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?

Reply to
Shades
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if TBI, check fuel pressure

allot before it starts, still idles

in idle quality and throttle

A.I.R. pump and belt).

Reply to
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.

Reply to
Mike Levy

Still doesn't explain the high idle. Gotta be CTS or FPR.

Doc

Reply to
"Doc"

...but with no codes? I have worked on EFI vehicles before and have almost always had a code!

| > >if TBI, check fuel pressure | > >

| >

| > 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. | | Still doesn't explain the high idle. Gotta be CTS or FPR. | | Doc | | | >

| > >

| > >>

| > >> 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? | > >>

| > >>

| > >

| >

| |

Reply to
Shades

no, but it might fix the 'still cranks a lot before it starts'...................

Reply to
TranSurgeon

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!

Reply to
sdingess

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!

Reply to
sdingess

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

Reply to
"Doc"

How about the IAC(idleaircontrol) valve sticking? Doug

Reply to
Doug

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

Doc

Reply to
"Doc"

check your fuel pressure. be sure it is 14psi for the low pressre system or 30psi for the high pressure system

res

Reply to
rfs

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

>
Reply to
"Doc"

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