Hi all,
I have problems with my -91 BLAZER S-10. I have too high HC so I can't get it to pass inspection and I also have quite high fuel consumption and some petrol smell. I have connected my laptop to the ALDL-interface. No error codes.
I have changed oil, plugs, spark wires, distributor, O2 sensor but nothing seems to do any bigger difference. I have tested the fuel pump and it's OK too...
One thing I discovered today however, is that there is no knock sensor. None what so ever...The wire just hangs there. Could this maybe be the root to my problems? Shouldn't I get an error code, 'Check Engine' or something like that when there is no knock sensor present? No knock sensor must have an impact on the ignition I would imagine.
Please let me here some of your thoughts on these matters!
Best regards and thanx in advance,
/Kim

 

Run your tank down to about 1/8 or less, then go buy a gallon bottle of METHYLHYDRATE at your parts store, pour it all into your tank, go for your test, then dilute it with a full tank of gas. This stuff is really hard on the gaskets in your fuel system, so dont go out hotrodding cause you can peel the tires really easy now. Do the test, and get gas back in there. You may need to retard the timing a hair cause alchohol pops much faster than gasoline. I didnt adjust anything when i did mine.

Its alchohol, which is not an HC (Hydrocarbon) and therefore will not register high HC when you burn it through your engine.... You will have alot more power than on gasoline too, and yes the engine will make more noise.

I did it and it worked like a charm. I used 2 gallons into an 8th tank and brought my HC number down by over 100 points.

If they make your truck turn the dyno with the rear tires, make sure you blow max pressure into your tires. Harder tires have less rolling resistance on the dyno.

You gassy smell and major consumption is more than likely the internal leak that most of us have battled. Do a search on CPI SPIDER and see the threads we discussed this many many many times over. Every week actually. Your pump can test fine, but that doesnt mean you arent leaking down. How did you test your pump?

As for the knock sensor not being hooked up... you must be looking at the wrong wire, cause you sure would get the SES light if it wasnt working. Your knock sensor is down behind your distributor on the passenger side I beleive. Really hard to see. Take a photo for us please. I think you might be seeing your fuel pump bypass wire dangling there and have it confused.

 

The knock sensor should be located behind the left cylinder head down on the block where it extends out to meet the transmission bell housing sticking up towards the brake booster. Is this the location of the wire you are questioning?

 

Hi again,
Thanks for your answers so far...
I have taken a couple of pics to clarify. The first shows the connector in detail. The wire is blue and short. The second pic shows more of the location. A bit blurry though.
I still can't find the knock sensor. I have been searching like mad with flashlight, mirrors, standing on my head... Can't find it!
I have also been trying to get a knock reading on the computer by hammering on different locations on the engine where the sensor might be hiding, different rpm on the engine but not a single knock indication.
Am I missing a knock sensor or...?!?
/Kim

 

Is it possible that the engin runs quite well (but with the problems I have alredy mentioned) without the knock sensor???
'ohsofly': Thanx for your answer! But about the CPI spider. My engine have no CPI spider I believe. It's not a Vortec engine. VIN Z. Or am I wrong about this? I know that I can pass tests with alcohol, but that won't fix the problem permanently. I really want to understand why I have these problems with the engine and to fix them by the book.
'swartlkk': Thank you as well for answering. Look at the pics in my last message. I believe that I am in the right neighborhood, but I just can't find it.

Any ideas will be most welcome! //Kim

 

Here is a schematic from the newer SCFI engines, but the knock sensor location shows the same for your truck:


As far as it running correctly without the knock sensor... Well, the engine won't know if there is detonation so it won't be able to dial back timing to save itself. But if you aren't having problems with detonation (pinging), then the knock sensor really wouldn't be doing much.