SHOnot running well, need help.

[BeautifulDisasterSho]

Hey guys,

My 90 SHO has been sitting around for a good couple weeks now because something is wrong with it and I can't figure it out. This problem started out of the blue one day and ran great before. When I start up it will vibrate unusually bad like a missfire and has a real tough time accelerating.
It even takes a while to rev up it seems. Also, it backfired through the intake a couple of times when revving it. It gave me a 02 code that said it was running lean, but I have replaced both of the sensors a few months back. I unplugged the MAF while running, then went and cleaned it off but there was no difference, still ran like crap. I have checked all the plug wells and nothing shows. I have new plugs/wires, good fuel pressure, front 60k'd as well. Does anybody have any ideas for me?

I would greatly appreciate any help with this, thanks.

-Dougie

 

[autobahnsho]

I'd try running the codes, and looking at the plug wires.
Maybe one of the wires is partially unplugged on the spark plug or plugged into the wrong spot on the coilpack.

Good luck!

 

[BeautifulDisasterSho]

No luck yet.. I checked all of the plug wires to see if they were partially unplugged, but that wasn't it. I'm thinking maybe a cat is clogged because the power is poor, but then what would be causing the intake backfire? I do have another coil that I will try today and see if that is the cause. Does anyone know if a bad DIS acts like this?

 

[BeautifulDisasterSho]

Well, I put in the other coil pack and that didn't work. I also checked the timing belt tension to make sure it didn't jump, still tight. Anyone have anymore thoughts on what could be causing the intake to backfire and the loss of power? I think I'll take it to the shop soon to see what they come up with.

 

[projectSHO89]

Run the cylinder balance test portion of the Quick test.

Steve

 

[philw349]

Don't mean to alarm you, but I had some of those symptoms with crank cancer. It would also "pop" when revving it up high, and take forever to rev.

Here is a thread on what it looks like

http://www.shoforum.com/showthread.php?t=26773

Here is a thread on the symptoms I had

http://www.shoforum.com/showthread.php?t=26221

 

[BeautifulDisasterSho]

Steve, I had a friends dad try using his digital code reader today and the there were no codes for either KOEO or KOER. Although, I remember when I tried it a couple weeks ago it gave me pass for KOEO, but did give me a couple codes that I've always had during KOER.. For right now I am checking the plug gap on all of them. I guess I don't know if my crank sensor is going already, I replaced it 5 months ago?

 

[BeautifulDisasterSho]

I sure hope the crank was tightened well cuz I'd hate to have to pull that apart again. Only of my plugs was out of gap at .030, but they all seem to look the same as if fuel was burning properly. It's got to be something simple..

 

[Jim Merriman]

What about the crank shaft sensor? What would the symptoms be if that's gone bad? I know when the camshaft sensor goes bad - usually when the car is cold, it has a hard time starting. And when the engine is warm, the engine shuts off. But quite frankly, I'm unfamiliar with crank shaft sensor symptoms. Was the crank shaft sensor replaced when the water pump was last replaced? I always replace the crank shaft sensor when doing a water pump or timing belt, it's right there, ya can't miss it!

Another thing is to try a completely different spark plug wire. If you don't have a spare set but have a number 1 or number 4 spare you can reach each spark plug and try them all, one at a time, to double check the wires. Internally, one might be damaged, though that's a long shot. I guess I'd check the wires as well at the coil pack, they don't have a cylinder running order:

cylinder running order:
firewall passenger side: 1,2,3
front of car passenger side: 4,5 6

The coils's a little different: The sparks plugs wires from the cylinders are placed in the following coil recepticles:
5 1
6 2
4 3
with the main connector on the right hand side as you view these numbers

Has the ICM (Ignition Control Module) been tested? I don't even know how to, but if that's going bad, it can't process all the information between the crankshaftshaft and camshaft sensors, PCM (powertrain control module), IDM (ignition diagnostic module), and PIP (Profile Ignition Pickup). Geez, this is enough to make you wonder how anything works right sometimes...

Do you have any oil in the spark plug wells? That would short out the spark plug and create a missing symptom. The fix for that are new camshaft cover gaskets and dome seals.

Any other ideas on the basics guys?

 

[S_Mazza]

Dougie, it sounds like you have a consistent misfire. That would account for the lean code and the rough running. To check for a dead cylinder, you can start the engine and then (carefully ... don't get shocked, cut, burned, or otherwise maimed) unplug one spark plug wire or injector electrical plug at a time. If you remove the plug wire or unplug the injector on a good cylinder, the idle should get worse or even die. If you unplug one of those and the idle doesn't change, that means that cylinder is dead.

If you find something this way, you can then test the possible causes: misrouted plug wires, bad coil pack, bad injector, shorted wiring, bad sensor, etc.

So did you change anything or do any work just before the problem started, or did it just start by itself?

 

[BeautifulDisasterSho]

I fixed it and it runs great again! That's all I did was re-gap those plugs and bought a new battery because it was dead when I tried starting it 2 days ago. The battery could have been causing the elecronics to not funtion right. One of the plugs must not have been gapped right because it was one hundreth off, that was probably my mistake. That can make a big difference on performance.

 

[BeautifulDisasterSho]

BTW, no I had not done any work on it before this happened, like I said, it happened out of the blue.

 

[S_Mazza]

Hey, I'm glad you got it all fixed. I did read your post which said "out of the blue," but I just wanted to make sure I understood you right. I wonder if it was the plug, the battery, or a combination?