JConXtsy

95 T100 DX with about 210k miles

I first acquired this vehicle from the father-in-law when he lost his ability to drive in about 2007. It already had about 200k miles on it.

From the get-go, the engine would flutter if you gassed it too much - mainly above 3500 rpms. It's an old vehicle, so there was never a reason for me to be gassing it that much anyhow. I just use it for weekend chores - hauling junk to the waste transfer station and picking up home improvement stuff.

The issue finally got worse this past fall. The truck sat for maybe 3 months, and the next time I tried driving it, it was driving the same for about 2 miles from the house, and then it suddenly got worse. Not really gradual...

The problem now occurs at about 2000 rpms and instead of just fluttering, the engine will choke itself to death if I don't let off the gas quickly. It's basically unable to operate, because you need more than 2000 to get uphill or to accelerate at any appropriate rate from stops. I was able to get it home, but I was driving Miss Daisy all of the way back.

I heard a whirring from the fuel pump, so I just decided to change it. I figured it was relatively easy to change, was cheap, and if it wasn't bad yet, it soon would be after 20 years. So I changed the fuel pump and changed the fuel filter along with it, but the problem remained to the same degree.

I looked for vacuum hose problem and saw none. I tried cleaning the MAF. Same issue. I tried replacing the MAF. Same issue.

So tonight, I decided to give the vacuum hoses a better look. I started carefully following each of them and making sure there weren't any hidden ones that I missed on my first quick pass. That's when I found this dangling cable between the engine and the firewall.

It has very short play in the cable, so there's not a large area where it could go. However, I cannot find anywhere for this guy to plug into for the life of me. It's a tight fit behind there, and I'm not quite tall enough to lean all of the way back there and see everything between the engine and firewall, so maybe I'm not seeing something.

Does anyone know what this cable is and where it belongs? Could it be a source of my issues? O2 sensor? Or is it just a red herring?

More info about the cable - it looks like it joins into the cable cluster carrying the spark plug connections to the far passenger side and into the firewall.

I really appreciate any suggestions. My next plan of attack if I don't get better ideas is to figure out where the O2 sensors are and replace them. Relatively cheap replacement, and other than any hidden vacuum leaks, I can't think of anything else that could be messing up my fuel/air mixture. Clogged exhaust?

JasonYota

iTrader: (1)

The white piece looks to be some sort of plug. Is the check engine light on? Looking at the engine it looks to be a 3.4?
Since you already replaced the fuel pump and filter, look at the timing belt to see if it jumped time.

JConXtsy

Well, I'm glad you asked me for the codes.

Interestingly, I didn't have any codes when all of the issues started happening.
After I replaced the fuel pump, then I finally got a code - P0170. Fuel trim malfunction, which was pretty obvious from my issues.

Now that you asked me for the code again, I went to double check the P0170 and make sure I had it right. Now, I have 3 codes (I did the MAF replacement in between these code checks).
P0170 - Fuel Trim
P0100 - MAF malfunction
P0110 - Intake Air Temperature

So, I'm guessing that dangling wire is the intake air temperature sensor. Agreed???

Thanks for the suggestion about the timing belt. I'm a novice having only worked on my 2002 Maxima for years. I've done just about everything in it, but haven't worked on other vehicles much at all. It has a timing chain, so I'm unfamiliar with timing adjustments. I'll have to read up on that and take a look once I understand what I'm looking for.

Thanks again.

JasonYota

iTrader: (1)

The intake air temp is apart of the MAF sensor. The plug you found may just be a blank plug, just guessing because the white piece plugs into it.
Have you tried resetting the ECU? Just disconnect the battery for a few minutes

JConXtsy

I think you're right about it being a blank. So it was just a red herring.

I've mailed it in for the night. I'm going to take another crack at the problem this weekend. Check the timing and maybe replace all of the vacuum hoses.

I'll be sure to update the thread with failures and solutions.

Thanks

JConXtsy

Three months later and still no progress. I did what I could, and then I had it towed to an auto shop. They have spent the last 2 months trying to fix it here and there, and they have given up. It's getting towed to a dealership today.

What's been done:

New Fuel Pump
New Fuel Filter
Fuel Pressure Checked (good)
New MAF
New Chamshaft Position Sensor
Checked TPS for ohm-sweeping - OK
New Plugs and Wires
New ECM
Cleaned Throttle Body
Electrical Wiring Checked - OK
Checked Timing Belt - looked brand new and timing marks all lined up

Not a single bit of difference on the issue. Still starts and idles perfectly - like a brand new vehicle - chokes and dies with gas at around 2500 rpms.

Hopefully the dealership has new ideas.

v_man

be sure to check back in if you find a solution... best of luck

JConXtsy

They finally got a master technician to look at what I've done to the vehicle and make a prediction - no actual work done yet other than exposing the cams and the top of the timing belt. He has a good prediction on it though - the crankshaft position sensor.

The timing belt was changed by PepBoys just before I took possession of the vehicle a couple of years ago. The truck has always had a flutter at high rpm in my possession, but I just figured it was a 200,000 mile truck, so why would I gas it anyhow? I just drove it like a baby.

He suggests that they probably bumped the sensor or didn't tighten the crankshaft pulley properly during the timing belt change. He says it's a common mistake on these engines since the sensor is so close to the pulley. He even admitted to messing up the first one that he did as well.

Will report back in the coming week.

DownRiver

You promised! What was the outcome?

JConXtsy

It was the crankshaft position sensor.

Everybody be careful when you're changing the timing belt!

It's a Hall Effect sensor, so proximity to the belt is of utmost importance. As I understand it, the belt has a piece of metal imbedded which disrupts the magnetic field as it passes through the sensor. This let's the car know where the belt position is and sets up the timing.