How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Mike S. Your Own Question
Mike S.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 6777
Experience:  ASE Certified Master Technician
20625509
Type Your Chevy Question Here...
Mike S. is online now
A new question is answered every 9 seconds

I have a '94 Chevy blazer 5.7l with some issues

Customer Question

I have a '94 Chevy blazer 5.7l with some issues
Submitted: 10 months ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 10 months ago.

Hi, My name is ***** ***** for the delay.

I will do my best to assist you.

thanks for your service,,

tell me,after it dies,does it start right back up?

does it idle well?

does the engine light stay on?if so,can you give me the computer codes?

thanks

Customer: replied 10 months ago.
I spent over a week looking at suggestions on the Web and tried alot. When it died the second time I drove, it started and died after seconds. Tried different stuff and got a few gallons of gas from road ranger while still on expressway. Saw on Internet about coolant temp sensor. Unplugged it. New problem, starter spun but not engaged. Got towed home. Replaced starter. Back to engine starts and dies after seconds. Replaced fuel pump relay, then oil pressure switch. Unplugged all vacuum lines, engine started and stayed on longer but died. Switch out most sensors with vacuum with ones from friends working truck. Adjusted idle air control sensor. Engine Only starts and stays running with everything except map sensor vacuum plugged in. Idle drops to close to 900 rpm if i plug tha vacuum with finger or rubber plug. Drove a few blocks, bogged down accelerating from traffic light. Pulled into gas station, started fine again. Drove back home but died 3 times at the light accelerating from full stop with cop right behind me. Had to start, Rev high from neutral and throw into drive to get home.
Customer: replied 10 months ago.
Service engine soon light comes on after engine has been running a while. I've gotten many codes since problem started. 33 34 35 45 54 are the ones i remember. Idle... i hear a slight hesitation when it stays running. Not too sure what to think of it since this is the first perfomance engine I've had. Previous engine was stock and pretty worn down.
Customer: replied 10 months ago.
When engine was cutting off, I noticed a slight increase in the rpm before it would cut off.
Expert:  Tim's Auto Repair replied 10 months ago.

ok

two things here..

1-emove the wire harness plugs that plug into the computer under dash behind the glove box,,clean the terminals with electronics parts cleaner then plug back up..

but,the problem seems to be the pick- up in the distributor,,you may just want to replace the complete distributer with a new rebuilt unit sense the distributor will need to come out and apart to replace it

thanks

Expert:  Tim's Auto Repair replied 10 months ago.

If you are satisfied with my answer, Please Rate my answer by clicking the rating button so I can get credit for my work. I’m not always going to be giving you good news, so please don't let this stand in the way of you accepting my answer. .it does not cost you more money and we will still be able to communicate, ,.please understand, i can not see, hear or touch the vehicle and only know what you tell me. Bonuses and positive feedback are appreciated.. if you are not satisfied with my answer, please do not leave bad feedback ,i will gladly opt out and let another expert handle the question. .if i have sent any diagrams, please print them. .sometimes you may need to right click the image [,then save picture as]to save it to your computer so you can open it with your picture program...Please ask if you need more help.

Customer: replied 10 months ago.
Swapped out distributor and cleaned connections to ecm. Problem persists. Engine only starts and runs with MAP sensor vacuum disconnected. Replaced map sensor, coolant temp sensor, nothing changes. Engines struggles after running a while and shuts off.
Customer: replied 10 months ago.
Sorry took so long but I get called away frequently last minute (military)
Expert:  Tim's Auto Repair replied 10 months ago.

lets try this..

remove and clean the egr valve,make sure it is closing all the way,,then re-install it..then disconnect the vacuum line fom the egr valve and plug it,,if it runs better with the vacuum disconnected,,replace the egr solenoid

thanks

Customer: replied 10 months ago.
Removed and cleaned egr valve. Reinstalled and plugged vacuum. Same results. Only starts and stays on with map sensor vacuum line disconnected or plugged with something. If I let the engine run a bit and try to hook up the vacuum to the sensor, it dies.
Expert:  Tim's Auto Repair replied 10 months ago.

please stand by,perhaps one of the other guys has a clue to what is going on.

someone will be right with you

thanks

Expert:  Mike S. replied 10 months ago.

You said it only runs with the map sensor disconnected. Was the vacuum hose plugged or not? If not plugged or plugged , try the opposite and let me know what happens.

Customer: replied 10 months ago.
As long as the vacuum line from the tbi is not connected to the map sensor (vacuum line plugged or unplugged), engine will start and stay on. I found this out after trying to find if it was a vacuum leak somewhere. I already replaced the map sensor itself.
Expert:  Mike S. replied 10 months ago.

I would think that unplugging the vacuum line from the map sensor, then the map sensor would tell the computer that there is no vacuum and the computer would naturally think that the accelerator pedal is all the way down so the computer would adjust the fuel mixture accordingly like the gas pedal was floored but this isn't the case, is it. The gas pedal is at idle. At idle the fuel mixture usually rich I believe. Leaning it out makes it run better meaning it's too rich at idle. That is what I am gathering. So, if it's too rich, either afuel injector is dripping, the fuel pressure is too high or the air filter is clogged if it's even on.

It should be easy to see if a fuel injector is dripping. have you checked the fuel pressure?

Expert:  Mike S. replied 10 months ago.

Another thing, is the coolant temp sensor may be giving the wrong info to the computer making it think the engine is warm when it isn't and/or visa versa.

Customer: replied 10 months ago.
I'm doing all these checks with air filter off. Put everything together and results are the same with filter off or on. The idle start out at about 1400 rpm and settles to 1100 rpm after a while. I checked coolant temp sensor wires with voltmeter, 5 volts. Replaced the sensor and have not seen the gauge move much from 100 degrees
Customer: replied 10 months ago.
The injectors are spraying a steady cone. I don't have a way to check the pressure.
Expert:  Mike S. replied 10 months ago.

Are there any drips in the fuel injector spray cones? You have to look closely.

Expert:  Mike S. replied 10 months ago.

Did you replace the coolant temperature sensor or the coolant temperature switch, sometimes there are 2, one works the gauge and the other is for the computer to adjust things like fuel mixture, dwell and timing.

Expert:  Mike S. replied 10 months ago.

Don't you have an auto-parts store near you hat will allow you to rent or borrow their fuel system pressure tester? If not, order one from harbor freight or somewhere.

Customer: replied 10 months ago.
No drips in the cones. I replaced the sensor at the top front of intake manifold. Fuel pressure testing for this tbi has the auto part people stumped.
Expert:  Mike S. replied 10 months ago.

Doesn't this have the soda can sized fuel filter right on the frame rail under the driver seat? If s, unhook the fuel line going into that fuel filter from the tank and screw the fuel pressure tester T fitting in there.

Customer: replied 10 months ago.
it does. Those kits at auto part did not have a fitting to hook up there. I'll look into finding a kit and see if those do.
Expert:  Mike S. replied 10 months ago.

Which kits, the ones they sell or the ones they rent or allow you to borrow? They should have the t fitting.

Expert:  Mike S. replied 10 months ago.
Customer: replied 9 months ago.
I asked if they sold the kits and they said not anymore. And the kit they rent did not have anything I could use. I got a temperature switch I'll swap out tomorrow. It started raining and I don't have any cover to work under.
Expert:  Mike S. replied 9 months ago.

ok

Customer: replied 9 months ago.
Replaced temperature switch on driver side of block. Idle seems less hesitant than before but still at about 1400 rpm... all in all, still only starts and runs with map sensor vacuum disconnected. Tried to adjust TPS to lower the idle but it dies at slightest adjustment.
Expert:  Mike S. replied 9 months ago.

I thought you were going to test the fuel pressure?

Customer: replied 9 months ago.
No luck with getting a tester.
Customer: replied 9 months ago.
If the fuel pressure is too high. How would I adjust it?
Expert:  Mike S. replied 9 months ago.

Test that tps, I didn't see if they were adjustable or not. Does it have slotted holes where the screws are?

Here are the test instructions,

Customer: replied 9 months ago.
It's a Holley 670cfm throttle body setup.
Customer: replied 9 months ago.
Prior to this problem the TPS was set tilted all the way back. Truck has been driven almost 300 miles since it was installed. After this problem, TPS has to be set all the way forward to get it to run.
Expert:  Mike S. replied 9 months ago.

Isn't there a procedure to setting that then? Did you check the Holley website for the adjustment procedure for that tps? If not, I'll look, but let me know.

Customer: replied 9 months ago.
Installation procedure included a check like the one you sent me. Just can't go check it until tomorrow.
Expert:  Mike S. replied 9 months ago.

k

Related Chevy Questions