engine timing

[mr.ricoe]

DOES ANYONE KNOW HOW TO ADJUST THE TIMING ON A 87 GN AND WHERE IT'S SUPPOSED TO BE AT? I HAD A PROBLEM THE OTHER NIGHT ON THE FREEWAY WHER THE CAR TURNED OFF ON ME AT ABOUT 70 MPH AND IT STARTED BACKFIRING LIKE LOUD BANGS FROM THE BOTTOM OF THE CAR. I ADJUSTED THE TPS TO .42 AND MY RMP DROPPED TO ABOUT 7000.

 

[notacarlo]

Timing is controlled solely by the ecm and can be adjusted with the use of an aftermarket chip - that has that feature.

The backfiring had nothing to do with timing.

You didn't mess with the cam-sensor cap did you? Possibly try to turn it to advance/retard timing? That would be bad.

My guess is you detonated and took out the head gaskets due to too much boost and inadequate fueling.

TPS.....7000 rpm!? is this a typo?

 

[mr.ricoe]

I'm sorry I meant to say 700 for the rpm. I have not touch the cam sensor cap. I just bought the car a couple of months ago and trying to get it running right.

 

["Turbo-T"]

If your car has the Turbo Tweak chip in it and a Scanmaster, you can adjust the timing that way, but it's not adjustable like a typical rotary distrbutor is.

Not sure why your car would be doing what it's doing but I don't think it's a timing issue, there's lots of electrical gizmos to go bad and make the car do wierd things.....like bad MAF sensors, bad coil packs....someone will chime in here before long.

 

[mr.ricoe]

Not sure if the car has a chip in it or not, I bought the ScanMaster and hooked it up. That's how I adjusted the TPS to .42, but other than that I dont know what else I can use the ScanMaster for. I also added a heated oxygen sensor that I purchased from jay's gn. I've drove the car since the incident and it has been driving fine. This is my first Grand National; I've always own el camino's, ss monte carlo's and 83 hurst oldsmobile they were easey to work on, but this GN is something else.

 

["Turbo-T"]

The Scanmaster is a very useful tool. It not only monitors your knock retard and 02 millivolts (which are both very critical on these cars) but it can also tell you the speedo mph, coolant temp, air intake temp...if the SES light comes on it also displays codes....very useful tool to have.

If you don't already have the Turbo Tweak chip I recommend you splurge $85 and get one. It will allow you to change timing and fuel curves via the Scanmaster. Plus it will run better as the TT chips are made to run on todays gasoline. Your ECM might even already have one. Pull your right kick panel. Pull the small cover off the ECM, I think it's a 10 mm screw. It will say Turbo Tweak on the chip if it is.

And yes the GN is not like your typical small block Chevy or Olds. For the most part the GN has all sorts of gizmos and such that require a new understanding. I've sort of summed it up as the ECM times the ignition and injectors and relies on the MAF, TPS, Cam and crank sensor and some other things to make it all work.

 

[GN owner]

The backfiring could be caused by a number of things including a MAF sensor that might be going bad, a defective coil pack, or even a fuel pump starting to go bad. The MAF sensor could be checked by letting the car idle and tapping on it and see if the engine starts running rough or even die out. For the fuel pump get a fuel pressure gauge and monitor the fuel pressure as you drive around to see if that might be your problem. Check with your chip manufacturer and make sure that the fuel pressure at idle with the vacuum hose removed from the fuel pressure regulator is what it supposed to be. When the boost starts increasing the fuel pressure should be increasing also. In other words if the boost increases 10 PSI then the fuel pressure should increase 10 PSI and the total pressure should equal the 10PSI plus whatever the fuel pressure is at idle.