I have an 89 IROC with a 86 305 TPI motor. My timing is retarding 4-6* on acceleration. I know this is not right, I'm getting a code 42, could a bad ignition module cause this? What I would really like to know how the timing is controlled, is it through the ignition module? -James

 

How do you know it's retarding?

 

I hooked a timing light up to it and reved it and you could see it retard 4-6*, I assume it would do this under driving conditions as well. I should have worded that first post a little better.

 

That's normal. The ECM will retard the timing when manifold vacuum drops.

 

timing is controlled by computer

 

Well I have a huge hesitation on the bottom end, I'm also getting a code 42, what do you guys think? Am I sniffing around in the right area?

 

A wiring fault or defective ignition module could cause a code 42.

 

code 42 isnt that an ESC module could be that haven't done my codes in awhile im a lil rusty lol

 

Here is the entire situation, when i got the car it had bad valve guides, put new 416's (what came off) on the car, it ran like crap, changed the cam and found I had a bad came, lifters, timing chain and a burned valve, had that fixed, put it back together, runs the same, today I replaced the module (why not), no different, If I ease on the gas the timing advances, if I punch it, it retards and hesitates (free rev or in drive), I also checked my vacuum, if I ease on the gas it stays good, if I punch it it spikes down to almost nothing. I dont know where else to go I've replaced the o2 my code 13, and ignition module code 42, and nothing has changed, I didnt drive it yet to see if the 42 comes back but I am still getting a 13. (sorry for getting a little off topic this car just frustrates me).

EDIT: What parts/sensors that could be bad or not working right cause a 13 and 42?

 

i know when i replace my O2 i used gm parts only had bad problems with the aftermarkets before