2,000 miles of torture

[Shran]

I believe the truck has BOTH. There is a sensor with a vacuum hose and electrical plug on the firewall, directly above the exhaust manifold(but at the top of the firewall). And there is a sensor on the airbox, that is plumbed to the inside of the airbox, and has an electrical connection on it. The one I disconnected before was the one on the airbox that made the engine die. I did try it again the other day(engine was cold this time though), and it sputtered, then picked up idle and kept running. Haven't driven it yet though.

The one with the vacuum hose is a MAP sensor. Disconnecting that one should make it run like shit. There is not a MAF sensor on that truck because it's a speed density system.

I'm not sure what the one on the air box is, unless you mean that it's in the intake right by the throttle butterfly. That one would be the throttle position sensor.

 

[Speedwagon]

The one with the vacuum hose is a MAP sensor. Disconnecting that one should make it run like shit. There is not a MAF sensor on that truck because it's a speed density system.

I'm not sure what the one on the air box is, unless you mean that it's in the intake right by the throttle butterfly. That one would be the throttle position sensor.

No, on the airbox holding the airfilter. I'll get a pic of it tomorrow.

 

[Speedwagon]

Here's a picture of the sensors. The circle on the left is what I disconnected, and made the truck die. It's currently disconnected, and whereas the truck doesn't like to idle when I first start it, it finds it's idle and will run now without it connected.

edit: Now that I think of it, is that the IAC?

 

[explodan]

THE SENSOR ON THE AIRBOX IS THE IAC. TRY UNBOLTING IT AND CLEAN OUT THE PART THAT BOLTS TO THE AIR BOX. THIS MIGHT WORK, I HAVE DONE THAT BEFORE AND IT WORKED FOR AWHILE. IF THAT FIXES IT, I WOULD REPLACE IT WITH A NEW ONE.

GOOD LUCK

explodan@verizon.net

 

[highwayman]

So runs well cold, but worse as it warms. Sounds like a bad ECT to me.

 

[Speedwagon]

So runs well cold, but worse as it warms. Sounds like a bad ECT to me.

ECT?

 

[MAranger]

I swapped my cnn for nbc, both were nfg, and I wound up using a bbc.

 

[Shran]

ETC = coolant temp sensor. I don't think this is the problem. If it idles BETTER with the idle air control unplugged, there is a problem with that.

 

[Exploder_Chick]

Check your air filter? My truck ran similar because my AF was plugged completely with sand and dirt. changed it and the truck ran completely fine.

 

[johndeeregarner]

Had something similar to this happen to me. You might check the fuel pump. Turns out that the pump in the tank was bad on mine.

 

[Speedwagon]

Update:
Replaced MAP sensor with one from the junkyard, didn't solve the problem.

Replaced the fuel pressure regulator(new), didn't solve the problem.

Replaced the coolant temp sensor(new), didn't solve the problem.

Pulled the plugs again to take a look, and they indicate a lean condition(very white), with ash(I think) deposits. According to the Haynes, ash indicates oil consumption, but I already know it burns oil on startup(valve stem seals).

Replaced the fuel filter this morning, and there was a LOT of rust colored gas on the inlet side. I'm sure that wasn't helping things.

Just did a vacuum check again, and it was reading 14-15. Spec is 17 to 22 at sea level, with -1 for every 1,000ft about 2,000ft. So 14-15 should be the same as 17-18. It varies from steady, to slight(within 1-2) fluctuation, and the haynes tells me that indicates a possible ignition system problem.

If I hold the engine steady at around 2-3k(I think, no tach), the engine varies from steady to fluctuating rpms. I have noticed this while driving around at times too. I haven't driven much since changing the fuel filter, so I don't know if the big under powered on load mid throttle problem is still there, but I will find out later tonight. But it still does do afterfires when I shift gears at full throttle.

As for the ignition: Coil, plugs, cap, rotor are all new. The only thing I haven't replaced this year are the wires. Also has a new air filter that I put on before I took this trip, and it is good still.

 

[Speedwagon]

Just did the KOEO/KOER tests again. Got a 14, 64, 31 on the KOEO, and 42, 13 on KOER. Since I actually bought the $30 tester, going to do the cylinder balance test now as well and see what I get.

Also, during the test, the book tells me to run the engine at about 2 minutes around 2k rpm, to ensure the EGO is warmed up. So I did this with my hand throttle, and the engine was surging while the throttle was steady. Took a video of it with my phone. At one point the RPM kicked way up(i'm guessing maybe 4-5k, no tach) and held until I kicked the throttle back down, though the throttle had been held steady during this time.

I was obviously overloading the mic on my phone, but you can kind of hear the surging idle...
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&videoid=61700792

Compression test this time around:
Dry: 140/135/145/150
Wet: 135/130/140(very slowly, took about 5 extra seconds to stablize at 140)/140

Forgot to add, during the KOER testing, I was watching my exhaust as well. After long periods of idle, if I blipped the throttle I would get a large cloud of gray(oil) smoke out the tailpipe.

 

[Speedwagon]

I may have located part of(or maybe all) my problem. Apparently it is a bad idea to have large rocks hit your gas tank directly under the fuel pump, thereby pushing the bottom of the tank into the pump and bending things. There was a rusty mark where the fuel screen has been rubbing on the tank. It was also the highest area of the tank(directly under the pump). I'll know tomorrow after I pickup some new parts and get it back together.

If my assumptions are correct, it appears that I was getting both fuel starvation, and fuel dumping. The pump appears have been blocked, as well as the fuel return.