did a compression test. still have problems. Update: worse

[Guest myth66]

Hi again I didn't get any help in the last post so I did some tests myself. I figured since my 82 zx was backfiring I should check the compression. the results were 1=130psi, 2=145psi, 3=150psi, 4=150psi, 5=145psi and 6=150psi I guess thats not too bad but what concerns me is that when I pulled out the spark plug to test it they were all oil fouled pretty bad. these were new bosch platinum plugs too. Any ideas?

[Drax240z]

Buy NGK BPR6EY-11 plugs. Seriously. Gap them at ~0.035" and start fresh. Had a Z in here yesterday that was running new bosch platinums, and we swapped them out for the NGK's. Solved all the problems the owner was having with the cars drivability.

 

Even if it doesn't solve your problem, it's a very good place to start IMHO.

[JMortensen]

I'll second that. I ran Bosch platinums in my first ever car, a '79 Mustang 2.3 (OH YEAH BABY!) and that thing ran like dog poop. I think I bought them because they were the most expensive, so they had to be the best, right??? Swapped in the cheapest set of Champion plugs I could find and it ran 100 times better, which was still pretty bad but you get the point.

 

I should also say that I've seen Volvos run like crap with NGK's, Datsuns run like crap with Bosch, and Chevy's run like crap with NGK's too. I don't know what the manufacturers do differently, maybe they set the rest of the ignition system up around the plugs, but if you get the right plug for the car it seems to run best.

 

Also seen Bosch O2 sensor make a Chevy Lumina get 15mpg. Put in a Delco O2, 25 mpg.

 

Sounds like conspiracy theory, and I probably wouldn't believe it if I hadn't seen it myself, but that's been my experience.

[Guest myth66]

Alright I'll take your word for it. I went out and bought some of those NGK plugs you suggested. My friend at the parts store said that they would be changing the part no. on those to "6261" the box currently has both numbers on it but he said they would stop looking them up by that number soon. just thought I'd let you in on that so i feel like I'm contributing something in return . Maybe you already knew. Any way I've got my car on the charger right now the battery is dead from all the cranking I did on the compression test. I'll let you know how it turns out in an hour or so.

 

 

EDIT:

Well it runs a little smoother now once I get it warmed up. I'm sure those plugs are helping a little. also there was a small vacuum leak that had gone unnoticed. It's still backfiring when I hit the gas . Im' starting to worry about sticky valves or leaky valve seals that would explain the oily plugs before. I think I'll have a look under the valve cover.

[Guest myth66]

I started tearing it down a little more and checking out all the sensors. I was shocked when I looked at the throttle body and found oily carbon buildup . It's my understanding that this area is usually supposed to be the cleanest part of the engine. I'm fearing the worst. what now?

[JMortensen]

It's really common for throttle bodies to get dirty. You can take it off and clean it if you have a new TB gasket, or just open the butterfly and clean the blade itself and the throttle body with carb cleaner and a rag.

[Guest myth66]

Oh, I guess I've been spoiled by the newer late 80's cars. I'm used to looking into the TB and having it squeaky clean inside except maybe a little gelled gas. I had never seen anything like that before. It still doesn't really explain the backfiring. Maybe it's just the timing? (that'd be nice )Ive' been putting off adjusting it because the power steering pump is right in my line of vision when I try to read it. Any way around that or do I have to pull the stupid thing out? Maybe squint really hard?