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Intermittent spark knock under acceleration

14K views 13 replies 5 participants last post by  fsmith2845 
#1 ·
I have a 2004 Dodge Caravan sxt with the 3.3L V6 engine. It has had instances where under load (going uphill, slow accelration, etc.) there is a distinct and annoying spark knock. It was very intermittent at first but got to be more frequent. (BTW this does not cause it to throw a code). I took it a few weeks ago to the Dodge dealership near where i work (ironically one of the dealerships that Dodge cut loose) and was told after diagnostics that the PCM on these cars are sometimes defective and would need to be replaced and reflashed. Oh and the kicker, they don't make them anymore, but can get a refurb for it. (doesn't that mean it would be defective too i thought). Anyway, I was wondering if anyone else had encountered this one.

I wasn't quite ready to lay out $800 at the time to do it:Wow1::Wow1:, just tried to adjust driving style to limit the amount of knock (and also fuel system additive has helped a little). Oh and a new development, getting a code P0406 today. Used my reader and the internet (this forum) to figure out i need to replace the EGR valve. Wonder if this would help my other situation (doubt it but one can still dream right?)

Would appreciate any input on the spark knock issue though.. thanks all
 
#4 ·
It used to be possible to clean these babies, I have done it. Is that still the case? Try highest octane gasoline when you get on empty next time, if that stops it, try midgrade, if that works try half mid grade half regular. Cheaper than the alternatives. There is a thread about a month old, even less that has all kinds of advice on eliminating knock (some is fine, and expected).
 
#5 ·
Welcome to the forum fsmith2845
Yes, If you have an EGR (not all came with one) that is a very good place to start. You're not sharing miles.

When was the last time you got out on the highway and opened it up? What's the "quality" (not grade), of the gas (and station) you're filling up at? If your EGR has been leaking for awhile, it may be time for plugs (and wires). If you go this route, make sure you get a good 9mm wire, not the cheap 7mm. There are lots of threads here discussing plugs. Simply do a SEARCH and happy reading. :thumb:
 
#11 ·
Forgot to include miles... it's currently at 87K. It get driven daily back and forth by my wife in commuter traffic. Occasionally I drive it to work to "give it good blow out" (my drive to work is almost all interstate and light traffic). I haven't done that in a while, but will likely do so once i get the EGR is replaced. As for quality of gas and gas station... Not sure where she is buying gas regularly. Last fill up was at Exxon station 87 octane. We have tried super unleaded with no real change on the knocking.

While i'm playing with the EGR i'll pull a plug and take a look and see what they look like. I have also used some lucas oil fuel additive and it seemed to quiet things down a bit!! :)

Thanks to all for all the feedback.
 
#13 ·
Excessive idling, short trips, defective PCV, poor quality gas, even a stuck open thermostat can contribute to carbon build up.
Even good gas isn't all the clean burning. Very possible there are deposits although the 3.3L and 3.8L are known to be real bad for carbon.

Many modern fuel injection systems aren't as precise as they would have you think. GM still has tons of problem with carbon build up!
 
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