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Discussion Starter #1
An update on my 1996 HB cutting out at 2000 rpm.
On my last post I had questions about the ECU. The shop gave me a diagnosis of needing a replacement. They located one locally for $175 no warranty. I passed.

I wound up going to the yard where they had found if and purchased it for $75. No warranty. I installed the ECU and the truck fired right up. It did not fix the problem. The truck still cuts out at 2000 rpm. It runs perfectly until it hits 2000 rpm. By whatever means if you can keep the needle off 2000 rpm the truck will run fine. When it hits 2000 rpm it just cuts out and you need to back off the pedal and wait about five seconds and your back to normal until you hit 2000 rpm again.

I notified Pep Boys and told them I had been given a bad diagnosis and wasn't to happy. To my surprise they refunded me $129. They seemed like they were really interested in finding the problem because they spent a lot of time on it. I'm am afraid to take it back there though just got a bad feeling.

The junk yard guy says he's seen this problem and thinks it's a bad distributor. I've decided to just drive it until the wheels fall off or whatever is wrong just stops the truck. The codes say bad TPS but the fourth replacement has been determined good. They say no signal from ECU to PTS but still the same with replacement . All wires to ECU have been determined good.
Just thought you guys might like to know.
Thanks for all your help.
 

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Sup Mod keeping the peace
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You most likely have a problem with the MAF or it's associated wiring. The ECU is programmed to go into what's called 'fail safe' when a problem with the MAF is detected. The ECU will limit the RPMs to around 2,000.

First check the MAF harness connectors for any oxidation on the pins or loose connections.
 

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NF Mod/Nissan Master Tech
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I'd be interested in see what shows on the scan tool datastream for the TPS; specifically, I would graph the signal. Pep Boys is not the place I would go to for engine control diagnostics...nor would I use their electric or electronic parts that they sell.
 

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I'd be interested in see what shows on the scan tool datastream for the TPS; specifically, I would graph the signal. Pep Boys is not the place I would go to for engine control diagnostics...nor would I use their electric or electronic parts that they sell.
Do Nissan dealerships still have the parts to do these tests?

Just curious at what point Nissan stops carrying specialized parts for older vehicles.

If Nissan doesn't carry these, where would you suggest someone go (besides Pep Boys)?
 

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NF Mod/Nissan Master Tech
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You'd be surprised how long Nissan carries some parts. You have to remember that some models, such as the Hardbodies and B13 Sentras, continued into production in some countries (i.e. Mexico) long after they were discontinued in the US.

Any dealer or independent shop with a descent scantool can do signal graphing of a TPS, among other things, or view datastreaming.

As for the TPS, for 96-97 Hardbodies:

Federal emissions (single plug connector): Nissan #22620-31U0A MSRP: $68.33
California emissions(two plug connectors): Nissan #22620-65F2A MSRP: $136.85
*Note: you can get these parts cheaper at online dealers such as 1stAAANissanParts.com
*Note: there was a TSB released on proper adjustment for the CA emission type TPS, used on a number of Nissan models. The closed throttle switch setting must be learned after the adjustment procedure of the throttle position sensor.
 

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Any dealer or independent shop with a descent scantool can do signal graphing of a TPS, among other things, or view datastreaming.
Are all scan tools only useful on ODBII vehicles like his?

I know my 1994 has a consult port under the dash, but I don't know of anything that can use it.
 

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Discussion Starter #8
MAF ,TPS , IAC all replaced June 2013 set up by reputable electronics shop. Truck ran fine until Sept. 2014. Forth TPS replaced by shop in Nov. 2014 and declared good. Code reads problem with TPS system. All wires to and from ECU have been checked and show good.
 

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Discussion Starter #10
I agree about Pep Boys. Problem is when I explain history to shops they say " I don't think it sounds like something we'd be interested in ". I am avoiding the dealer because of $$$$. I've already got to much into a truck this old. I'll try and find " A Guy "
 

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Sounds like the TPS you are getting from Pep Boys is cheap junk.

You should do a Google search on the Nissan part number, and get the real thing. A little more, but you won't be buying 3 or 4 of them a year.

SMJ already gave you a website and the part numbers above, but I'll quote them here again:

As for the TPS, for 96-97 Hardbodies:

Federal emissions (single plug connector): Nissan #22620-31U0A MSRP: $68.33
California emissions(two plug connectors): Nissan #22620-65F2A MSRP: $136.85
*Note: you can get these parts cheaper at online dealers such as 1stAAANissanParts.com
 

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NF Mod/Nissan Master Tech
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Are all scan tools only useful on ODBII vehicles like his?

I know my 1994 has a consult port under the dash, but I don't know of anything that can use it.
You can get generic scan tools that will work on OBD I systems, but they are usually several thousand dollars. These will typically include a number of different connectors for various, OBD I systems, like GM, Nissan, Ford EEC, etc. At the shop where I work sometimes, we have two that'll work on the Nissan OBD I sytems. The older unit is an OTC Genysis scan tool. The "newer" one, which is now about 5 or 6 years old, is an X431 scan tool. The X431 is made in China and works on a lot of different manufacturers and is less expensive than many other scan tools, but they don't give you a lot of information on how to use it; you sort of learn "on the fly." For me, having some experience with Consult I & II, Chrysler DRB III, Ford WDS and GM Tech 2, it wasn't too bad after playing around with it, but I would imagine it would be rather difficult for someone with little to no scantool experience.
 

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Discussion Starter #14
Rogman;

The truck will run fine at any RPM except 2000 rpm. This is when it cuts out and takes five seconds to recover. If you run it past 2000 it will keep on going as long as it doesn't come back down to 2000. 0 - rpm -1900 rpm truck runs fine. 2100 rpm -4000 rpm truck runs fine. If it hits and stays at 2000 like starting out in first gear it will stumble. If you run it right past 2000 it will go to any rpm.

So it does not limit to 2000 it just cuts out at 2000 unless you run it right past 2000.
So if you run first gear to 2500
run second gear to 2500
run third gear to 3000
forth gear to 3000
fifth gear to 2500
The truck fly's down the freeway.
If it lingers at 2000 for a second it will stumble.
 

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Discussion Starter #15
jp2code;

No Pep Boys parts used in this truck

Original (Nissan TPS ) Good.
Auto Zone TPS good
O'rileys TPS good
Second Auto Zone TPS which is in truck now good.
There has never been a bad TPS in this truck. Each one was installed because each shop it was taken to read a bad TPS code.
Each shop refused to believe the TPS was good because it showed a bad TPS code. So each shop required a replacement of the TPS before they would go any further on this truck. They didn't want to hear from me that the TPS had been tested good.
Once they found that wasn't the problem they put back my original "Nissan" TPS which I still have and it is good.
 

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NF Mod/Nissan Master Tech
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Yeah, I remember doing a few of those repairs; there was a Nissan TSB on the issue. It seemed to occur on 94-95 models primarily, but anything's possible. The one thing I would add to the repair performed at that thread is that you don't need to cut out the crimp-splice and twist the wires together before soldering. You just leave the crimp splice and solder the connections. You can usually verify this as the issue by grapping the harness and wiggling it with the engine running, noticing a change in the way the engine is running, i.e. an engine surge, etc.
 

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Discussion Starter #18
jp2code;

Yes I'm aware of that problem. SMJ999 told me about it in my original thread.
I am considering it down the road but I am very reluctant as all the wires to and from the ECU have been declared good. Thanks for that thread it shows the wires very nicely and will defiantly be of help if I decide to take that road.

It's just so hard to think about cutting into that harness. This is an Arizona truck and as far as corrosion goes it just does not exist here. You can unbolt a muffler clamp or hanger after it has been on for ten years like it was butter no penetrating oil necessary.

I do like the guy below with the Z car though. He had the exact problem and took a hammer to the harness. My hammer is in my tool box along with the vice grips and duct tape.
 

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Discussion Starter #19
SMJ999;

Good advice on not cutting out that clamp if I ever get into that harness I'll remember that.
THANKS
 
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