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Sporadic rpm during acceleration


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Hi all,

I am new to the forum. I have a 1988 Pathfinder SE-V6 with 316K miles on it and it has an automatic transmission (the trans was replaced 500 miles ago). Recently when I was driving, I experienced a problem with acceleration. I was on the highway going up a hill, and to maintain speed I gave it some gas, when it down shifted to get more power it hit 4100 rpm and started to become sporadic ( rpm fluctuating and engine cutting in and out). This only lasted until I let off the gas pedal a little. I discovered if I didn't press the gas pedal too aggressively it will maintain speed, shift and accelerate fine. On the way home the problem seemed to get worse. It got so bad I couldn't even get past 40MPH, any time the rpms would try to pass 2,000 rpm the engine would start to cut in and out sporadically. I eventually pulled over and turned the pathfinder off for ten minutes. This seemed temporarily fix the problem or reset the vehicle for about 15 minutes. So I kept doing this until I made it the rest of the way home. The next day I took it out for a little while maybe for an hour and it didn't have any problems until the last 10 or 15 minutes. If I put it in neutral the problem isn't present , only when it's in gear. It seems after the car has been sitting a while without running the problem is nonexistent, until it warms up. The longer it runs the worse the problem gets. I have checked the ECU for falts in Mode 3 and received a 55 which from what I read means no faults present. Please help!

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Sounds to me like a bad connection at your Maf, or possibly a dirty maf.

 

Have you tried cleaning it and seeing of it makes any difference? On my 87 it was both corroded connections and a dirty maf. When you put it back together be sure to put some dielectric grease in the plug to keep moisture out

 

Sent from my SCH-I545 using Tapatalk

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Thank you for your response! Before i took took it on my camping trip, i took out the MAF and sprayed electrical cleaner on the probes and took fine emery clothe to the electrical connector contacts as well. But i didnt try the dieltectric grease. So i ill give that a go an see if it helps.

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Thank you for your response! Before i took took it on my camping trip, i took out the MAF and sprayed electrical cleaner on the probes and took fine emery clothe to the electrical connector contacts as well. But i didnt try the dieltectric grease. So i ill give that a go an see if it helps.

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Hopefully cleaning the MAF helps. I haven't had much luck just spraying them with a can; the corner of a rag and some alcohol do a good job if they're really dirty, so long as you're careful about it.

 

If that doesn't help, I'd check the operation of the oxygen sensor. There's an ECU mode for that, or you can just unplug it and see if the truck runs better guessing at mixture than running off what the O2 tells it. Failing as it warms up also has me thinking distributor (there's a position sensor in there that gets unhappy when the bushings wear out, and for some reason they tend to act up more when they're warm), but I'd try the easy stuff first.

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The O2 sensors were good. I asked a buddy who is an auto tech if he had any ideas. He said he thought it sounded like the throttle position sensor was going bad. It seemed easier and cheaper than messing with the distributor so i replaced the TPS. I took it out for a 30 mile ride to test it, i even took it on a mountian road so that it would have a fairly large load on it. I had no problems, so I believe this was the fix...if it comes back i will give an update.

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