Question about 1992 Chevrolet Suburban
I've narrowed the problem down to the fuel injection system using NOID lights. It a 1992 Suburban 1500 with the 5.7 L with TBI. I have full battery voltage to injectors. Injectors operate fine for a while and then begin to "misfire" causing the engine to stumble. This will go on for a bit until it finally stalls out. Sometimes the truck will start back up, sometimes it has to sit over night before I can get it going again. A short shot of starting fluid will give the engine a short breath of life so it appears that the ignition system is unaffected. I've tested continuity of both signal wires from injectors back to the PCM and they test good. I've checked the resistance of all grounds for the PCM, again all check good. I replaced the PCM and the problem persists.
I'm an ex-Ford tech and was a Ford electrical systems specialist but I can't get a factory quality manual for this vehicle. My best guess at this point is that the problem lies with what ever GM uses to signal the PCM to fire the injectors (ie: camshaft position sensor, crank sensor, hall-effect, etc.) None of the reference material I've been able to get my greasy hands on has given any kind of explanation of the fuel injection system inputs to the PCM, only outputs. As the saying goes, "Garbage in, garbage out". I'm just not familiar enough with GM products to know the source of the garbage.
Thanks for any help you can send my way.
I am almost %100 sure that your problem is a faulty distributor module. These have a tendency to fail and show the exact same symtoms you are describing. In fact this happened to me once. The ECM uses the signal from the distributor to calculate when to fire an injector pulse. When these modules go out they tend to overheat, and after the module heats up, it will start sending erratic signals to the ECM and it will begin to misfire the injectors, causing it to stumble and stall. After the distributor module has cooled, you can usually resume operation temporarily until it overheats again. Also keep in mind that in more extreme cases (when the distributor module is just completely fried, which i have also experienced) you may not get any spark or injector pulse at all, and very erratic fuel pump operation, or none at all.
As a bit of advice, I would recommend you just replace the entire distributor, because about the time these modules start dying, the shaft seals start to fail and the magnetic points will lose their magnetism, causing similar problems. O'Rielly has them rebuilt with a lifetime warranty for about $100
If you need anything else, just let me know. I know TBI engines better than any other engine.
Posted on Nov 17, 2008
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Posted on Jan 02, 2017
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