I know this is not a diesel, but I was hoping you guys might be able to offer a suggestion anyway.


I have been trying to figure this out with no success.


Vehicle:
1995 CHEVROLET TRUCK ASTRO VAN
2WD Automatic Transmission
6 Cylinders 4.3L CPI
105,000 miles

Symptoms:
The van always starts and runs fine for at least a minute or two.
However after a short distance it will not accelerate properly and it will try to stall. As it progresses I might get some popping at the engine and eventually it will die. When I press the accelerator it acts like it wants to die.

It takes as much as 10 to 15 minutes of regular city driving to cause these symptoms or 2-3 minutes of driving under a load (when I hot-rod it). It does not seem to be directly related to engine temperature.

If the van completely dies, I can turn it off for 10 seconds then right back on and it definitely drives better (not completely normal). If I leave it off for 15 minutes it usually runs quite a bit better. Overnight and it runs normal when I first start it.

Parts Replaced:
Leaky CPI (spider)
Inlet outlet fuel lines (nut kit)
Fuel Filter
Fuel Pump and strainer
Exhaust from O2 sensor back
Drained the gas
Ignition coil
PCV Valve
Tune up (plugs,wires,cap,rotor)(6 months ago)
Oxygen sensor (6 months ago)


Current Diagnostic (I am a complete amateur so some/all items could be irrelevant)

EGR (sticking)
Tapping/ticking started after I removed/checked this. I am pretty sure I just need to take it off again and clean or replace. I do not believe this is my main problem because I took it off, closed the valve, and reinstalled without hooking it up. This test did not change any of the symptoms listed above.

Distributor
I just examined the distributor and one of the plug wires and probes on the distributor was severely corroded; the rest were fine. I will get a new cap and wire tonight and check the plug.

Fuel Pressure
Test with a fuel pressure gauge. After sitting overnight, turn key on and I get 62psi pressure (in spec). Turn key off and it holds 25psi pressure (there is no spec that I know of for this).
While running it never drops below 50psi (in spec) even when it is acting up. While it is acting up and I accelerate the needle will sweep between 50psi to 70psi very fast.
What concerns me is that after it is acting up and I turn the key off the fuel pressure instantly DROPS to 0psi. It this an issue?
If I let the van sit for two minutes and turn the key on (pump on) then back off again it will still drop to 0psi. If I let it sit overnight it will again hold 25psi of pressure with the key off.

Codes
The check engine light (service engine soon) does work, but does NOT turn on. I do not get any codes. To verify I rented an “Actron Super AutoScanner” and checked the codes. I do not get any.

I know I can monitor real time data with this device (scanner) but I do not know what to look for (suggestions?).



Do you guys have any suggestions on what to try next? I am about out of ideas and I am thinking about taking it to the shop. If/when I take it in, do you have and advice on what type of shop or diagnostic test I should ask them to run (or not to run)?

 

DaveG_01 I have (my wife has) the same exact van 95 gmc safari. You Must have 50psi at all time, period. When you replace your fuel pump $85 roughly. Besides getting a new screen, get a new pulsator. I run Lucas fuel treatment, seems to make them last longer. Enjoy dropping the tank.

 

The fuel pressure should drop right away. Whatever fuel is not used goes back to the tank through the return line. That is normal.

Can you pull out a spark plug or two and tell us what it looks like? I have an idea that might help you but only if a plug confirms what I think is wrong.

 

Do what you will, I just replaced the fuel pump in my wifes van this past weekend. You MUST have minimum of 50psi of fuel pressure at all times. When you first start it you should get between 55 and 60 psi and run down the road between 50 and 55 psi. Have documentation and the experience to prove it. I have fixed several vans and s10 blazer/s15 jimmy with the same motor combo and problem. You can confirm with alldata or even the dealer, i did.

 

Thanks, I will pull 2 plugs after work and post the results, hopefully by 9 CST

 

You say that you already replaced the fuel pump. hmmmmmmmmmm sounds to me like something is sucking up and blocking the strainer. After it shuts down it falls back in the tank until it sucks back up again. 67 hotrod is probably right about the 50 psi. It sounds about right. The issue is why are you losing pressure. Either a bad pump, something blocking the pick-up, or a leaky line????????

 

I just replaced cap and wire; it did not help.

I check the plugs; they are white on the ends.

As for fuel I am not convinced it is my problem. My pressure guage says it is holding between 50 and 60psi of pressure while it is running which is in spec. Though I do not understand why it is dropping to 0psi only after the trouble begins.

I might try and find a place to put it on blocks and drop the tank again this weekend. It is such a pain since I live in Chicago

 

Sounds like its running lean or running out of fuel with white tips on the plugs.

 

The MAF sensor is sending the wrong signals to the computer, or the computer is fried.

 

You could have a variety of problems starting. Vacuum lines could be deteriorated and leaking sending boggus signals to the comp, The knock sensor could be bad, too low of octane fuel causing knock, pick up coil in dist shorting out when warm, Exhaust leaks letting air in causing boggus o2 signal, Injectors leaking, Spark plugs gapped wrong. You say you have no codes so it has to be something that is starting to go bad but is still within the parameters of the comp or a non computer controled component.
Good luck

 

Dave, sorry man. I was banking on black wet plugs. Since you have white tipped plugs that blow my whole theory out of the water.

Your MAF sensor may be going dead. It is the main sensor to help regualte how much fuel is injected given the current airflow.

 

I just went out and kissed my 12v!!!

(sorry to hear about your woes... I know trouble shooting can be a real nightmare!)

Forrest

 

I had a gasser do the exact same thing, would run great until warmed up good. Turned out to be the catalytic converter would get hot, and restrict exhaust flow so much that it would barely run. Let it cool off, and it would be good again for a little while. I even did a valve job on it, and when I put it back together it ran great w/out the exhaust hooked up. Hooked up the exhaust, and no go. Had to replace it, problem solved.

 

DaveG_01 I have heard of few of these having the two composite lines in the intake by the cpi getting a crack in them and loosing pressure there. Might be able to smell the gas in the engine oil, no guarantee though. You need to find out why your loosing fuel pressure.

 

I replaced the 2 fuel lines when I changed the CPI. I also replaced catalytic converter and exhaust.

I will look into changing/checking that sensor though.

What type of diagnostic test could a shop run that would give me more insight?