Engine Misfire

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

rolledover

Active Member
Joined
Oct 23, 2019
Posts
41
Reaction score
30
Location
Fremont, MI
How many miles do you have on the engine? I had a very small shake at idle (No CEL, no misfires) but it has since gone away. I'm running a few bottles of Sea Foam through my fuel system and might do the intake version as well... but having a valve stick sucks... I'm at 94k miles.
I was at about 150k when it started, am at exactly 168k when I started tearing it apart a few weeks ago. I ran a few bottles of BG 44k through the fuel system when this first started, used the CRC GDI Intake cleaner stuff, pretty much tried everything cheap before getting a leak-down test to confirm my worst suspicions. This went on for over a year before I decided to fix it properly. The shop that did the leak-down quoted me 7k to do this job.
 

pete0rz

Member
Joined
Jun 15, 2021
Posts
5
Reaction score
0
Location
Boston, MA
I have a quick update to share (via indy shop tech) and will know more re: options Monday. Didn't take tech long, in the engine tear down, to find cause of the misfire: 1 of the intake valve seats is completely gone / burned out (in #5) and tech advised that the (passenger side) cylinder head will need to be replaced. In video shared with me tech commented: that issue wasn't detrimental to the cylinder block per se and while there's no obvious mars on cylinder walls, there were a couple overheat (dark) marks on the block. Tech commented that some cylinder cross hatch was still present, but also saw some scratches, probably due to sealant loss. Btw, it was hard to tell if the scratches present were in the head or the block, but the overheat marks were adjacent to those. Towards end of video tech showed the spark plug electrode which was white, indicative of running lean, but that no pieces of ceramic were peeling off or present in the cylinder. I've run 93 and at times 91 (when 93 wasn't available), but nothing else so unsure why a lean condition would present.

Wondering if folks who've had cylinder head replaced could comment on engine afterwards. Will replacing head (will probably do timing chains too) buy me another few years of engine life? Again aside from the rough idle, 305/316 coupled with an occasional 305 misfire, no other DTCs were present.
 

johnr7255

New Member
Joined
Nov 23, 2021
Posts
1
Reaction score
0
Location
Benton City, WA
New member. I have 156K on mine. 2010, 5.0 engine. Have exact CEL as you (#5). I bet I have a similar issue. I will have a leak down test performed. Also have been loosing coolant. about 2 quarts a year.
 

gillygong

Active Member
Joined
Feb 11, 2023
Posts
29
Reaction score
4
Location
Pasadena
I have a quick update to share (via indy shop tech) and will know more re: options Monday. Didn't take tech long, in the engine tear down, to find cause of the misfire: 1 of the intake valve seats is completely gone / burned out (in #5) and tech advised that the (passenger side) cylinder head will need to be replaced. In video shared with me tech commented: that issue wasn't detrimental to the cylinder block per se and while there's no obvious mars on cylinder walls, there were a couple overheat (dark) marks on the block. Tech commented that some cylinder cross hatch was still present, but also saw some scratches, probably due to sealant loss. Btw, it was hard to tell if the scratches present were in the head or the block, but the overheat marks were adjacent to those. Towards end of video tech showed the spark plug electrode which was white, indicative of running lean, but that no pieces of ceramic were peeling off or present in the cylinder. I've run 93 and at times 91 (when 93 wasn't available), but nothing else so unsure why a lean condition would present.

Wondering if folks who've had cylinder head replaced could comment on engine afterwards. Will replacing head (will probably do timing chains too) buy me another few years of engine life? Again aside from the rough idle, 305/316 coupled with an occasional 305 misfire, no other DTCs were present.
I recently started getting exact same 305/316 combo after filling up. 2013 LR4 with 145k miles.

Interestingly, it started immediately after sorting out an evap system leak where a connector above the gas tank wasn’t fully seated. I was getting consistent p0456 faults before. Now that those have stopped, I immediately started getting the misfire codes. Haven’t tested disconnecting purge valve yet.

I’m thinking I should have a leak down test done. But wondering what you ending up doing with yours, and if anyone has any other troubleshooting advice before taking to my shop.
 

powershift

Full Access Member
Joined
Jul 20, 2023
Posts
425
Reaction score
125
Location
Nevada
I'm curious if the misfire is coincidental and unrelated to the evap leak. I'd check the coils, spark plugs and try narrow down the problem.
 

gillygong

Active Member
Joined
Feb 11, 2023
Posts
29
Reaction score
4
Location
Pasadena
I'm curious if the misfire is coincidental and unrelated to the evap leak. I'd check the coils, spark plugs and try narrow down the problem.
First troubleshooting step I did was swap the plug and coil between cylinder 5 and 1, and the misfire did not follow.
 

Latest posts

Members online

Forum statistics

Threads
36,223
Posts
217,601
Members
30,474
Latest member
sawcut
Top