New AC Delco Iridiums at 80K ???

[NewGuy]

I have a 2004 Tahoe with the 5.3L engine. The idle has gotten a little rough recently. It is noticeable enough to see the steering wheel shake slightly upon idle. I asked the dealership and they suggested an injector cleaning ($200+), but not a spark plug replacement until 100K.

I can't help but think that at least one of the OEM AC Delco Iridium plugs is going bad. I bought a set at AAP for ~$7 each and I am considering a change this weekend. Has anyone else had a similar experience? Did changing the plugs smooth the idle? Has anyone found the injector cleaning a benefit?

Thanks.

 

[porcupine73]

A cheap thing to try might be a bottle of redline SI-1 injector cleaner, maybe $8 at the chain parts stores, I've had good results with that. Yah, Ok, so iridiums aren't supposed to need a change until 100k doesn't mean something can't go funny with them before that.

 

[Matt_S]

Spark plugs will gradually lose their efficiency over their lifetime and I think you will notice a difference if you change them now. I've also heard that the intake cleaning is beneficial, but I'd be more prone to do that myself. If you go that route, just be careful of the MAF sensor. Use only 90% rubbing alcohol, or something that evaporates cleanly and a soft touch to clean that.

 

[JHZR2]

what I fround on my 4.3L v6, is that a slight shake will occur that coincides with some leakage at the coil and the boot of a spark plug wire that is otherwise A-OK.

Heavier wires and a new coil fix it up.

JMH

 

[Mike_dup1]

Quote:

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OEM AC Delco Iridium plugs

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How do you know you have Iridum plugs as oem?

see this, it would suggest otherwise..

 

[unDummy]

Plugs don't last forever. Its life depends on original gap, the engine, and the driving style.

If it is an easy remove/replace, you can check/clean/regap them and see if issue resolves. If plug is PITA to replace, then definitely invest in new super duper plugs.

I like the FI cleaner recommendation. Run a couple tanks with quality FI cleaners. Redline, Regane, Techron, Seafoam, B12, and a bunch of others are available at your local stores. Some, like Regane and Techron, come in big and little bottles. Make sure the bottle treats the fuel tank capacity. If not, use the bigger bottle or 2 small bottles. A little IVD or FI deposits can cause the same issues.

 

[Islandvic]

Dont pay the stealership $200 for a fuel injection service. Total rip off.

Go ahead and change the plugs. Here are some other suggestions they may help, and are good maint anyways.

Buy a can of SeaFoam Aerosol Deep Creep, and with shop shop towels and a soft tooth brush, clean your Throttle Body.

Next buy a can of Quick Dry Electric Contact Cleaner and hose down your MAF sensor with it. Be wure not to physically touch the sensor with your finger or tube from the can. Just hit it with the stream of cleaner. Only use this type of cleaner for the MAF sensor.

Try changing your fuel filter. WIX makes an excellent filter.

Also try running SeaFoam, Chevron Techron, or the Redline fuel system cleaners for two tanks of gas.


I have a feeling it may be the fuel pressure regulator. I had one replaced on a 5.3 '00 Silverado in 2005 only after 20k miles of service. GM was having problems with them on the Vortec truck engines, though they may have resolved the problem by your model year. After it was replaced, no more idle issues!

Good luck.

 

[Terry]

Based on poor oil analysis and MPG results for SBC modular applications above I have been recommending to my GM customers to run the AC iridiums gapped at .040 with tremendously GOOD results in terms of drivability,cleanliness of oil analysis results and MPG gains. One negative you will hear is slight spark knock and ECU advances timing. Using FP seems to help, I also suggest cleaning the IAC probe and any areas you can find dust/oil/carbon deposits.

Pull a stinking plug and look for yourself but MOST 4.8/5.3/5.7/6.0 engines at 80K will have had Platinum tipped plugs and the gap and erosion will not be optimum.

Good luck. Use oil analysis (properly interpreted) to gain insight and a predictive, proactive approach to vehicle maintaining and save $$.

Terry

 

[NewGuy]

Thanks to everyone for all the comments. Terry and Mike were exactly right. The OEM plugs were platinums and the widest gap was almost 0.080 (vs. 0.060). I replaced these plugs with the AC Delco 41-985 (Iridiums) suggested by the manual, Terry and Mike. The gap on these Iridiums was 0.040.

The engine is now much smoother with a noticeable increase in power and response. I did hear the spark knock at first, but it went away quickly. My MPG had dropped significantly over the past 3 months. I have a 250 miles trip to Atlanta on Monday. It will be interesting to compare the MPG.

I run a tank of Techron every 3K miles. I also used FP until I ran out 6 months ago. I had a feeling that the spark plugs were the issue. The rough idle seems to be much improved.

Thanks again for all of the advice and comments. I had a Dyson Analysis performed in 11/05 on this engine with good results. I plan to submit this existing sample at 5K for another oil analysis. I will post the data.

 

[Matt_S]

You probably had the double platinum plugs with the platinum puck on the ground electrode that tends to fall off with use. That's a common problem that's solved by the iridium plugs since they don't have that same puck.