Almost done, but a little glitch

[Donf]

Thanks to all the help I've received here I have my new injector "spider" working. Seems to be doing well.
My new problem is a fast idle - about 1300 RPM in neutral. Idles at 20 MPH in gear.
I have ;
double checked all connections,
cleaned the throttle body
removed and cleaned the IAC
scanned for codes (none).

Next most likely suspect please?
Thanks, Don

 

[exp500]

Check for vacuum leaks, especially around master vac connections, also look for your heater vacuum line and your map sensor installed ok. Spray can may help too.

 

[OR VietVet]

I have removed the IAC valves and cleaned with success but also had to replace them. The other thing to look for is the area in the throttle body where the port is for the IAC valve. That gets carboned too and causes air flow problems. It's been long enough that I had worked on one that I can't remember but is there a idle screw on the throttle body and make sure there is no binding with the throttle cable.

 

[exp500]

Another little test is to unplug MAF and see what it does. Hot plugging that is OK. See if your Idle changes much. And then there is the battery disconnect, touch both cables to discharge whole system and reconnect. Downside to that is a clear codes and Drive Cycle of about 50 miles - which with new Spider not a bad Idea.

 

[east302]

Check for vacuum leaks, especially around master vac connections, also look for your heater vacuum line and your map sensor installed ok. Spray can may help too.

Adding to that, spray some carb cleaner (engine cold to reduce fire hazard) around the area under the injector harness where the spider assembly goes through the upper intake. See if the idle changes. The gasket may have slipped when you reseated the upper intake over it, causing a vacuum leak.

Brake booster vacuum line is another thing, along with the hard vacuum line that runs from the PCV across the intake over to the water valve’s solenoid under the accumulator (Tahoe/Suburban only).

Have you verified that the throttle is actually closing - that the cable isn’t somehow binding and preventing the spring from closing the blade?

If you have a scanner, see what the throttle position is (%) as reported by the TPS.


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[Donf]

Thanks to all of you, busy today but I'll get to that stuff tonight.

Do I need to clear codes? My scanner does not show the previous codes from before the spider transplant. The battery was disconnected a few weeks.

 

[Donf]

OK, I checked all vacuum (brake booster and heater line)lines, they look good.
Throttle cable very smooth, no kinks or binding. Throttle plate closing all the way.
My idle is perfect, totally smooth, just high, around 1200 to 1400 RPM in Park, 900 to 1000 in gear.
Next up is to unplug the MAf and spray the carb leaner around the injector body.

Accelerates nicely but around 4k or so starts to feel like it's missing or something.
Removed MAP sensor, gasket torn and shot. replaced gasket but still idles high.

At least the copious water flow from the tailpipe has stopped after a ten minute drive, started it today and had just the typical1 to 2 inch spot then it stopped dripping. That had me worried.

 

[east302]

Here are the IAC valve diagnostics for a 98, maybe it’ll help...














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[Donf]

OK, I unplugged the MAF, immediate drop in RPM followed within a few seconds of an increase to the original 1300 or so. Plugging it back in did not change any thing nor did subsequent unpluggings and repluggings.

Tried the non scan tool reset,3 times, no effect at all.

Sprayed carb cleaner all around the spider. Nothing.
Sprayed carb cleaner around all vacuum fittings, nothing.

There is a red gasket that fits between the throttle body and whatever the big black plastic thing is that sits atop the TB. It is original, old and blackened. Pressing downward on the thing does nothing but could that be my problem?

 

[east302]

Does your scanner show TPS voltage? At closed throttle, it should be less than 1-Volt, say 0.5 to 0.8 or so.

Also check commanded versus actual idle speed along with the IAC valve counts. Zero count is closed, the computer trying to lower the rpm. I think that 100 or so is normal on a cold engine, but it should drop down to maybe a quarter of that when warmed up.

As for that o-ring on the intake, it wasn’t a separate part. It came with the intake piece. Your front clips are intact on it, right? I don’t know if I’d call that a vacuum leak (pretty much just air bypassing the MAF) but could see how that could cause a high idle.

You might try putting a small bead of RTV on it and see if that changes anything. I’ve also heard of people blowing smoke into the PCV fitting and seeing smoke come out of that gasket when it’s worn.


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