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Username Post: Extremely rough running at idle.        (Topic#354156)
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-07-18 10:35 AM - Post#2753742    
    In response to 65_Impala

Okay, after all the checking, I found a vacuum tube that was cemented to the purge solenoid, and after getting off the old tubing, and putting some tubing that was in better shape, it runs a good bit better in closed loop. Don't worry, I feel dumb for overlooking it. Here's a video for it running, about half way through the video, I cut it off and back on again to show that it's still surging a bit, not nearly as bad though.

https://youtu.be/sxUrdC6ibIg

The BLM is still super low, but the O2 is working much better than before and the heater on it is working. I had checked the tubing before when I changed the intake gasket and sprayed starter fluid around it after the replacement, but it didn't show any sign of degradation until now, but maybe I missed something. Either way, it's a bit more drive-able, I'd still like to get to the bottom of the weird BLM.



 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-07-18 02:17 PM - Post#2753761    
    In response to Smallen96

Update: The truck still surges for a minute or so on cold startup and warm startup, but runs fine after a minute or so. Also, when it switches from open loop to closed loop, its now seamless. That's the symptoms that started my journey of repairs with the truck and I'm guessing the vacuum leak exacerbated the symptoms. The BLM is still dropping steadily to 110ish, which is still very rich and I'm not sure what to check next.



 
Sabino 
Member
Posts: 42

Reg: 07-16-05
12-08-18 08:12 AM - Post#2753856    
    In response to someotherguy

I don’t know if applicable here, but in using Tunerpro on my 93 c1500, for the ECU and code running I found that knock retard was not actually output. In the .adx file there was a comment for knock retard For data logging "Knock Retard" instead of "Battery Voltage". The bin must be change at L51FE to support this.
If same for this ECU perhaps knock retard output is not correct?

65 Belair 350
68 Camaro 327
85 Caprice 5.0L
93 Suburban 5.7L TBI


 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-08-18 10:33 PM - Post#2753946    
    In response to Sabino

I don't think the knock is an issue because as the dude before said, the knock count isn't actively rising, which means that it's not actively knocking, so there wouldn't be and retard anyway



 
gfm64 
Poster
Posts: 34

Reg: 09-06-16
12-10-18 03:21 PM - Post#2754096    
    In response to Smallen96

May I suggest checking the fuel pressure regulator if you have a TBI? In the past I have had it go out, rebuilt it ,but did not change the spring only to find it had broken into pieces.



 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-10-18 05:23 PM - Post#2754109    
    In response to gfm64

Yeah, I've already rebuilt mine, and then because I wasn't sure, bought a brand new assembly, so I hope that's not it.



 
Dirtywerk 
Poster
Posts: 16

Reg: 09-01-13
12-11-18 01:49 PM - Post#2754162    
    In response to Smallen96

I'd change out all of the vacuum lines and any check valves on those. Vac leaks don't throw a code.

Dirtywerk

East Texas


 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-11-18 04:25 PM - Post#2754183    
    In response to Dirtywerk

I did that just this past Monday, so that shouldn't be an issue anymore, but does the computer take time to learn to run right after having a vacuum leak?



 
marsmann 
Poster
Posts: 12

Reg: 10-25-18
12-11-18 06:09 PM - Post#2754194    
    In response to Smallen96

  • Smallen96 Said:
I did that just this past Monday, so that shouldn't be an issue anymore, but does the computer take time to learn to run right after having a vacuum leak?



Not really. A good run for about 10-20 minutes and usually taking it up past 42mph is enough to relearn things. Especially with a few starts/stops in between. It won't take days or anything.

I need to catch up on some of the more recent posts. This is a bit perplexing at this point. Some good advice has been given/shown here collectively.

If it wasn't for the fact that you have confirmed 11-12psi at idle for fuel pressure even during surging I would almost bet that it was excessive fuel pressure causing your low blms and your PCM pulling back and leaning out your idle.

Yes, the vacuum leaks would have contributed to the surging so the more recent repairs have helped some in eliminating any of the leaks.

Question; The fuel pump in the truck is the regular low pressure pump and not the later pump for the vortecs right? Just in case it is pushing too much volume causing your regulator to throttle it down to 11-12....

I'll try to summarize for myself everything done so far from the first post to see where we are at... it could still be electrical and I still recommend checking out your alternator and charging system.... has the battery voltage improved since it was reading in the mid 13s a few days ago?





 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-11-18 06:16 PM - Post#2754195    
    In response to marsmann

On the last diagnostic run I did, the voltage sat between 13.9 and 14.1 Volts. And as far as I know, the fuel pump is stock, is there any way to tell if it's one made for the vortec engines?



 
CowboyTrukr 
"7th Year" Silver Supporting Member
Posts: 4097
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
12-11-18 06:54 PM - Post#2754200    
    In response to Smallen96

If it’s stock, then it’s not a Vortec pump. Before going any further, check your pump pressure. You’ll need to rent or buy a TBI fuel pressure test kit that is made for GM TBI engines. Connect it at the throttle body inlet. Driver side line.

Check pressure under three situations:
Key on, engine off
Start it
Put the engine under load. Suggestion here: route the gauge out under the hood and secure it under a wiper. The. Drive it and have a passenger observe the pressure.

If you’ve never replaced your pump, it may be the cause of many of your issues.

Let us know what your pressure is.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-12-18 03:23 AM - Post#2754217    
    In response to CowboyTrukr

I did 2 of the three tests, but with an adapter that went where the fuel filter goes. With key on engine off, I got up to 12 psi before the pump shut off. And when I cut the engine on and revved, still 12 psi. I haven't driven with it though, mainly because there are no tags on it because I haven't situated that after I inherited it from my dad, but should be resolved soon.



 
CowboyTrukr 
"7th Year" Silver Supporting Member
Posts: 4097
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
12-12-18 05:22 AM - Post#2754225    
    In response to Smallen96

Ok, good. 12psi is perfect.

New filter, too, right?

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD
‘87 GMC S15 SCLB 4.3 Auto - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Smallen96 
Poster
Posts: 22

Reg: 11-13-18
12-12-18 07:56 AM - Post#2754237    
    In response to CowboyTrukr

That is correct



 
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