Misfire, where do i go from here. (Page 2/18)
ArthurPeale FEB 10, 01:07 PM

quote
Originally posted by Dukesterpro:

The timing was initially set to something, who knows, I never checked since it had been working fine *facepalm*

I filled it up with 91 octane from empty to see if it would change, there was an immediate improvement. Drove it 20 miles home. Retarded the timing slightly with terminal A and B jumped and In the dark found a spark plug arching to the exhaust manifold. Fixed. No more stumble. However, Idle is still too high, and now I have some pretty clear pinging that starts under load at mid-throttle and seems to get better or sometimes disappear at wide open. I plugged every port except the map and still high idle and pinging. I think, here's another video for your expert ears




When you said your tach was bouncing, I meant to bring up the checking the engine in the dark. Totally spaced.

Glad that you're making forward progress!
Dukesterpro FEB 10, 01:37 PM

quote
Originally posted by ArthurPeale:


When you said your tach was bouncing, I meant to bring up the checking the engine in the dark. Totally spaced.

Glad that you're making forward progress!


Well unfortunately that didn't fix the bouncing tach, its still all over the place. But its still not misfiring so that still good.

The tach works fine until the car gets warm then it starts bouncing around.

Im just ecstatic to make some movement. The fiero is only allowed to die when I say it can die lol
ArthurPeale FEB 10, 03:25 PM

quote
Originally posted by Dukesterpro:

Well unfortunately that didn't fix the bouncing tach, its still all over the place. But its still not misfiring so that still good.

The tach works fine until the car gets warm then it starts bouncing around.

Im just ecstatic to make some movement. The fiero is only allowed to die when I say it can die lol



Take another look, spray down the wires with a spray bottle of water (in the dark). It's secondary loss, it's a good way to cook your ICM.
Dukesterpro FEB 10, 03:41 PM
Will do tonight
Patrick FEB 10, 05:08 PM

quote
Originally posted by Dukesterpro:

Not able to check the EGR right now as I am at work. But if it fails either of two tests, should I just replace it.



If the diaphragm has failed, yes, replace the EGR valve.

In regards to the bouncing tach, this is something that's often been discussed... Click Might be a bad tach filter.

I might also add that when the ICM is replaced, it's usually a good idea to replace the pickup coil as well. (Not referring to ignition coil.) It's cheap insurance to do so.
Dukesterpro FEB 10, 08:41 PM
Since I had a coupon for o-reillys I just went ahead and replaced the EGR anyway. No improvement.

Something is rubbing me the wrong way about this idle. When I started the car with the new EGR it idled properly. After driving and warming up it was still knocking a bit, so I retarded timing even farther. Now it was missing and stumbling again on acceleration so I had to split the difference. When I shorted the A and B terminals idle dropped to normal. When I disconnect it would stay normal for a while then slowly climb back up to 11-1500 over the course of 15 seconds or so. Whenever it idled normally, there was no smoke out the tailpipe but when the idle increased I got some faint smoke.

It also feels like my exhaust has gotten louder somehow??? The engine sounds like it becoming more rattly.

I noticed when I pulled the 2x2 plug on the back right of the throttle body. No check engine light came on. Is this for the IAC?

What should I do from here, I am lost.

I'm losing my mind.

Thanks,
George
Patrick FEB 10, 09:08 PM

quote
Originally posted by Dukesterpro:

Since I had a coupon for o-reillys I just went ahead and replaced the EGR anyway. No improvement.



Which indicates the original EGR valve was probably fine... which is why I wanted you to test it first.


quote
Originally posted by Dukesterpro:

When I shorted the A and B terminals idle dropped to normal.



Jumping those terminals retards the ignition timing. The ECU no longer has control of advancing the timing.


quote
Originally posted by Dukesterpro:

When I disconnect it would stay normal for a while then slowly climb back up to 11-1500 over the course of 15 seconds or so.



The ECU has control of idle speed through the IAC valve. It's possible the CTS* is faulty and is reporting to the ECU a very low temperature reading. This is where a scanner and/or WinALDL comes in handy.

* Note, I am not referring to the temperature gauge sending unit.

[This message has been edited by Patrick (edited 02-10-2023).]

Dukesterpro FEB 10, 09:11 PM
The parts cannon is racking up for another round. I was considering swapping to the double-plug coolant sensor. I will try that and get back to you. It ran like this earlier when I first got the car and the coolant sensor was unplugged. I will keep everyone posted
Dukesterpro FEB 14, 12:18 AM
I slapped a new coolant sensor on, a new style to pin plug as recommended by the ogre. No change.

Should unplugging the IAC throw a code? I noticed it doesn't when I open it. In fact, even with the ridiculously high idle the computer still isn't tripping a code 35 which I would expect.
What is a good starting point from here, We know the EGR is good. It has a fresh intake gasket. Plugging all the vacuum ports doest fix the high idle. I'm guessing it isn't a vacuum leak. Spraying break cleaner around the intake doesn't induce a higher rev or smoke more. So I am guessing its not vacuum.

It has a new ICM, and a new TPS. I put a new map on but it was bad out of the box. Through a code 34 as soon as the car warmed up. Putting the old one on stopped the light.

What now?
Patrick FEB 14, 01:34 AM

quote
Originally posted by Dukesterpro:

I slapped a new coolant sensor on, a new style to pin plug as recommended by the ogre. No change.



Until you use a scanner and/or WinALDL, you don't really know what info the ECU is being fed.


quote
Originally posted by Dukesterpro:

...high idle. I'm guessing it isn't a vacuum leak.



This may seem obvious, but... Is the throttle plate closing as far as it's supposed to? Is the throttle cable binding at all? Has the idle stop screw been tampered with? Is the plug covering it still in place?

I might also add that the engine will want to idle faster if the ignition is still advanced (within reason) beyond the factory specified setting.

[This message has been edited by Patrick (edited 02-14-2023).]