84 IAC removal
 

Does anyone know what size socket I need to remove the IAC motors on the 84 Crossfire? It measures out at 1.265" which converts to 32.131 mm.
So do I buy a 33mm socket? 1 1/4"? or something else? My adjustable is too bulky to get at either.

1 1/8

A wrench is obviously better, but mine came right out with a pair of channel locks.

Thanks folks. Being as how I'm still building the tool collection, a 32mm socket seemed to work fine... although I had to remove one of the intake MF bolts to get at the LS IAC. It looked fairly new. The RS looked older and seemed to be stuck more than the LS... but both (plungers?) were very hard to maneuver. A little wd40 and some rocking back and forth seemed to free them up a bit. The coils ohm'd out at 53 and 54 so they seem to be good.

I'm trying to resolve an idle issue where the thing starts and immediately goes to 1800 RPM.... when warm it goes down to about 1600.

Next steps will be from this article... http://forums.corvetteforum.com/c4-t...dle-speed.html

1984 Crossfire TPS
 

Well... I did the steps in the article, Things went from bad to worse. I cannot get more than .069VDC between the top 2 wires on the TPS. It will not start now. It will start briefly with a shot of starting fluid. I get spray from both injectors.

back probing for voltage results measured with negative lead on engine ground. TPS Connected.
KOEO-top tps pin(C)=5.19vdc.
KOEO-middle tps pin(B)=5.13vdc
KOEO-bottom tps pin(A)=.031vdc

TPS Disconnected, Harness side measurements:
KOEO-top tps pin(C)=5.19vdc.
KOEO-middle tps pin(B)=.035vdc
KOEO-bottom tps pin(A)=.031vdc

Harness Disconnected TPS Resistance measurements.
top pin(C) to middle pin(B) 15ohms - no change at WOT
middle pin(B) to bottom pin(A) 1075ohms - smooth transition to 3800 at WOT
top pin(C) to bottom pin(A) 1883 ohms - smooth transition to 3800 at WOT

Any idea where I should look next? Replace the TPS?

That article was written for 1985 and later TPI engines- not the 1984 Crossfire injection system. I'd recommend checking the 84 FSM for the TPS settings....

Crap... I guess that's why it's not working.
Thanks for the heads up.

I'm looking through the PDF version of the FSM for the 84 and have yet to find a TPS test... still have a few sections to go through, though.----

--- NM... just found it. Figure 68 on page 6E2-69.---
Looks like I was measuring the wrong 2 pins... voltage between the "bottom" 2 pins (A&B) should be .525 +/- .075 vdc.

Just got home and measured the voltage between the bottom 2 pins... 5.08vdc closed throttle... to 5.14vdc WOT. Looks like I'll be ordering a TPS.


... Just picked a TPS up at Carquest $65.. now the voltage reads right. .525vdc. Damn thing still won't start though. Wants to... and when she does fire up (with lots of fancy footwork on the accelerator pedal) ... she runs for a second or 2 spitting and sputtering ... and dies.

Frustrating....

Are you getting any engine codes? Fuel pressure? The first symptoms almost sound like a vacuum leak....(the fast idle speeds)

I am no master mechanic but I agree with Vermin. Kinda sounds like a vac leak. Since it got worse and you said you had to remove a manifold bolt to get the IAC motor out maybe the intake manifold gasket? You did put the bolt back?

Good luck!

No Codes except code 12 when I jump A-B on the ALCL... according to the manual that means the ECM is functional.

I have replaced several vacuum lines so far due to cracking, etc.... maybe I just haven't hit the culprit yet. I'll keep replacing them and maybe get lucky... and maybe not.

I'm still working thru the check steps between steps 4 & 5 in figure 16 Chart A-3 page 6E2-19.

Found the TPS bad yesterday.. so I replaced it. Tonight I'll check the coolant sensor circuit, and find/replace the fuel filter.... then I'll continue through the list.... EGR Chart C-7... Crank Signal Chart C-28.

I've ordered a pressure gauge so that test will have to wait. I do get a spray cone from both injectors when cranking and no spray/drips when they are disconnected and cranking the engine.

Not sure if this means anything, but the engine won't even consider starting unless the air-cleaner is on and secured (not enough fuel?).
When the air cleaner was off and I tried to start it... I did have the vacuum line that runs to the air cleaner (THERMAC?) blocked.

You have a vacuum leak on on the CFI engine, it is most likely, the plenum lid gasket. Spray "carb cleaner" or some facsimile there of, around the engine to locate vacuum leaks (once you actually get it to run)

The TPS setting/adjusting procedure is basically the same, CFI>TPI or, '84>'85. The only MEANINGFUL difference with the CFI is that before you set your "minimum air" (which you do on a TPI motor too), you need to make sure that your two throttle plates are relatively well synchronized.

No start: CHECK YOUR FUEL PRESSURE. Very common problem to have weak fuel pressure on these engines.

You have a Crank signal; if you didn't, you wouldn't have spark, OR injector firing while cranking -which you say you have.

EGR won't affect starting if it's not functioning...however it will make a "vacuum leak" if it's hung open with carbon or something. Easy to check physically. Manipulate the diaphragm w/your hands.

Engine should run fine, air cleaner on or off.

-Tom

Thanks for the info/direction. I'm sure you saved me several hours of frustration. I'll start down that road tonight.

I didn't order a professional Pressure tester... just this one http://www.amazon.com/gp/product/B000CPINHA It measures up to 15 lbs pressure.... but it looks like I'll need to find a rubber hose to test the pressure. Suggestions?

The tester that you bought will work (barely) with the parts included. That tester is meant for testing pressure on a carbureted engine; 5-7ish lbs of pressure. Fortunately, the CFI system operates on only "9-13 lbs" though many have benefited from boosting up the pressure slightly.

At any rate, us the supplied hose and cut a 2"-3" piece off of it. Attach that to one leg of the supplied "T", the remaining to another leg...then to the gauge. Finally, there is a rubber line that runs from the frame rail on the passengers side to the engine. Disconnect that hose from the hard line, and "T" in there, connecting the factory rubber hose to the final leg of your "T". Then test while cranking/running. Should make and HOLD, set pressure (somewhere between 9 and 14 lbs) under ALL conditions. If pressure falters, a new pump is likely needed. If you get to the point of diagnosing the fuel pump as an issue, then be sure to replace it with a better pump than stock. '85 and newer, after market...what ever. But don't replace an '84 pump with another '84 pump.

-Tom

Thanks for the info Tom, very much appreciated.

Question about the 85 and up fuel pump:

Will the pressure regulator in the throttle body take care of the higher pressure rating...keeping the injectors within their operating parameters? Then route excess fuel back to the tank?

I looked at the difference between aftermarket pumps for the 84 vs 85 and the minimum/max pressure for the 1985 > models is 65/95 PSI vs the 1984@12/17 PSI. Seems like a vast difference to ask of the fuel system components. Although... one could argue that the higher pressure will surely expose any weaknesses in the system.


--- A little research revealed the answer ---
Quote from: http://forum.grumpysperformance.com/....php?f=32&t=33
"Running a high-pressure capable GSS340M pump does not cause abnormally high fuel pressure. Fuel pressure is controlled by the regulator on the fuel rail."

So... I'm thinking the same is true for the regulators on the Crossfire TB.

You are correct. The stock regulator will have no problem dealing with the '85^ pump's volume, and the regulator is what sets the pressure. :)

-Tom

Short version: No measurable fuel pressure... replaced pump - IT STARTED!!!


Long Version:
I didn't want to waste a weekend waiting for the pressure gauge to arrive in the mail. While I was at AutoZone, I inquired if they had any pressure gauges. They had a pressure gauge kit that I could rent for free. All I Had to do was pay for it then return it when I was finished. Pretty cool.. I'll have to remember that for future projects. Anyway....

I checked the fuel pump electrical circuit with the VOM and found contacts in the fuel pump relay were not making contact in it's un-powered state... so I cleaned those up with some 600 grit sandpaper. Contacts tested ok now. I was getting power to the pump and could hear the pump whirring ...

... I connected the pressure gauge in the place of the fuel filter. Apparently a previous owner replaced it with an aftermarket filter that has 2 hose nibs rather than the machined fittings... so that made things somewhat easier. I turned the key on and could hear things click (relay) and could hear the pump cycle on for 2 seconds. No matter how many times I cycled the power on/off or tried to start the engine... that damn pressure gauge wouldn't budge off zero....

... just to be sure I double checked that I had done things correctly and even put the pressure gauge on the compressor to make sure it was good. It was. (Note: Apparently MY lungs would not generate the amount of pressure necessary to make the needle budge on the 100 LB gauge ... that's why the compressor test was necessary)

Off to AZ to buy a new fuel pump and strainer. I had to order a gasket so it'll be here this week. I made a temporary tank gasket until it does.

I took the old pump out, repaired the old wiring, solder-spliced in the new power connector (ground wire was a little flaky and fell off the old connector when jostled)... Installed the new pump and put things back together.

I turned the key on (after reconnecting the battery) and the pressure gauge immediately jumped to 12 PSI... so I tried to start it. IT STARTED!!!! WOOHOO!!! It went straight to 1200 RPM and stared coming down and settled at 1100 RPM after a minute or so. Looks like I still have to find that vacuum leak.

I'm trying to get it back on the road and noticed the front brake pads were less than 1/8" so I got those at AZ and replaced the R/F so far. (That was the side on jack stands to get to the fuel filter)... and the brake fluid was really dark... so I cleaned up the front reservoir and flushed the old fluid. Also... figure I might as well replace the rotors while I'm there... so I'll pick those up sometime this week... hopefully.

It's really hard to NOT fix things that I see that are wrong... so it'll probably be a while before I get it on the road again... But thanks to the help on this forum... I'm a step or 2 closer.

VICTORY!! That was a great story! :thumbs:



Remember that it's possible that the throttle adjustments are out of whack, and that could cause the symptom. However, it is more likely a plain old vacuum leak. I mention the throttle b/c it is a possibility, and it's really pretty easy to check...just by looking at the things, for starters.

-Tom

My '84 has the rubber hose-to-hose nibs too, (listed as factory specs). I think they went to the steel line and fittings in '85 when the pressures went higher. In the '84, if the fuel filter got clogged, the pressure behind it would be about 14 lbs, but if you put in the '85 pump and the filter clogged, I wonder how safe that 26 yr old rubber hose and nibs setup would be with the higher pressure from the newer pump. (?)

Good point Squirmin, I'll replace that section of hose while it's up on stands. I did install a new filter and will make it a regular maintenance item.

I'll also check the throttle adjustments after I eliminate the vacuum leak possibility. I can tell it (throttle adj.) has been mucked with because the seal over the throttle stop/adjust screw is missing.

She's up on jack stands now. All the rotors were less than minimum spec... so I'm replacing all four corners.
Looks like all the bushings need to be replaced as well as the Ball joints (rubber dry rotted and leaking grease) and tie rod ends. Gonna take my time on those as I want to at least be able to drive her a little between repairs.