# 97 pickup has a miss



## ronboonville (Nov 13, 2015)

I bought this truck with only 62xxx miles, clean, in good condition. I could detect a little misfire. I replaced cap, rotor, plugs, and wires. Check engine light was on. Found and fixed broken wire going to bottom of air cleaner. I unhooked battery and hooked back up, engine light off. Still have miss at around 1500 rpm and 2400 rpm. I found a small vacuum hose unhooked and put it back on. I still have this miss around 2400. No miss at idle or over 2500 rpm. Can't find any vacuum leaks. Where do I go now? Also I cleaned the maf sensor and ran some sea foam thru engine. checked the resistance on the injectors. I disconnected maf and no change. Checked plugs, wires and cap and rotor all good with good spark. any help would be great!
thanks, ron


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## ronboonville (Nov 13, 2015)

engine is 2.4 4cylinder


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## jp2code (Jun 2, 2011)

Pull the codes. It sounds like the ECU is in "fail safe" (limp) mode. If it detects something not working correctly, it will go into fail safe mode to get you to fix it.

Unfortunately, a lot of people have spent lots of dollars trying to fix "what it acts like" when the ECU is in fail safe mode.


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## ronboonville (Nov 13, 2015)

I understand the ecu is under the passenger seat and I have to remove the seat to get to it. Is that right? or can I just have it scanned at the parts store. engine light is no on.


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## jp2code (Jun 2, 2011)

Nissan went to ODBII in 1996, so you should be able to use a code reader from the auto parts store.


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## ronboonville (Nov 13, 2015)

pulled the codes, 5 long, 5 short. which means no problems found.


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## jp2code (Jun 2, 2011)

Shoot.

An old distributor cap and rotor, old plug wires, or old plugs could all cause a slight miss.

Auto parts stuff would make it go away. In my experience, though same parts from the Nissan dealership will last you 5 times as long.


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## ronboonville (Nov 13, 2015)

replaced plugs, wires, cap, rotor. pulled all plugs and wires and all looked good. spark from cap is good. did not recheck cap and rotor, will do in morn.


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## jp2code (Jun 2, 2011)

Here's a video I did a while back showing an old rotor:

https://www.youtube.com/watch?v=o2FoKyooox8


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## smj999smj (Jan 1, 2006)

If the engine revs above 2500 RPM, it's not in fail safe mode. Fail safe will cause the engine to hit a wall at 2500 RPM and not let you go above it, causing the engine to surge violently unless you keep it under 2500 RPM. 
Misfire can obviously caused by a number of things, including a worn out distributor cap or rotor. Vacuum leaks are fairly common on these engines at a number of places, including the intake manifold gasket, throttle body gasket, and from a sticking EGR valve; there was a TSB on the later for an updated EGR valve. It was more common on 94-95 models than 97 models, but poor grounding of several engine management sensors could occur due to bad splices in the engine harness. Try wiggling and pulling on the engine harness near the bend off of the firewall and where the harness runs alongside the fuel injectors. If there is a surge when you move the harness, you should cut open the harness wear it runs by the fuel injectors and locate all of the splice crimps and solder them.
Make sure you stick with NGK or genuine Nissan ignition components.


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## ronboonville (Nov 13, 2015)

I finally got a code for misfire on cylinder 4. I have an upstream o2 sensor on order. I may replace the egr valve next. I'm thinking the top one first, that's the vacuum part, right? 
I don't think I can replace the intake manifold gasket. I may be able to do the throttle body gasket. will post progress.


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## jp2code (Jun 2, 2011)

> I'm thinking the top one first, that's the vacuum part, right? 

Well, that depends. What was the error code?


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