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Sudden high idle after a little driving?


SquadCarPathfinder
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So recently my dad and I just replaced a bunch of vacuum hoses and coolant lines after replacing injectors, driver side rocker cover gasket, and to do that we had to remove the intake plenum and the distributor cap. Cold start idle is at 1200, after warmed up it settles to about 850-700rpm, but after driving around a little bit I come back home, and set it to park and the idle jumps up to 1500rpm.

 

The actual timing done by the timing belt is fine, we just set the distributor timing indicator to 15 degrees as the FSM says, but it still jumps up to 1500rpm after a little drive and then a park. The A/C isn't on and I am thinking it could be the Idle Air Control Valve (the valve near the firewall on the intake and a small screw for a adjustment). Hoping to know if anyone has any experience with this after a similar repair. Any help is appreciated.

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Might be, I popped the hood and wiggled the throttle where the cable connects and the rpms dropped. Though when i tried to push it down a little bit, it didnt go further. Do I need to reposition the sensor so that it reads properly? Or just disconnect and reconnect the sensor?

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I checked the TPS and it didnt have corrosion. I installed another new one just to check. It felt fine at first, but the problem came back again after driving several miles. I've cleared the ECU just to check it wasn't just that, but every time I start the car and turn it off, the check engine light comes back when in the ON position. Is there anything at all that could cause the engine to run so badly? Horrible mileage, high idle....still no codes stored...

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I checked the TPS and it didnt have corrosion. I installed another new one just to check. It felt fine at first, but the problem came back again after driving several miles. I've cleared the ECU just to check it wasn't just that, but every time I start the car and turn it off, the check engine light comes back when in the ON position. Is there anything at all that could cause the engine to run so badly? Horrible mileage, high idle....still no codes stored...

After you replaced the TPS, did you set it properly? It can be a bit of a ordeal to get it just right.

 

 

Sent from my iPhone using Tapatalk

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The idle didn't change at all so we went to tighten the screws and I snapped the head off the top adjusting screw. Luckily my father is taking next week off to work on it. I've been thinking maybe the EGR isn't functioning properly but it shouldn't be causing the hesitation on the highway right?

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The idle didn't change at all so we went to tighten the screws and I snapped the head off the top adjusting screw. Luckily my father is taking next week off to work on it. I've been thinking maybe the EGR isn't functioning properly but it shouldn't be causing the hesitation on the highway right?

 

 

I don't think the EGR would cause hesitation on the highway. But it would affect your idle if the pintle isn't seating properly.

 

As for the TPS, after I adjusted mine the way the Haynes manual suggested by finding continuity in the 'Closed/wide open throttle' switch, my problems with accelerating and hesitation went away.

 

Hang on and I'll try to take a picture of the page in the hayne's manual.

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There is a video on YouTube https://youtu.be/_EFvu76LQO0 that shows how to adjust it using TPS reference voltage. It is an okay way to do it in a pinch, but my pathfinder ran way better after using the Haynes manual method. See pics below....

 

2718648292bc74f4973a14d09f8ee844.jpg

95f28bcd7cfa5171e231fb0e8aa59e28.jpg967e427d34fa5630c1e79cbc679b2e0f.jpge527037e426c23fffa18df2faab1ac49.jpgd59c765edeb813f746d5642d97fee256.jpg

 

 

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I don't think the EGR would cause hesitation on the highway. But it would affect your idle if the pintle isn't seating properly.

 

As for the TPS, after I adjusted mine the way the Haynes manual suggested by finding continuity in the 'Closed/wide open throttle' switch, my problems with accelerating and hesitation went away.

 

Hang on and I'll try to take a picture of the page in the hayne's manual

 

Can you explain more what the pintle is?

And regarding the TPS adjustment my pathy is the 95 model so i have the 3.0 and the TPS sensor looks completely different. How would I go about checking if the EGR is properly seated? It is supposed to have a gasket that connects to the intake plenum if i remember correctly.

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i'm not great at understanding it either, but as I understand it, when vacuum is applied to the EGR valve, the vacuum pulls up on a diaphragm and the pintle is what pulls out of an opening to open the valve. When they get carbon gunk on them, they don't seat properly.

 

I'm not sure how to exactly check it. on mine, if I disconnect and plug the vacuum line going to the EGR, the valve will eventually settle closed after a bit of driving.

 

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^ One of these days, I need to pick up one of those vacuum testers. I've tested vacuum components just by sucking on the hose, and that works, but the taste leaves something to be desired.

 

The test I've heard for the EGR valve itself (doesn't test the diaphragm) is to reach a finger under the diaphragm with the engine idling, and push up on it, which should cause the valve to open. If the engine idles fine on its own, then stumbles when you open the EGR valve, the EGR valve is working.

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  • 1 month later...

Okay so I eliminated the EGR valve as a problem. I have diagnosed the symptoms of a TPS sensor issue. I know that the sensor works but I need to readjust it. I just don't know the recommended resistance it should be set to. The Service manual I have says for Automatic transmission the "Engine speed (at idle in "N" position) +250+-150rpm"

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EF&EC-12 has a good diagram of the TPS. I'd just hook an ohmmeter to the closed throttle position switch pins and mount the sensor so that those pins connect just slightly before the butterfly goes to dead stopped, but you could also probe the center connector and try to match the voltage graph there.

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So I tried to adjust the TPS by voltage resistance. During idle I set it to 0.36V and it sounded better than the high idle it used to have. The idle after warmup and in park is about 750rpm. I know that the later VG33Es from the frontier and xterra are set to around .45V but when I set my pathy to that it sounds high and sends the RPM to around 1300. I also have the question about a CEL when i set the car to ON? There is no stored codes, and when I clear it with the ECU, after I start it, it comes back on. I know that other cars show the check engine light when you turn the key to ON. But when I had nothing wrong with the car all that would show is the ABS light and battery light.

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All the dash lights should come on when you first put the key in run. It is a self check of the circuits. On some cars the needles on the gauges also do a full sweep.

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Mine also turns the CEL on with the key on/engine off, and so did my '95.

 

The CEL, at least as near as I can tell, is wired to the red LED on the ECU. If you watch the dash while running codes, the CEL flashes along with the red light on the ECU. So the five blinks you saw may have been the first part of the ECU flashing a code 55 (all clear) if you left it in that test mode. My suspicion is that one of the ECU's test modes turns that red light off when you're key on/engine off, and the last guy to work on your truck left it in that test mode. Then you took it out of that mode to check codes, and the CEL returned to normal operation.

 

Or, I dunno, gremlins. Either way, sounds like you've got the idle sorted out.

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Yeah you were right. The reason it blinked was because it was set to the Code reader. I set it to mode 4, turned it off. And then put the key in the ignition and i guess the CEL IS supposed to be on. So I guess im worrying for nothing and all is Good! Amazing this car has lasted this long.

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This same thing is happening to my TD27. It idles fine upon start up at 750 rpm where it should be then after driving for around 4 mins it's idle is at 800 rom and if I put in P it shoots up to 1,000 sometimes even 1,100 it's annoying. I guess I'll try carby cleaner to eliminate.

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This same thing is happening to my TD27. It idles fine upon start up at 750 rpm where it should be then after driving for around 4 mins it's idle is at 800 rom and if I put in P it shoots up to 1,000 sometimes even 1,100 it's annoying. I guess I'll try carby cleaner to eliminate.

 

I fixed my engine. What it needed was to have the TPS (throttle position sensor) set to the proper idle speed. Set the TPS using a voltmeter set to millivolts. I dont know exactly how to word it but I think there is a thread somewhere here on how to set it. Once you are able to adjust it, move the sensor so that at warmed up idle, the RPMS will be around 750. I can't say for sure it will fix the problem but if your situation is similar to mine it may help.

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