Misfiring at the start

[wisemonkey]

Hi,
Should I attribute this to different gas (filled up at particular gas station for first time) and wait for gas to be used or should I check anything more?

Symptoms:
Car would misfire / shake at start for maybe 2 minutes and then start running smoothly.

 

[Comet]

Year of vehicle? Maintenance done prior to the misfire?

 

[mjosoba]

It could be any number of things. My experience:

Has it gotten worse? Any white smoke accompanying? This happened to my ‘94. Initially a barely noticeable rough idle at start up. Then it became a miss/roughness at temp. Then one day after I got gas it started hard and was pouring white smoke out. I immediately shut it down and had it towed to a mechanic. It sounded like it had started leaking slightly, then completely gave way. I’m glad I wasn’t going at highway speeds, I worry it could’ve done some damage.

 

[wisemonkey]

Year of vehicle? Maintenance done prior to the misfire?

1997 LX 450, about time for oil change (nothing mechanical in recent time). Replaced speaker but I'm assuming it doesn't matter?

 

[wisemonkey]

It could be any number of things. My experience:

Has it gotten worse? Any white smoke accompanying? This happened to my ‘94. Initially a barely noticeable rough idle at start up. Then it became a miss/roughness at temp. Then one day after I got gas it started hard and was pouring white smoke out. I immediately shut it down and had it towed to a mechanic. It sounded like it had started leaking slightly, then completely gave way. I’m glad I was going at highway speeds, I worry it could’ve done some damage.

Just started a day ago and only at start.
I see P300 and P306 (6th cylinder misfiring).
Haven't noticed white smoke yet, will check closely today.

 

[vipergrhd]

Just started a day ago and only at start.
I see P300 and P306 (6th cylinder misfiring).
Haven't noticed white smoke yet, will check closely today.

Possible coolant or fuel leak in that cylinder (#6). Do a leak down test with radiator cap off when cold and check also fuel pressure drop if you can get a gauge set.

 

[mjosoba]

Agree with @vipergrhd Also, I can’t believe I wrote that whole post, and neglected to mention it was the headgasket. . But if you know, you know.

 

[mudgudgeon]

But if you know, you know.

Ain't that the sad truth!

 

[mjosoba]

Ain't that the sad truth!

Now it runs so good I don’t want to pull it for a swap. So I’ll prob sell it soon and look for one with a bad engine.

 

[Rusty Marlin]

OK, don't panic. I had this last year on number 4 and it was just a bad ignition wire.

 

[robnicko]

check for oil leak in the distributor cap as well

 

[wisemonkey]

And haven't seen misfiring in last 2/3 days.
I will schedule a mechanic visit just in case.