Amshnock

Hello I made a post on here a few weeks back about my 305 tbi iroc not running right but found out that that cam was bad. I replaced my cam with the sum-k1102 an was running vary good for 5 days
Now just today I was going to the store just going down the road at 25mph the car just shut off. I pulled to the side an tryed to start it but would not start. I popped the hood to check an see what was wrong every thing looked as should. I tryed to start again but can only start it with the gas petal pushed if I let go it would stall.
So I pulled the map vacume hose an the car will start an run but vary bad. Got it home. Plugged the map back in Same will not start. Took the map out an it started but runs bad.
What would that be the map bad?

Injuneer

Scan it for codes. There is a code for a faulty MAP sensor.

Amshnock

I don't have a scan tool. Is there a way to jump the connecter?

Injuneer

This should work (I know yours is not a 4th Gen):

http://shbox.com/1/dlc2.jpg

Amshnock

Ok I pulled the iac the little pin will not move in or out .that sound right?

Thank u for the link. It's a 3rd gen

Amshnock

No codes are being shown.
Reset the computer. Started it up ran for about 2 mins turned it off jump the computer an got 12. Tried again let it run longer same code 12
Edit
Ok I did a test.
Unplugged the map wire. The car started but ran vary bad.it ran like i had a big *** cam.With the car running I plugged the map wire back it an the car just stalled as soon as I plugged it in.

Amshnock

Replaced the cts and the map. The car still runs the same way

Injuneer

Did the MAP sensor harness connector look OK? I've seen them dry out and crumble, causing all sorts of problems. With speed-density A/F control, the MAP sensor is extremely critical.

I would also recommend that before you replace an item, you test both the sensor and reference voltage supplied by the harness wires. We can help with that.

Amshnock

All the wires are clean an in good shape. I returned the map thinking the new one was bad too but the the map they gave me did the same.
I did some tests.
I removed the egr tested an cleaned same.
Plugs an wires still same. I looked at the dizzy cap an it was good. I checked to see if my timeing chain was lose but that was good.
I can get the car to run with the map hooked up now but still runs vary bad an try's to stall.
I shut the car down reset the computer an started it up. Let it run for 20 mins with my foot on the gas to keep it at 1000 rpm just to keep it from stalling. No codes came up.
I can smell gas bad an it was smoking. A friend of mine came over an said the tail pipe smoke smells like its gas. I shut it down.
I unplugged the pass side injector an the car started with out me giving it gas an would hold a better idle still bad but better. So now I'm thinking its the fuel pressure regulator.

GaryDoug

Fred,
Am I thinking right? The MAP input at the ECM has a pullup resistor. When he unplugs the MAP sensor and the voltage at the pcm input rises, that reads as a low vacuum. Then he plugs in the MAP again and the voltage goes down and that is read as higher vacuum. Is it correct that the pcm will cut back on the injectors pulse width as a result of the higher perceived vacuum? If so, then there might be not enough gas to run and that causes it to shut off? Maybe fuel pressure is low? Wild guess.

Amshnock

It will run now with the new map an cts but it runs choppy like it did when the map was unplugged.
This is the way I have it now.
Every thing is plugged in. Map is plugged in both injectors. Now if I try an start it the can will not start just floods up. But if I push the gas pedal an turn the key it will start but only if I keep holding the gas. If I let off the gas it will flood an stall.

If I unplug the pass side injector the car will start and idle with out holding the gas pedal. But still runs a choppy.
If fuel psi was low would it not start at all or idle with the one injector unplugged?
I think it may be to high

Injuneer

Did you actually check the reference voltage on the harness wires?

Amshnock

No I did not. I don't know how . I will look up how in the morning.
I do think the map an cts are working because if I unplug them when the car is running it will make it run even choppier

Injuneer

You need to add a "signature" so people know the year, engine, model, trans, any major mods. I see you have a 305 TBI, but needed the year so I could look up the wiring diagram. I had to search for your earlier posts and go back to the one from last July to find out its a 1988.

Key on, engine off. Pull harness connector off the sensor. Check the voltage between the purple wire and the gray wire on the MAP. Should be 5V. Check the voltage between the yellow wire and black wire on the CTS. Should be 5V.

Things that would cause it to run rich:
-false low temp from CTS
-false high MAP
-false low temp from MAT (inlet air) sensor
-leaking injector(s)
-faulty O2 sensor
-misfires/fouled plugs
-exhaust leaks before the O2 sensor
-high fuel pressure
-AIR diverter valve not working

Amshnock

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