Need to tune the old gal up

[Donf]

The truck - 1999 4 door, 2 wheel drive, LT Tahoe.
The history - owned by me since new, garage kept .Light duty, 140,000 miles. dealer maintained until 2009. Not driven since 2012.(but started every 3 or 4 months). No rust, paint/leather good to excellent, no accidents. Cleaned the throttle body right before parking it in 2012.
The issue - misfire codes, downstream O2 sensor codes (both). Review of paper work indicates that plugs/wires/ cap & rotor have not ever been changed (!).
Advice so far - The guy at the State Inspection facility suggested that I just do plugs/wires cap and rotor then rund 2 tanks of gas w/RXP through it to clear o2 sensors. I'll likely follow this advice.

The question - Reading around here and other web sources seems to indicate that these old Vortecs are happiest when treated to OE parts during tune ups. Seems reasonable, not too expensive, and easy to obtain. BUT - I see 2 sets of wires, apparently the same wire, one set is simply 'cut to length' as were the original wires and the other are a 'one size reaches all cylinders'. For the price difference I am inclined to spend a bit more for the proper length, however various reviews on-line indicate that it might not be the best choice. A fair amount of complaints of assorted causes for the correct length set and many happy reviews for the single length wires. Still, many, but not all, do not seem to be from Tahoe "enthusiasts" but just guys on the street. I would prefer to stay with the GM parts and since I'm not upgrading the coil and using stock plugs it doesn't seem worth it to get 'performance' wires.

 

[bigfootchiro]

Welcome to the forum! Some people will get DIY kits, which you would cut to length based on your current plug wires, but I would rather spend a few more dollars by purchasing the cut-to-length wires. There are lots of good brands out there; however, you are right, some prefer to stick with AC Delco or Delphi. On a side note, when it comes to those brands and certain parts for your truck, for example, I bought a CarQuest water pump vs AC Delco, because the AC Delco warranty was 1 years, vs Lifetime with the CarQuest (and it was cheaper).

A new cap and rotor would not be a bad idea, plus check your timing with a scanner that reads live data if you have one. If not, you can buy a wifi or bluetooth OBD reader, plug into your OBD port, and hook up to your phone or tablet. I use DashCommand (with the Chevy add-on pack), and some like Torque app. This allows you to read/clear codes, read live data, record live data to play later, set up additional gauges to watch, and much more.

 

[Donf]

Thanks. Just ordered the wires. Don't really like long loopy wires flopping all over the engine bay anyway.
I'm embarrassed to admit I didn't think about the timing! Thanks for the info on the OBD suggestion, I've been saying I've been going to get one for a while and this looks like a good "excuse".

 

[iamdub]

The timing isn't adjustable on these engines. If there's a problem with the timing, it's because a crank or cam or maybe even a knock sensor is out of whack. You'd get code(s) for any of these. Really, the only thing involved in a tune-up is replacing the ignition components and fuel and air filters if they're due. A good fuel and top-end engine cleaning wouldn't hurt, either.

Sitting is bad for any engine, especially these older ones. It's good that you ran it, but 3-4 months is still quite a stretch. You heard right that these engines are finicky about wanting OEM or at least good quality aftermarket parts, especially sensor and ignition components. I'd stick to ACDelco, Delphi or Borg-Warner (now BWD?) with brass terminals for the cap and rotor. There's a good chance that the cap's terminals and rotor corroded with it sitting and is causing the misfiring. If it had ethanol gas in it, that can cause the fuel system to be gunked up and injectors clogged which could also cause misfires. The downstream O2 codes could be catalyst inefficiency codes from the catalyst collecting moisture over such a long period of time. Get everything ahead of the cats (fueling and ignition) squared away and let the cats get hot to burn themselves clean a few times and that problem will likely clear itself. I'd replace the fuel filter and get as much fresh gas in it as possible. Check and clean the spark plugs while you're tuning up the ignition system. If they're original, surely they're worn. Factory original or direct-replacement (AC Delco or NGK) are best here as well- no gimmicky plugs necessary.

 

[bigfootchiro]

The timing isn't adjustable on these engines. .

The timing is adjustable on the Vortec 350, you just can't use a timing light to check the timing. Using live data on a scan tool, you bring the RPMs up to around 1100 RPM, then check CMP Retard, which should be between -2 to 2 degrees to be "in time". The distributor hold-down bolt is loosened enough to where you can just barely turn the distributor while holding at 1100 RPM and watching CMP Retard, making sure you bring it as close to 0 as possible, tighten back down, and you're good to go.

 

[iamdub]

The timing is adjustable on the Vortec 350, you just can't use a timing light to check the timing. Using live data on a scan tool, you bring the RPMs up to around 1100 RPM, then check CMP Retard, which should be between -2 to 2 degrees to be "in time". The distributor hold-down bolt is loosened enough to where you can just barely turn the distributor while holding at 1100 RPM and watching CMP Retard, making sure you bring it as close to 0 as possible, tighten back down, and you're good to go.

Got me on a technicality. lol

 

[bigfootchiro]

Got me on a technicality. lol

Lol I knew you knew better than that.

 

[Donf]

Thanks again guys. Yeah - the plugs are original. I suspect they ain't going to be pretty when I get them out. The codes came up BEFORE I parked her, I'm hoping that the cats were just throwing a code do ti the ignition components extreme age and wear. If not I can do them too.
As far as timing, as I said, always looking for an excuse to buy a new toy.....err, I mean tool. (As far as my wife is concerned, an ABSOLUTELY NECESSARY tool. )

Top end cleaners - I ran a half bottle of Marvel Mystery Oil in it for a few minutes last week. drained, filled, new filter, repeated with 2nd half, then drained refilled and new filter with straight synthetic. Hopefully that cleaned it out sufficiently. So far, no oil leaks.

 

[iamdub]

Thanks again guys. Yeah - the plugs are original. I suspect they ain't going to be pretty when I get them out. The codes came up BEFORE I parked her, I'm hoping that the cats were just throwing a code do ti the ignition components extreme age and wear. If not I can do them too.
As far as timing, as I said, always looking for an excuse to buy a new toy.....err, I mean tool. (As far as my wife is concerned, an ABSOLUTELY NECESSARY tool. )

Top end cleaners - I ran a half bottle of Marvel Mystery Oil in it for a few minutes last week. drained, filled, new filter, repeated with 2nd half, then drained refilled and new filter with straight synthetic. Hopefully that cleaned it out sufficiently. So far, no oil leaks.

MMO in the crankcase (pouring in oil filler spout) helps to clean gunk in the oil passages (galleys, lifters, push rods, etc.). What I believe is more important is to clean the upper end (intake manifold, throttle body, etc.) but especially the fuel system. Old gas sitting in it can gum up the injectors and cause a weak or total loss of fueling to some, or eventually, all cylinders.

 

[HiHoeSilver]

MMO in the crankcase (pouring in oil filler spout) helps to clean gunk in the oil passages (galleys, lifters, push rods, etc.). What I believe is more important is to clean the upper end (intake manifold, throttle body, etc.) but especially the fuel system. Old gas sitting in it can gum up the injectors and cause a weak or total loss of fueling to some, or eventually, all cylinders.

Kreen for both short of actually getting in there.