GM people...a little help? 

"HeycanIgetaride" (latetotheparty72) 01/26/2015 at 19:36 • Filed to: None

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Hi fellow Opponauts,

Been forever since I've been able to post so I don't know if this will even show up...seems like the last couple of times I've tried to do something it never got out of gray. I guess that's the price I pay for being a teacher instead of working in an office and being able to read Jalopnik/Oppo all day—not that there's anything wrong with that.

Anywho, I have a bitch of a problem going on with my 2000 GMC Sierra, 4.3L V6. I posted long ago that I thought the transmission was possibly dying, but the shudder and slipping turned out to be a misfire problem instead. So I took it to a guy down the road with great reviews on Yelp and paid $500 for a new cap and rotor and to reset the timing. It worked great, for about 6 months. Then it started again—just a slight blip now and again, a little shudder usually only at highway speed.

Being a pretty low-level home mechanic short on experience but long on desire to learn, I researched for hours and decided I'd try to fix it myself this time. I bought a brand new AC Delco distributor, disconnected everything to access the old one, and pulled the #1 spark plug. As far as I understood it, if I could get the #1 cylinder to TDC then I can simply use the marks on the distributor to set the timing and make sure it's installed correctly.

So this weekend I go out and buy a damn $30 !!!error: Indecipherable SUB-paragraph formatting!!! , but the shitty little rubber tip doesn't fit into the spark plug hole. Then I go to OReilly and rent their compression tester kit with the screw-in adapter and hook it up to my gauge. I get under the truck and hand turn the crank....nothing. The needle doesn't move. Either way. I try and try and try....nothing. I re-installed the old distributor and try again. I can see the rotor moving, at least a little, so ostensibly it's working, but still the needle isn't moving. I messed with this damn setup for hours and wasted my whole Saturday and got nowhere but $30 poorer and am so frustrated because this should be a very easy fix, assuming I can get it to TDC. But I can't.

What am I doing wrong? Any advice/tips/help? About ready to call in the shadetree guy but thought I'd see if my fellow Opponauts might be able to help first.

As always, thanks for reading and here is a 1951 Ford Deluxe for your time:

thebigbossyboss > HeycanIgetaride 01/26/2015 at 19:42

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A) No idea. But B) Welcome back and hopefully someone smarter than me can help you. Engine timing scares the bejeezus out of me.

bob and john > HeycanIgetaride 01/26/2015 at 19:43

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hmm, unless he really bugger up the install, i have a feeling its something else as well.

what you got wasnt for testing engine compression. it for literally every thing else.

to test for compression, it best to have a buddy or 2 around. you want the starter to be doing the cranking.


try a new set of spark plugs. make sure they are gapped right and the correct ones. then, make sure you didnt bugger up the distributor timing or anything.

Arch Duke Maxyenko, Shit Talk Extraordinaire > HeycanIgetaride 01/26/2015 at 19:46

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Sounds like there's no compression on the cylinder, which would be your problem. But that's assuming that the gauge was working properly, and for that, I have no idea.

HeycanIgetaride > bob and john 01/26/2015 at 19:50

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Ok, so I screwed up and got the wrong gauge...what can I say, I am pretty new to this stuff. I don't necessarily need to test the compression as be able to see when it's going from upstroke/downstroke. So what do I need to gauge that?

The plugs were changed (by a professional) about 20,000 miles ago, if that makes any difference. The one I pulled was slightly blackened but didn't look particularly bad. I guess six plugs would've been cheaper than buying the wrong tool and a new distributor.

bob and john > HeycanIgetaride 01/26/2015 at 19:58

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so you got the wrong gauge. meh, big deal.

for what you want to do...the engine should have smoe sort of mark on it where its TDC. if not.

get a siff peice of...something. a long ruler, a metal tube, something. that fits in the spark plug who. just get your buddy to turn it over BY HAND until it get to its highest point.

AMGtech - now with more recalls! > Arch Duke Maxyenko, Shit Talk Extraordinaire 01/26/2015 at 21:30

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There's no compression because the engine was turning far too slowly. It has to be turned by the starter to register properly. If it were completely dead it wouldn't ever fire.

AMGtech - now with more recalls! > HeycanIgetaride 01/26/2015 at 21:35

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I use a screwdriver with about an 8" shank to feel where the piston is. You don't need a compression gauge for this, as Peter Black said.

To properly set timing after installing the new dizzy you will need a timing light, you can't really just slap the new one in where the old one was as that could still be a few degrees off. That will get you close enough to run but rarely will that get you right on.

This may be obvious to others but I've been away from GM for a long time. So what brought you to the conclusion that you need a new distributor?

AMGtech - now with more recalls! > bob and john 01/26/2015 at 21:38

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I agree that it may be something else causing all of this. Could be something like moisture getting into the cap and corroding the contacts. Or even just cheap replacement parts, or a weak ignition coil that's strong enough to fire through new contacts but not worn contacts.

Nobi > HeycanIgetaride 01/26/2015 at 21:47

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I ran into this on a Silverado like yours once. The fix was installing a flex pipe in the exhaust. Apparently when cruising, the exhaust resonates so badly it shakes the whole truck to the point where you think there's something wrong with the trans.

HeycanIgetaride > AMGtech - now with more recalls! 01/26/2015 at 21:49

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Well, at the risk of sounding like a complete idiot, the cap and rotor had been changed twice in the last 20k miles or so, including the last 6 months as described in the original post. That clearly hadn't worked and the plugs and wires had also been changed in the last 20k when I had the head gasket done, so in the various places I had looked around and tried to research that seemed to be the next logical step (of course through all this, the CEL only came on intermittently, never long enough for me to have it read and get a better idea). When I found the new one on Amazon for $170 I figured that was cheap enough to give it a shot, especially on a 15 year old truck with 150,000 miles that I plan to keep for some time to come.

That said, it didn't look at all bad when I pulled it and I immediately wondered if it had been necessary. Oh well, a good opportunity to learn more about my truck I suppose. Seems the only way for me to gain experience working on cars is to throw caution and reason out the window and try it and see what happens, so I guess I will mark this one down as a learning experience.

I guess I will try the screwdriver trick—saw someone do that on Youtube somewhere but I figured using a gauge seemed more legit.

HeycanIgetaride > Nobi 01/26/2015 at 21:52

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Funny you mention that...that is an altogether separate problem that I'd been having and the reason I took it to the mechanic to have the timing reset in the first place. It does exactly what you described but only in the window from like 45-60 mph and not on acceleration. Interesting to note....If I can manage to make it out of this without destroying the damn thing I will have to investigate this further. Thanks for the tip.

Nobi > HeycanIgetaride 01/26/2015 at 21:55

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I think there's a bulletin through GM on it. If you know anyone with access to that, it'll tell you where to put the flex pipe.

XJDano > HeycanIgetaride 01/26/2015 at 21:55

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Ok I have learned that YouTube is your friend for stuff like this. The video above isn't great, but if nothing else is about minutes of comedy.

This second video may help more I didn't watch the whole thing, but it's a 99 jimmy with a misfire code and I guess the guy fixes that. He also goes over video one at about 7 minutes in and looke like there is a second part to it.

Part 2

Hope this helps. Good luck.

AMGtech - now with more recalls! > HeycanIgetaride 01/26/2015 at 22:22

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It does seem like the next logical step, but distributors are actually quite simple and aren't often the cause of issues like this. Just did an image search on that dizzy, looks like it's just the mechanical rotating mechanism with a pick-up coil (the sensor that tells where the engine is at in its revolution). So there's really not a lot to fail there. Was there any moisture in the cap or signs of corrosion?

Faults should remain stored for a while even after the CEL extinguishes. So it wouldn't hurt to get it scanned.

I'm kind of leaning towards ignition coil, but like I said I've been away from GM for a long time.

The gauge you would actually want to use to find TDC would be a dial indicator. Though it would do the exact same thing ad the screwdriver with the addition of telling you right down the the thousandth where the piston is. But that kind of accuracy isn't necessary unless you're rebuilding/blueprinting the engine.

AMGtech - now with more recalls! > Nobi 01/26/2015 at 22:23

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Huh. Neat. Learn something every day.

HeycanIgetaride > XJDano 01/26/2015 at 23:19

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Awesome, thanks. Will give these a watch and see what I can figure out.

Tinfoil Hat in a thunderstorm, now with added diecast > HeycanIgetaride 01/27/2015 at 00:22

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Just read through the comments and this wasn't mentioned.

Make sure your on the compression stroke and NOT the exhaust stroke! If you get the piston TDC on the exhaust stroke your timing will be exactly 180 degrees out. Not sure if there's an easier way but the way I know to check involves rocker cover removal to check that the valves are closed, if not, and the piston is up the top then your on the exhaust stroke. Good luck

Tinfoil Hat in a thunderstorm, now with added diecast > Tinfoil Hat in a thunderstorm, now with added diecast 01/27/2015 at 03:29

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Oh, of course another way to check if it's the compression stroke would be with a compression tester! (but obviously you had issues trying that already.)

Nobi > AMGtech - now with more recalls! 01/27/2015 at 11:46

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Yeah, never would have thought it was the exhaust. When I worked for a Honda dealership, we had a 2004 Silverado come in with a vibration whenever the torque converter would lock up. I told them to send it to a Chevy dealership, but they wanted the money to stay in-house. We put a new driveshaft in it, rebuilt the transmission, then replaced the transmission and torque converter. Nothing worked. Finally, they listened and sent the truck to a Chevy dealer, and the fix was putting a flex pipe in the exhaust. Problem solved.