# 95 Nissan HB 2.4l when cold won't rev in gear



## pkane (Sep 25, 2011)

Hi everyone,

I have a 95 Nissan pickup (4 cyl) XE with a manual transmission. It is pushing 270,000 miles and it truly has been a workhorse since I bought it. I've been having a lot of issues with it recently at start up... when cold and in gear it won't rev past 2,000 rpm. As it warms up it gets better but after 15 minutes, I'm still barely breaking 3,000 rpm. It sputters and limits the revs when I try to push it and it's worse in 2nd and 4th gear. If in neutral, it will have no problem breaking 4,000 rpm.

Clutch was replaced 11 months ago, regular maintenance has been done, new radiator and all my fluids are in working order (except I haven't checked the transmission fluid).

Any ideas?

Thanks!

pkane


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## rogoman (Dec 16, 2004)

Looks like you may have a defective MAF.


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## pkane (Sep 25, 2011)

Took apart the throttle body... all sensors look solid. Distributor cap and wires are good... timing is alright...

I disconnected the o2 sensor on the exhaust manifold and its allowing me to run the car but it cuts out at 3,700 rpm in 2nd, 3rd and 4th... I can at least get around for now until I get a new sensor in the morning.

Thanks!


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## SPEEDO (Jun 9, 2003)

any codes?


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## pkane (Sep 25, 2011)

I have a code for the oxygen sensor before the cat. Haven't had a chance to replace it yet but I'll do it tomorrow and see if it clears... if not I'm really running out of options. I'm starting to think that a vacuum hose may be cracked, if not the carb may need to be re calibrated...


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## pkane (Sep 25, 2011)

Any ideas?


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## TheRepairMan (Jun 30, 2009)

pkane said:


> Any ideas?


Although the front o2 sensor can cause some drivability problems it's not likely to on a cold engine. Those weren't the symptoms mine had when my o2 failed. It would just stumble a cruise around 2 to 3 grand, but would accelerate through that just fine.

However, the MAF sensor, as rogoman posted, may very well be the problem. There are quite a few threads about them failing and causing lots of performance problems. I also recall a thread on testing and cleaning the MAF. It's a fairly delicate and expensive item to replace, so carefully cleaning and testing is always recommended first.

Mass Air Flow Sensors can get contaminated or dirty and just get out of range. They often won't even set a code, but since they report air volume and density to the ECU, if they aren't right it causes the fuel mixture to be incorrect, cold or hot.

Fuel pressure, and an Engine Coolant Temperature Sensor are also possible problems. High mileage vehicles can have ignition system failures that cause harsh acceleration also such as a dried out, overheated, dirty or cracked Distributor Cap, Rotor Button, or Spark Plug Wires, or worn plugs.

The wiring harness, electrical connectors for all sensors and Fuel Injectors, and even the Battery, Alternator, and associated wiring can cause such symptoms when they start to fail.

Sometimes you just have to try the process of elimination. Learning to test components and systems is just a part of doing your own work successfully.

Well, there are some ideas!

-Roger


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## pkane (Sep 25, 2011)

Haha that should cover it! I've checked the distributor, plugs, wires... definitely not those. I've just ordered a new MAF sensor. It should be in at the end of the week but after looking at my wiring harness, I'm seeing a ton of amateur wiring which may explain it. The connections don't seem solid so that would be my biggest fear to have to replace it. I will take a look at the engine coolant sensor, that is something I hadn't thought about and it's a relatively cheap part. After that, it will be the fuel pump and if that doesn't cover it... I'm afraid nothing will.

The annoying part of it all is that I'm going to be relocating for work in a few months (no idea in how many) and I will only have 2 weeks notice, so starting a project or buying a new car would just be ridiculous at this point.

Thanks for all the advice!


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## TheRepairMan (Jun 30, 2009)

Keep us posted, Patrick.

-R


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## pkane (Sep 25, 2011)

Any advice as to how to change to O2 sensor before the cat? There is a heat guard on top of the exhaust manifold which is blocking access to any part of the sensor I can get a grip on. Can't remove the heat guard without removing the sensor and I can't remove the sensor haha...

I changed the engine coolant sensor yesterday. Major improvement since but I still had some issues this morning in 2nd gear. MAF sensor is in the mail and it should be installed by Friday.

Thanks again for all the help!


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