Problems after plug replacement...

[9c3]

1999, 3.8

I unbolted the strut mounts rolled the engine forward and locked it into position by putting a bolt through the extra hole on the left mount. I changed the plugs and put everything back.

Now when the car sits for a while, it sometimes takes two tries to start it. On the first attempt, it will fire up for a split second, then die. It usually starts no problem on the second try, but the RPMs will pulsate between 900 and 1100 and on occasion a really loud sucking noise will come from the vicinity of the air filter housing. This usually goes away after 5 - 10 seconds and the car will run fine.

I'm not sure if this is related, but after I put everything back, I started the engine and revved it as couple times. When I would ease off the gas pedal, the engine would slightly shudder and make a thumping noise. I tightened the strut mount bolts and the problem went away, but the engine seems to pitch forward further now than it did before i changed the plugs.

EDIT: Car pitched further because it was still in neutral. Disregard

[jeffcoslacker]

Start and die on cold start is usually too lean, too lean after putting a set of plugs in probably means you accidentally created a vacuum leak. Make sure you didn't knock something off...go back over everything you messed with.

[john51md]

Originally Posted by jeffcoslacker

Start and die on cold start is usually too lean, too lean after putting a set of plugs in probably means you accidentally created a vacuum leak. Make sure you didn't knock something off...go back over everything you messed with.

And recheck the firing order of the plug wires, its very easy to get 2 crossed up

[9c3]

I changed the plugs one at a time so the firing order is probably ok.

One odd thing that I noticed and it may be unrelated, is that the plastic fuel line connectors that pop on to the back fuel rail leaks gas when depressed with the engine running. Is it supposed to do that or is there a bad o-ring in there? I took the big plastic cover off the engine, as judging from the indents on it's underside, it's putting a lot of pressure on the connector and the problem went away for a day, but came back. I was messing with the connector today again and the problem went away for a bit but again came back.

I should mention that I have had this problem for the last three years but haven't really done anything since it would only happen once every six months or so. The plug replacement has caused it happen almost everytime I start the car cold now.

Also, when the car is sputtering, the exhaust has an odd smell to it.

I checked for loose vacuum hoses but everything seems ok, unless I'm missing something. Is there a diagram somewhere of the routing of the hoses?

[richtazz]

I would double check the center and drivers side rear plugs (cyl # 4 and 6). They are difficult to install (trying to work around the oxygen sensor), and you could have accidentally cracked the porcelain which would cause a sputter/miss. You need to get that fuel line leak fixed, as it could get worse and cause an underhood fire.

[9c3]

I got a code reader and it's saying P0102 MAF Circuit Low Input.

It will show this code intermittently when the car is starting and idling fine and it always shows it when it's sputtering and surging on start up.

I pulled out the MAF and sprayed the small wires with contact cleaner and nothing changed.

I also unplugged it and drove around for a while and the only difference I noticed was a slightly higher idle (1000RPM). It still intermittently idled like crap on start up.

I removed the climate control vacuum line off the big brake booster line and hooked up a vacuum gauge. When the car is idling fine it's a steady 21Hg.

When the car is sputtering on start up, it reads 7Hg and slowly rises to around 20, at which point the engine revs up, the gauge hits 24 and comes back down to 21. Everything works fine after that.

Could there be something up with the plenum. I was sort of leaning on it while changing the rear plugs.

[jeffcoslacker]

Try jarring the MAF while it's idling...tap it with a screwdriver handle and see if it makes the motor stumble or set the code...

Didn't split the intake duct or knock the breather line off of it or anything?

[9c3]

When I tap the body of the MAF, nothing happens. When I tap the electrical connector on it, it does change the idle a bit, but not always.

I ran the car without the intake duct and it really made no difference. I did notice that the throttle body screen has dents in it. Not sure if that would make any difference though. I'm gonna have the MAF itself tested at a shop next week.

Could one of the spark plug holes perhaps be oversized causing excess air to leak into the combustion chamber?