does the 1997 gmc sonoma 4.3 vortex have a timing chain or belt?

It’s a pushrod engine so it has a timing chain.


ok, would that cause a p0300 code because i get random backfires, too, and when i turn the truck one way, the truck will make a vibration noise or when stopped on some slopes in the road.

That’s a really vague question with no clear answer.

The “fire” requires 4 things: 1) fuel; 2) air; 3) compression; 4) spark. You need to check them all. I recall you posting something else about this in another thread. If you have been messing with it for a while w/ no success, check the compression. If you want feedback post the very specific numbers in psi for each cylinder.

If the compression is good, then you check fuel pressure, injector operation, vacuum leaks (including intake manifold & things that might act like vacuum leaks such as EGR), plugs & wires along with other ignition components (e.g. cap & rotor).

It would really help to know which cylinders are misfiring. Unfortunately, for GM of that era all you’re going to get with a basic code reader is the random misfire code. You need to find someone with an actual scan tool that gives data and has the capability to display cylinder misfires, both current and history. No basic code reader I know of does that.

I suspect a fuel injector issue, but since the injector assembly is inside the engine on your truck it can be difficult for a DIY to test those. Do you have a fuel pressure gauge you could hook up to the schrader valve–left rear of engine near firewall?

asemaster makes an excellent suggestion. At 15 years old, your central fuel injection unit may very well be leaking. You may be able to detect this with a fuel pressure test. If the residual fuel pressure bleeds off rather quickly, the fuel injection unit or fuel pressure regulator is probably leaking. You may still need to pull the plenum to have a look, though. The hoses coming off the injector unit (the “legs” of the “spider” as it is often referred to as) often develop leaks which, IIRC, will not show up on the residual fuel pressure test.

so what you guys are saying it could be in the fuel injectors located in the throttle body

well the even side is missing i changed the fuel filter plugs wire cap and rotor maf sensor and coil

Actually this truck has multiport fuel injection, GM did away with the TBI and CPI setups in 1995.

no, it has tbi.

"no it has tbi "

Sure about that? The last year for the TBI 4.3L was 1995. The TBI engines only have two injectors. For a 1997, it should have six injectors, they are all mounted closely together though, with hoses running to each intake port. It’s sort of a half-assed hybrid TBI/Multiport arrangement.

i’m sure because there is no fuel rail. there are two injectors on the throttle body.


Is the engine in the truck the original?

If this engine has throttle body injection as described, either it is not a 1997 or somebody has gone to the trouble of converting it to OBD1 to work with this engine. I believe 1993 or 1994 (not sure which) was the last year the TBI version of the 4.3L V6 in the compact trucks. It was definitely not available in the compact trucks by 1995. Full size trucks still got TBI till 1995. After that, they were all MPFI. A 1997 Sonoma V6 should definitely have the MPFI system, which is contained underneath the plenum, in the space between the plastic upper plenum and the lower intake manifold. Another way to tell: if the word “vortec” appears anywhere other than on the valve cover, it is not throttle body injected.

The 1997 GM 4.3 Vortex engine utilizes the Central Port Fuel Injection system. Or also called the Spider Assembly fuel injection system. This means that the fuel injector assembly is located below the lower intake manifold assembly. The engine does have a throttle body, but there are no injectors mounted in the throttle body.

Here’s an image of the spider assembly. http://www.justfuelinjectors.com/servlet/the-6502/Complete-“Spider”-Fuel-Injector/Detail


If your truck has two injectors in a circular “2-barrel” throttle body assembly it is not a 1997 US model year. Can you post the VIN for us? TBI and Central port are 2 completely different systems.


Hey tester Thanks!! Thats a great site. I priced the injectors for my 97 5L Vortex $199.95 Thanks again.

the vin is 1GTDT14X1V8503258

i understand now that it has port injection now it has spider injectors