5.7 TBI runs rich, hesitates... - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rfmaster · 07-01-2011, 10:03 PM

Quote:

Originally Posted by JCampbell

Hmmm...12 psi, but blocking the return line bumps the line pressure up to about 14-15 psi.

Fuel pressure reg?

This is a tough one to call - fuel pressure regulator is doing its job by keeping FP at 12 PSI. The pump has just enough to dead head pressure (14-15pSi) - like to see 20+ psi to be sure. Does not look like FP is at fault here...

//RF

*JCampbell* · 07-02-2011, 02:13 AM

Dirty injectors?

*JCampbell* · 07-02-2011, 05:16 PM

Well...now I did it.

Picked up a TBI rebuild kit from Napa. Basically tore down the throttle body, cleaned it up with carb cleaner, replaced all the gaskets and reassembled. Fired her up and she went straight to high idle. Won't kick down. Any ideas?

Solvent left in the throttle body from cleaning?

rfmaster · 07-02-2011, 09:34 PM

Quote:

Originally Posted by JCampbell

Well...now I did it.

Picked up a TBI rebuild kit from Napa. Basically tore down the throttle body, cleaned it up with carb cleaner, replaced all the gaskets and reassembled. Fired her up and she went straight to high idle. Won't kick down. Any ideas?

Solvent left in the throttle body from cleaning?

Did you set timing with EST connector open to 0 deg??

Did re connect TPS??

//RF

*JCampbell* · 07-02-2011, 08:26 PM

Ran through the procedure to reset the IAC (jumped A & B on diagnostic port, waited approx 30 sec, disconnected IAC, pulled diagnostic jumper, started engine), no avail.

Thought maybe a vacuum leak: checked all vac fittings...good and tight. TB gasket seems to be correctly in place.

Note of interest...when I reset the IAC, the plunger did move into position...I can see the cone when looking down into the TB.

*JCampbell* · 07-03-2011, 01:46 PM

Yes.

Yes.

This is really starting to frustrate me.

Went through all the hullabaloo for re-setting the IAC several times and have had no significant changes in the high idle situation. Got the idea to physically check the position of the IAC when the truck was running...went out and looked down the TB before I started her up and I noticed the IAC was in a fully retracted position. I have not verified the position of the IAC with the truck running yet because I think it's pretty obvious that it is fully retracted when running.

So it would appear that even though I have reset the IAC several times, it still wants to default into a fully retracted position as soon as the truck is started.

I'm not really into buying and replacing parts as a method of troubleshooting, but I'm wondering if I have a bad IAC. I read somewhere (of course, this was after the fact ) that you are not supposed to use any kind of solvent while cleaning the IAC. So naturally, I used about half a can of carb cleaner on the damn thing when I was cleaning it.

*JCampbell* · 07-03-2011, 02:10 PM

...and, yes, I did check for vacuum leaks by spraying ether around the base of the TB with no noticeable change in idle speed.

It would appear to me that that vacuum leaks are not the issue here.

*JCampbell* · 07-03-2011, 03:12 PM

HA!

I feel like such an idiot. The linkage from the cruise control diaphragm to the throttle body was bound up at the diaphragm causing the throttle blades to be held open partially. Freed up the linkage and BAM!...went to a perfect idle. Took her for a ride around the block and she ran like a raped ape!

May need to bump the minimum idle setting up a hair...it kinda seems a little low. Need to pick up a tach to get it just right.

rfmaster · 07-03-2011, 09:22 PM

Man - I feel it for you!!!

Now you know how tough it is troubleshoot without being there - that truck still has many miles left in it.

IAC will compensate idle over time - ECM has re learn after IAC reset.

Happy Fourth of July (and be safe)

//RF

*JCampbell* · 07-04-2011, 12:04 AM

Yeah, it's already idling a lot better.

*JCampbell* · 07-17-2011, 04:23 PM

@#$%!

Finally got around to adjusting the timing. Was set at 4*BTC and about 10* advanced. Disconnected EST, brought it back down to 0*BTC/0* advanced. Idled fine, got in it and ran around the block, SES lights up, truck starts running like s____, no power, missing, etc.

WTF?

rfmaster · 07-17-2011, 11:50 PM

Quote:

Originally Posted by JCampbell

@#$%!

Finally got around to adjusting the timing. Was set at 4*BTC and about 10* advanced. Disconnected EST, brought it back down to 0*BTC/0* advanced. Idled fine, got in it and ran around the block, SES lights up, truck starts running like s____, no power, missing, etc.

WTF?

After you set base timing (EST connector open ~ 0 to 2 deg BTDC) shut off engine and disconnect battery. This will clear code 42 which is set when ECM detects EST connector open. If you forget to clear this DTC (after reconnecting EST) - SES will be lit on re-start. You can always pull DTC codes by shorting pins A & B of ALDL connector. Without re-starting engine move key into run position you should get 3x DTC 12 followed by 3x other codes (if any).

If EST connector is not fully plugged in ( or you have a broken wire in set EST circuit) your timing will be fixed to about 0 to 10 deg (depending on ICM) - absence of SA advance explains lack luster engine power.

//RF

*JCampbell* · 07-18-2011, 11:36 AM

Yeah, I plugged the EST back in and disconnected the ground from the battery after I set the timing. Though one thing that’s been gnawing at me is that the weather tight connector I assume to be the EST isn’t tan/blk, but looks more like an orange/blk. Could be a non-issue, except that I noticed when I unplug it, it doesn’t cause the SES to light up. Makes me wonder if I’m unplugging the wrong thing - although it seems unlikely as it is the only weather-tight single-wire connector near the booster, save for a purple/blk single wire connector that is more of a “press-fit” than a weather-tight connector like you posted.

Feeling a bit frustrated, but I have a plan:

Jump ALDL to see if there are any DTC – report/investigate findings

If no DTC:
-Pull plugs – inspect – replace if necessary
-Bump timing to 2* - see if that helps.

Jonboy · 07-18-2011, 12:32 PM

I think ppl/blk is O2 sensor, on the left side of the engine. The EST may be on the passenger side also, near the A/C box.

edit- when you unplug it, it will DEFINITELY turn on the SES light.

*JCampbell* · 07-18-2011, 12:54 PM

Hmmm...okay.

*JCampbell* · 08-05-2011, 11:16 PM

Victory!

...I think.

Finally got around to fooling with my rig again and just as I was beginning to suspect, I was unplugging the wrong connector.

Found the actual EST, unplugged it, SES lit up, set timing to 0 degrees, reset DTC's & took her for a spin around the hood. It appears all is right in my little TBI world.

No hesitation or lean pops, just a smooth running smallblock. I won't feel like I'm totally out of the woods until I put some more miles on her, but for now it looks like my TBI and I are making up.

07-02-2011, 02:13 AM	#2
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Dirty injectors?

07-02-2011, 05:16 PM	#3
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Well...now I did it. Picked up a TBI rebuild kit from Napa. Basically tore down the throttle body, cleaned it up with carb cleaner, replaced all the gaskets and reassembled. Fired her up and she went straight to high idle. Won't kick down. Any ideas? Solvent left in the throttle body from cleaning?

07-02-2011, 08:26 PM	#5
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Ran through the procedure to reset the IAC (jumped A & B on diagnostic port, waited approx 30 sec, disconnected IAC, pulled diagnostic jumper, started engine), no avail. Thought maybe a vacuum leak: checked all vac fittings...good and tight. TB gasket seems to be correctly in place. Note of interest...when I reset the IAC, the plunger did move into position...I can see the cone when looking down into the TB.

07-03-2011, 01:46 PM	#6
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Yes. Yes. This is really starting to frustrate me. Went through all the hullabaloo for re-setting the IAC several times and have had no significant changes in the high idle situation. Got the idea to physically check the position of the IAC when the truck was running...went out and looked down the TB before I started her up and I noticed the IAC was in a fully retracted position. I have not verified the position of the IAC with the truck running yet because I think it's pretty obvious that it is fully retracted when running. So it would appear that even though I have reset the IAC several times, it still wants to default into a fully retracted position as soon as the truck is started. I'm not really into buying and replacing parts as a method of troubleshooting, but I'm wondering if I have a bad IAC. I read somewhere (of course, this was after the fact ) that you are not supposed to use any kind of solvent while cleaning the IAC. So naturally, I used about half a can of carb cleaner on the damn thing when I was cleaning it. Last edited by JCampbell; 07-03-2011 at 02:07 PM.

07-03-2011, 02:10 PM	#7
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... ...and, yes, I did check for vacuum leaks by spraying ether around the base of the TB with no noticeable change in idle speed. It would appear to me that that vacuum leaks are not the issue here.

07-03-2011, 03:12 PM	#8
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... HA! I feel like such an idiot. The linkage from the cruise control diaphragm to the throttle body was bound up at the diaphragm causing the throttle blades to be held open partially. Freed up the linkage and BAM!...went to a perfect idle. Took her for a ride around the block and she ran like a raped ape! May need to bump the minimum idle setting up a hair...it kinda seems a little low. Need to pick up a tach to get it just right.

07-03-2011, 09:22 PM	#9
rfmaster Registered User Join Date: Oct 2003 Location: OC CA Posts: 1,374	Re: 5.7 TBI runs rich, hesitates... Man - I feel it for you!!! Now you know how tough it is troubleshoot without being there - that truck still has many miles left in it. IAC will compensate idle over time - ECM has re learn after IAC reset. Happy Fourth of July (and be safe) //RF __________________ "The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17)

07-04-2011, 12:04 AM	#10
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Yeah, it's already idling a lot better.

07-17-2011, 04:23 PM	#11
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... @#$%! Finally got around to adjusting the timing. Was set at 4BTC and about 10 advanced. Disconnected EST, brought it back down to 0BTC/0 advanced. Idled fine, got in it and ran around the block, SES lights up, truck starts running like s____, no power, missing, etc. WTF?

07-18-2011, 11:36 AM	#13
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Yeah, I plugged the EST back in and disconnected the ground from the battery after I set the timing. Though one thing that’s been gnawing at me is that the weather tight connector I assume to be the EST isn’t tan/blk, but looks more like an orange/blk. Could be a non-issue, except that I noticed when I unplug it, it doesn’t cause the SES to light up. Makes me wonder if I’m unplugging the wrong thing - although it seems unlikely as it is the only weather-tight single-wire connector near the booster, save for a purple/blk single wire connector that is more of a “press-fit” than a weather-tight connector like you posted. Feeling a bit frustrated, but I have a plan: Jump ALDL to see if there are any DTC – report/investigate findings If no DTC: -Pull plugs – inspect – replace if necessary -Bump timing to 2* - see if that helps.

07-18-2011, 12:32 PM	#14
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: 5.7 TBI runs rich, hesitates... I think ppl/blk is O2 sensor, on the left side of the engine. The EST may be on the passenger side also, near the A/C box. edit- when you unplug it, it will DEFINITELY turn on the SES light. __________________ 1974 Jimmy- 5.3/4L80e/NP241

07-18-2011, 12:54 PM	#15
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Hmmm...okay.

08-05-2011, 11:16 PM	#16
JCampbell Account Suspended Join Date: Apr 2008 Location: Hesperia, Ca Posts: 1,332	Re: 5.7 TBI runs rich, hesitates... Victory! ...I think. Finally got around to fooling with my rig again and just as I was beginning to suspect, I was unplugging the wrong connector. Found the actual EST, unplugged it, SES lit up, set timing to 0 degrees, reset DTC's & took her for a spin around the hood. It appears all is right in my little TBI world. No hesitation or lean pops, just a smooth running smallblock. I won't feel like I'm totally out of the woods until I put some more miles on her, but for now it looks like my TBI and I are making up.



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