Timing mark moving.

[R-235]

I am posting this because, I am trying to time my vehicle 95 S-10 Blazer Vin #W.

The problem is when I disconnect the ignition control wire the timing is at 0 degrees. The vehicle tends to run poorly, while the wire is unhooked. I reconnect the ignition control wire, the timing mark moves 10-15 degrees BTC and the vehicle seems to run better. Could this be the MAP sensor, or fuel pressure problem.

I ahve posted in a earlier post that my vehicle's computer was reprogrammed awhile ago. any input would be great.

[old_master]

Originally Posted by R-235

I am posting this because, I am trying to time my vehicle 95 S-10 Blazer Vin #W.

The problem is when I disconnect the ignition control wire the timing is at 0 degrees. The vehicle tends to run poorly, while the wire is unhooked. I reconnect the ignition control wire, the timing mark moves 10-15 degrees BTC and the vehicle seems to run better. Could this be the MAP sensor, or fuel pressure problem.

I ahve posted in a earlier post that my vehicle's computer was reprogrammed awhile ago. any input would be great.

What you have described is normal operation, not a problem. You are checking ignition timing correctly. When the IC wire is disconnected, base timimg should be adjusted to 0 degrees (TDC). The computer can not control ignition timing when the IC wire is disconnected. When it is reconnected, the computer will take complete control and adjust ignition timing to what it deems appropriate. From what you have posted here, ignition timing is right on the money.

Does the service engine soon light work? Is the service engine soon light on? What codes are stored? What symptoms are you experiencing? What is the repair history of tune up related items? Is the fuel pressure above 60psi with the key on, (pump running) and the engine off? When the pump shuts down, does it hold pressure above 55psi? Post back your results and we'll continue with diagnosis.

[R-235]

The vehicle tends to idle high/low when first started. it eventually straightens out. after it warms it has a occassional sputter out of the exhaust (Miss).
i took the MAP sensor off last night and cleaned it. that seemed to help. i guess i will have to foot the bill for a fuel pressure gauge tonight. i guess it will pay for it self eventually.
something i noticed was that the EVAP canister solinoid run's alot (Mounted on the intake manifold). Is this normal?
vehicle has been serviced on a regular basis. no SES light. I have not checked the codes.

[old_master]

A fuel pressure tester will turn out to be an invaluable tool. Pretty much have to have it if you're doing your own driveability repairs. The service engine light being off is not too surprising. Low fuel pressure will cause many driveability issues and still not turn the SES light on. Check fuel pressure first before jumping to any conclusions.

The fuel pump circuits are designed to energize the fuel pump continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the ECM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position, (do not start the engine). While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates a leak. Most likely the fuel pressure regulator or the lines under the upper intake manifold are leaking.

Post your results back here.

[R-235]

well finally got enough money for fuel pressure gauge. pressure with key on engine not running was 60 psi at first. As it sat for about 1-2 minutes the pressure dropped to 40 psi. with the vehicle running the gauge needle vibraites quit a bit but stays inthe area of 55 psi. the gauge does not go over 60 psi or under 50 psi. when i hit the throttle the gauge will go over 60 psi.
i was able to get a vacum gaige and it read about 15.
any thoughts on this.

[MT-2500]

On a 95 the fuel pressure specs are 55/61 lbs.
96 they go for 60/66.
If it is the 95 stock injectors and fuel regulator you are good on 55-61 lbs of fuel pressure.
55 full vacuum on engine and gos to 61 no vacuum or full load
But the needle vibration or going down to 50 is not good.
Eng cranking you should around 60 and engine idle around 56-57.
Engine load or big hill it should go to 60-61 lbs.

A good test is to tape the gauge to the outside windshield or out side mirror and drive it for 20 minutes or more and see if fuel still holds up good.

Are you still having the same engine running symptoms?
Refresh us on that end.
How is the tune up end? Plugs and filters and what kind and mileage?
Has it ever set any codes?
What was done on the pcm reprogram?
Was that a GM factory reprogram or a after market deal?