Author Topic: Misfire's in the morning. (Read 4207 times)

lindol · « **on:** March 19, 2008, 12:54:16 AM »

Strange as that sounds, for the last 6 or 7 mornings on my way to work I've had occasional hiccups or misfires starting about 20 minutes in to my 60 minute commute. These are occurring in top gear while driving at a steady 120kph(75mph), around 3000rpm, interestingly while driving this same speed in the afternoon drive home there have been no misfires. When it is happening it's not enough to cause the engine to stop, it's just disturbing as the car seems to suddenly, but only momentarily lose power and then it carries on as if nothing happened until the next occurrence. About 35 minutes in to my commute I exit the motorway and drive along a smaller road at around 100kph (62mph) for the rest of the journey, I have experienced some misfires on this part of the trip, but not significantly different then at highway speeds, there have also been days without misfires during this part of the trip. After the first occurence, I thought it might be either dirty fuel or a dirty fuel tank as it was only at about 1/4 of a tank, so after work I put a bottle of injection cleaner in as well as filled it up. As it ran perfectly on the way home I thought I'd cured it, only to be dissapointed the next morning!So with the next tank of fuel I added Redline Water Remover, this again gave me cause for hope as I had a round trip without misfires, that was only for 1 day though until the misfiring returned. I've had a look around the engine compartment yesterday afternoon and as usual the engine ran fine at idle and at higher speeds. There isn't anything obvious that I can see wrong and I pulled and pushed all the electrical wiring in the engine compartment without effecting the performance of the motor. I can also mention that I've had the car since December and during the first weeks I changed the plugs, as well as the air and fuel filters. The car had run well for several weeks before this problem started. I'd appreciate any ideas of what I might be looking for to track down this intermittent problem.:confused:

hoevesruperd · « **Reply #1 on:** March 19, 2008, 07:04:05 AM »

check your alternator belt. it might be a loose and might slip with morning dew or condensation. does any warning light lights up? check engine or battery?

lindol · « **Reply #2 on:** March 20, 2008, 12:29:52 AM »

Hi Alex,
You would also understand the climate I'm in, -5C to -15C, so plenty of frost or snow in the morning, but above zero, even feeling like spring at this time of year around 4:00PM. It's the differences between the morning and the afternoon and what it's doing to either the electrics or the rubber components that I've been thinking about too. I'll have a look at the belts after work today, but I'm not getting any alternator lights or battery warnings so I'm a little doubtful-but it certainly won't hurt to have a look. Thanks! Any other ideas out there??

individualist · « **Reply #3 on:** March 20, 2008, 03:36:20 AM »

Check the plug wires for abrasions, especially near the plug sockets. Also check, with a flashlight, the sockets themselves for frost, dew or water accumulation. Your plug wire voltage may be finding an intermittent path to ground in this area.

bmwpower · « **Reply #4 on:** March 20, 2008, 06:23:14 AM »

Pull the wires off the car and bench test them. Move/bend the wires as you're testing them.

I had the same exact problem on another car. They tested fine on the car, but when I took them off the car and moved them around while testing for continuity, they failed.

lindol · « **Reply #5 on:** March 30, 2008, 11:24:02 PM »

Checked the plug wires and down the plug holes as recommended, nothing found out of the ordinary. However, the problem has gone away, I've driven the last week without any misfires. Makes me wonder if the problem was dirty fuel like I originally suspected. Hopefully, it won't return, fingers crossed!

hoevesruperd · « **Reply #6 on:** March 31, 2008, 06:08:54 AM »

Quote from: lindol;45803

Makes me wonder if the problem was dirty fuel like I originally suspected.

that's good news. i hope my misfire problem is something just as simple (it propably the case since i have a pierced gas tank and got a little off road into a ditch)

if it comes back try some water neutralizer products in your tank

xsjado · « **Reply #7 on:** April 01, 2008, 10:10:18 AM »

mine misfired today after 24 hrs not driving it....just while accelerating but then it disappeared when it finally warmed up...wiered

r0ckrat · « **Reply #8 on:** April 03, 2008, 02:17:06 PM »

Might also check each coil pack for cracked housings. I had an off-idle stumble and high RPM miss after the engine would warm up due to a crack in one of the coil housings allowing arcing to the frame. Took a long time to diagnose.

txleadfoot · « **Reply #9 on:** April 06, 2008, 09:17:33 PM »

What range of resistance should I be looking for when bench testing the spark plug leads?

lindol · « **Reply #10 on:** April 18, 2008, 12:52:11 AM »

The problem re-appeared today after a few weeks of problem free running. Guess I'll have to inspect vacuum lines, spark plugs, spark plug wires, etc., etc. May even pull the rear seat to see that all the electrical connections to the fuel pump are shiny & tight.
But, I think the vacuum lines are the most likely culprits as this problem only appears on the morning comute.