Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Postby AstroTan [OP] » October 17th 2020, 5:26am

Hi all, I've tried to do my due diligence on this one but after hours of research and some parts replacing, i'm pretty stumped.

Ze problem:

My 02 AWD astro with 216k miles, over the past couple months, has developed an issue where it will be hard to start after it's been allowed to fully cool. This is most noticeable after it has sat overnight. It seems to be cranking fine, but not starting right away. I have taken to cranking it for 1-2 seconds, letting off, then trying again at which point it starts right up. Aside from this, it additionally seems to have a slight roughness/vibration in the idle. Maybe a bit of a stumble every few seconds? Not too serious and it never seems like it's about to stall. Acceleration and power seem alright and I really don't notice any drivability issues. I tried to take a video capturing the idle but I don't think the roughness is really substantial enough to be noticeable with the mediocre audio. It's more of a vibration you can feel. No codes stored or pending.

Recent maintenance probably relevant to the issue:
- when I bought the van 5k mile ago it had an intermittent p0101. Pulled the MAF sensor, which was filthy, and hosed it with CRC MAF cleaner. No code since.
-new battery
-Put in Delco iridium plugs 4k miles ago with Standard ignition cap, rotor, wires from O'reilly.
All within the last month:
-Recently noticed the cap and wires arcing with the doghouse off at night so I replaced the cap, rotor, wires, and distributor drive gear with Delco
-Delco ignition coil and ICM and PCV valve
-new motor mounts
- Removed and thoroughly cleaned the throttle body and IACV. Then just replaced the IACV with a new Delco unit when things didn't improve. No dice....
-replace fuel filter with a Napa gold
- I am now 3/4 of the way through a full tank of gas to which I added a bottle of Delco fuel system cleaner plus to. I picked this up from the dealer the other day after reading a post by AstroTurf saying it cured his slight miss. No results yet but I did buy a second bottle I can try...
-I plan on re-sealing the leaky, whiny, hydroboost this weekend but can't imagine that will solve any of the described problems.

Diagnostics:

-fuel pressure test:
warm after drive to autozone to rent pressure tester:
KOEO: 58 PSI, settles down to 51 after 10 min. Steady at 50 with engine on and idling.

Cold the next morning:
KOEO: 56, drops to 50 after 5 min, 46 after 15 min. turned key on and off again: 57 PSI. Try and start and get the same crank, no start the first time. Second time fires right up. Idles at 50-52 PSI.

Based on what I read here, these numbers seem to be on the low end of acceptable but did not strike me as damming either the fuel pump or fuel pressure regulator. Or maybe I am off base and wasting everyone's time and just need to replace the fuel pump before trying anything else. I have a new delco unit sitting in the box waiting just in case....

-Tried unplugging the MAF sensor other day to see if it idled any better but no luck. On the first start after unplugging, the engine quickly stalled and died. Trying again, it started ( a bit rough), then idled like normal (same as plugged in), presumably after the computer took over assuming the air flow?

-Starting fluid:
Maybe this could tell me if it's fuel related? I got a can but am not really sure a what point in the intake I should spray it. Is it ok to get on the MAF and IAT sensors? should i pull the intake hose off the plastic piece over the throttle body and send it in there? but then the MAF would be unplugged and results would be skewed right?

- Vaccuum leaks?
I had already replaced many of the vac hoses but sprayed around with the starter fluid and did not detect any change in idle.

What next??

So my $500 van has quickly become a $6k van with all the parts i've put in this summer: brakes, front end rebuild with CV axles, steering gear, PS pump, 2+1 lift, shocks all around, new 29" KO2's, and I LOVE it. At 215K i'm not really opposed to just swapping parts as I've already said my vows and plan to rebuild everything as needed.... BUT I would definitely appreciate your diagnostic advice.

If there is no conclusive diagnostic test than I guess my parts change list, by priority, should be something like:

-fuel pump
-Spider injector
- MAP sensor?
-Crankshaft position sensor?
-Camshaft position sensor?
-MAF sensor? could it still be at fault if there doesn't seem to be a change in idle with it unplugged?

:blah: :blah: :blah:

Throw me a bone?

Thanks!
Original Poster [OP]
AstroTan
Fueling (Empty tank)
Fueling (Empty tank)
Posts: 7
Topics: 2
Joined: January 2020
Gender: Male
Alias (AKA): Tanner
Van Model Year: 2002
Van Make/Model: Chevrolet Astro
Extra Info: AWD

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Re: Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Postby MechBob » October 17th 2020, 11:14am

When parking it for the evening,try loosening or removing the fuel cap,then see how it starts in the AM.
User avatar
MechBob
Firing on 1 Cylinder (L2)
Firing on 1 Cylinder (L2)
Years of Membership: MechBob has been a member for 2 full yearsMechBob has been a member for 2 full years
Posts: 1147
Topics: 11
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Gender: Male
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Van Model Year: 1994
Van Make/Model: Chevrolet Astro
Extra Info: 4x4

Re: Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Postby AstroTan [OP] » October 17th 2020, 10:04pm

Thanks Bob, I'll give that a try tonight. What's the logic behind it?
Original Poster [OP]
AstroTan
Fueling (Empty tank)
Fueling (Empty tank)
Posts: 7
Topics: 2
Joined: January 2020
Gender: Male
Alias (AKA): Tanner
Van Model Year: 2002
Van Make/Model: Chevrolet Astro
Extra Info: AWD

Re: Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Postby MechBob » October 18th 2020, 1:13am

Valve in cap can go bad.When tank cools down,can siphon all the fuel out of the fuel lines,leaving them empty in the AM.Rare,but happens.
User avatar
MechBob
Firing on 1 Cylinder (L2)
Firing on 1 Cylinder (L2)
Years of Membership: MechBob has been a member for 2 full yearsMechBob has been a member for 2 full years
Posts: 1147
Topics: 11
Images: 12
Joined: August 2018
Gender: Male
Alias (AKA): Bob
Van Model Year: 1994
Van Make/Model: Chevrolet Astro
Extra Info: 4x4

Re: Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Postby AstroTan [OP] » October 21st 2020, 7:43pm

Update: no dice with the gas cap or a new fuel pump. Still a slow start this morning.The pump looked like it was about ready for retirement with a scummy looking filter sock so I'll tell myself it was time well spent. I did some cleaning and painting and changed the transfer case fluid while I was down there.

Will order an injector spider and lower intake gasket today! I'll justify that job with the current tiny coolant seep at the intake. :whistle:
Original Poster [OP]
AstroTan
Fueling (Empty tank)
Fueling (Empty tank)
Posts: 7
Topics: 2
Joined: January 2020
Gender: Male
Alias (AKA): Tanner
Van Model Year: 2002
Van Make/Model: Chevrolet Astro
Extra Info: AWD

Re: Hard Cold Start and Rough Idle. No Codes. Diagnosis?

Postby AstroTan [OP] » October 21st 2020, 8:42pm

New and old comparison:
Attachments
IMG_20201018_162024222.jpg
Original Poster [OP]
AstroTan
Fueling (Empty tank)
Fueling (Empty tank)
Posts: 7
Topics: 2
Joined: January 2020
Gender: Male
Alias (AKA): Tanner
Van Model Year: 2002
Van Make/Model: Chevrolet Astro
Extra Info: AWD


 
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