98 lumina 3.1L misfire/ reluctance accelerating
When trying to acquire speed it feels like too little fuel or some kind of back pressure. It has happened with a hard acceleration, while in idle and simply pushing down on gas petal, or just trying to go from 25 to 30 mph. It seems to be random. Happens one day and then won't act up again for two weeks. No check engine light.
I have changed fuel filter, fuel line, mass air flow sensor, and recently a catalytic converter. The catalytic converter seemed to fix the problem for a few months, but almost as a band-aid. This will be my second catalytic converter in 2 years so problem might be fouling the converter out too.
Any help is greatly appreciated.
I already answered this on another post you made for the same problem, but the way you described it there wasn't quite the same description you offered here.. Bottom line, you have global OBD-2....you need to take advantage of it for diagnosing your vehicle. Do a data-stream on the car and check out your sensor values...you have an intermittent problem, so your issue is going to be intermittent as well. Find or get yourself a scantool...you can get a fairly powerful OBD-2-only Scantool for $150 or less from various sources... Now take note of the values when it's running normally. The MAF signal response when stabbing the throttle from idle to wide open and returning to idle, as well as the Throttle Position sensor on a graph with the Key On, Engine Off...slowly opening it up from 0% all the way to 100% and back down, it should be a smooth linear graph taking into account your un-precise foot movement of course. Now take note of your ECT (Engine Coolant Temp) value, Misfire Counts, and your Short Term and Long Term fuel trims (STFT) and (LTFT). Those are the biggies. Take it with you always, and when it starts to act up, go through the values and compare them to what you had previously. Obviously do this pulled over and in a safe place.
I believe you might want to check all the simple things first... especially if you or someone else had recently been working on the car, like changing the oil or something. Check ALL and EVERY BIT of your Wiring, Connectors and Vacuum Hoses. After you think you've checked them all and real good... check them again. See that none came loose, fell apart, cracked, burnt, etc... I had a similar problem with my old 90 Lumina Euro Coupe with a 3.1 V6. It's sometimes hard to tell with a visual. You have to tug on things, pop them off, look real close. Especially the Vacuum Hoses. They sometimes get split at where they connect up to... and it's hard to notice, especially when they're in tight, dark, places. After that, call around and see if you can borrow a Scan Tool. AutoZone has a Tool Borrowing program. You pay for the tool and get refuned when you bring it back... but it's for select tools only. Other places, like Advance also have a program like that. But call others and see if they'll help you out. After that, I'd go straight to eBay! I've never been disappointed there after over a thousand transactions. The sellers rely on feedback so they're not apt to screw you. I've saved a lot of money, and a lot of trips to auto parts stores and junk yards at eBay. Good LUck! John B. Ps. When I bought the car last year, the engine compartment was a mess. Under the Power Steering Pump was a huge bundle of wires mashed into the engine block. Many of the wires had melted and/or lost their insulation. I used "Liquid Tape" to repair the insulation. I also used "Liquid Tape" to seal some vacuum connections.
Thank you very much; I hadn't thought about utilizing the OBD2 scan tool while driving and observing levels.
Sounds like the problem I had. Cheap scanners won't detect your problem. Had the car scanned by 3 different mechanics, couldn't find the problem. Find a good mechanic with the factory GM scanner. My problem ended up being the fuel injectors. They were releasing fuel at will, and the rest of the system was overcompensating by sending extra oxygen. Check the fuel/air mix scan, if its outside +/- 5 range, there's a push in the right direction.
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