NO CODES!

'88 GMC Suburban 4x4 350/TH700
I checked my computer for codes and came up with none! Still cranks allot before it starts, still idles high, still slowly winds down to the fast idle after snapping the throttle...
I don't have to crack the throttle any more to get it to start.
I did plugs, wires, cap, and rotor tune up with noticeable difference in idle quality and throttle response(the cap was disgusting) but with little to no effect on Idle speed.
No vacuum leaks.
Everything that is supposed to be on the engine is there(even the A.I.R. pump and belt).
What do I check next?
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if TBI, check fuel pressure

allot before it starts, still idles

throttle...
in idle quality and throttle

speed.
A.I.R. pump and belt).

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On Wed, 21 Apr 2004 00:10:28 GMT, "TranSurgeon"

How about the fuel pump relay, if TBI? Sounds like it cranks till oil pressure builds and then fires off. Fuel pressure relay will let it fire faster but the engine will die if oil pressure isn't seen right away. Something along those lines anyway.

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difference
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...but with no codes? I have worked on EFI vehicles before and have almost always had a code!
| > >> '88 GMC Suburban 4x4 350/TH700 | > >> | > >> | > >> I checked my computer for codes and came up with none! Still cranks | > >allot before it starts, still idles | > >> high, still slowly winds down to the fast idle after snapping the | > >throttle... | > >> | > >> I don't have to crack the throttle any more to get it to start. | > >> | > >> I did plugs, wires, cap, and rotor tune up with noticeable | difference | > >in idle quality and throttle | > >> response(the cap was disgusting) but with little to no effect on Idle | > >speed. | > >> | > >> No vacuum leaks. | > >> | > >> Everything that is supposed to be on the engine is there(even the | > >A.I.R. pump and belt). | > >> | > >> What do I check next? | > >> | > >> | > > | > | |
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no, but it might fix the 'still cranks a lot before it starts'...................
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I'm thinkin' since he had to crack the throttle plates to get her to start before the tune up, and now after the tune up with a hotter spark he doesn't have to crack the plates to get it to fire, plus the high idle, that there is just way too much gas making it's way into the mixture for some reason or another.
Then again, high idle could be a FUBAR'ed EFI component and the fuel pump/filter/realy could be shot causing the hard start.
Gotta love it when she doesn't spit codes at ya..............
Doc

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\"Doc\" wrote:

How about the IAC(idleaircontrol) valve sticking? Doug

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start
doesn't
there
reason or

I already suggested that a few days ago in another thread. He cleaned it and said the pintle is moving around just fine................
Doc

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Try the gasket between the tbi or carb. I had a 96 S-10 Blazer that had the same symptoms and a friend suggested I check it out. It was a $7.99 fix!
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Try the gasket between the tbi or carb. I had a 96 S-10 Blazer that had the same symptoms and a friend suggested I check it out. It was a $7.99 fix!
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check your fuel pressure. be sure it is 14psi for the low pressre system or 30psi for the high pressure system
res
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Bonehead:
TBI is 9-13 psi
CPI/MPFI is 60-66 psi.
The 7.4L TBI runs at 26-32 psi, but he's got a 350, so it ain't the "high pressure system."
Goddamn webbies...........
Doc

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