4mydogs

Yikkes! My check engine light has been coming on for a week now, after the truck begins to warm up and I get out on the road, and the moment it comes on I lose power. I took it to my regular mechanics who just told me that they get two codes when they "plug it in," the ignitor and knock sensor. They said that to replace both, parts and labor, will be close to a grand. :cry: That's a lot of money to me.

Any thoughts or suggestions?

19RUNNER86

second opinion! dealer maybe?

4mydogs

Thinking about a second opinion, but the dealers around here . . . well, let's just say I think they're sub-par.

19RUNNER86

ask around for a reputable shop. im sure theres someone around... if not sell it to me for cheap

kmcc78240

The ignitor should be pretty easy, its on the drivers side wheel well, The part is a little expensive from the deal, but somebody just bought one for like 50 bucks and a junk yard. here it is, https://www.yotatech.com/forums/f116/3vze-wont-start-when-hot-now-wont-start-all-w-o-starter-fluid-102617/

BC Rider

I've had (have) the knock sensor problem and am still struggling with it. I'm guessing that the $1000 you got quoted is mostly the Knock sensor labour - its a PITA to get at (under the intake manifold). Find out how much just the ignitor is to replace and then consider the following POSSIBLE solutions for the knock sensor I've seen on this board via the search function.

1. clean off the knock sensor contacts where it plugs into the harness. This has apparently worked for some on this board - I did this and it behaved for a week or so, then came back. You might get lucky.

2. One fellow here just got a new knock sensor and attached it to his lift lug. This saves you the labour.

3. Another guy reported that his KNK code went away after the mechanic fixed a vacuum leak. Worth checking.

If none of the above appeals to you prepare to pull the timing belt, intake plenum, and intake manifold - then replace knock sensor (over $100 for the sensor).

FYI - apparently most KNK failures are attributed to the wire from the harness to the sensor - wire become brittle with age and grounds out. Wire is only $10 - BUT you need to consider the labour to get at it and as far as I can determine there is NO way to check a knock sensor if you have the CEL light on. You can check a good sensor by rapping the block and watching the timing retard - but I have yet to hear of a way to determine if your sensor is good or bad once you are in the retarded timing safe mode.

Good luck.

Firefightertaco

I would go to auto zone or advance auto and have them hook up there code reader and make sure that what the shop told you is true.

midiwall

Like others have said, the $$$ is wrapped up in the labor to get to the knock sensor. I've done it a few times on my 3.4 and it's 3 hours to get to it, 10 minutes to swap the sensor, and another 2+ hours to put it all back together. From what I've seen people say, your engine's just as nasty.

On top of this, knock sensors are stoopid expensive.


The real thing I wanted to add is to explain why you lose power. When the ECU finds an issue with a knock sensor, it will put the engine into full ignition retard. That'll kill your power.

This is the 3.0, right? is there one or two knock sensors? I had a rash of issues with knock sensors and finally gave up replacing one or the other (there are two on th 3.4) so I tied the ECU inputs together and fed them both off of the "good" one that was left. Worked great.


I's a 95, so you need to find a shop that has an OBD I reader or a fit for the DIAGNOSTICS connector on the block.

Or actually, can't you pull the codes from this ECU by pin jumping? I think so...

4mydogs

Thanks for all the replies. First, regarding the ignitor, he told me it's not uncommon for them to become a problem on Toyotas with this many miles. Of course that is the cheaper part and easier to replace. Regarding the knock sensor, I'm the guy that told about the mechanic finding a vacuum leak and that doing away with the code -- and that was over a year ago and I haven't had any problems/codes until now.

I guess I still have two questions:
1. Why does it only do it once I've gone a short distance? When I start her up there's no light and power feels normal.
2. How certain can I be that what the codes say is correct? Any chance I replace both of these and still have a problem? I only ask this because years ago I had a Bronco that confounded mechanics because (they said) it gave incorrect codes.

I lied -- one more question:
Why did Toyota make the knock sensor so difficult to get at?

midiwall

1. Why does it only do it once I've gone a short distance? When I start her up there's no light and power feels normal.
   
   The ECU needs to see a certain number of failures before it reports the failure and "takes action". The delay you're seeing is the time it takes the ECU to figure out it's something to deal with. Not sure about your engine, but on the 3.4 I think it's 3 failures within the range of 1800-3200rpm
   
   
   
2. How certain can I be that what the codes say is correct? Any chance I replace both of these and still have a problem? I only ask this because years ago I had a Bronco that confounded mechanics because (they said) it gave incorrect codes.
   
   The only thing you can do is go on historical data from the folks here. I can tell you that my ECU codes (and I've thrown a LOT of them!) have always been dead-on. A knock sensor failure is pretty "easy" for the ECU to figure out.
   
   
   
3. Why did Toyota make the knock sensor so difficult to get at?
   
   The concept of a knock sensor is such that it really needs to be near a cylinder. Putting it under the intake manifold probably makes sense for an install that happens when the engine's torn apart on a production line. Plus, the knock sensor is something that "should" _NEVER_ go out - it's a crystal, seriously, as in a rock. But, no matter how hard you mount the rock in it's steel sleeve, it still has to vibrate so that it can produce a voltage when struck hard. Now add to that a truck bouncing around on a trail or rocks or dunes for 12 years and... things brak.

GT88Yota

Knock sensor from Napa= $200+

I just replaced mine because the plastic part was broken (˟˟˟˟ing previous owner!).

If yours is faulty I suggest going to the local pull-a-part and looking around for one, spending $5-20 for a sensor (depends on 'yard) is a lot easier to stomach then a new one.

GT88Yota

Also, try removing the splash guard on the passenger side wheel well. On my '88 pickup it was not that hard to get to, I think it takes a 22mm wrench but I could be off slightly.

Targetnut

Just because there is a code, does not mean that it is a component failure. All it means is that there is something wrong with the signal. This can easily be caused by a wiring problem.

Ignitors very rarely fail on that model, In fact I've only ever seen two, one was jump started backwards,(had a bunch of other fried stuff as well), the other had a shorted ignition coil.

The knock sensors usually are not bad either. As was mentioned before it's usually the short harness that goes under the manifold. Still a PITA to replace though. I don't think that a '95 will retard the spark in the event of a knock sensor failure either. Probably would do to check the timing when the check engine light is on.

A lot of people (would be mechanics as well) quickly start throwing parts on in an attempt to fix codes. Sometimes it fixes them sometimes it doesn't

BC Rider

GT88- is your truck a 4cyl or a V6? I'd love to try your trick, but I don't believe it applies to the V6.

4mydogs - I have the same concern as you about the CEL code being false (I'd hate to spend all that time wrenching to find another problem). So I've ordered a KNK sensor from ebay for about U$45 and got the wire from Toyota (C$13 IIRC). I'll wire it up to the engine lift lug like mentioned before. If my CEL goes away I'll be able to confirm that this is the solution and then do the wrenching to replace the wire and the sensor propertly.

FYI - some other things mentioned as potential culprits that I will also do.
Change the fuel filter (possible lean condition)
Change the spark plugs for OEM nippodenso ones
Check the TPS for setting as well as linear response

GT88Yota

ahh, I didn't see in his sig that it was a V6.....mine is a 4 banger...

4mydogs

UPDATE:
I picked my truck up last night after they replaced both. Have only traveled about 25 miles, but so far so good. Two odd things, though. It's idling higher, around 1200 rpm's in neutral. And it seems noisier when accelerating, kind of like a rush of air. Once up to cruising speed it sounds normal.

dcg9381

They should have checked the timing after replacing the ignitor, if it really was an ignitor issue..

timebandit

There really no way to check a knock sensor with a meter or anything. It is not a signal you can measure. It is a micrphone that hears any and all noise. The computer is responsible for filtering out what is normal and what is pining. Because the spark advance is known to the computer it filters down to a window just before and after the firing event in the cylinder occurs. Anything just before is pre-ignition and just after is pinging. They do go bad. (Ford's). I once owned a 3.0L Sable '87 that drove me crazy. It drove like I wanted to blame the auto trans for all my problems. It took a long time to find out what was wrong. Oh, but I found out.

I doubt the ignitor goes bad. Unless the coil is shorted.

Many times will have a lot of false codes and only one of them is real.

4mydogs

Follow-up x 2:

The noise I was hearing is now more apparent, and it sounds like an exhaust leak. Would they have done anything with the exhaust manifold while doing this work?

slater442w30

The leak is probably the egr pipe or valve, That bolts up to the pass front of the engine and would come off to get the intake off (You do have the 3.0 right?) and the other guys, I have changed the knock sensors and wiring for them on my 3.4 and they still throw codes, I graphed them with the snap on modis (diagnostic computer), the are working perfect, but still throwing codes, any ideas? The old ones were aftermarket and failed half the tests but were spotless and shiny new. Toyota ones were 120 each from the dealer.