Misfire During Warm-up Followed By Bluish Smoke After Idle

1lugloose

Member
Apr 28, 2012
53
0
6
Los Angeles
UPDATE 5/23: looks like there is a leak somewhere on the driver's side of the intake manifold. Significant coolant can be found at the front of the manifold at the metal coolant elbow. Do I need a new manifold?

Ok, So I'm thinking of doing a full tune up with the car. The issues I'm having are both only intermittent, but progressively are getting worse. Still no CEL.

First, the car starts and runs fine for it's first 5-10 minutes (depending on ambient temp and traffic) until right after the the temp needle starts to rise. At the point the car starts to come up to a normal temp (just to the left a little of half), the car will misfire when under even light load until higher RPMs seem to smooth it out, sometimes, but most often it continues to miss until the car is well warmed up. There is no sign of misfire at idle, though. Of interest, is a tiny bit of coolant had somehow developed near the driver's front COP, on the head. It hasn't really reappeared since I wiped it up. Of note, one day, on a 30 minute 10 mile drive to work last week, the misfire was light the whole way (as was traffic) but would, for once, clear up at higher revs. I'm guessing new MSD COPs and new plugs should help, but could that leak becoming from the water jacket right there on the intake manifold(it does have the improved manifold already)? Don't wanna burn up fresh COPs with an unaddressed coolant leak, from what I've read. Haven't popped out the plug boot yet to check the plug well for moisture, but so far the boot looks pretty dry.

The second issue has appeared before, but the last time I saw it (6+ months ago), I found a plastic bag melting on my Bassani cat-back, so I could have mistaken it. So far, only after idling for a few minutes with a warm motor, the car will blow a bluish smoke out the tailpipes when you blip the throttle. It happened once on my way home today. With a relatively warm motor from the beginning, about 8 minutes into the drive home the car misfired just for 2 gear changes, and then seemed to straighten out. But after driving about a mile through a 20 MPH zone, and then sitting in traffic for 5 minutes or so, I gave it a blip before I started to ease the clutch, and I got a pretty solid cloud of bluish smoke out both tailpipes before I even started to move.

After this, the car had to sit in more traffic, but it wouldn't smoke anymore. I may have been too paranoid though, and revving the motor before it had a chance to build up. For the rest of the drive home, there were only a couple of times where it would seem to drop off and lose power as I tried to ease away (not responding to throttle correction either), and it wouldn't make any signs of a misfire, just a stumble and surge, like it was choking. From a stop, I would rev the car normal, drop the clutch normal and increase the throttle normal and it would hesitate and then try and catch up.

So I get home, park the car in the garage which is nice and level, and I leave the car running and pop the hood. The motor is definitely hot, and the majority of the CAI is heat-soaked. I let it run for a couple of minutes poking around a bit, then blipped the throttle at the body, and watched the rear of the car and sure enough I got the smoke. I ran over and smelled it, and it was definitely more blue than gray, and more gray than white. I'd have to say it smells more like fuel, rather than the oil I expected, and am wondering if maybe I've burned up a cat, or a valve seal, PCV valve, or even my MAF? Placing your nose or hand near the tailpipe, and it definitely smells dirtier than it used to and feels hotter as well, but my fear could be playing that up more than anything, but I did notice this before I checked the forums.

No CEL either. I don't have a code reader, but I think autozone does hook theirs up for free and they're 6 blocks from my place. I've never noticed smoke at start up, but will be checking everything even more often though.

Will take pics or vids as necessary.
 
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1lugloose

Member
Apr 28, 2012
53
0
6
Los Angeles
Check Engine Light just came on yesterday, finally. Anyone know where I can get a cheap code reader? Planning on replacing all 8 COPs with MSD ones and new Motorcraft plugs. Would be nice to know which cylinder is the trouble maker, though.
 

Rejekt

Member
Aug 12, 2010
546
13
18
Raleigh, NC
Autozone, Advance and Pep Boys do free CEL checks. Make sure they give you the codes though, cause I had some jackass who just tried to tell me what could be causing it instead of just giving me the codes. I ended up getting a CarMD from my in laws for Christmas... lol so I use that. It's come in handy quite a bit.
 

1lugloose

Member
Apr 28, 2012
53
0
6
Los Angeles
Ok, did a thermostat, coolant flush, new plugs, and MSD COPs all about a week ago and my service engine soon light is still on. The car has better throttle response and runs better generally, but I now have an issue where if I go to give the car a light rev (up to 1200 rpms), like before leaving a stop light or creeping in traffic, the car will fall below normal idle and occasionally die. Revving the car to save it generally makes it pop and sound like a misfire until you hold the RPMs up above 2k for a second before lifting off and letting them fall back to normal again. I've tried to reset the computer into it's learn mode by disconnecting the battery a couple of times already, and each time, the service engine soon light goes away until I complete the requisite 10 miles plus driving to let it re-learn, then shut it down. As soon as the car is started the next time, the service engine soon light comes on and stays on.

I've started a build thread for this issue and others. Please visit Project True Blues for your replies and more.
 

evolucion311

Member
Mar 19, 2009
236
2
18
My initial theory: You have a cracked intake manifold with a hairline fracture that only allows the coolant to leak once the temperature and pressure rise enough. This coolant is fouling your COP(s) and causing the cylinders in question to misfire. No spark = no burned fuel = smell of gas coming out.

Do you have catalytic converters on the car? Unburned fuel going into cats will clog and destroy them. Ask me how I know :)

An alternate theory may be that you have a cracked head or blown gasket. A compression test might help find your problem.

I am subscribing to this thread and will be monitoring your progress. Keep us updated.
 

1lugloose

Member
Apr 28, 2012
53
0
6
Los Angeles
My initial theory: You have a cracked intake manifold with a hairline fracture that only allows the coolant to leak once the temperature and pressure rise enough. This coolant is fouling your COP(s) and causing the cylinders in question to misfire. No spark = no burned fuel = smell of gas coming out.

Do you have catalytic converters on the car? Unburned fuel going into cats will clog and destroy them. Ask me how I know :)

An alternate theory may be that you have a cracked head or blown gasket. A compression test might help find your problem.

I am subscribing to this thread and will be monitoring your progress. Keep us updated.

Thanks for the tips. I replied in my other thread.

I do have cats on the car, and I fear the time spent driving the car before the tune up burned up at least one of my cats. This especially sucks because in california, you have to keep all four. No modification beyond stock replacements is acceptable.

I pray I don't have a compression leak. Reason being, is once I get that, I'll want to rebuild the whole damn thing for safety's sake. Nevertheless, if the codes don't lead to a solution, I'll have to check the cylinders.

If it were valve stems, it would always smoke on start up right? Mine never does.


Trying to kill this one and keep every thing in the other thread, for the ease to follow and communicate. If you could, reply back in the other thread rather than this one.

How would I check for an intake manifold crack? Take it off and inspect?
The car has not been misfiring since the MSD COPs and new Motorcraft plugs installed.
The car still makes the bluish-greyish (definitely not white), oily-fuel scented smoke if left to idle at a stop on a hot motor and then given a good stab before taking off (a long traffic light, for example).
Does not consistently emit vapor/smoke/steam anywhere else, ever, otherwise.
Dead cat?