EFI relay unplugged

[rcb280z]

OK I just pulled the AFM to see how the 7 pins looked....looking for corrosion and found none. Couldn't remember if I had check last time it was off. The inside of my AFM seemed a little oily. Like an oily residue. Could that be from the popping through the intake I get occasionally? I just richend the AFM slightly so it would run a little better and to help avoid the backfire through the AFM. Don't think I'm too concerned because it is the original with the anti-backfire spring but none the less.

[Zed Head]

After all of these posts a video would help in showing what this popping sounds like. Do both kinds of popping happen all of the time or only when cold?

Here's a thought, since it looks like you've exhausted all of the more basic possibilities: a worn exhaust valve cam lobe can cause popping through the intake. It's one of the more common small block chevy failures. It's very evident when the engine is revved up. Have you done a cylinder pressure or leak-down test? Checked your valve timing (the notch on the cam sprocket)? Adjusted your valve lash?

To summarize what you're looking at - the engine won't start cold and hold idle unless you open the throttle for a little while until it stabilizes. It pops back through the intake (how bad and when, low RPM, all the time or open throttle?), it pops through the exhaust (how bad and when?). When it's warmed up, do the problems go away or is this only a cold start problem?

Just trying to help you clarify. The thread jumps around too much to go back and try to read all of the posts. Summarizing occasionally is usually a good idea. A methodical approach from the basics of cylinder pressure, valves opening and closing, fuel delivery and spark might uncover something.

[rcb280z]

The popping,

After leaning the AFM...turning wheel (spring) CW about 8 teeth if I rev the engine it will at times, although rare, pop through the AFM. So I know it is lean. It runs perfect cold. I don't think it pops at all when it's cold. You can tell when it's warming up because that's when it starts popping through the exhaust. During idle it pops, if I slowly rev the engine up and hold it at any rpm it pops. When coasting it pops. It really seems to pop (backfire) through the exhaust at all times but when it's cold. I did a compression test and the results are in post# 76. Adjusted valves about 4 months ago. I do it 1-2 times a year. I haven't checked actual valve timing or done a leak down test. But that gives me another direction to go in which is why I'm here asking for help. I know the post is jumping around some and that's why I did a "summed up" post (#129). There have been a lot of ideas and I have done, and will continue to do, my best at getting the results back. So I just ask that you bare with me. I tried a video recording but my camcorder stinks! It wouldn't pick up anything clearly. Will see if I can barrow one. Zed, one question, If it had anything to do with the combustion chamber would it (pop / backfire) all the time? Cold or hot.

Once again, thank you, to all of you.

Edited February 26, 2012 by rcb280z

[rcb280z]

Almost forgot something important. My wife and I jumped in the Z and drove it down the PCH through Malibu to Santa Monica and it ran ok if we were driving and not going through stop and go traffic. It was nice to get it out and run it. But, by the time we got back home it was really running rich. I had my wife rev it a couple of times and it was blowing black smoke out the exhaust. And I leaned it out by 8 teeth before we left on the drive. So I pulled a couple of plugs and they look good to me.

Edited February 26, 2012 by rcb280z

[240260280z]

They look a little lean. There is no colour on the insulator.

[rcb280z]

Blue, I agree with you. But if you could experience how it is running you would think different. That's why I pulled the plugs because I expected to see them fuel fouled. 16 miles per gallon is all I got yesterday on that short trip. City and highway driving.

[240260280z]

What is their temperature rating ?

[Captain Obvious]

I'm not getting it either. The black smoke says rich, but those plugs look lean.

Here's a question for ya... You're in CA, right? Have you got a catalytic converter on your car? If so, how does the cat come into play with your exhaust sniffer results? Is it conceivable that the sniffer results at the tailpipe exit are very different than the composition going into the cat?

[Mike]

(crappy content management software for this site removes "spaces" so the table above looks screwy... it looks perfect when editing however)

Blue, you have some good information here about the EFI system. I wanted to let you know that I modified your post and put your data about temp vs resistance in a table using the WYSIWYG editor. In the future, if you want to build a table, click on the "Go Advanced" link in your reply and then click on the WYSIWYG button on the upper left side. You'll have the full capability of displaying & editing tables.

Hope this helps!

Mike

[rcb280z]

Hey guys, sorry it's taken so long to get back to you. They are the stock heat range. B6ES11. Capt. Obvious, yes I do have a CAT and it's not even 2 years old yet but have contemplated taking it in for a new one. They are not too expensive. I couldn't tell you anything about the composition.

[240260280z]

It looks lean.

As CO says, the CAT will affect O2 readings so you have to measure upstream from it.

btw if you want to check AFM against RPM (no load) you can refer to these:

Below Step 6.

AFM wiper at

1500 rpm

3000 rpm

4000 rpm

http://atlanticz.ca/zclub/techtips/afm/sizeupgrade/index.html

[Captain Obvious]

My point about the cat is that now realizing you have one on your car, all of your dyno sniffer diagnostic results are suspect because they aren't a true representation of how the engine is running. Basically, they dyno sniffer is telling you what's coming out of the tailpipe after the cat has modified the composition of the gasses, not what's coming out of the engine.

That's why Blue said if you want a true representation of what's going on, you have to sniff between the engine and the cat. I'm not up on cat theory, but I do know cats will affect HC and O2 values.

Here's your dyno sniffer results. Maybe someone who knows more about emissions can wade through this with the understanding that there's a cat installed and can provide some insight accordingly? For starters, knowing full well these readings are downstream of the cat... Does this look rich, or lean?

15 mph:

• HC-263 (too high),
  
• CO-1.8 (max-0.5),
  
• CO2-13.0?,
  
• NO-335?,
  
• O2-1.3,
  
• MPH-15.3,
  
• LOAD-134.3?
  

25 mph:

• HC-152 (ok),
  
• CO-2.5 (max-0.5!),
  
• CO2-13.3,
  
• NO-130,
  
• O2-0.3,
  
• MPH-25.3,
  
• load-74.6.