(Video) Misfiring issue

[rendyx]

Okay, today I went out and tried a few tests on the SHO to troubleshoot my strange misfire. Once again, it only happens at idle, it goes away after driving, and does not seem to affect driving (well, except a hesitation in the video below).

So I filmed my problem. I take us to look at the car after I ran it around for a while, then did codes. I got no codes, (including in the cyl. balance test, and it was missing at the time), except some odd one (524, so I read it wrong, this is an 89, it's probably my 24 code). I took plug wires out of the coil and rearranged them for the heck of it. I also tried spraying C&C (yes, I know it's engine degreaser, I tihnk I'm getting dumber or something grabbing that!) on the missing bolt (in the video).

Here's the link, it's about 9.8MB, a Windows Media file, and around 6 minutes long. I know it's a little big, I have dial-up myself. But it's worth it, and I put some details into it, along with a WOT run in an 89!

http://users.superford.org/rendyx/downloads/misfiring.wmv

After I left the school, I got some braking coming down the hill. I was in great fear I had damaged the differential, and then it went away. However, a quick check of the brakes led to the RR one being extremely hot. My SHO definately loves me! But that's another problem...

So I assume go after the bolt? Thanks for any help with this problem again!

Of course now I "brummmmpppppphhhhhhh, brumph, brumphh, brummmmmmmpphh!" is going to replace "WOOOOOOO WOOOOOOOO!"

 

[rendyx]

Just another question, a fellow SHO owner noticed a different sound than other SHO's, along with not being able to hear the secondaries open, although they did. Anything seem wrong, or is my SHO just a bit different?

 

[Slo-Sho]

The next time it misfires, pull the ignition wires at the coil one at a time until you figure out which cylinder it is. As long as the remaining intake manifold bolts are tight, the leak should only be marginal. Although minor, I'd get that taken care of. It is a 10mm bolt.

<small>[ February 20, 2003, 06:54 PM: Message edited by: slosho ]</small>

 

[ScotSHO]

Hey, just a thought. We cleaned the intake, but we never took the IAB off the intake. I wonder if there is some crud that lodged in the IAB... Your problem is at idle, and the IAB only comes into play at idle. I'd clean the IAB when we go after the intake bolt.

Scot Hewitt

 

[rendyx]

Scot Hewitt - 95 mtx:
Hey, just a thought. We cleaned the intake, but we never took the IAB off the intake. I wonder if there is some crud that lodged in the IAB... Your problem is at idle, and the IAB only comes into play at idle. I'd clean the IAB when we go after the intake bolt.

Scot Hewitt

Not a bad idea. The IAB is new, (of course it could be faulty) but may have gotten dirty when everything was cleaned.

 

[KyngofPop]

slosho:
The next time it misfires, pull the ignition wires at the coil one at a time until you figure out which cylinder it is.

How would this tell which cylinder is misfiring and is this danrgerous to do?? I did this once on my Pontiac SSE and got schocked really bad. I'm also trying to figure a misfiring problem that is very similar to Rendyx's on my 93 ATX. The only difference is that my car will slightly hesitate and not misfire when cold, but as soon as it gets warm it misfires HORRIBLY!

 

[Slo-Sho]

When it is misfiring, eliminating plug wires only helps to narrow down which cylinder is misfiring. The next step would be examining the plug and wire at the affected cylinder. If there is no change in rpm when pulling the wire then you've found it. I wouldn't pull the plug wire with my hand, I'd use a pair of insulated pliers. A plug can tell you ALOT about how the engine is running.

 

[DavidT]

hey, I noticed when you are in idle (with the hood open), your engine sounds like mine... similar to a sewing machine. Except at times, mine gets much more animated. Is this normal? I am going to inspect my timing chain tensioner. When you had your 60K, did Scot examine yours... if so, how did they appear?

 

[rendyx]

dkautumna:
hey, I noticed when you are in idle (with the hood open), your engine sounds like mine... similar to a sewing machine. Except at times, mine gets much more animated. Is this normal? I am going to inspect my timing chain tensioner. When you had your 60K, did Scot examine yours... if so, how did they appear?

Mine were looking pretty decent. Someone else noticed this noise too, and it worries me a little. However, as long as it's not causing an immediate problem, I can wait. My SHO makes way to many noises! thumbs_u

 

[DavidT]

yeah, mine too (look at my sig wink )
How did the cam lobes appear?
Have you had your rod bearings checked?
Lastly, the clacking noise on my sho...well, sometimes, is just plain scary. From inside the car, when coming to a stop, it sounds like I'm in a big tractor trailer (diesel) oh_my It only does it on occasion (the really loud sound)
I have tried to capture this scary noise on video, but by the time I get the hood open, it has subsided to the same sound as yours. I will email you a clip IYI.
Without the aid of a stethoscope, I think the sound is coming from under the driver side rear valve cover. shrug

<small>[ February 21, 2003, 06:35 PM: Message edited by: dkautumna ]</small>

 

[sdpatt]

The IAB valve, whether clean or dirty, can only affect the idle speed. It will not cause a misfire. It basically works like a small, electrically controlled throttle valve. Throttle valves don't cause misfires.

 

[Mr Anonymous]

Well, I finally had the time to watch/listen to your video, and I am convinced that your problem is not a misfire per se (the plugs are firing properly and fuel is properly being metered to the combustion chamber), but an intermittently rough idle due to unmetered air entering the combustion chamber causing an over-lean mixture, resulting in detonation.

I believe this is 100% the result of your missing bolt. I had inferred from your earlier posts that the bolt you were missing was one of the bolts which secured the crossover tube to either side of the intake (crucial to the DIS ground path), not realizing you were talking about one of the intake-to-head bolts. The fact that spraying carb cleaner by the bolt hole results in changes in the engine sound and white smoke out the exhaust confirms that there is not an air-tight seal where there is supposed to be one.

Not noticing the problem at higher RPM's is probably the result of the additional fuel flow at throttle and timing changes reducing the detonation.

Replace that bolt and your problem should be solved! You may find the intake to head gasket may have lost its coating during this time and might require replacement to completely alleviate the problem.

<small>[ February 21, 2003, 07:29 PM: Message edited by: SHOooo ]</small>

 

[HopefulSHO]

Holy smokes! That's not carb & choke cleaner - that's engine degreaser

 

[RI-SHO]

From my past expericence with my SHO i'd say to give each injector a tap with a long flat screwdriver and see if the condition of the idle improves while tapping a certain injector.

My SHO sounded similiar when the #2 and #5 injectors were gone and keep going on and off.

This is more timing related but this is what my SHO did after it stopped running in idle like your SHO is doing now: www.ri-sho.com/shop1.wmv (1.5MB - 46sec)

<small>[ February 21, 2003, 08:30 PM: Message edited by: RI-SHO ]</small>

 

[rendyx]

David: I took a look at your clip, and wow! That is noisy! I'd do some more research on it if you haven't already. Sort of sounds like mine though.

Edien: That's a new sound! What exactly causes this slipping sort of noise? Very weird.

Now I just have to fix my brakes...

 

[haydenm315]

slosho:
The next time it misfires, pull the ignition wires at the coil one at a time until you figure out which cylinder it is. As long as the remaining intake manifold bolts are tight, the leak should only be marginal. Although minor, I'd get that taken care of. It is a 10mm bolt.

After I did my 60k I had missed tightening one or two of those bolts and my car sounded loud like in the video. I think every one of those bolts is important. With the bolt loose my car did backfire if I reved it up a little when it was coming back down to idle.