I posted this one over at cz28.com and no one has responded. I figured I would see if anyone here has any suggestions since this board seems to have more tech gurus

We did a cam swap over the winter on a friends 30k mi 97 WS6 Formula.

We have been trying to fix a slight miss now for months and I'm out of ideas. We have an appt at a local speed shop but can't get in 'till the middle of next month so were are going to keep looking for the problem until that time.

The cam we installed was a 221/227 .542"/.560", 112lsa we also did springs and 1.6 SA roller rockers and a re-tune from PCMforless. The car already had macs and a 52 mm throttle body and PCMforless tune.

The car sometimes runs normally and feels really strong but usually has a slight miss during idle and low rpm that gets worse when the car gets warmer. It's also down on power when it has the miss... go figure

The wires are new, plugs are fresh and we just changed the opti and harness this weekend. It still behaves the same way.

I have adjusted the rockers several times thinking I had them too tight. They are about 1/2 turn past zero lash right now. I tried 1/4 turn but they were a tad nosiy so I went back to 1/2 turn. I did them with the car running.

We just recently we noticed that the temperatue gauge goes off and on when the car starts missing. No other lights or gauges seem effected. We put a new sensor in and same story.

The car has been converted to OBDI. We put the original PCM back in and the car still has the miss and throws a P0300 random misfire code. I have heard this code is common for a cammed car.


I have an autotap but I am not sure if I can data log with the OBDI pcm and what parameters to look log. I could install the OBDII pcm if anyone thinks it would make life easier. I also checked fuel pressure and it's OK.

Any ideas?

 

Its always real hard trying to solve a problem like this over the net.
I would say your best bet is to put the ob2 back in it and use a-tap to log some runs and find out whats going on when the miss occurs.

The random miss fire code is common durring idle or very low rpms. But you should not get it while driving.I would use a-tape and see if it missfireing in the same cyl or all over the place.

 

Glad I seen this post in a way(not happy you an I have this problem). I have installed a cam in my 96 with obdI setup also about 250 miles ago. Ran fine for a little while then it started to feel like it's missing. I pulled al the pluggs. they all look fine. Like if it was down one cylinder you would expect to see that plug all nasty. But they all look the same and look good. So it's not overly rich or lean. Some times it will seem fine for a mile or two then it start it's shutter/miss feel and feels down on power.
Have you tried the coil? Do you know how much they are? I was thinking of trying that. I have not swpped my opti out like you but mine is fairly new and never had an issue before the swap.

 

check all your grounds. with intermitten problems like this it is a good idea to simply check connections and grounds, it could be something loose not necessarily something bad or wrong.

beyond that its hard to say. get some data logged on the car while its messing up and while its not. what would be best is to log it while it goes from good to bad if thats possible.

 

I had nearly forgotton about this post. We got this fixed earlier this summer.

I'm a little embarassed to say this but it was our own fault. I think the new opti fixed the first miss but when we did the wires, #6 got a little too close to the header.

We replaced the wire, the car ran great. Live and learn I guess.