engine runs smoother with vacuum hose pulled from Master Brake Cylinder...
THX
-J-


The stuck cable is for your transmission kick-down. With it stuck like this it will exhibit problems shifting into the higher gears. Sometimes you can work penetrating oil down into the cable to free it up, but you will likely need to have the cable replaced. It attaches to the valve body inside the transmission and the valve body needs to be removed to access the connection point inside the transmission. A mechanically inclined person with the help of the factory service manual should be able to replace. If you're not that person, then I would suggest taking it into a transmission shop.

The rough running could be any number of things. The Previa is known for oil fouling the inside of the distributor, so I'd pull the cap again just to make sure there's no oil in there. If there is, then that could be the cause of your problem. There is an o-ring that can be replaced to correct this issue. If that's not it, then check the trouble codes. Here's a quote from a recent post:

timsrv
04-25-2014, 10:45 AM
If you're talking two thirds of a quart over filled, then that won't hurt anything. If you're talking 2 - 3 quarts overfilled, then that could cause problems.

ArtisticJS
05-07-2014, 02:38 PM
Hey Tim,
I finally got the error codes & they are: 21, 25 & 26. I've been looking around for error codes list on the web but no luck... appreciate your time to look up.
Regards, -J-




OK, thanks Tim. I'll check the distributor. Could the engine oil being 2/3 quart over the full line have anything to do with rough engine? Another clue I did not mention earlier: Engine runs smoother with vacuum hose pulled from Master Brake Cylinder...
THX
-J-

timsrv
05-07-2014, 10:14 PM
#21 is a bad primary o2 sensor (the one ahead of the cat). #25 is a lean air-fuel ratio (points to a bad primary o2 sensor). #26 is a rich air-fuel ratio (also an indication of a bad primary o2 sensor). 25 & 26 can be caused by other faults, but since all 3 of these point to a bad primary o2 sensor, I would recommend replacing that, resetting the codes, then check codes again after a tank of gas. If they stay gone, then you're good. Tim

ArtisticJS
05-08-2014, 12:37 AM
Thanks for the code explanations Tim. I'll search for an upstream sensor - should be fun getting the old one out!
Regards,
-J-

Wow! Timing was just right for shopping at Rock Auto- wholesaler clearance going on for sensors. At these prices, I figure why not replace both?
Good deal, yes? I don't even care if I have to make some connectors...


1558



#21 is a bad primary o2 sensor (the one ahead of the cat). #25 is a lean air-fuel ratio (points to a bad primary o2 sensor). #26 is a rich air-fuel ratio (also an indication of a bad primary o2 sensor). 25 & 26 can be caused by other faults, but since all 3 of these point to a bad primary o2 sensor, I would recommend replacing that, resetting the codes, then check codes again after a tank of gas. If they stay gone, then you're good. Tim

timsrv
05-08-2014, 03:45 AM
That's a good deal. They are both under the van mounted to the catalytic converter assembly. The cats on these are big (about 3' long) as Toyota incorporates pipe and sells as an assy. The sensor on the front pipe of cat is the primary. The one on the back pipe is secondary. Tim

ArtisticJS
05-08-2014, 12:01 PM
That's a good deal. They are both under the van mounted to the catalytic converter assembly. The cats on these are big (about 3' long) as Toyota incorporates pipe and sells as an assy. The sensor on the front pipe of cat is the primary. The one on the back pipe is secondary. Tim

Is there an easy way to reset the check engine light after sensor replacement? I don't have a code reader - especially the older one for this '92.
THX -J-

timsrv
05-08-2014, 12:32 PM
This old style doesn't use a code reader (all self contained). To reset simply pull the 15A EFI fuse (middle row far right), wait 30 seconds or more, then plug it back in. An alternate way is to disconnect the battery for 30 seconds or more, but then you'll need to reset your clock. Tim