'86.5 D21 VG30i AT 2Wd Bucks & Stutters on grade ?

[RediNico]

In answer to a previous post: the 86.5 does not have a Engine Check Light.

I posted a variation of this question in regard to transmission, but after having my mechanic test drive it and speaking with a transmission guy think it's something else.

Symptoms: when pulling a grade and activating the Trans Power feature the truck bucks or stutters. It's as if it can't decide on a lower gear.

This now occurs almost every time these conditions prevail, though of course when I took to my mechanic it didn't (in the A.M.)

In the heat of the day (not necessarily when the vehicle is warmed up) the bucking or stuttering occurs even without the Power activated. That is, when trying to accelerate (and therefore downshift) it happens. So, when my mechanic tested in the P.M. during 90+ ambient temps it happened.

My mechanic couldn't test further because the 86.5 has no Check Engine Light.

I'm wondering here if any others have experienced these symptoms.

Advice and comments appreciated.Cliff

[Rev_D21]

Throttle position sensor. It's a wiper style resistor that wears out in certain spots causing the computer to freak out.

[RediNico]

Thanks again Reverend.

Is this sensor something I might be able to change myself?

Cliff

[RediNico]

I find this in my Haynes Manual

Self-Diagnosis System Trouble Codes (Mode III)Display Code 43: ( 4 red flashes, 5 green flashes)Malfunctioning Component/circuit: Throttle sensorCheck/repair procedure: The Throttle sensor circuit is open or shorted. This repair must be performed by a dealership service department.

Is this the sensor to which you refer?Will a qualified local mechanic be able to do this?My nearest dealership is 60 miles away.

ThanksCliff

[Rev_D21]

That would be the sensor I am talking about. It's a $50 small black box located on the back side of the throttle body. It's held in by 2 small screws, use a stubby screw drive to remove it. Remove the harness connected to then install the new one. Make a mental note the position of the old one and try to set the new one to the same angle so you don't have to re-adjust it.

#16259 in this picture.

[RediNico]

That's very interesting and helpful.Thank you.

I called the nearest dealer and he quoted me $207

The Haynes manual says repair must be performed by dealer service department.Any idea why?

[Rev_D21]

Wow $207? Was $33 when I did it back in 1999. They probably tell you to take it to the dealer because of the adjustments to it that might be needed after the install. Plus Haynes sucks, the mech doing the work in that book is a *****.

[RediNico]

Searching around I found another thread on the TCS where the correspondent mentioned $33 for after market and $300 OEM. Whew. Any idea where one gets an after market unit?

[RediNico]

I checked the ECU lights and verified your diagnosis of Throttle Control Sensor problem Local Parts store provided for $85.I removed the air filter to DIY install but decided I'm in the Haynes category Local mechanic will install for under an hour, probably best if it needs adjusting.

Also found in the process that the top A.B. Valve hose is cracked.Who knows? That could cause problems.That had to be a dealer order and I can install that one.

Thanks for the helpCliff

[RediNico]

The Throttle Control Sensor either was/is not the problemor maybe the tech did not adjust properly.(what would be the symptoms in such a case.

In either case, the symptoms persisted immediately after installationon a triple digit temperature day.

Of course, I have the "customer-self-diagnosis" jam on my faceas I slink back for their diagnosis.

additional comments appreciatedCliff

[Rev_D21]

Damn, I could have swore it would be the TPS. My fathers 87 Pathfinder did the exact some thing for a long time. Mechanics all over town said it was this or that. He even had a short block installed with no change. I was working for a Toyota dealer at the time, one that also owned a Nissan franchise, I described the symptoms to a friend of mine, a Nissan tech who had been turning wrenches on Nissans since 1988, he said...TPS. I tried it, never stumbled again. Sorry this educated guess didn't work in your case. When you said "verified my diagnosis" how did you go about doing that?

[RediNico]

I verified by reading the lights on the ECU.Definitely came up TCS.On another forum someone has suggested a short in the wiring to the TCS.I'm trying to explore that now.

BTW, what symptoms might one expect if the TCS was not adjusted properly?

As always, suggestions appreciated.

Cliff

[RediNico]

Someone has suggested a short in the wiring.I'm looking into this and seems reasonable, howeverI cannot get the wiring clip off the TCS

see this:

http://www.thecriticalcrab.net....html

Suggestions appreciated.

[Rev_D21]

Use a small pick to lift the metal clip out of the sleeve it is sitting in. Be careful though, it can become a projectile in a hurry. Once that is out the plug should slide off.

[RediNico]

This thread could, I guess, warrant a change of title since I've now determined that the problem is not "pulling a grade" specific, but ambient temperature specific.

To update: we changed the Throttle Position Sensor and the problem persists.

So, I'm inviting anyone monitoring this thread to test drive my truck with me. We'll drive it when the ambient temp is under 85, when it is over 95, on the flat and on a grade.

Hop in:

http://thecriticalcrab.net/pos....html

Let me know what you thinkCliff

[RediNico]

It’s been almost a year since the last post on this problem and I just resolve it last month.But, since these threads serve as a kind of problem/troubleshooting archive, I’ll post the history of my solution.

I decided to send my ECM (EECU) to a “rebuilder” and chose Direct Automotive Products (http://www.directautomotiveproducts.com/) who subed-out their ECU repairs to an outfit named Python. Python was unable to detect a problem but re-soldered the CBs and charged me for a “rebuild”. The returned ECM preformed with the same malfunction.

Direct Automotive Products and Python accepted a warranty return, but again were unable to bench reproduce the problem. They continued insisting that the error was on my end, even though I provided detailed report and evidence of my extensive on-board testing and determination that the problem was in the ECU itself.

Direct Automotive Products' web site promised that there would be no charge if the ECU was un-repairable (they’ve changed their web site now). In the end, after I got Discover Card involved, Direct Automotive Products agreed to charge me for testing only, and refunded the balance.

My intention here is not to flame Direct Automotive Products, but in retrospect if I’d known in advance that one could never speak directly to a Direct Automotive Products warranty agent (e-mail only) I certainly would have considered alternative vendors (“your mileage may vary”).

A local technician recommended AutoECMs (http://www.autoecms.com/). AutoECM sends you a replacement in exchange for your core. In contrast to DAP, you have no down time. However, another tech told me that in their experience, they would receive a replacement that had different problems and had to keep exchanging until they received a working unit.

In the end, I purchased a factory refurbished unit from the Nissan Dealer and the problem disappeared.

Observations and speculation

* All the techs with whom I discussed the problem stated that they rarely see ECM problems.

* Direct Automotive Products & Python stated that most problems were resolved by resoldering, that is to say, cracked solder joints are the common problem.

* I suspect that Python and other non-factory “rebuilders” only resolder and play the percentages.

* Even a vendor who exchanges may merely send used, untested and/or merely resoldered units and also play the percentages.

* Historically the USA auto fleet turns over very 15 years, but some reports suggest that this will likely change (with difficult economic times) and extend to 20 or 25 years.

* It seems likely that older vehicles will begin showing component failure in the electronics.

hthCliff