I recently started a repair project on my 89 Maxima which was focused at replacing a couple fuel injectors and fixing a coolant leak. The engine did get really hot from a blown water pump gasket while i was driving and I shut it off to cool before limping it home on side streets - what damage happened is a mystery. All in all, I replaced the water pump, thermostat, fuel injectors, plug wires, PCV, and all appropriate gaskets for each part as well as valve cover gaskets. After all of this, the engine runs much much better but I still have light smoke coming from what looks to be the exhaust manifold as well as a slight surging in engine rpm's during idle.
My question is: How do i know whether or not the smoke is from an exhaust manifold leak or if it's a leaky head gasket ?
One of the leaky head gasket symptoms I DID have, there was a slight milky residue on inside of oil cap.....but other than that nada. The smoke doesn't smell like burning coolant or oil, more like unfiltered exhaust in my opinion. It's just tough to tell for sure because of how close the exhaust manifold is to the head gasket on the block.
Has anyone had engine bay smoke from a blown head gasket ? or is that not very common
Also, if the head gasket was blown, would that cause the engine to surge like that? probably only a 50-100 rpm change at most - it's really slight.

Any help would be greatly appreciated, I just want to stop ripping my hair out trying to guess. Thx guys

 

bubbles in your radiator? Carefully feel around the exhaust manifolds for a exhaust leak.....

 

well, after letting it warm up and run to operating temp a few times a day for the last 2 days - seems like most the smoking disappeared. I think it could have been old residue on the exhaust manifold from before the valve cover gaskets were fixed. I DID find a small leak coming from the exhaust manifold gasket as well as the flexible section of tubing where the two manifolds collect to the main exhaust (front exhaust pipe) At least the leaks were found though.

Now I'm just trying to figure out why it seems to be running a little rich on the fuel mixture.......exhaust from tailpipe smells pretty strong. I'm thinking I'll start by cleaning the MAF and see what happens, other than that - most of the components that should affect fuel mixture should be pretty clean.

 

I also bled alot of air from the coolant system, and replaced the radiator cap because I wasn't getting good pressure in the system. Lemme tell ya - trying to tilt a maxima front bumper to 38" above the ground ??? not the most fun in the world.... But it seems like MOST of the air is gone from the system and it hasn't been leaking at all .

 

Have you ever replaced your O2 sensor? Even though they may not fail, they get tired, and when they do, fuel readings get less accurate.

 

I have not - though I am considering it since I have to replace the Y-pipe (leak in flex-tube section) and the exhaust manifold gaskets anyways. I've also had a mechanic in the past say that my ECU wasn't communicating with the code reader - perhaps there's a ECU issue ?

 

Not commonly.

 

Maybe the mechanic expects OBDII because he doesn't realize what year your car is.

 

Yeah, that could have been. he didn't seem like the brightest bulb on the tree...

 

With that being said... Don't end up like others on here who had kooky mechanics steer them in the wrong direction. Use better judgment towards suggestions/advice he gives you.

 

yeah, it's really a problem and one of the main reasons why I'm trying to go back to school and get ASE certs......I hate trusting mechanics (most the time) to do work I'm more than capable of doing.

 

also make sure the wires on the connector for OBD1 connectors are not broken. this happened to me when i hooked up the OBD1 reader and it wasn't communicating, found wires broken once i removed the electrical tape after the connector. fixed wiring and now reader communicates with my ECU. hope you also got the correct injectors for your car too.

 

interesting, I'll have to check it out. And yeah, I got the right ones