Rough Idle/Hesitation/Backfire

[XfireZ51]

Originally Posted by Gary Yarbrough

Thanks for the suggestions so far. When I pull the plug wires 1 at a time, all of them do make the idle rougher. However, there are some with a very strong loud spark (I can actually see it) and others that seem much weaker. So, I'm thinking I need new coils as suggested. So, I have a related question. Given that the plugs and wires are about 1 year old, should I also replace them when I do the coils or are they most likely okay?

If you find that the weak spark comes from a pair of plugs with a common coil,
ie 1-6, 3-2, then that would be a clue on needing coils.

[jeasen]

I had the same problem a couple of weeks ago with my ZR1. I found that I had water in my gas. Add some gas dry to your gas tank to see if this fixes the problem before you embark on a much harder and costly fix.

I think this is going to be a common problem now that the gas stations are charging more for premium fuel. The price for premium is no longer 20 cents more than regular and people are not buying it like they use to. Therefore the gas stations do not have the turn over like they use to have and I think we will see more water in the gas problems.

I hope this helps.
Jeasen

[Z51JEFF]

Ive heard nothing possitive about the Accel coils so if you havent replaced the plenum yet I would replace those coils.As far as the slapping noise,a miss will get the DM flywheel jumpin around and just might get the cam chains to make a racket.When I had an injector die I got a noise that sounded like a rod knock but knew it was the flywheel.

[Gary Yarbrough]

Well....I changed the coils today and the problem is still there. On the upside, I now have a very strong spark when I pull the plug wires. So, it's plugs tomorrow (if I get a chance). I have three questions:
What's the proper torque for the plugs when i put them in?
How do I get out the rear plug on the passengers side?
Any other suggestions for what I should be looking for?

Thanks for any help I can get!

[Kb7tif]

Originally Posted by Gary Yarbrough

Well....I changed the coils today and the problem is still there. On the upside, I now have a very strong spark when I pull the plug wires. So, it's plugs tomorrow (if I get a chance). I have three questions:
What's the proper torque for the plugs when i put them in?
How do I get out the rear plug on the passengers side?
Any other suggestions for what I should be looking for?

Thanks for any help I can get!

Did you use d545 coils?

[Gary Yarbrough]

Maybe the TPS is my problem. I saw three wires: blue, white and black.
Between the back and the other two, I get ~4.5 and 4.0 volts. Does that sound possible and what's next?

[Gary Yarbrough]

I used Accel coils.

[ZR1Vette]

Rear plug... bit of a challenge but basically you need a plug socket, short (1 1/2") extension, universal and then a longer (4") extension

Have you checked your ALDL/DIC for any fault codes?

[tomtom72]

Just thought you might look this over about #8 plug r&r...

http://www.zr1netregistry.com/ZR1_techtips.htm

This is the ticket. 20 N-m ( 15 lb-ft ) on the 90 plugs w/the flat seats & flat washer.


Tom

On the TPS, Black is sensor ground, Dark Blue is the signal to the ECM, and Grey is 5v reference signal from the ECM. ckt #'s 452, 417 & 416 respectively. Therefore you should read the TPS signal from the TPS to the ECM at the Dark Blue wire. A back probe on the Dark Blue (417) should yield a reading between .46v & .62v. If I understand the book correctly.

[XfireZ51]

Gary,

With key ON, the TPS signal (between black wire and blue)
should be around .54v. Once you have it set up, read the TPS signal voltage as you open and close throttle with motor off but key ON. See if the voltage change is smooth or changes in a "choppy" manner. Does the reading change abruptly? Also, make certain the TPS switch assembly is securely attached and not loose. Move switch wires around and make certain voltage readings aren't changing.