where to begin........

[butlar]

Ok, end of last summer my timing belt slipped...bent a few valves..same old same old, ive been there before. So this year i replaced timing belt...valves.new tensioner and so on, and timed car following instructions to a tee. I also installed a set of 272 cams, 750cc injectors and a motorguys garage socketed eprom set for 750 injectors. Car starts but runs terrible, almost as if timing is off..but i swear it isnt...when i hook datalogger up to it it shows something like 30 DEGREES ADVANCE>>>WHICH SEEMS VERY ODD> i am kind of leaning towards maby the coil pack or cas>

secondly< with my datalogging software i can turn off injectors when car is running ( hand held halo software) it seems it alternates from injectors number 1 and 4>>sometimes there is no change when i turn off number 1 AND SOMETIMES NO CHANGE IN WAY CAR RUNS WHEN I TURN OFF numbert 4. So this may suggest CAS i would assume. The vacuum my car shows is -10 which seems fairly weak to me, but the car is cammed.

I thought i may have seen arching from the coil pack, but this is when wire is removed from plug and left on coil when car is running..but it occurs between numbers 1 and 4 ( 1 and 2 on coil), i did this to try and determine dead cylinders.
Also fireing order is correct....we have all done this at one time.

The car runs very badly....dosnt take gas well..stumbles constantly, dosnt run well enough to drive.....not responsive, just plain shitty,,backfires,,running extremely rich. I am running gm maf with translator..and car is throwing code air sensor, but i dont think that is my problem..although it is a problem

Any help would be appreciated, i am no newbie to dsm..but no expert , so any suggestions i will try.. a new CAS and coil will probley be in order, also boost leak tested..no leaks...compression is good across the board...thanks again

This is one oif those posts that everyone hates because it could be so many things, my gm maf sensor checks out fine though and appears to be working correctly...just were the idle is so in consistent it may be throwing off the sensor.

 

[outkastracing]

first things first have you ohmed out your coil pack to see if its good??? i had this same type of problem and i found that one of my spark plug wires was not in the coil pack good enough your manual should walk you threw how to do this! do you have a spare cas, coilpack? thats also and easy way to test! when you did all this did you replace your spark plugs? are they gapped propperly? just some things to try good luck

 

[srumel]

Check your ignition base timing if you can. There is a write-up on vfaq.com describing how to ground the connector pin, etc. Rotate cam sensor clockwise to advance, and coutnerclockwise to retard ignition base timing. A good starting point, if you don't know where the ignition timing is set, is to adjust the sensor to roughly the center position and go from there. If it's full one way or the other, you know you have a problem.

Also, since you just did the timing belt, the CAS could be 180 deg. out of adjustment. With the motor at TDC and timing marks lined up, remove the CAS and if the notch in the "cog," sorry don't know what else to call it, and the notch in the body of the sensor aren't lined up with each other, then just line-em-up and reinstall, and set base timing.

Another thing to try, as long as you have the ecu chipped for the 750s, is to unplug the maf sensors all together. This will throw the computer into a "limp" mode and if it results in the car running better, then you know where your problem is.

 

[spectr019]

I had that same problem...I had my timing belt replaced at a garage...not a Tuffy, another one I can't remember right now. They called me to tell me that my car was done, and asked me if my car had always run like that. I thought they were just referring to loud (from exhaust?), and I said yeah it did. I got there, did all the business, started it up, and it was acting like the MAS was unplugged. After a few days of arguing with them, ultimately I told them to redo the process and make sure everything was connected and timing was correct and EVERYTHING was as it was. I even gave them my Haynes manual to look through and go by that. When they redid it, it was working fine. I'm GUESSING that they found out what they did wrong, but just said "wow I dunno, I did the exact same thing." So from MY PERSONAL experience, I would say that your coil is fine and everything, just recheck and DOUBLE CHECK your work to a precision. Hopefully you won't have to spend any money on buying new parts and that it's just something that was overlooked. Best of luck man, I know I was worried that I had lost my car when this happened.

Ben

 

[turbo_nic]

With the vacuum being so low like that, I would recheck your timing belt work. Guessing you got it off 1 tooth, that would be why your timing is so crazy on the logger and the low vacuum and running so horrible. Yes, the cams will lower vacuum but not that much. I know you say your timing isn't off, but at least take off the timing covers and double check the timing marks, wouldn't be surprised if it's off.