'87 Pathfinder 6cyl Low power and starting to backfire

[mejonny]

I bought an '87 Pathfinder last week with 137K miles. The motor is good but I am only getting 60-70% power and now it's starting to sputter and backfire especially when decreasing speed in gear.

 

In 1st gear it wants to hesitate then will start to gain power and run smoother once I pop the clutch and hit the gas pedal. 3rd gear runs at low power state too until I increase gas. There is a smell of gasoline/exhaust when I opened the hood. It also sounds rough under the exhaust system.

 

I already replaced the fuel and air filters. I know the spark plugs and wires are looking old too so I will replace those myself - But what else could be causing the low power and backfiring?

 

The timing belt? Exhaust leak? Bad 02 sensors? Bad catalytic converter?

 

Any thoughts will be appreciated.

Edited May 14, 2013 by mejonny

[Kingman]

If the belt hadn't been changed , should have been twice by now, it may be loose and skipped a tooth. I'd pop the top cover off and look. Also, try cleaning the MAF with a q tip and rubbing alcohol as well as make sire there's no corrosion on the plug contacts.

 

Checking for codes from the ECU will tell a lot as well and it might even be that you have a bad O2 sensor, however if its not entirely failed (open circuit or out of parameters) the ECU won't know its bad. Another common failure point is the CHTS, which you can see ad a yellow plug behind the timing belt cover. That is the ECUs lifeline next to the MAF for running good, it tells the ECU what temperature the engine is so it can adjust the air/ fuel ratio, injector duty cycle, and timing. If it is bad, it'll throw everything out of whack and in my eyes the ONLY replacement is a genuine Nissan one along with the sub harness.

[Kingman]

Another thing, if you're smelling raw fuel from under the hood, pull the vacuum line off of the fuel pressure regulator and see if it spits fuel out. If it does the diaphragm has failed, causing your issues.

[mejonny]

Kingman,

 

Sounds like you are a Pathfinder Master. I will do all of the above and let you know which one or more of the issues caused/are causing the problems and post. Thanks so much!

 

Jonny

[mejonny]

Yes I don't believe the previous 2 owners did that type of maintenance (timing chain) very often. I'm working on the brake system too and everything needs to be done- front: (did the pads today), Right caliper leaking, rotors good till next brake job; rear - needs drums, shoes, and cylinders are leaking.

 

This Pathfinder needs some TLC but it's worth it - The years 1987-'89 were the original, all around good looks and solid performance Pathfinders to date. Good motor/tranny, clean body no dents, sport package (towing, front grill) and the black paint is still glossy.

 

I'll post some pics soon.

 

Thanks again King Man.

[ahardb0dy]

Sounds like the timing belt jumped a tooth or two and it's out of timing

[mejonny]

Thanks Hardbody,

 

Yes my friend told me "timing is everything" and once I get that in sync, things will smooth out and any other issues will be localized.

 

It seems that the first place to look deals with the timing belt/teeth. I will start from there and hopefully the performance/punch will come back to the motor. I know these Pathfinders are way more torquey and punchy when things are running right.

 

Thanks to all replies.

[vagabond]

Don't want to scare you but like Kingman said check that T belt, those are interference engines and if the belt goes your going to end up with at least some bent valves

[Alkorahil]

I agree with the others, with low power and backfire this defiantely sounds like a timing issue!

Besides the timing belt which I would also defientely check as the others have said, you could have the distributor rotated too far advanced or retarted. You can check this with a timing light.

[mejonny]

Will do. I don't want to turn a seemingly simple timing belt replacement (hope that's the only thing wrong) turn into bent valves or worse - more money more problems! Gotta drive this puppy it's my daily driver. Thanks to all! I will replace and have other issues and recommendations above checked out ASAP.

[parkerhdr]

It could possibly be the electric full pump in the tank. just suggesting something to check.

[87Fathpinder]

Another thing, if you're smelling raw fuel from under the hood, pull the vacuum line off of the fuel pressure regulator and see if it spits fuel out. If it does the diaphragm has failed, causing your issues.

By "spits fuel out" what exactly do you mean? If it just drips a few times does that qualify as spitting it out?

[Kingman]

Out of the vacuum line, yes. Any fuel at all coming out means the diaphragm has failed.

[ezlife]

Change the belt. Trust me!!! lol. I did bend a valve and weeks later finally worked through all the problems caused by a broken timing belt. It's really not that bad of a job. Two hours or less if you have all the tools lined up.