Rough Idle/Hesitation/Backfire

[Gary Yarbrough]

I'll be checking the Accel coils soon. I just finished checking the wires and here is what I got:
1: 8,700
2: 7,730
3: 7,720
4: 7,760
5: 6,370
6: 6,320
7: 5,260
8: 7,000

That seems like a lot of variability to me. However, I need some more experienced opinions as to whether I need new plug wires.

[Gary Yarbrough]

The new Accel coils check as follows:

0.9/7.35K
0.8/7.10K
0.8/7.10K
0.7/7.30K

[A26B]

First, doesn't look like you got an answer re the MAP sensor. Here's a photo of the underside. Suck on the tube & see if it holds vacuum. If it does, nothing broken inside.




Plug wire resistance: All are within spec. Longer wires should have more resistance, all is good there except #8 is a little high but should be fine.

I don't read where you ever did a VISUAL spark test. Put a plug in one wire at a time, lay it on the cam cover or plenum, start the engine, pull the plug away from the ground slowly. A strong spark should be blue and 3/4"~1" jump. A weak spark will be orange. You should try that as it costs nothing and has often revealed the reason for a miss ocurring under load at low rpm. Such a miss shows up most often when accelerating in 6th gear from 50mph. If all is good, acceleration should be smooth with no bucking.

Such a miss is often not aparrent at high rpm or normal driving except for sub-par performance, unlike a dead-miss. A bad coil or wire/coil tower/plug with corroded connections are generally the problem.

[jeasen]

On Sunday and Monday I checked to many coils to count. I took my multi-meter to the auto parts store and checked them right there on their counter. I made them order in more before before I bought a set of four. From what I read coils should read .5 to .6 on the primary side and in the 5.5 to 6.0 on the secondary side. Coils that read more than the above on either side are out of spec and should not be used.

I installed the coils I bought yesterday but have not finished to let you know how my ZR1 runs with the new coils. I should finish up tonight and have a report for you by tomorrow.
Jeasen

[Gary Yarbrough]

Originally Posted by A26B

First, doesn't look like you got an answer re the MAP sensor. Here's a photo of the underside. Suck on the tube & see if it holds vacuum. If it does, nothing broken inside.


Plug wire resistance: All are within spec. Longer wires should have more resistance, all is good there except #8 is a little high but should be fine.

I don't read where you ever did a VISUAL spark test. .

How much vacuum should the MAP sensor hold?

When I get the radiator on tomorrow, I'll do the visual spark test.

[jeasen]

I forgot to mention that I did find one dead coil (no ohm reading at all between the secondary terminals). I had questionable spark coming from one side of two other coils. Anyway I decided that if I was going to pull the plenum to replace a dead coil then I was going to replace all four coils. I figured that it would only be a matter of time before the other coils failed. I changed coils on other cars but I got to tell you this was by far the hardest (longest) job to date but the results were well worth the work.

I did drive the car last night. The motor idles much smoother and I did not detect any high speed miss. The car pulls really hard all the way to the redline.

Jeasen

[Gary Yarbrough]

Originally Posted by jeasen

I did drive the car last night. The motor idles much smoother and I did not detect any high speed miss. The car pulls really hard all the way to the redline.

Jeasen

That's great news! I hope it keeps working for you.
I hope I'm so luck tonight if I get mine back together.

[Gary Yarbrough]

Weeks later....

I got my new radiator on and the cooling is better than ever. I've still got the hesitation. I did a "rough" visual spark test and everything looked good. I say rough because I wasn't exactly sure how to do it. Should it be idle only or should the car be rev'd up?

[tccrab]

Originally Posted by Gary Yarbrough

Weeks later....

I got my new radiator on and the cooling is better than ever. I've still got the hesitation. I did a "rough" visual spark test and everything looked good. I say rough because I wasn't exactly sure how to do it. Should it be idle only or should the car be rev'd up?

Gary:

The "Visual Spark Test" will tell you all you need to know at idle.
One of these "Noids" are very handy and can potentially save you from any electrical related problems from allowing that much voltage to go to ground on top of your motor.
http://www.oreillyauto.com/site/c/de...PartType=C0103

TomC
"Crabs"

Originally Posted by Gary Yarbrough

Weeks later....

I got my new radiator on and the cooling is better than ever. I've still got the hesitation. I did a "rough" visual spark test and everything looked good. I say rough because I wasn't exactly sure how to do it. Should it be idle only or should the car be rev'd up?

Doing it at idle is fine. And it's not so much a visual, but you should be able to hear it arcing.