Spark Knock

[rico47635]

Well, here I go again. *sigh* I thought I had everything lined out on this truck. I bought a camper today. It's an older one, '74 18' Prowler. I know this thing doesn't weigh more than 3600-3800 lbs. I hook on to it after paying the fella we get it from, head on down the road grinnin from ear to ear 'cause we finally got a camper, get down the road just a few miles and there it started--spark knock up the wazoo.

I read where my truck has a knock sensor but I don't know exactly where it's a located. There's a way to see if its working and I want to try it before I buy a new one. If it turns out to not be the knock sensor, what can I do to not have this problem when towing? Should I switch to premium gas any time I am planning on going camping, should I adjust the timing (something I do not know how to do on a TBI engine), or should I just say the hell with it and get a one ton dually with a 454 to tow my itty bitty camper (I actually like this idea best ). 1988 K1500 5.7L TBI

 

[FastOrange]

knock sensor is just above the oil pan on bottom of block.

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[rico47635]

Well, I tired the tapping on the block near the sensor thing, and there was no change in how the truck ran, so I am assuming that the sensor is bad. That is what it said in the article I read. You would think that the SES light would be on, but it isn't.

 

[DRAGGIN95]

Have you chacked your timing to make sure it's set at 0 degree's or TDC?

 

[rico47635]

Nope. I do not know if the procedure for checking timing on a TBI engine is the same as a carbd one. Is it? This is my first TBI vehicle that I have worked on myself.

 

[DRAGGIN95]

Well here is a quick run through, first get the truck up to normal running temp. then shut off the truck and unplug the EST wire, it's a tan wire with a black stripe, on 88-early94 it's under the black plastic cover on the passenger side firewall, it's a single wire connector, and it's the only one like it. On late 94 and 95 it's under the glovebox inside the truck. unpluging this wire takes out the computer controlled advance so you can correctly set the timing. The next step is to set the timing to 0 degree's or TDC on these truck's, also I alway's loosten up the distributor hold down first it's a 14mm bolt, when you have the timing set to 0 shut the truck off, retighten the holddown bolt, and then plug the single wire connector back in. That's it, one thing to remeber when you unplug the single wire, the service engine soon light will come on while it's unplugged and that's normal, it will go out after you plug it back in. I hope this help's!

 

[rico47635]

Thanks. So, once I disconnect that wire, evenything else is just like setting the time on anything else. Sounds easy enough. I will get a timing light tomorrow and get it taken care of.

 

[DRAGGIN95]

Yeah after the wire is unplugged it's basically like timing a regular old HEI chevy.

 

[rico47635]

An update. Well, this didn't quite go as easily as I had hoped, but we got it done. I had a little trouble finding the tan wire with the black stripe on it, but I finally found it. When I checked the timing, it was all the way up to the 12 mark! So, we got it down to the 0 mark and buttoned it up. This is where things got interesting.

I went ahead and bought the knock sensor. It was only $30. My son kept saying something was loose on the connector on the one that was on the truck, so I figured something was broken. Sure enough, the plastic part of it was broken and the pin was bent. What we didn't realize was that the engine coolant would come pouring out of the hole where the sensor mounts! My poor son got a very unpleasant surprise. Thankfully, he didn't swallow any of the antifreeze when it poured onto his face.and we got the new installed.

Back to the timing issue: We knew that the coolant had drained out of the engine. The timing thing was real quick, so I did it with whatever coolant was left in the system from replacing the sensor. No biggie. I sent my son in our van to go get some more coolant. I started pouring it into the engine and could barely get one gallon into it. I knew that the system had to hold more than that, but I couldn't get it to take more. So, I thought I'd take the truck for a little spin around the block to see if that would help (of course, I filled up the resevoir). I got in the truck to take off, the damn check guages light was on, and the temp guage was pegged. The only problem was that I knew good and damn well that the engine wasn't hot! So, I went for a ride, burbed the cooling system (thank you for a good cap on the radiator) and finally got the thing to take another two gallons (one was water, the other antifreeze).

Oh! I almost forgot to mention this. While we were doing the timing thing, I took the air cleaner assembly off. I happened to notice that something didn't quite look right about the plugs on one of the injectors. I could not believe it when it dawned on me that it was just sitting over the injector and not fully plugged in! I don't know if it was arcing this whole time, or if it was connected just enough to work, or what the deal with it was. All I know is that the injector plug on passenger side was not clicked into place.

I am pleased to report that my truck is now a tire squeeling get the eff outta my way cause I'm coming through powerhouse! I cannot believe the difference in how this thing runs! The spark knock went away, the truck sounds much better coming out of the exhaust, the engine doesn't shake a bit, and I have more off the line power.

I really hope that I am done for a while with having to work on this truck. I realize this is a Chevy forum, but I have to be honest with you. I have had to work on this Chevy more in the last five months that I have had it than I have had to work on any of my Fords in the last five years. I don't regret buying this truck because I think it has a lot of that "cool" factor that Chevy's are known for. I just want to get it to where I don't have to work on it every time I turn around.

 

[FastOrange]

Sounds good man!

I think no matter which kind of truck you buy, you always get one that has problems, i have sunk over $2000 into my 1996 F150 in the last couple months.