My 08 Avenger 3.5L V6 just started "chugging" when in 5th or 6th gear, under load, at between 1700 and 2000 rpm. Above and below that it is smooth. In park, I hear somewhat of a knocking noise at about the same rpm range. The noise seems to be coming from the top middle of the engine. It otherwise seems to run fine. Any ideas?
There are a few possibilities; There is an Electronic Load Sensor, (ELS), that will have varying affects depending on situation
Sometimes there is a fuel system management issue. Check for trouble codes with an OBD II sensor. Some posssiblilites there may be; Speed sensore, O2 sensor, EGR or Mass air flow sensors.
Let me know if this helps.
June, 9, 2011 AT 1:22 AM
Thanks, DrCranknWrench. No trouble codes--used the ignition on-off 3 time--only those from when I had the front plug coils disconnected. I just ran it again in the garage. The knocking seems to be coming from the aft center or aft right (passenger side) cylinder. I revved the engine up to about 3000 rpm and the knocking gets a little louder, but then I saw a new characteristic. As I held the pedal fixed, the rpm dropped to 2000. I could push the pedal to the floor and it wouldn't go above 2000. If I let up, I could accelerate the engine above 2000 again. Also, I could not find any info in my electronic manuals on the ELS. Could this be the absolute MAP sensor?
June, 9, 2011 AT 7:31 AM
I don't have a manual on your car either. The ELS system may be part of an integrated unit. Either it has a MAP or a MAIF air flow sensing sytem.
Faults on these generally show on trouble codes.
I am wondering if there is a spark issue such as a bad coil pack or wire, etc.
I will get back with some more info ASAP.
June, 9, 2011 AT 1:41 PM
Thanks. I was thinking spark plug or injector on the aft right or aft center cylinder, but of course, access to the back bank requires removing the upper intake manifold. Hopefully, it's something "easy" like that rather than a collapsed lifter.
June, 10, 2011 AT 1:23 PM
Last night I swapped the front and back spark plugs and coils. I did not notice an appreciable difference. Still getting the knocking noise. I did not take it out on the road, but this weekend I plan to put some B-12 into the gas tank and see if that helps. Could be a bad fuel issue. What do you think?
June, 11, 2011 AT 2:02 PM
If it is a knocking noise that is consistent with engine speed, it most likely is a fault with the lifters. I am away from home and will be back tomorrow where I would be able to access our database to get more information for you.
Just hang on till then.
Symptoms does not indicate it is a fuel issue. Have the compression checked/tested idf possible.
June, 11, 2011 AT 9:00 PM
Thanks KHLow2008. I just got back from putting the B-12 and 89 octane in the tank. Drove for about 15 miles with no appreciable change. The knocking noise is consistent with engine speed and is loudest when under load and accelerating. It goes away at higher (above about 2500) rpms. Would an exhaust leak be possible?
June, 12, 2011 AT 11:10 AM
Exhaust leak would be different, it would not sound like a knocking noise, more like a roaring kind of noise.
The symptoms do indicate a possible fault with the hydraulic valve lifters.
As to the hesitation and no response from the throttle pedal, it seems to be a fault with the EGR and/or O2 sensor. Have those checked.
June, 13, 2011 AT 1:47 PM
Thanks. I was reading on one of the forums about TSBs for wrist pins and for rocker arms, but was unable to find any. I looked through several TSB lists to no avail. Do you know of any?
June, 13, 2011 AT 3:39 PM
I could not find any TSB from our database regarding rocker arms etc for your engine.