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Discussion Starter #1
Hey guys,

On my way in to work this morning my car flashed a CEL, started running even worse than usual and I had to floor the car to get it to go 50-55mph.

I got to work and read the codes and I get a code 43. It says it's related to a knock sensor. I replaced the knock sensor and the pigtail maybe 6 months ago. The car did the exact same thing before too.

What should I be looking at? I'm at a loss.
 

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On my '92 there was a dealer memo sent out that said spark plug wires too near the ESC module could cause problems, and to reroute those wires.

If it happened before in an identical manner, and replacing the knock sensor remedied it, it would seem that the knock sensor is bad, even though it's only 6 months old.

There was an article once on the automatic transmission that said it was the first automotive black box that the home mechanic didn't have a chance on fixing and that it might as well be running on magic.

Unfortunately, instead of converting to a reasonable fuel, the auto industry added a zillion parts to cars, parts that might as well run on magic because even the top mechanics don't have a clue how they work.

The only way I've figured to deal with this mess was by disassembling a '92 Roadmaster so that I have all the "magic" parts so I can swap them.

I don't see any choice but for you to swap another knock sensor in there.
I guess you could unplug your ECM and other electrical connections and spray some electrical cleaner in there but it seems like more than that.

I don't see any way at what I call "definitive analysis", which drives me nuts because what you're left with is trial and error.

I guess I'd throw another sensor in there, at least you'd have a spare if that isn't it... this "magic" box stuff sure feels like a scam... after all these "improvements" a 1959 Mini still gets way better gas mileage than almost anything on the road on 2009.
 

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Discussion Starter #3
On my '92 there was a dealer memo sent out that said spark plug wires too near the ESC module could cause problems, and to reroute those wires.

If it happened before in an identical manner, and replacing the knock sensor remedied it, it would seem that the knock sensor is bad, even though it's only 6 months old.

There was an article once on the automatic transmission that said it was the first automotive black box that the home mechanic didn't have a chance on fixing and that it might as well be running on magic.

Unfortunately, instead of converting to a reasonable fuel, the auto industry added a zillion parts to cars, parts that might as well run on magic because even the top mechanics don't have a clue how they work.

The only way I've figured to deal with this mess was by disassembling a '92 Roadmaster so that I have all the "magic" parts so I can swap them.

I don't see any choice but for you to swap another knock sensor in there.
I guess you could unplug your ECM and other electrical connections and spray some electrical cleaner in there but it seems like more than that.

I don't see any way at what I call "definitive analysis", which drives me nuts because what you're left with is trial and error.

I guess I'd throw another sensor in there, at least you'd have a spare if that isn't it... this "magic" box stuff sure feels like a scam... after all these "improvements" a 1959 Mini still gets way better gas mileage than almost anything on the road on 2009.
Actually, after thinking about it, this has happened before. Anytime I really step on it, this problem has resurfaced. It has happened less since I swapped out the sensor but it has happened nonetheless. I know I must have a timing issue, amd that is likely tripping the knock sensor. Though I will check out the plug wires. That's a good thought.

Thanks!
 

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What year is this car?

just thinking out loud:

On my 92's the IAC valve on the throttle body can be removed and cleaned, the EGR can be sprayed with carb cleaner... the throttle position sensor can screw things up like you're experiencing... dying fuel pumps can work except when you step on it... maybe run a timing light on the engine and rev it to see that the timing advances as it should, and that it doesn't jump around... unplug the ECM and spray contact cleaner on the big connector... I had a bad ECM on my '92 that I only solved by swapping...

Sometimes it's hard to figure out if problems like this are fuel or spark related, the symptoms can be similar.

So often when you get into things like this it ends up being a something simple like a bad spark plug, plug cable, cap and rotor etc...
 

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Discussion Starter #5
Sorry. 1991 non-cop Caprice. 305. No mods except a trailer trash CAI. I haven't messed with the IAC. Someone told me (and could have been wrong) that if you pull it you'll mess up the adjustment and it's a bitch to get right. It looks like the IAC just screws into the throttle body at a 45 degree lateral angle towards the battery, correct?

I think my EGR valve is sticky, though I need a another (non-idiot) opinion. People are telling me that the EGR just feels sticky though it really isn't. From what I can tell, the EGR only moves 1/4 to -maybe- 1/2 an inch at most. Should I get more movement than that?

My TPS went bad last fall so I already swapped that. Could be a fuel pump except that if I'm going 45-55 and step on it, she roars to life and goes. As long as I don't step on it for more than a few seconds, or that damn knock sensor trips. The real problem is just at low RPM, especially if I'm turning onto a main street from a small one and have to go quickly. It sputters and wants to die, sometimes just totally stops for 1/2 to 1 second (which is weird) and then goes. It doesn't stall out and no lights come on.

Thanks again for your help. I really want to get this problem solved so I don't stall out on an on-ramp or something and get killed!

Sorry.. I'm having a bald moment. ECM? What's that? I know I have a ESC that connects to the knock sensor & some other stuff. Wait.. do you mean the main computer? Hmm... where is that on a '91?

Thank you again Dinty!

What year is this car?

just thinking out loud:

On my 92's the IAC valve on the throttle body can be removed and cleaned, the EGR can be sprayed with carb cleaner... the throttle position sensor can screw things up like you're experiencing... dying fuel pumps can work except when you step on it... maybe run a timing light on the engine and rev it to see that the timing advances as it should, and that it doesn't jump around... unplug the ECM and spray contact cleaner on the big connector... I had a bad ECM on my '92 that I only solved by swapping...

Sometimes it's hard to figure out if problems like this are fuel or spark related, the symptoms can be similar.

So often when you get into things like this it ends up being a something simple like a bad spark plug, plug cable, cap and rotor etc...
 

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By ECM I meant the main computer which is located to the right of where the front passenger's right foot is, behind the small carpeted panel. But the ECM is probably fine, they seldom screw up.

I took the IAC out of 3 1992's and it was no problem. If you take it out and clean it there's no adjustment needed. Each time the valve was really sooted up so it's worth cleaning, but I don't think that it could cause your symptoms, but maybe it would run a little smoother if it needs cleaning.

It sounds like your TPS and fuel pump are good.

You might try and spray some carb cleaner on the rod in the EGR and work the thing up and down as you do. It should move around 1/2", yours probably moves the right amount but sticks. The classic thing that happens when the EGR is funky is: Especially when the car is cold, you take your foot off of the gas, or slam on the brakes, and the car stalls. It's because there's corrosion on the rod in the EGR. It's sticky and the valve doesn't close fast enough, acting like a massive vacuum leak.

Seems like that type of EGR failure is predictable in these cars, I'd try working on that first.
 

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Discussion Starter #7
Eeh. That's really not the problem, though I will for sure work on that. I'll see about pulling that IAC valve too and clean it out. Hopefully tonight if the rain holds off! =)

The problem doesn't happen when I let off the throttle, it's when I step on it to go.

Thanks for the hints!
 

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Hmmn, sounds like it's NOT the fuel pump, EGR, TPS or knock sensor...

The IAC isn't really a candidate.

How many miles are on the engine and does it idle smoothly (how much vibration at idle)?
The direction of those questions is thinking: is the engine high mileage and actually has some knock that triggers the knock sensor and the engine poops out?

Is it worth trying the car with the knock sensor unplugged to see what happens?

Does the gas spray pattern look normal?

I have this cheap in-line spark plug tester; the type that goes between the plug and the wire that normally goes on that plug. I'd plug that in, and then hook up the timing light without undoing the connector you normally undo when you do the timing. Then I'd run the engine and rev it up by hand while I was watching the timing marks. The illuminated mark should advance smoothly and not jump around. If it jumps around there's something wrong, like maybe a worn distributer shaft. If the spark goes weak maybe it's a bad coil that can't cycle fast enough. I'd try to make the car fail - step on it and see that the spark remains strong and the timing is good.

Also, a stethoscope might be nice to hear if it's actually knocking, since that's what the OBD code was.

Another thing is new stuff, like the knock sensor or TPS, that's actually bad - that can be hard to figure out. The best method I've found is to understand the shop manual and have parts off of a car that worked you can swap.

There is something wrong, and the car is trying to tell you!

Can be frustrating... good luck!
 

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Discussion Starter #9 (Edited)
She's got 122k on the clock but it's actually closer to 130k (the VSS was bad for a good 6-9 months before I figured it out)

Not a lot of vibration, though it is loud. It does spark knock a little bit on acceleration though not enough IMHO to trip a knock sensor.

Gas spray pattern looks good as far as I can tell. A nice conical shape with little to no sputtering.

I suppose that new knock sensor could be bad. Hell if I know.

I have one of those same spark plug testers. I'll play with that. It was raining last night so I couldn't do much. The wife's going to go shopping & a fake bake tonight. Maybe then! =)

Also: the knock sensor going off and the shitty performance are seemingly unrelated. The car always tries to die out on me at low speeds. The knock sensor only when I -really- step on it like to get away from an oncoming Kenworth. And that only happens once every few months or so. The crappy running is literally every day - every time I start the beast.
 

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Dying out at low speeds sure sounds like EGR sticking...

Sounds like vacuum leak problems I've had. You could put a vac guage on it somewhere but I don't know what right is. I could test mine as a reference.

My '92 was running bad and it ended up being a vac hose that went to the ac/heater controls was off. All the vents on these cars are vacuum operated (a bad day at GM).

I know this is stupid but just to cover everything make sure your spark plug wires are 18436572 and you might want to put that tester on each plug. I've had great looking spark plug wires that were broken inside near the plug.

I'd think simple stuff like wires, vac hoses etc..., that stuff fails way more than ECM's and sensors.

I had a '89 Olds wagon that came to life when I took of the clogged cat.

fake bake?
 

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Discussion Starter #11
Dying out at low speeds sure sounds like EGR sticking...

Sounds like vacuum leak problems I've had. You could put a vac guage on it somewhere but I don't know what right is. I could test mine as a reference.

My '92 was running bad and it ended up being a vac hose that went to the ac/heater controls was off. All the vents on these cars are vacuum operated (a bad day at GM).

I know this is stupid but just to cover everything make sure your spark plug wires are 18436572 and you might want to put that tester on each plug. I've had great looking spark plug wires that were broken inside near the plug.

I'd think simple stuff like wires, vac hoses etc..., that stuff fails way more than ECM's and sensors.

I had a '89 Olds wagon that came to life when I took of the clogged cat.

fake bake?
Yeah, I need a good full day to go thru vacuum lines and whatnot. I wouldn't be surprised if my cat's clogged but it looks like it's welded on and i don't have a welder or the skillz to try to get it off. (That's what she said!) Though I honestly haven't looked all that hard. I think I went thru spark plug wires last year but it certainly won't hurt to check the sequence again! =)

Hehe... fake bake = tanning booth visit. We don't get much sun in NW Ohio! I feel like a damn Briton 4/5 of the year!

Thanks again man!

If you ever have any computer problems or needs (or if anyone else does for that matter) feel free to PM/email me (that's my true forte'). I keep tons of spare parts and whole PC's all the time!
 

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Discussion Starter #13
OK.. checked the wires on the 5 I could easily get to. All seem ok. There was a good steady spark going thru, though there was the occasional brighter one that came thru, especially when gunning it a little.

After talking to a few more people, I'm thinking the cat might be plugged up or close to it.

Might be time to call my exhaust friend!
 

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frustrating for sure...

I'm wondering if you held a rag maybe a 1/2" away from the tailpipe and somebody revved the engine if you could sense that not enough air was going through? The engine is basically an air pump.

On other cars I had with clogged cats it felt like the engine was constipated. I'm not sure why it would make the car stumble, maybe I guess if the lack of air flow made the gas mixture super rich.
 

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Discussion Starter #15
frustrating for sure...

I'm wondering if you held a rag maybe a 1/2" away from the tailpipe and somebody revved the engine if you could sense that not enough air was going through? The engine is basically an air pump.

On other cars I had with clogged cats it felt like the engine was constipated. I'm not sure why it would make the car stumble, maybe I guess if the lack of air flow made the gas mixture super rich.
Ha! Yeah it does act constipated, or as I like to say, like someone's squeezing it's neck and choking it.

A guy once told me about the air pump analogy. The quicker you can get more air thru an engine, the better it will perform. I've shared it along in my travels and it's helped!
 

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And so.......?

You can check the knock sensor, kind of, with a ohm meter.
Unplug the wire on the knock sensor, stick one wire from a ohm meter
to a ground (has to stay there by it's self) put the other to the pin on
the sensor. Lightly tap the block with a metal object on the same side.
The meter should flash, the harder you hit the longer the flash (reading).

Same thing to check with it out lightly clamp it in a vice and tap the
vice with a hammer.:smile:
 

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Discussion Starter #17
Yeah, I need to do some homework on that and find out what kind of resistance there should be. I've tried studying it more lately on my way to/from work and I seem to more often get the CEL right after I hit a rough patch pn the road or after going over railroad tracks. I'm thinking more that I have a loose wire between the sensor and the ESC module.

Supposedly the CEL is supposed to indicate a lack of signal from the sensor to the ESC. That would tell me either a very high resistance in that sensor (from the shock of RR tracks or rough roads) or a loose wire.

Thanks though!

More to come...
 

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I am assuming the timing is set to specs.

The knock sensor is basically a microphone.

Can you shit-can the sensor?
i.e. pull it, plug the hole with a correct fitting, and have the knock sensor connected sitting on the side somewhere?

Why fight so hard to keep the part?

Somehow I got through the 60's, 70's and 80's with these same engines with no knock sensor and I can still dance pretty good.

I am of the mind that 90%+ of what GM added to these engines in the last 50 years made them run worse and were just "tricks" to satisfy government bozos that are clueless about cars.

It's not that complicated that all these extra parts are needed. The solution isn't adding parts, it's changing to the right fuel, and all these extra parts, like your knock sensor were more to keep us being Shell and Exxon addicts, and had zero to do with reality.
 

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Here's something that's puzzled me about this whole thread:
How come this guy can't reach the distributer hold down bolt and some of the spark plugs when I have the same car and can reach all of them?

Here's what I came up with...
Here's some of my museum quality tools:

The one on the left is the standard 3/8" socket ratchet. I must have 7 or 8 of these, all pretty and shiny because they are, to me, next to useless. They always come with sets and I can imagine that that's what many people use all the time. I use them maybe 4 times a decade.

The stellar setup in the middle is what I use. It's a New Britain brand ratchet - old school steel like you don't find anymore, but that's not the point. It's longer than the stock wrenches and has a pivoting head that I put masking tape around to make it semi-flexible. I leave a 12" extension on it and that's the default way I use it. That way I can put my left hand on the extension to keep the socket at the right angle, and with the extension I'm much less likely to hit my knuckles when the socket breaks loose. That's my stock wrench setup I always try first. It gets my hands up out of the "danger zone".

I rarely use just a socket on a straight ratchet - that almost never works for me.

The extension on the right is the shortest I can find, and I can't reach the spark plugs on GM engines (especially #8) without that. I use it a lot.

Also, I avoid 12 pt sockets and cheap brand sockets, and have a strong preference for old steel. I use 1/4" tools when possible, and a lot. Craftsman from 1963 is a totally different animal than 2009.

I've had sockets explode and hit my glasses like they were shot out of a rifle, that's why I don't like cheap stuff.

This is stuff that's helped me, as usual I hope it helps you.
Everybody ends up finding their own way.
 

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Discussion Starter #20
I suppose that knock sensor could be neutered like you say, I never thought of doing that. I honestly have never even heard of a knock sensor before all this BS started, let alone it's true function. I just do what I know to do, search google and then ask here! :biggrin:

See my "Caprice timing" thread. I posted a pic there getting as close as I could to show the distributor and thus the bolt. From what I can tell, I'd need a wrench shaped like steps and hands about 1/2 the size they are now. I have rather large hands, which makes work like that difficult at best.

Which is also a problem getting to spark plugs 8, 6 & 4. I can take off the wheel and get to number 2 by going under the inner fender and ripping off that old tar-paper cover. I still haven't figured out how to get to those 3 plugs.

I think timing is ok, I'm also having problems with that. (I know, quite the sad sack!) The timing lights I'm using don't have a very bright light and it's hard to see especially during the day. And I'm not totally certain that I have the correct electronic advance connector. I think I do, timing seems to change when it's unplugged as opposed to plugged in, but I get this incredibly loud hiss that I can't localize.

It's really a matter of having the time, the proper tools and the patience to do it. Time has been in short supply this summer, since we're either busy with other stuff or it's raining. The proper tools I'm figuring out slowly but surely. The patience will come when I'm not rushed because my girls have to get to baton practice or some shit. I'm working in the driveway usually in the evening basically right under my kids' window so I can't work past bedtime.

Ugh! :confused:
 
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