Won't stay running......

[Bigjeepin]

Hello everyone. I have joined this forum in hopes that someone can help me with my problem. I have a 1989 Full Size Blazer, Fuel Injected 350.
My problem: It starts perfectly. Will run for about a minute or so, then slowly stalls out and cuts off. It will restart with no problem, then run for about 20 seconds or so and cut off. It seems as if it warms up, and then this occurs. Once it is warm, before it stalls out, if you shift it into gear, reverse or drive, it dies instantly. As if it can't handle the load. WIll run in Park and neutral, but not in gear, at least until it warms up. It is driveable, if I 'powerbrake' it at stops signs and lights. But seems as if it doesn't have as much power either. Like it is starving. Upon starting to track this problem, several mechains have gave me their suggestions. Therefore the list of replaced parts has grown, but has not fixed the problem. If anyone has any ideas, please let me know. I am

beating my head against a wall here

.

Here is my list of replaced parts:
1. Fuel Filter
2. Spark Plugs - Bosch Platinum 2
3. Distributor Cap
4. Rotor
5. Ignition Module
5. Oxygen Sensor
6. Idle Air Control Valve
7. Map Sensor
8. Fuel Pressure Regulator
9. Throttle Positioning Sensor
10. PCV Valve
11. Gasket between Manifold and carburator
12. Gasket between carb and throttle body

These parts were bought, checked, and since no difference was noted, I returned them:
1. ECM Computer
2. Fuel Pump Relay
3. Timing 'adjuster' next to throttle body
4. Coil

I removed and thoroughly cleaned the fuel injectors, as well as replaced them with another set I had, and no change.

Checked for vacuum leak as well as replaced several hoses just in case.

And lastly, approximately one year ago, I replaced gas tank and sending unit.

Problem started one day out of the blue, and can't seem to figure it out.
Please HELP
I need to remove the demons!!! Thanks...Jason

I got one of the 'plug in' code readers, and all it said was O2 Sensor. I replaced it, and no change. A Diagnostics test with Fuel Pressure Check is next, but not sure what that will show if anything???

 

[cegusman]

Could be the fuel pump.

 

[Bigjeepin]

I replaced the fuel pump ( sending unit) a little over a year ago. Thinking maybe it is not functioning properly, and I guess the Fuel pressure check will tell me. Since it does run(electric), and you can hear it, not real sure. Maybe it's just not pumping enough. Thanks.....

 

[diesel4me]

one thing you missed??

Did you check the EGR valve?--it might be opening at the wrong time,if its carboned up,or its temp sensor or solenoid is acting up!..that'll slowly stall it out,by "smothering" it with exhaust fumes ,not to mention the manifold vacuum loss when it opens...

Only other thing is fuel--since it shuts off "slowly",rather than suddenly quit,that means its a fuel problem 90% of the time..I have seen pick up coils do this too though,and intermittently,mostly when hot..

BTW,I hate Bosch Platinum plugs..I'd say toss them in the rubbish!..but I doubt they are causing this particular problem..I've had chevy's I put those plugs in run WORSE than it did before!..like they weren't firing!--you could pull the plug wire on/off and no change in idle speed!--put the old AC plugs back in,and it ran sweet again! ..

 

[loafer]

Coolant Temp Sensor

Check the coolant temp. sensor. A Hayne's or Chilton's manual will explain how to do this. Also check the sensor connections and wires.

 

[Bigjeepin]

Thanks for the info. Sorry, I forgot to add that item!! I replaced the EGR valve already as well. No change. And the old plugs were all black and looked terrible, so I went with the 'better' ones. At least I hoped. Butonce again no change. I was told it was probably a fuel problem as well, but it cuts off only after it warms up, therefore I was on the thought of something electrical that once warm, malfunctioned. I will check on the coolant temp. sensor. Hey, at this point, I am doing a hit or miss, and I really appreciate the help. I really enjoy tinkering with her anyway, so this is just a reason to do more. I put a brand new coil on, 'reset' the computer just in case, and started it up. Strated great, ran for about 2 minutes and cut off. Took the coil off and returned it. Made no change.....

 

[loafer]

It sounds to me like it is leaning out as it starts to warrm up, which could very well result from a faulty coolant temp sensor or circuit.

Try this:
Romove the air cleaner and start the engine when cold. Wait until it starts to die and spay a little starting fluid directly into the throttle body and see if comes back. If starting fluid keeps it running than you most definately have a lean condition.

Thanks for the info. Sorry, I forgot to add that item!! I replaced the EGR valve already as well. No change. And the old plugs were all black and looked terrible, so I went with the 'better' ones. At least I hoped. Butonce again no change. I was told it was probably a fuel problem as well, but it cuts off only after it warms up, therefore I was on the thought of something electrical that once warm, malfunctioned. I will check on the coolant temp. sensor. Hey, at this point, I am doing a hit or miss, and I really appreciate the help. I really enjoy tinkering with her anyway, so this is just a reason to do more. I put a brand new coil on, 'reset' the computer just in case, and started it up. Strated great, ran for about 2 minutes and cut off. Took the coil off and returned it. Made no change.....

 

[Bigjeepin]

I just removed the Coolant sensor and am going to get a new one and try it tonight. I already ran the motor for a little bit, and it being 105 degrees here in Georgia right now.....the engine stays warm!!! I will replace the sensor this evening, and try the 'cold' strat idea then. Thanks. What about a Air Temperature Sensor? Someone asked me about it, and I am not sure anything about it. Any ideas of where or if have one on it? Thanks again. This site has been wonderful and very useful with ideas and information, as i was beating my head against a wall!!!!

 

[diesel4me]

sniff test..

I'd take it to an inspection station that does inspection stickers,and have them use the "sniffer" to measure the hydrocarbons,and fuel air ratio..it might be cheaper than buying parts that most places consider "non returnable"(no parts store here will take any "used" parts back!)..

..you could watch the fuel/air ratio meter as it goes thru its stalling phase,and see if its too rich,or too lean..could be electrical too,but you already replaced everything but the pickup coil (if your truck even HAS one!--might have a crank sensor instead)..the machine will help diagnose it if its a fuel problem. sounds like lack of fuel pressure --perhaps the "sock" filter is clogged up,or the fuel pump is croaking slowly..

A faulty gas cap might not let air into the tank,and keep fuel from being pumped out to the engine too..rare,but not impossible...but usually the gas tank collapses from vacuum when that happens..

I also remember a friends 62 Valliant having a similar problem..we replaced just about everything--carb,fuel pump,filter,coil,points and condensor,etc..he got tired of it quitting after 10 minutes,and having to sit for 10 more before it would fire right up again like nothing was wrong--it still had spark,but little fuel when it stalled,not dry though..he sold it to another kid,and he pulled the gas tank out of it..and found about 20 ping pong balls in it!..it never acted up again!..they must float on top of the gas until the fuel pump sucks them against the "sock" filter in the tank,resticted the flow!--then floated back up after the suction dies off!..

 

[PeteH]

maybe park nuetral switch...wait maybe not..
you said it dies instantly when you put it in gear or reverse but then how do you get it going enough that you can drive it around? are you giving it gas.

what is you timing at?
some of the stuff might be working..like the iac, tps, timing...but if not setup up correctly then the truck will run like crap. i forget which to do first, but i think..timing iac then tps.

 

[kookydoright]

this may sound crazy, but you said you have to powerjack it a lights and stop signs and it seems powerless, well i had a 350 in a old 76 a few years a ago that had the same symptoms. i know it wasn't TBI, but here me out. after many confused days and nights, a friend suggested i pull the plugs and check the compression. believe it or not a valve in the head had broke and was scrapping my piston! i never heard a bang or a pop, but the truck had 3" pipe and duel chamber flowmasters cut off under the cab, so i not saying it didn't. anyways i swapped on a pair of 305 heads a friend had and drove it another year and a half with a scarred piston (god i love chevys!). im not saying thats your problem, but if all else fails try checking your compression. there was no pop or banging sound just loss of power and trouble idleling with mine and i would have never thought a valve because i have never seen it happen before or since. sometimes i think the people i bought the truck off of had sabatoged it.........way to many gremlins!

 

[TheSunDanceKid]

alight well ill tell you this to save you some money here man it saved me quite a bit take that the part you want to replace to see if its the problem take that old part well anything like sencors and other elctrical componets down to an autozone or something like that and they will put it on a computer and have it checked and tell you if it works or not thats a hell of alot cheaper then just buying rancom new parts when the old are still fine

 

[Bigjeepin]

Well, here it goes. I replaced the Coolant Temperature switch, and.....nothing changed. To answer previous respones....In georgia, I can't take it to shops that do inspections and get the hydrocarbon test done, because here they have NO state inspections. Ain't that just great!! Nice thought, but I guess all that is rolled up into the Diagnostics/Fuel pressure test. Next thing, most , if not all of the components that were removed and replaced were electrical, and can't be tested. EGR valve, IAC valve, Coolant temp switch, Map sensor and others, they just tell me, well try it and see if it works. All with no change. I 'reset' the computer each time as well. I even replaced the ECM and chip, and still no change. If I felt like I needed the parts, I kept them, otherwise, I took them back. I got a manager hook up at Advance, so I can return anything. Now comes to where I am an idiot. I want to check the timing, but I read that I need to unplug the brown wire on the passenger side of the vehicle. Supposed to be under the carpet/floormat or in the engine compartment. I can not seem to locate it, so I haven't checked the timing yet. When I can and do need to drive it, I have to powerbrake it. It works, and I am only going short distances as well.
I had the whole tank, sending unit and all replaced approx. one year ago, so I really do not think it is the fuel pump. The pick-up sock is new as well, but wouldn't think it was it, but at this point, I may end up dropping the tank and taking a peek for myself. I am really running out of things to check. I have a diagnostics check scheduled for next Friday, but between now and then, I may tinker some more and see what I can come up with. Has anyone ever dropped the tank and checked it out for themself?? It is only like two or four straps holding it, but I never took the pump out or anything, so not real sure from there. Any pointers on this would be greatly appreciated, as I have never messed with it. Also, food for thought, it has acted the same on a full tank and a almost empty tank as well. It made no difference. If that helps out at all!!! Thanks everyone for all your help and ideas......someone is going to figure this thing out, and I can't wait!!!