car question

I hit the nice big 176K on my way home today from school. Talking with someone tonight brought up the question about timing chains. I was wondering if anyone knew off the top of their head how my ignition systems fired? It’s a 1993 Pontiac Grand Prix. So how does my ignition fire exactly?

P.s. – Let’s keep the OP and not turn this into a debate about imports v. domestics ok?

After re-reading it, what I was actually trying to ask is, what kind of distributor is there?

I had a 88 Bonneville, and now have a 96 Bonneville, both with Pontiac’s 3.8 6-cylinder, fuel injected V-6. The Grand Prix is little smaller, but I think had engine choices similar to the Bonneville. If not, this may not help much.

Both Bonnevilles had/have all solid-state electronic ignition. In other words, no mechanical distributor at all, it’s a completely solid-state module that gets its timing signals from the main computer. So the timing belt (not a chain on that particular engine) has nothing to do with the distributor timing.

However, even though these engines don’t have a mechanical rotor for a distributor, the timing belt drives the camshaft, which must be kept in sync with crankshaft, or your valves open and close at the wrong time. So the belt and gears still need to be replaced at some point.

IIRC, Pontiac recommends replacing the timing belt and gears at around 100,000 miles. I had the one on my 88 replaced at around 165,000, even though it was still running strong. But I was heading out on a 3 thousand mile trip and figured it was time to do it just out of CYA concerns. (On a side note, that car ran another 50,000 before I gave it to my sister, who drove it for 2 ½ more years before she crashed it. It was still running strong and had never had any major engine work.)


To answer the original question: the '93 Gran Prix does not have a distributor. It has a distributorless ignition system (DIS–which GM calls Direct Ignition System), which is integrated with the electronic control system (“computer”). It uses signals from a crankshaft position sensor and a camshaft position sensor as its primary inputs to regulate ignition timing, along with additional relevant data from other sensors as applicable (e.g. knock sensor). The timing chain is not a factor in this, other than that it runs the camshaft (or intermediate shaft if the engine is a 3.4)–but then that’s necessary for the engine to run at all.

To clarify terminology in RJKUgly’s post: electronic ignition does not mean no distributor. It means no points. Points are a mechanical switch that were the state of the art through the 60’s. During the 70’s and 80’s, all manufacturers abandoned points in favor of electronic ignition, using magnetic or optical switches with electronic signal amplifiers to do the job that points used to do. For years, these systems were incorporated into distributors. In the last ten years or so, the trend has been to forgo distributors in favor of DIS and, more recently, COP (coil on plug) systems. These are also electronic ignition systems. So, all distributorless systems are electronic, but not all electronic systems are distributorless.

I have never seen, nor do my books show, a GM 3.8 engine with a timing belt. They are timing chain engines.