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Dr.Nelson

Stumble on take off

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I recently bought my daughter's old Pathfinder. She needed money and I need something other than my one ton 4 door long box to daily drive.

It needed minor repairs, I put a muffler and tail pipe, installed the front drive line, and replaced the auto hubs with Warn manual hubs.

It has what sounds to be a lifter rattle some times on start up. No biggie.

My only real concern is when taking off from a stop the engine falls flat on it face. I first thought it was plugs and wires. So I replaced the plugs, wires, cap and rotor. It did not fix the take off concern. It doesn't do it all the time either ...

 

Could I have a TP sensor and MAF sensor going bad? If so how do I test the MAF and TP

And also the engine coolant temp gauge doesn't work it's stuck a 1/4 up off cold. I'm sure it's not related but I thought I should mention it.

Thanks Dusty

 

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The Throttle Position sensor is possible but I suspect that the intake just needs a good cleaning for starters (watch the coolant lines going to the bottom of the throttle body and the 1 vacuum line on the bottom of the boot from the MAF). After that I would be at the aux. air idle thingy just in front of the firewall and next to the brake booster.... the tall thing with the electrical plug on the top of it.... that probably needs a good cleaning as well since its usually gunked up with PCV leftovers...

 

As far as the MAF, cleaning _will_ help but adding an additional ground wire will also help. The TP adjustment is kind of finiky but requires a multimeter and someone who has the info for what values are needed for closed and full throttle.... @adamzan or @Mr.Reverse possibly. I don't recall those off of the top of my head. (You might want to do a search for TP sensor setting in here or google).

 

The engine coolant temp is likely a poor ground on the back of the cluster or a thermostat that's stuck open. IF you go with the cluster make sure you have a 2" #2 Phillips screwdriver for the one screw at the top of the cluster and a 6" #2 for the rest of them. You'll then need a #1 or a #1 JIS to snug the screws on the back of the cluster down.

 

That's about all I can help you with!

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Man that's a bunch of great places to look, thanks for the tips!!
This old girl has 245K miles so a sludged up intake is a great place to start!
Thanks again!

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While you're in there make sure the idle air control is working. Mine ended up having a crack in it allowing un-metered air in. It only happened on cold starts and once it was warm it was okay. Worse in the winter. 

 

Does it happen hot or cold? I spent months chasing down a similar issue that occurred when cold but slowly got better as the motor warmed up.

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It does it hot or cold.
But I'll pay more attention to see if there's a time that it happens more frequent

Sent from my moto g(6) using Tapatalk

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Sorry if I missed it, what year is the pathy and is it auto or manual trans? 

 

The intermittent nature of the off idle power loss leads me to think of a loose connection at the MAF or TPS. It is also possible the distributor is starting to have a mechanical failure in the bearings, though that tends to show more often as hard start. Easy way to check is to remove the cap and rotor. Then remove the dust shield at the bottom and look for dust in the bottom of the distributor under the slotted disc near the shaft. If there is, the bearings are going out. Other method is to remove the distributor and turn it by hand at the gear. With the cap off, it should turn smoothly without much drag. 

 

Finally, any idea of how old the timing belt is? Might be worn and if it is an early 93 or older, it is supposed to be replaced every 65k miles.  Late 93 and newer has a different design that has a replacement interval of 105k miles. When replacing the timing belt, I strongly recommend replacing the cam, crank seals, tensioner, water pump, thermostat, coolant hoses, and the bloody $.97 woodruff key in the crank for the timing belt sprocket. Skipping that little bugger cost me my original engine in my 93. I have come across a couple more over the years where that key failed and ruined the crankshaft. 

Edited by Mr_Reverse

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16 hours ago, Dr.Nelson said:

 

I recently bought my daughter's old Pathfinder. She needed money and I need something other than my one ton 4 door long box to daily drive.

It needed minor repairs, I put a muffler and tail pipe, installed the front drive line, and replaced the auto hubs with Warn manual hubs.

It has what sounds to be a lifter rattle some times on start up. No biggie.

My only real concern is when taking off from a stop the engine falls flat on it face. I first thought it was plugs and wires. So I replaced the plugs, wires, cap and rotor. It did not fix the take off concern. It doesn't do it all the time either ...

 

Could I have a TP sensor and MAF sensor going bad? If so how do I test the MAF and TP

And also the engine coolant temp gauge doesn't work it's stuck a 1/4 up off cold. I'm sure it's not related but I thought I should mention it.

Thanks Dusty

 

Sent from my moto g(6) using Tapatalk

 

 

 

my buddy has an is300 and he had some throttle response issues (not very relevant here) but after he cleaned the maf  he noticed a bigger performance gain and better throttle response as it was pretty gunky from what i hear. Its not a bad idea to check it either way. 

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So over the weekend I paid more attention to when my Pathfinder, it seamed to be more noticeable after a hot soak.
If I've a cross town shut it off go grocery shopping come out start it up and it spits and sputters for about 2-5 seconds.

So I'm learning towards carbonned up intake valves. I filled my tank with non ethanol fuel and it seems to be a lot better but still doing it.

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