Antichrist

Ok I'm desperate for help....

And I'm not the Antichrist, it's a name I've used playing Wolfenstein for years, and it just makes it easy to remember.

After hundreds, if not thousands of google searches, I've ended up here repeatedly, so hopefully you guys don't crucify me for not owning a 3rd gen... I just found a ton of helpful suggestions here, so I thought asking you guys directly might help me a little more.

I'm working on trying to fix an idle issue, stalling, occasional no start, and light acceleration sluggishness.

1995 Tahoe 5.7 TBI. 136K

Cold start crank times seem too long. 3-5sec in 60-70 degree weather. 40 degree weather, crank times are up towards 5-8sec.

I have had 2 no-starts since buying the truck this past August. The first time, it took about 10 minutes of trying to start it before it finally fired up. The second time I just got a ride from my girlfriend.

At idle in park, it idles smooth at about 700RPM.
At idle in drive, it idles smooth at about 550 RPM
When engine temps reach 140-150, and I'm in gear, stopped at a light for a minute or so, I get RPM fluctuations, a stumble, and then a surge OR stall.

This is a video I made with my phone of the tach when the problem started to occur. You can hear the truck shake as the idle drops: http://www.youtube.com/watch?v=4cJyu2VtNog

Now While the RPMs start to surge, if I shift into neutral, all problems stop, The idle comes up to 700ish, and it runs like a brand new truck.

While driving: It holds cruising speed perfectly. I can floor it and the truck downshifts smoothly, and hauls nicely. If I'm holding speed at 35mph, and want to get up to 40mph with light acceleration, the truck idle becomes rough, almost like a mis... but not 100% on that.

Codes:
I had a DTC 33 - Replaced MAP sens, and code hasn't returned.
I had a DTC 22 - Low TPS voltage and/or Fuel cutoff relay circuit open/shorted.
I had a DTC 54 - Low fuel pump voltage/Fuel pump relay/EGR solenoid #2 failure/Quad-Driver (QDM) output failure/Mixture Control (M/C) solenoid circuit voltage too high.

Actions taken so far:
Checked for vacuum leaks. Base of TB. All emissions hoses. All fittings. I've checked 3 times so far, all I've done is waste carb cleaner.

Bench tested fuel pump relay, operates. I replaced relay with a known working unit from my parents truck (1997 Tahoe) and the problem still exists.

TPS was backprobed and tested. .23V idle, 4+v WOT.

EGR valve hand tested, and it holds vacuum indefinitely. EGR ports are clear, EGR pintle moves freely.

EGR solenoid was checked, I ran some vacuum line from the solenoid to the throttle so I could operate both, with truck running as I increase RPMs and hold I have vacuum from the solenoid for 1 second, and then it quickly bleeds off, This was tested using brand new vacuum line. I'm not sure this is proper solenoid operation, or if I have a kink/break in the line somewhere.

I have cleaned the IAC thoroughly, and there was no change. I replaced the IAC with a brand new unit, and no change. I also replaced the IAC with a spare that I had, and still no change.

The inside of the distributor had some carbon fouling on the points and rotor, which was cleaned using a file and sandpaper, and no change.

The ignition coil terminal was covered in white powdery corrosion, and the inside of the wire on the coil had slight surface rust, both cleaned off and no change.

I listened to the gas tank with a stethoscope for proper fuel pump operation, it works great, doesn't sound weak, and works every single time.

Plug wires, and plugs are all new, only about 7k on them so far.

Injector spray pattern was tested with a timing light, and both patterns look great, inside of TB is clean as well.

I tried to check the timing on the truck, but for whatever reason, can't see the line on the balancer. I located the line, highlighted it with white paint, but when the truck is running, I just can't see it with a flashlight, or timing light.

On a cold start I can unplug the coolant temp sens, and it starts normal, with the longer crank times. When warm, if I unplug the coolant temp sens, the truck doesn't want to start at all.
I have not yet tested resistance of the CTS.

All grounds on the thermostat housing have been completely ground down to remove all rust, and all copper terminals were sanded to remove corrosion. I found one wire that has broken out of a ring terminal, and repaired that connection, but still have the same problems.

Dist cap was originally a little loose with about 1/16-1/8" of wobble, I tightened the screws, and nothing has changed.
The distributor itself is firmly installed with holddown properly tightened as well.

The heat inside the truck works great, better than most cars that I've owned actually.. I have never had a problem with the truck overheating, and just drove out to the reservation for smokes yesterday, 30 minutes one-way, and had no problems with overheating.

I'm probably forgetting a few more things that I've done, I'll respond with updates as necessary.

My concerns right now are the EGR solenoid bleeding off so quickly, and the coolant temp sensor. Viewing the CTS, it has 2 parts basically, the metal threaded section, and the upper plastic section for the 2-wire harness. The plastic section can easily be spun by hand within the threaded section... is this normal?

I apologize for such a long post, I just wanted to be as thorough as possible so you guys knew what was done up to this point so far. I know it's difficult to diagnose these things online, I usually do this crap myself, but this one has me stumped... and every truck forum I've posted on people just scream "OMG fuel pump" without even reading symptoms :-/

58mark

iTrader: (3)

here you go

http://www.gmtruckclub.com/forum/

juansupreme

Good Call!

Antichrist

It's a 5.7L TBI engine. I'm not asking about a honda.

I thought you guys might have some knowledge or insight about my problem..

Is it too much to ask for a little help?

58mark

iTrader: (3)

All non third gen discussion gets shut down. I was trying to throw you a helpful link before your thread gets locked

Antichrist

https://www.thirdgen.org/forums/tech...-but-help.html

But you know.. it's ok to ask about a Nissan here.. and receive a little help if you signed up here with your F-body..

I own a GM truck, with an engine that I'm sure many of you have worked on, but can't even get one suggestion, other than a link to a half dead truck forum.

I guess I should have mentioned my GTA in storage, maybe I'd get some help.

Have a nice day.

58mark

iTrader: (3)

I belong to that forum, and find it very helpful