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My '87 is running terribly and won't start when hot.


TheRadBaron
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I have an '87 Pathfinder 4x4 with a 3.0 and 5-speed. I recently bought the truck and I've only put about 2,000 miles on it so far. It's always run very well and it was running very well when I was driving it around yesterday evening. This morning it fired right up and I drove off to work. About 10 miles into the trip it starts running badly, though. It didn't want to take throttle. If I accelerated very gently I could get it up to interstate speed but if I gave it any real throttle it would sputter and stumbled and the truck would jerk violently. I made it to work and I was fiddling with it in the parking lot. If I punched the gas it would sputter badly and then the revs would go up a bit. The idle quality was fine and the truck ran down the road pretty well as long as you didn't accelerate even moderately.

 

When I left work this afternoon the truck fired right up. I looked under the hood for any obvious problems and the only thing that I saw that looked bad was a device that's just behind the passenger-side headlight that has something to do with the exhaust (like maybe the EGR or air injection). It had a large pipe going down to the exhaust manifold. I didn't look at it that closely but there's a little vacuum dashpot on top that was corroded and falling apart. It could be lifted up by hand and it would sound slightly loud and like the exhaust. It didn't seem to effect the way the motor was idling but I ziptied it down into the position that it was supposed to be in. Another thing that I noticed was that there was another device that was attached to the one behind the headlight. It looked sort of like a bellows with a large tube coming out of it to the other device. Sorry, I know that I could look this stuff up but I don't have time right now. I'm really scrambling around. Anyway, the bellows device is making sort of a gurgling sound when the engine is running and seems to be leaking a little bit of water. Again, this stuff is connected to the exhaust manifold with a large diameter pipe. I have no idea if it's related to these problems.

 

So I drove off in the truck and it was behaving just the same as before. I drove it across town to NAPA and shut it off. When I went back out it wouldn't start. It would crank and crank but wouldn't even hint at firing. I tried giving it throttle to no effect. It smelled like it was getting gas but it was hard to tell. I removed the air cleaner assembly so I could look around and I didn't see anything out of sorts. I tried a bunch of different things but nothing worked. I let it sit for an hour and cool down and then I was able to start it up. It ran really badly for a few seconds and didn't want to idle but then it settled in and idled. I drove it home but the condition had worsened. I could barely hit 55 this time and it just all around ran terribly.

 

I once had a Chevy van that I accidently ran low on oil once. The hydraulic lifters collapsed and it ran almost exactly like my Pathy is now until I filled up the oil. My oil gauge isn't working but the idiot light does and it never came on. When I got home I checked the oil and it's full on the dipstick. It's probably not this but do these oil pumps have a pickup that can fall off or anything like that?

 

Does anyone have any ideas or seen anything like this? I'm a pretty good mechanic but I'm not an expert at fuel injection systems. I'm not sure where to even start troubleshooting. I supposed I can check fuel pressure and do some other basic tests but I'm hoping someone here has some insight. Thanks a lot.

 

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The throttle body on mine was super coked up when I bought it. It wouldn't stay running and you'd have to feather the throttle to keep it running. I put a new one on because it was laying around for a project that rust killed.

 

But the idle air control bits were filled with carbon buildup.

 

 

The fuel injection on the 2 doors is very basic. It uses the injectors to atomize the fuel, rather than a venturi and a jet, if you are familiar with carburetion.

 

The fuel mixture is measured with one o2 sensor in the exhaust which sends a voltage signal to the ECM. The ECM then cycles the injectors at a different rate, enriching or leaning out the mixture.

 

You may want to check your ECM for codes. I believe there is a pinned post for it in the garage section.

The oil pickup is bolted to the crank girdle, so it shouldn't be an issue.

 

 

Pictures are worth 1000 words.

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Thanks for the responses and ideas. The ignition system tuneup parts all look very new and seem to be good. The previous owner installed a new distributor, distributor cap & rotor, plugs, and wires a few thousand miles ago. I pulled the distributor cap and everything looked good inside.

I'll head over to the garage section next and try to find the pinned topic about ECM codes. I also have a factory service manual that has detailed troubleshooting info.

I identified the corroded exhaust components as the AIV system. It sounds like a known problem and some guys remove them with good luck. No emission inspections where I live so I'll be going this route.

The throttle body injector is also relatively new and doesn't seem to be coked up at all. Something to look at for sure, though.

Thanks again and I'll report back when I learn something new.

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Alright. I read the pinned post about the codes and went out and pulled mine. Here are the codes that were indicated: (I verified these with my FSM and listed the codes as they appeared in the manual rather than the pinned post)

 

- 11 - Crank angle sensor

- 12 - Air flow meter circuit

- 13 - Cylinder head/ Water temperature sensor circuit

 

I guess I'll start digging into these components and checking them as per the FSM. Anyone know anything about these specific to Pathfinders?

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The angle sensor is built into the distributor and seems to be a common source of issues on these. You can remove it (mark where the rotor points first so you can get it back in right) and spin it to see if the bearing's alright.

 

Check the MAF plug and wiring, pull the MAF itself, check the filaments for grime, clean very carefully with solvent that won't leave a residue. I've used isopropyl alcohol on the corner of a rag with good results.

 

When the coolant temp starts reading wrong, the fuel mix gets weird. Again, check the plug first. I think the FSM lists the normal resistance vs temperature for a good sensor.

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Those 3 sensors share common grounds if I remember right, I would check that first thing. Sometimes knocking one sensor out can cascade effect into the others.

 

An open ( bad sensor or wiring) CHTS will most certainly cause problems when hot, as will a CAS.

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Alright. Thanks for the tips. I should get a chance to start troubleshooting it later this week or weekend. I'm happy to have a direction to go in. I love this truck and I want to get it back on the road ASAP.

Hey slartidbartfast, you're on ADVrider, aren't you? I spend a lot of time on that forum and I recognize your username. It's a pretty unique one. I'm TheRadBaron on there, too. Is it the BMW GS section that I see you on?

Anyway, thanks again and hopefully I have some luck with the multimeter.

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I have removed the AIV from my 86.5 hardbody with good results.

 

A bad MAF could cause all sorts of issues. Grab a copy of the FSM. The hardbody and the pathy are the same mechanically so the FSM version doesn't really matter.

 

Sent from my C6603 using Tapatalk

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That's funny. I haven't read that book and I didn't catch the reference. I often wondered just what the heck that username meant. I'll have to look that up.

I made some progress this evening. It seems that my coolant temperature sensor has a bad electrical connection. The resistance value at 68 degrees (about what it was today) across the two terminals in the connector from the sensor should have been around 2.5 kilohms (2,500 ohms), but I was reading around 7 megohms (7,000,000 ohms).

The sensor isn't exactly easy to get to but I got the connector off and found the terminals to be very corroded and the wires in bad shape. I then tested the terminals on the sensor directly and got the correct 2.5 kilohms. This suggests that the sensor itself is good and the problem lies in the bad wiring. I ordered a new connector pigtail that should arrive on Saturday.

I'm really hoping that this solves the problem. I also checked the power and ground wires to the MAF sensor and crank angle sensor and visually inspected them. I checked the power and all the grounds to the ECM per the service manual as well. All of those were good. I didn't check the input wires or remove/clean the MAF sensor yet. If the new CTS wiring doesn't fix the problem I'll start with those thing.

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Alright! The coolant temperature sensor wiring was the culprit. I bought a new connector pigtail (BWD #PT5630) and spliced it onto the original section of wiring. This connector was a bit hard to find, though. This basic type of 2-pin connector is very common through our trucks but most of them have the indexing slot cenetered in the connector. The CTS has an offset indexing slot so it takes a very specific connector.

Truck runs prefectly now. In fact it runs noticably better, especially at idle. I think this is due to my removal of the IAV system.

Man, I'm glad I got it fixed. It was really bringing me down. Thanks for the help, everyone.

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