03 Montero, high compression, pinging noise, rough idle

  • js696700
  • Topic Author
  • Offline
  • 1st Gear
  • 1st Gear
More
1 week 5 days ago #201360 by js696700
2003 Montero Limited 113,000 miles
I've only had it a few months, daily driver, 2-5hr highway trips on the weekends
No CELs or pending codes

Issue: starting to hear a rattling-type pinging sound when on highway. Onlywhen in OD and I push the accelerator under load. This transmission does tend to want to stay in 5th when I would prefer it kick down to 4th sooner. The pinging may happen no matter if it actually does kick down to 4th or if it stays in 5th when gassed.

Idle is a little rough. Otherwise runs smoothly (feels underpowered, but I think that's probably because it is). Has the common 2200rpm Montero engine vibration, but it's fairly mild.
Compression test results:
RIGHT 185, 190, 185
LEFT 210, 240, 180 (rechecked)
Long term fuel trims average about + 9-10 for the left (drivers) bank and + 3-4 for the right bank. The drop to near zero when on the highway.

I am using 93 octane. I have run techron and seafoam through a couple half tanks of gas.
New plugs, coils, wires, valve cover gaskets, timing belt, water pump
Vacuum leak test didn't find anything
Manifold vacuum test rock steady at 21 or 22 hg at idle


Question: What's up with the high compression in those two left cylinders? Is the timing off a tooth (was done by dealer but who knows)? Carbon buildup?
I assume the pinging is related to the high compression. Please let me know what you think. I think the next step is probably to stick a scope in the high cylinders and look to confirm carbon, but I don't really know. That seems easier than checking the cam timing (I don't have much space or shelter to do much work on the vehicle now).

Thanks!

Matt

Please Log in or Create an account to join the conversation.

Advertisement
  • nightflyr
  • nightflyr's Avatar
  • Away
  • 6th Gear
  • 6th Gear
  • 2002 Nissan Xterra 3.3L 4X4
More
1 week 5 days ago #201368 by nightflyr
I may be wrong but,
I believe the 3.0L and 3.5L engines recommend Regular (87) octane.
The 3.8L is the only variant that requires Premium (93) octane.
So if your vehicle is equipped with other than the 3.8L that may be the cause of your pinging.
Another possible cause:
Mitsubishi recommends timing belt replacement on most of the models 60,000 miles.
Do you know when the last time it was replaced?
A worn timing belt could throw off the engine timing.

Question: What's up with the high compression in those two left cylinders? Is the timing off a tooth (was done by dealer but who knows)? Carbon buildup?
Easy enough to check for carbon build up with a inexpensive bore scope.
If the timing is off high compression would not be the result.
I assume the pinging is related to the high compression
Assuming things can be costly.
Better to pin point the cause.
The following user(s) said Thank You: js696700

Please Log in or Create an account to join the conversation.

  • js696700
  • Topic Author
  • Offline
  • 1st Gear
  • 1st Gear
More
1 week 5 days ago #201370 by js696700
Thanks!
Yes it is the 3.8L engine, which calls for 93 octane
I paid dealer to do the timing belt when I first got it
I will look in the cylinders for signs of carbon

Please Log in or Create an account to join the conversation.

Time to create page: 0.222 seconds