It's been a while since I've been here, but hopefully you guys can come save my day once more What's been happening is my Bird has started backfiring. But only on the freeway when I get going more then 60 or so (about 1500 or more rpms), and only when I let off the gas. And the other night it threw a code 45 (running rich) while I was driving home. I have no idea what to check for here. It's a '86 305 TPI car, but the previous owner tells me it has an '83 350. Still TPI, automatic tranny. Anyway, I already blew up one muffler and just replaced it with the flowmaster. But I can't afford another one so help me please


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'86 WS6 Trans Am

 

try replacing your oxygen sensor first and see if that will help you out.

 

Arawn,

The Sofa King's advice isn't bad - if your sensor is more than 30,000 miles old you might want to consider replacing it - but it might not be the final answer. The typical failure mode of the O2 sensor is toward a lean indication, not a rich one. Not that it can't happen, but it usually works the other way. Sometimes a completely toasted sensor or disconnected electrical connector can "fool" the ECM into thinking you have a rich condition.

However, since the sensor is telling the ECM that the mixture is rich, and it sounds like your muffler concurs, you might infer that the sensor is good and your mixture is actually rich. Blowing a muffler off is usually a good indication of that.

You'll need to dig a bit deeper and discover why you might have a rich condition. Leaking injectors (including the cold start injector), injector wiring that is shorted (to ground), and excessive fuel rail pressure can contribute to a rich condition. A plugged air filter element (or one saturated with water) can cause a rich condition. A sticking TPS can contribute, as can a malfunctioning EGR or plugged PCV system.

Get a little more detail and check back in. I'm thinking that you might find something by eliminating those possibilities.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Ok, I will check those tomarow. I'm thinking the TPS probably has something to do with it. This is probably related, and I didn;t mention it earlier. Sometimes when accelerating from a stop it surges really bad, revs up and down about 3 times then it runs just fine. Also on rare occasion whenI start it, it will not stay running unless I give it gas. Lastly, I have some fuel injector cleaner stuff that you add to your gas. Is that a good or bad idea?

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'86 WS6 Trans Am

 

Ok, I tried to tinker with the T/A at my dads house today. I wanted to set the timing, IAC, and the TPS. BUT, I have no tach, and as it turns out, no voltmeter. Hopefully tomarrow I can borrow those items. But as far as checking for leaky injectors, how do I go about doing that? Any special tools? Hundreds of dollars in parts?

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'86 WS6 Trans Am

 

The injector leakage test requires a fuel pressure gauge. Connect the gauge to the Schrader valve on the fuel rail and monitor pressureafter the engine is stopped. Fuel pressure should maintain for 30 minutes without substantial pressure drop.

Incidentally, if the engine is an '83 350, it must have come from a truck or police/SEO vehicle, since 350s weren't generally available in cars in 1983. You can check the casting numbers on the rear ledge of the block for cast number and date code.

As for injector cleaners in a can (fuel additive types) they might be acceptable as a preventive measure, but once plugging has occurrred, they probably don't do much good. If you live in an area where you can get (or must use) ethanol blended fuel, the alcohol is already cleaning your injectors better than most additives can. At that point, the only benefit of some of the cleaners is the slight lubrication they may provide to the injector pintles.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader