TOP END REFINISHING

[XfireZ51]

Yep, heat sink grease. Get it at RadioShack. Is that coolant I see on #1 cylinder?

[Dynomite]

Do NOT drop anything in those open Injector Housing Ports. First thing is to tape those ports as quickly as you can.

You are doing extremely good in taking photos....appreciate that

[Schrade]

Originally Posted by XfireZ51

Does the stumble continue if you keep the pedal at a steady 1.6% TPS? Or does it stumble on the initial tip in?

I missed this here Dominic - it lopes only as it I hit 1.6% throttle. No stumble at all, even on tip-in. I hit 1.6% TO, give it a TINY bit more gas - almost IMPERCEPTIBLE, and it starts to lope if I hold. Then it bounces from 1.6% - 2.4% TO, as shown on Datamaster. Once I get over 2.4%, it's perfect again through RPM range.

[XfireZ51]

I noticed in the vid that the TPS% jumps around a bit. By "lope" do you mean a bit of a surge up and down the rpm?

[Franke]

I noticed in the vid that TPS voltage was about .61 volt when it hit 1.6% tps then the rpms began rolling between 900 and 1275 rpms at one point. The TPS changed from .61 to .63 volts.

[Franke]

Schrade, there is a note in the FSM about cleaning the TB. Page 6e3-c2-16. Good info to know with the throttle valve, IAC and TPS.

[Schrade]

Originally Posted by Franke

Schrade, there is a note in the FSM about cleaning the TB. Page 6e3-c2-16. Good info to know with the throttle valve, IAC and TPS.

Uh-oh... I pulled the extension off of the TB first.

Didn't NOTICE any problem...

MEK for CLEANING? MEK is hardener for fiberglass resin. TPS wasn't immersed. IAC WAS liberally coated with WD and paint thinner mix (mostly kerosene in WD, and I pull excess off with a Shop-Vac).

Originally Posted by XfireZ51

I noticed in the vid that the TPS% jumps around a bit. By "lope" do you mean a bit of a surge up and down the rpm?

Yep...


and thanks to Darryl for changin' thread name here.

[Schrade]

Blow out the bolt holes with some lube til they run clean...



little spray on the bolts

[Franke]

I wouldn't try to take it out as I believe it is a tight press fit and you may not be able to re-seat it again. Its aluminum and is 23 years in there. Those hoses are crushed pretty good at the connections. I replaced mine with premium fuel line hose. Are you going to repaint anything while it's off?

From Marc Haibecks ZR-1 info (quote) "As far as I know GM has never documented any information about the use of Dag as a sealing and anti-friction method on the LT5 throttle body.
Dag is a general purpose material that is graphite based and is applied like paint. It's used in various industrial applications that need properties like a thick material buildup, low friction and high temperature range. DAG is a trademark of the Verick, Acheson Colloids company. It is easy to mistake the Dag for dirt. Dirt builds up on the Dag in the normal operation of the engine. These throttle bodies were cleaned so as to preserve the Dag. They were simply gently wiped with a soft dry cloth. The use of a solvent will remove the Dag.

The Dag was used to improve the seal of the secondary throttles. There are problems with the Dag coating. It wears off or chips off quite easily. It will come off if it is wiped hard. It will come off very easily if a solvent is used. It's easy for an uniformed maintenance person to remove it unintentionally. At a glance it looks like dirt.

Loss of the Dag coating can cause excess air leakage past the throttle plates and loss of idle speed control range for the engine control system.

I recommend that the LT5 throttle body bores should never be cleaned. In my experience a normally dirty throttle bore causes no problem. In fact a little oily grime around the throttle plates helps seal the throttles to minimize air leakage. It also lubricates the edges of the plates to avoid sticking. If the bore is extremely dirty or you just can't resist the urge to clean it, do it gently with a soft dry cloth.

I have tried to reseal throttle plates with little success. The problem has been with poor adhesion to the bore with the sealing material.

When the Dag is no longer effective I improve the fit of the throttle plates to the bores with a polishing process." (End quote)

[Schrade]

Thanks again for the info there Franke...

Now's a good time to do another fuel pressure test, with some hardware out of the way here.

Where do I jump the pump circuit? How about the 2 second shut-off for this test?

And how to cap the line in front of the FPR???