Newbie AWD Astro Overlander Build

[nobodyhome]

ENGINE UPDATE:

- I went and grabbed the van from the shop, they got too busy so I just brought it home. Noticed it is idling rough, especially after it warms up. Still throwing P0305 cyl5 misfire.
- Scope test came back with everything working just fine as suspected.
- Replaced the distributor and cam sensor anyways today, made no difference to the problem but now its all metal instead of plastic.
- Pulled #5 spark wire while running and didn't notice any real difference in the rough idle, so I pulled #1 to be sure it that made a HUGE difference. So, we confirmed #5 definitely has an issue.
- The shop did a compression test, all were hitting around 170psi. However, they did NOT do a leak down test.
- Using my compression tester fitting and an air compressor, I will do my own leak down test this weekend.
- If that passes, then I know my valves are OK and that means we are looking at a weak/ broken valve spring.
- If it fails... I'm selling the damn thing!

Next update will be next week... got my fingers crossed that its just a spring, we can change those without pulling the heads.

 

[Mwilliamshs]

Cam sensor is for ignition timing. Why was it replaced?

Crank sensor detects a misfire. What's its condition?

If all cylinders have ~170 lbs of compression but one cylinder has a steady misfire I don't think you're going to find a bad valve or spring or rocker, etc. Compression is the measure of a cylinder's sealing ability via rings and valves. The only way to seal a valve on a OHV Chevy is spring pressure, so if you had a broken spring not closing the valve, burned valve not sealing to the head, bent pushrod jamming it open, etc that cylinder would show substantially less compression than the others. Same on rings- if they were worn or broken or the piston had a hole in it, you'd have less compression in that hole.

A leak down test shows WHERE you're losing compression. At TDC, air pumped into the cylinder either comes out the throttle (past the intake valve) or the tailpipe (past the exhaust valve) or out the crankcase vent (past the piston/rings). Good test if you were losing compression to discover why but with 170psi x 6, you're not losing it, so not the tool for the job.

What's the #5 plug look like?

170psi + misfire = fuel or spark issue

An infrared thermometer comparison of exhaust manifold temps at each exhaust port of a running engine is a good diagnostic tool for a misfire. The cold cylinder is the dud. Old school way was spray water on each port (windex bottle, etc) and watch for one to not steam as much as the others. Start with a cold engine and compare all cylinders till the engine reaches normal operating temperature, then go for a drive and to get things hot and check them again immediately. If you really do have a misfire, this'll find it.

It's very possible you do not have a misfire on #5, just a fault in the misfire detection and either no misfire, or a random one that's being detected on #5 most often.

 

[Stroverlander]

Man, bummer to see you're still having misfire codes!

I definitely would hesitate to tell you to throw more parts at it but I'd sure want to swap the #5 plug/plug wire. Also, a new crank position sensor is cheap and you should have the "crank variation relearn" procedure performed. It's basically a five minute deal for any shop with a GM Tech 2 tool or similar scan tool but may help. Also, what's the status on the coil?

Hope you get this sorted out so and you keep the van!

 

[Mwilliamshs]

Post #2

Update 1: Basic Tune Up
...Cap, rotor, plugs, wires, MAF sensor and O2 sensor just installed. I thought I got it but well heck, here comes the code again... P0305 Cyl5 misfire... again...

Post #6

...There appears to be only 1 coil feeding all 6 angry squirrels.
UPDATE: I did also just find out that the cap and rotor were not replaced because they looked newer, so we are changing them out regardless. My money is on a bad cap, however we shall see....

Post #10

MISFIRE SAGA

This is fun... STILL have the van throwing a P0305 like it was on sale.2 weeks and $1K later we are no closer to a solution...
REPLACED:
NGK plugs/ wires
Injection spyder replaced
new (not acdelco) cap/ rotor
MAF sensor...

Post #15

All new spider, so all 6 [injectors] are new. Fuel pressure good. Replacing fuel filter this weekend...

Post #46

...
- Replaced the distributor and cam sensor anyways today, made no difference to the problem but now its all metal instead of plastic...

 

[nobodyhome]

AWESOME feedback, thanks!

OK here goes nothing (cracking knuckles)...

- CAM sensor came with new distributor... bonus!
- Crank sensor- no idea, will look/ ask the shop about the relearn procedure
- Fuel filter replaced, old one was in good shape but replaced anyways. No affect to misfire issue.
- Coil has not been replaced but spark appears to be plenty strong.
- Spark plug #5 will be pulled and I will post photo. The plugs have about 200 miles on them, so should get a good picture of the happenings (fouling, burned, etc).
- All plugs/ wires were replaced and the problem is still on #5, so not suspecting anything there.
- Found a few small vacuum leaks, to be addressed this weekend.

Newer development:
What appeared to be a "phantom" misfire turned into a real one. It seems like as soon as it warms up it makes the whole van shake, I will cold start and confirm. Cyl 5 is definitely not pulling its weight, the only question is... why not?
- Scope confirmed firing as it should.
- Pulling the wire away from the distributor showed that the van didn't really run differently. It also showed that it is sparking correctly and on time at idle and 2000 RPM.
- Clearing the code after that experiment and running still kicked out a P0305.
- The entire fuel injection spider was replaced, and the problem still remained.
- Engine analyzer at the shop showed #5 misfires were waaaaay more than the others, hundreds times more actually.
- Based on this, we feel like we have ruled out spark, fuel and compression.

Again, really appreciate the feedback, please let me know what other data I should be getting.

 

[Mwilliamshs]

...Found a few small vacuum leaks, to be addressed this weekend...

Depending on where these leaks are, like maybe the intake manifold, could be causing the misfire if #5 is sucking enough air on its own to run so lean as to misfire outside power enrichment, etc. If you hadn't already mentioned vacuum leaks my next guess was going to be dusting the intake manifold with propane or carb cleaner while idling hot to check for them.

Having said that, given the multiple missteps by the mechanic, I'd double check firing order and spark plug wire routing.

Also, I know you've replaced the entire spider assembly, which in and of itself is a little odd on a CSFI engine (96-) since you can replace individual components unlike the older CPI setup (92-95), but if you haven't done a fuel pressure bleed down test you haven't ruled out fuel as your problem's source.

 

[nobodyhome]

Vacuum Leaks: So far its the rubber elbow from the Decel valve to the interior vent system, and many hoses in that vent system.

- Wires all individually traced and confirmed in the correct positions. Firing order OK per Chevy diagram.

- Injector 5 was originally weeping a little, but we found it was only $20 more to replace the entire spider rather than buy the 1 injector. I will ask about the fuel pressure bleed-down test.

Thanks again!

 

[Stroverlander]

Day late and a dollar short but I was going to suggest vacuum leak possibilities and even something like a cracked intake. Sounds like you're finally on the right track.

I don't think it's that odd at all to replace the entire fuel injection spider assembly considering the mileage. The labor is all in getting to the components and so to replace the entire spider assembly actually makes more sense since you're getting six new/reman injectors, regulator, gaskets, etc.

FWIW, '02-'05 "X" engines have the upgraded MFI with six individual injectors on each intake port instead of SCPI with six injectors mounted centrally and poppets leading to intakes. The MFI is usually much more reliable and so those with earlier engines, the SCPI to MFI conversion is usually the way to go.

 

[nobodyhome]

Thanks bro, sorry this is becoming a ****** thread and less of a build thread.

 

[Stroverlander]

Nah, better than a "I sold my van" thread and you'll have a lot of maintenance stuff out of the way so can focus on other things. :beer:

You really narrowed down the possibilities to pretty much vacuum leak or less likely mechanical issue.

 

[Mwilliamshs]

...Injector 5 was originally weeping a little, but we found it was only $20 more to replace the entire spider rather than buy the 1 injector...

...I don't think it's that odd at all to replace the entire fuel injection spider assembly considering the mileage. The labor is all in getting to the components and so to replace the entire spider assembly actually makes more sense since you're getting six new/reman injectors, regulator, gaskets, etc...

I'd forgotten for a second we were on a 4.3 not a 5.7. Those 2 fewer cylinders make a difference on those part prices and I haven't messed with either in years. I'm sure the aftermarket parts prices have come down considerably in the interim.

 

[nobodyhome]

UPDATE:

Here's #5 plug... (DOES NOT) look the same as#6. They both have black gunk, but #5 is white on top.



Just for giggles, I did a compression test with my crappy HF gauge, got about 130 on #5, compared to 145 on #6. None of this appears noteworthy to my untrained eyes.


Luckily, my uncle has trained eyes, 45+ year mechanic.

- The white appearance on the top is due to excessive oxygen, likely a nearby vacuum leak.
- The black gunk around the electrode housing is from unburned gas.

Therefore, the computer detects a lean misfire and dumps in more gas to correct it. Cue the P0305 code!

I replaced all the vacuum lines I could find, some of which were significantly screwed up. My OBDII reported vacuum went up from 16.1 at idle, to 18.6. Still have the misfire, so now I have to figure out what the doo-hickey is that the PCV valve goes into. Also, looks like the MAP sensor goes into a vacuum port so I need to check around that for leaks. Carb-spray trick coming this weekend!

 

[nobodyhome]

Well... crap.

Picked up the FSM over the weekend, did all tests I could do. Looks like we've exhausted all affordable possibilities.
I floored it up an onramp last night, it started throwing codes left and right... Knock sensor, O2 sensor, misfire... you name it. That's it, I'm done...





Sorry guys, this project just died.





Thanks everyone for the support though this project. I can only hope that my designs and ideas will inspire others.

 

[tequilasunset]

Well this sucks... hate to see ya give up but I know them feelz...

 

[nobodyhome]

Thanks Tequila Jimi, sad day in mudville, especially when I have to flush $1k - $2k straight down the toilet. Best to cut the leg off than risk the whole body.
Hope your '05 build goes better.


POST MORTEM:

1) OLV kit is cool but expensive for what you get. Go with anybody's 2" pucks n bolts, space down the e-brake cable mount and get the S-10 rear leafs. All of this will cost about the same ($225), but you'll have new rear springs.
SAVINGS= $140

2) 235/75/16 are TOO BIG for this van with a 2" body lift, don't let anyone convince you otherwise. You gain a tiny bit in clearance you loose much more in wheel-well clearance when flexing. Try hitting up your local 4x4 shops and Craigslist for Jeep take-offs. The JK (2007+) comes stock with 225/75/16 Goodyear Wrangler tires, which slap right on to the later model year Astros. Little tight, but should be fine with the 2" lift.
* 235/75R16 = 29.9 X 9.3 R16
* 225/75R16 = 29.3 X 8.9 R16
Yes, the 1/2" actually makes a difference.
SAVINGS= $300-$500

3) Learn to do stuff yourself. The $1K shop bill with no measurable improvement is what blew my budget and killed the project.
SAVINGS= $600

4) There really is nothing like a good Factory Service Manual (FSM). I found mine on eBay, offered $60 and got it 3 days later.
SAVINGS= priceless

5) A Junk yard is your frickin FRIEND! Astros/ Safari vans litter them nationwide and they are looked down upon by many, so used parts are plentiful and cheap.
SAVINGS= Immeasurable