Why is #3 spark plug different?

[Mike70gtx]

Motor is running rough since I've put it back in after new headgaskets and bearings. It was running very rich at first. I now have new 4" pipe with maf built in, sent in trans plus to get it checked, have new cam sensor, new coil pack. It's not running as rich but it still coughs and sputters under load. All of the spark plugs look black except #3. Pulled plug and its firing. The cam has 5k on it and I put all the lifters back in the same spot. I had some scarry valve train noise on start up, but after awhile it finally left. I pulled the drivers valve cover and rockers seem to be moving up and down. If I wiped a cam would the number 3 valves move at all? What could be the problem?

 

[REGALTURBO]

Simple thing to check but often overlooked...check your plug wires. Since they may be somewhat hard to get at with these cars you can easily damage them pulling them off. I just went through this.

 

[Mike70gtx]

I found an old one and swapped it out but it didn't make any difference. I'll order some tomorrow since they don't have any in town. These were fairly new msd's. I ended up pullling the number one wire apart in the process. I don't think that's it but you never know.

 

[gunslinger]

Check the #3 injector for pulse and flow.
If one injector isn't firing, the O2 and ECM will drive the other five cylinders rich to compensate for the extra oxygen being pumped by the dead hole.
What are your INT and BL #s like?
Did You check compression on #3?
Highly doubt it's spark related.

 

[Mike70gtx]

How would I check the injector? I'll try to do the compression check tonight. The injectors are 60# and fairly new. Something caused me to blow a headgasket and that is why the motor got pulled. It ran good at track and got home and stepped on it going on to interstate and it back fired a couple of times and then the milkshake. I guess the injector could be the answer.

 

[kh440]

unplug the injector with the car running. if the injector is not firing there will be no drop in rpm or otherwise behave any differently.

 

[Mike70gtx]

I'll go out and do that now. I did check compression. The motor was not very hot, but it was 140#s on #3 and 150#s on number 1.

 

[Mike70gtx]

When I unhooked #3 injector it didn't seem to change, so I put it back on and unhooked #5 and it didn't seem to change either. Even at 1500 or more rpms it wasn't any different.

 

[Boost231]

compression looks fine. i would get a noid light and test the injector harness.

 

[Mike70gtx]

How do I check the harness. Is it one of the "stab the wires" lights? If so, will it intermitantly blink or light up?

 

[84BuickGNYorkPA]

they sell the noid lights at the local Advanced Auto and probably other chains. They go for about $15, and plug into your EFI wiring harness.

Chuck

 

[BoostKing]

not sure

this was just an idea and im new to buicks and fuel injection alike. could you not put a stethoscope on the injector and listen to it ticking????..

 

[Mike70gtx]

I wonder if that would work.
I'm going to get the noid light today. Depending on results, I will then swap the injector out with another cylinder and see what that does. If it is the injector, do I take it to an injector place to have it fixed or flowed or can you just get one new injector?

 

[Mike70gtx]

Update. Got a noid light and the harness checked out okay. Has a good pulse to #3. So I swapped the 3 and 5 injector and after I get everthing back together I turn on key and the injector on the other side is leaking. I cut the o-ring since I just tried to lift just one side out. I should have pulled every injector out and put in back in the rail. Now I"ll have to wait two days until I get another shot at it. I ran the car for about 30 seconds but I doubt if that was enough. I saw no change on the plugs. I felt like running it longer with the fuel shooting out. The eventual fire would have solved my car problem, but my parents live in an attached part to my garage. They were out of town though. Which reminds me that I need to change insurance from State Farm so I could get the full value if it does go up in smoke.
So, if it's not the injector. Do I have a cam/valve problem?

 

[Boost231]

if you are pulling the injectors send them to cody motorsports and have him flow and clean them. its cheap and you will find out if there is a problem or not with the injectors. it will cost less then 100 bucks

 

[Mike70gtx]

Now what? Just had the injectors flowed locally and they all checked out good. Today the plug wires come in and then I'll see what that does. If not, is this going to be the cam? The rockers were moving up and down. How do I measure to see if the valves on # 3 are moving as much as on the others?

 

[gunslinger]

If it is valvetrain related, you'd have little to no compression on #3.

Chances are, you've got a vacuum leak on the #3 intake runner. Is it possible you slipped or tore the intake gasket when you were putting the engine back together?
Easy way to check is to spray some carb cleaner (with the engine running) where the intake meets the head. If there's a leak, you'll notice a change in the idle.

 

[Mike70gtx]

Today put in plugs, the new wires and it ran worse with lots of backfiring. I pulled the coil to see if it was hooked up right and realized that my hand drawn diagram of the cylinder order on the coil had #3 and #5 mixed. It now runs and I actually made it to town and back.
Thanks for all the advice. Now for some tuning. I have a new air fuel ratio guage, so what do I aim for with my setup?