My wifes 04 Rainier with the lm4 5.3 spark knocks pretty heavy on regular but does not on premium. Did I miss something and have just been putting the wrong fuel in or is there maybe something else I should be looking at? I have no lights on and do not as of yet have anything to scan with.
Anyone ever had a problem with spark knock?
- Thread starter Biff85ta
- Start date
There are knock sensors that advise the PCM to deal with low octane fuel. I have no experience with modern engine knock reduction, but before electronic everything you also had to make sure you had clean cylinders without carbon build-up to generate hot spots that could promote preignition. I'd try a Seafoam treatment through the brake boost vacuum hose to see if you can remove some carbon.
How many miles, and what other maintenance history do you have? It's all possibly relevant.
How many miles, and what other maintenance history do you have? It's all possibly relevant.
135k and unfortunately I know nothing of the cars past. We bought it about two months ago and it nearly burnt on the way home and then it sat for almost a month waiting on a new harness from the dealer I purchased it from. It doesn't do it at all cold. It actually surprises me to get knock and makes me wonder if maybe someone has maybe put some sort of tune on it.
n0kfb
Member
- Dec 8, 2011
- 104
the roadie said:
20 years ago I would have not hesitated to say 'with the engine running at fast idle tap on the engine block with a hammer near the knock sensor and listen for a change in RPM". Today I've got to say I don't know.
How about this: "Go to the library and crack open the shop manual."
-- Dan Meyer
Wooluf1952
Member
n0kfb said:20 years ago I would have not hesitated to say 'with the engine running at fast idle tap on the engine block with a hammer near the knock sensor and listen for a change in RPM". Today I've got to say I don't know.
How about this: "Go to the library and crack open the shop manual."
-- Dan Meyer
That was my first thought too.
However, that only tells if the KS is working.
Since the OP says using premium fixes the problem, as Rodie stated, run a bottle or two through to get rid of as much carbon build up as possible first.
If the problem still exists, a competent mechanic will need to check to see if the engine was tuned for premium.
strat81
Member
- Dec 29, 2011
- 399
Biff85ta said:
My 2004 Rainier V8 runs fine on 87 octane. The PCM is stock (no tune). I'm about 1,800 feet above sea level and run straight gasoline, not E10.
+1 on trying a Sea Foam treatment. Some GM Top Engine Cleaner may also work. Run a tank/bottle or two of Techron through it too.
Pittdawg said:What nearly burnt, the engine?I would have taken that heap right back if that was the case...
The main interior harness melted from dvd install that someone removed and just shoved the exposed wires up under the headliner. The harness was a wad of melted and the dealer footed the bill for the new one as well as giving me a loaner. They probably would have doen the labor as well but I am kinda funny about other folks touching my cars. It was truly a freak thing as the fuse for the radio when it blew somehow fused itself together and then the mess started.
Wooluf1952 said:That was my first thought too.
However, that only tells if the KS is working.
Since the OP says using premium fixes the problem, as Rodie stated, run a bottle or two through to get rid of as much carbon build up as possible first.
If the problem still exists, a competent mechanic will need to check to see if the engine was tuned for premium.
I just added the torque app to my Phone and will be picking up a dongle so I can scan it and see what is going on. I wish there was something available for the GM OBD2 stuff like there is for my 95 firebird that would allow me to pull the tune and compare without spending an arm and a leg.
Finally got the bluetooth adaptor and it happened to set a code today for the knock sensor too. I think I know where the problem is.
