Decal on Support says "DO NOT TOUCH..."

[Suburbanite88]

A little help?

1988 V20 TBI 350/400 California Truck, 164,000 miles/40,000 on rebuilt TH400... Normally very strong, absolutely no hesitation, stall, or lag whatsoever, loves to run. Smog Check, tech said engine idle speed too high, showed me on computer screen 1200+ rpm at idle... Wanted to bring it down a little, I said "sure... Why not?" down to 900+ still steady, smooth and quiet idle...

After test, died at red light, then again, after that 50-60% of the time... Next day, filled up regular gas, then immediately rough idle, stalling more frequently, increasing hesitation, general loss of power, hard starting and backfire...

Condition worsened to UNDRIVEABLE... Lots of advice from ASE Cetrified Techs, to Backyard Mechs; everything from Fuel Pump, Tranny or Computer, to Vacuum leaks, Throttle Body Rebuild, to Bottom-end Rebuild...

Started with the cheapest thing first... After inspection, found: TBI Gasket Vacuum Leak; (5) Intake Manifold bolts took 10-15-degree-or-less turn; Distributor Cap, Rotor, and Plug Wire boots some corrosion...

With all issues mitigated, starts right up, but still won't idle...

Next, all new: IAC Valve, fuel filter (priming at 13psi); AC-Delco plugs, wires, coil, cap and rotor, buddy with a Timing Light tried to dial it in just right, but could not keep engine operating, between about 1500-2500rpm sounds like it's missing...

Replaced with new: MAP, TPS, ATS, knock sensor, fuel pressure regulator, ignition module, EGR Valve and Solenoid...

Starts easily, fires up great, prime burns off, rpms dive right past idle and...

Dead.

It all seems to go back to Smog Tech guy adjusting the idle from the idle set screw, now I just wanna get my Girl back on the road, any thoughts?

Thanks...

[68Timber]

Does this truck still have the original catalytic converter? I think 88 still had the original pellet style converter that didn't flow well new and they do clog up over time.

[Suburbanite88]

Don't know for sure, but I haven't replaced it myself... Brand new O2 sensor not long ago, "Check Engine" light is not on, passed smog with very high emissions, but since it's an '88, I skated right under the max limit:

HC (ppm) 15mph Measured: 104 Max: 104
HC (ppm) 25mph Measured: 92 Max: 108

I'm no expert, but I'm thinking emissions not the problem, but thanks just the same...

[68Timber]

That's not quite what I meant, they can clog up and not flow well enough for the engine to run when they go bad.

[Suburbanite88]

Yeah, I considered that, but I thought the "Check Engine" light would be on ("Service Engine Soon" light?) if the CAT was clogged, inefficient, not operating properly...

The only time it did, through the middle of all this, I had just replaced the EGR Valve and Solenoid, and the light went out...

Just trying to provide as much info as possible...

You don't think the Idle Set Screw Adjustment had anything to do with all this?

[Hertzdaddy]

You say it sounds like its missing. Try pulling one plug wire at a time and see if its a single cylinder issue.That would narrow it down some if so.

I'm not all that familiar with TBI but if it were carb I would remove and clean it out. Have you tried cleaning the injectors?

[Ford Assassin]

Originally Posted by Suburbanite88

Yeah, I considered that, but I thought the "Check Engine" light would be on ("Service Engine Soon" light?) if the CAT was clogged, inefficient, not operating properly...

I have had two GM TBI engines have the cats clog up and neither gave a check engine light. On OBD I computers, they had no way to know if the converter has gone bad.

On later model ('96+), there is a rear O2 sensor(s) after the cat(s) that will produce a check engine light if one goes bad.

[Suburbanite88]

I'll have to give that a try, just so I can rule it out, I guess...

Had the impression that bad/dirty/gummy injectors caused performance to wane, deteriorate over time...

...after the problems suddenly began, installed brand new AC Delco Plugs--correct .035 gap (the old ones looked fine, not fouled), ACCEL Plug Wires, ACCEL Distributor Cap and Rotor. So, if the problem existed, worsened, but no change after all that, can I still suspect the plugs?

[bluex]

Originally Posted by Suburbanite88

TBI Gasket Vacuum Leak;

A vacuum leak will cause a high idle. Since you have it fixed now its not getting as much air as it was so it wont idle. Turn the idle screw back up so it will idle at 900ish in park.

[Suburbanite88]

Originally Posted by bluex

A vacuum leak will cause a high idle. Since you have it fixed now its not getting as much air as it was so it wont idle. Turn the idle screw back up so it will idle at 900ish in park.

BlueX: A few days--week since last worked on this, been sitting, a travesty--but yesterday able to get (1) Started, easily, without throttle assistance; (2) Idling, although on forth start; (3) once idling, and warm (160-180 degrees), adjusted "Minimum Air Rate" adjustment screw, backed it out 1/10th at a time until 1/2 turn total and idle achieved down around 700-900 rpm (guess) in Park.

Although strong, fluctuating a bit (but not surging, as in faulty Fuel pump/sending unit) while idling high in Park sounds/feels smooth, strong and steady just exactly as brand new. Presence of foul, acrid smoke/exhaust engine compartment, a nasty, burned plastic/chemical/solvent smell, checked wiring harnesses, hoses and tubing, but nothing...

Still rough at higher (1500-2500) rpm's and definite feel like missing, especially while slowly throttling up, but absolutely refuses to rev... Shut it down for a few, inside smells foul, like same burning smell--although kinda sweet, without the choking smoke--inspected under dash, fuse panel, components, nothing...

Restart 30 minutes later; immediate start, revved-up, idled down, rough, but running, died in gear... Restart, died in gear... Third start held Brake/Throttle shifted into D with lurch--big power, like trying to ride a bull--100' brake, died...

Suggestions?

[bluex]

A clogged cat usually smells like sulfer/rotten eggs. This truck will only have one O2 sensor. If you can post a picture of the other sensor maybe we can tell you what it is, its possible its the knock sensor though as they are in about the same area.

Problems like this are hard to diagnosis over the internet. It could be fuel, ignition, timing, the converter.

You've checked the timing (did you disconnect the plug first before checking it? Plug it back in when done?) An replaced most of the ignition an sensors. Next I'd either take off the cat if it has flanges on both sides or I'd check the fuel pressure. If the fuel pressure is good then I'd remove the cat for sure....

[Suburbanite88]

No smell of sulfur/rotten eggs at all... Positive it's NOT http://www.autozone.com/autozone/par...ier=45338_0_0_ the Knock Sensor... It's on the Driver's side, just slightly behind, and slightly above the Oxygen Sensor, resembles this thing to a T: http://www.autozone.com/autozone/acc...er=131260_0_0_

I'm positive it's a Fuel/Air problem compounded by timing issues. One of which has to be the fact that it's real tough to fine-tune the timing if the motor won't idle... Especially when it's your buddy who actually owns a Timing Light--who's a bonafide car guy (although a f@rd guy) and has been his whole life--knows everything there is to know about the 350 Chevy V8, says my timing chain is stretched too far out can't time it, but didn't know about the ESC Module. Running like new before, didn't suddenly get stretched one day.

Think I still have a vacuum leak somewhere, gonna have to check again... Tried to run the motor with the EGR Valve vacuum line pulled, plugged: started strong, smooth, for a moment, then died. Tried something else: pulled IAC Valve (pintle was almost completely retracted, spring compressed), started immediately, ran fast engine speed right away, in less than 10 seconds, died again...

Gonna go try checking trouble codes, but I've never done that before, not sure how to proceed... I have the codes and a piece of wire...

Back soon... Thanks guys!

[Suburbanite88]

Okay gentlemen (and ladies, as you may be)... I think this whole thing is SOLVED!!!

Let's just try to step back a minute, you know... Away from the trees! Let's start over again... Here's my problem:

1988 V20 Suburban 350/400 TBI (40k on rebuilt THM400) Runs, drives like a champ! Strong running powerful, great condition... Suddenly, without warning, almost overnight:

Pulled into a gas station one day last month, into the lot, started sputtering, choking, stuttering...

Out of gas...

No way, nearly a quarter-tank left! Can't be empty!
Still I roll up to the pump dead...

MUST HAVE BEEN THAT SMOG GUY FROM YESTERDAY,
THE ONE WHO "ADJUSTED MY MINIMUM AIR RATE ADJUSTER!"

Yeah. Maybe so...



Symptoms:

Slipped into Reverse, dies.
Slipped into Gear, dies.
Hit the brakes, dies.
At a STOP sign, dies.
Now it's Hard Starting.
Low Engine Idle Speed.
Rough Idle, in Park, in Neutral.
Won't Idle in gear, ever.
Will not Rev.
Will NOT accelerate.
Stalls at speed.
Bogs.
Hesitates.
Coughs.
Sputters.
No power...

What is it?



What is the Problem?

SMOG Check guy, messing with the Minimum Air Rate Adjuster? I guess I'll never really know, now...
Because, coincidentally, my FUEL PUMP/SENDING UNIT is in the throes of it's own Death Rattle!

No winding up sound when I turn the key to start...
(Relative) Silence.

No high-pitched whining sound, either...
Probably not much to hear completely submerged in a...

FULL-TANK of GAS!

CODE 44

Thank you all so very much! I've learned a lot!