OK guys I have replaced the opti, spark plugs, wires, ignition coil, iat, and pcm. I have checked and cleaned the map, maf, iac. I have also had the injectors cleaned and tested the fuel pump. The pcm was showing codes 16 and 42 and the manual says to change the pcm. I just finished that and was thinking that it was the source of all my troubles but it is still missing. What is my next move besides changing the fuel pump? BTW my neighbor is the service manager at a local gm dealership so that is where I get my scanning done and also any work that I don't feel like doing myself. One more thing, my other pcm had a program on it( not sure what, it came on the car). I'm wondering if somehow that could be a part of it. I am gonna start checking my wires and plugs and go from there. I'm at a loss guys, please help? Ps sorry about the long post.

 

The best way I know to test your fuel system is to pull your fuel rail, make sure you clean around your injectors before you pull them out of the intake. Disconnect your coil, and have someone turn the car over and you can observe to make sure the injectors are all spraying correctly. It should be a misty conical pattern.

Also check fuel pressure with a guage if you havent already. If those are all fine, then your fuel system is in good shape.

You are having the same symptoms as me. I replaced everything electrical.

I had a broken valve spring and #8 valve guide seal is almost non existant. I sprayed water on all of my cylinders and had 4 cold cylinders. I have my motor on a stand right now to do a premptive rebuild. Just something to think about, not saying it is your problem, but pulling the vavle covers when I first got the miss, might have saved my a couple thousand dollars. It is not if your engine goes, its when.

Good luck:

Z

 

Thanks zman, I already removed the rail and checked the injectors and the pressure. I don't think it is internal ( I hope not anyway) because the new pcm got rid of the major miss. It still has a hard start and a slight miss as though something else has gone wrong. I'll post when I find anything out.

 

Do you know anyone where you could swap out an ignition control modue? If you have access to a Haynes manual, you can check the voltage on it also. This is the check:

Disconnect the ignition control module connector and at terminal A and D you should get 10 volts dc or more. If you do, then change the voltmeter to ac and at terminal B, you should get 1 to 4 volts.

A is the pink/black wire
B is the white wire
C is the black wire
D is the white/black wire.

I think shoebox has the same diagram on his website.

http://shbox.com/1/95_ign_system_schematic.jpg

ZMAN

 

I thought that I had already changed the icm but I did not so I will just change it anyway since it has never been removed. Thanks. I'll reply if this fixes my problem.

 

Did you do the ICM cooling mod where you put some washers between the coil and the cylinder head?

 

Zman, what are some good symptoms of a valve seal/spring problem??

 

The valve seal issue, you will/should get a nice puff of smoke when you first start the car. It's more pronounced after the car has sit for a while. My valve seal was non existant, and I was fouling out that plug. My plug was wet, looked more like gas, not oil, so it through me off. But after pulling the motor, the cylinder had a lot of oil sitting on top of my piston. I don't know if that was the cause of my broken valve spring.

My broken valve spring was cusing my miss. It acted almost identical to an electrical miss. I replace all of my electrical components except the ignition control module. I checked all my other sensors with a multimeter. My fuel system also checked good. I've had easy misses before where all I did was replace plugs/wires, and it fixed it. I've had non team players like this miss. But my bearings were very worn, so it was a matter of a few miles before it would have spun a bearing.

Z

 

Did you also have a hardstart, and crankcase contamination?? Cause I too have a slight miss along with a buddy, but its almost unnoticable, and it wont start at all in the rain, but when it is running in dry weather the miss is almost not even there. You hear it slightly when getting close to the exhaust, and you can feel it very very slightly at very low RPM like 1300 rpm cruising. I keep changing the oil trying to figure this all out. A few friends suggested the valve spring/seal problem, thats why I asked since you mentioned it too.

 

I had a few hard starts in the winter. My miss was pronounced. Sometimes I would throw a part at it, and it would clean up the miss, then it would start missing after a few minutes.

Z

 

i am still in the same situation, but my miss is alot bigger then a miss, its the whole bucking situation, and i have changed also everything, my friend is wanting to replace my opti system but it seems that axeman did that alreadyand it didnt work. i have also changed everything else including the computer! i dont even have any codes or check engine light on. so why am i still having this problem? anyone? lol i dont want to go out and buy the damn whole opti system when its not going to work and i dont even have a problem with it. ugh! this car is really starting to **** me off, being trying to fix this for a year now.! please help!!!

Leilani

 

Pull your valve covers and see if anything is broken.

Z

 

I finally found my low RPM stumble/miss.

Mine happened in closed and open loop mode. big clue

Blown head gasket at cylinder number 8. The blow-out was between the cylinder and an adjacent head bolt. I was losing compression into the valve cover area.

Compression check man, especially if it is in open and closed loop.

There were many other clues to my problem (oil in TB, high BLMs on one side only, etc), I can't detail them all right now. I need to go to a meeting.

Sean

 

i already did both of those, took the intake and cleaned the whole thing out, i looks like i am burning richer in the back 4? the front 4 where pretty clean.

 

Alright, I did the check on the icm and it was going out. But that was not the cause of my miss. Looks like I am going to have to wait for my neighbor to come back from vacation so I can get this thing scanned at the dealer. Thanks for all of your input and I promise to post the fix whatever it is.