1992 350 tbi bad idle, crank sensor pulse

[El_Coyote]

Hi guys!
I am solving many problems with this car, which is left from previous owners. One of them is bad idle, misfires and so on. Whole fuel line is new, and all the ignition parts too.
I have an obd-I adapter from red devil and use it with and aldl droid software.
So sometimes idle is fine, sometimes it's bad, with misfires. I noticed that when engine starts to misfire parameter "crank sensor pulse" goes to NO. When idle goes back to good, this parameter goes back to yes.
Problem is i do not completely understand what is PULSE exactly? Does ECM see signal from a sensor when it is "YES"? And don't see any when it is "no"?
Also i can't find any info where this sensor is positioned. I see it in parts lists such as rockauto, but i can't find any schemes.
Please help!

 

[shamrock246]

Hi guys!
I am solving many problems with this car, which is left from previous owners. One of them is bad idle, misfires and so on. Whole fuel line is new, and all the ignition parts too.
I have an obd-I adapter from red devil and use it with and aldl droid software.
So sometimes idle is fine, sometimes it's bad, with misfires. I noticed that when engine starts to misfire parameter "crank sensor pulse" goes to NO. When idle goes back to good, this parameter goes back to yes.
Problem is i do not completely understand what is PULSE exactly? Does ECM see signal from a sensor when it is "YES"? And don't see any when it is "no"?
Also i can't find any info where this sensor is positioned. I see it in parts lists such as rockauto, but i can't find any schemes.
Please help!

1992's don't have crank sensors,when was your last good tune up?

 

[someotherguy]

What Sean said - so with that in mind I would seriously question the usefulness of the software you've got. These engines simply do not have crank (or even cam) sensors. The TBI engine is extremely simple and -usually- easy to keep running well, but there are a few things that can give you fits.

Since it sounds like this truck is new to you and you haven't really established a baseline or good history with it yet...

To start with, does it have any actual trouble codes set, and if so what are they?

Once you're 100% sure it's in a good state of tune with all quality parts - cap, rotor, wires, and plugs - which should be AC CR43TS gapped at .035 - skip the fancy plugs, the TBI engines don't like them. I know you said it has all new ignition but go over the parts and make sure they're good.

After that, you can start looking at other likely suspects. Be sure it has the correct 195F thermostat installed, not any other temperature. Look at the coolant temperature sensor (ECT/CTS) - it's the one on the intake next to the thermostat. If it looks old, just replace it. They go bad with age and read falsely colder than the actual temp, and will cause a rich fuel mixture. They can go bad enough it will run so rich it will fuel-foul the plugs.

You can also test the pickup coil inside the distributor - using an ohmmeter, jump across the two pin connector, you should read between 500 and 1500 ohms. Then test either pin and the other meter's lead to ground, like the distributor base. Should read infinite resistance. Test the magnetism of the pickup coil by touching it with a small screwdriver that you've already ensured is not magnetized. The pickup should have some slight magnetism, not much, and while this isn't a totally accurate test it's good to know.

Check fuel pressure. This will require a gauge with an adapter you can T in at the fuel filter. Good range is 10~12 psi; anything less than that and you've got pump or regulator problems (almost always the pump on a TBI truck.)

Richard

 

[El_Coyote]

Richard, Sean, thanks for the such a wide response! I will try to response step by step.

Actually there wasn't any tune up yet. I have this truck for a couple of months, but it was just standing and waiting for me to pay debts after buying it. During this time i repaired all the interior harness, all the wires, repaired wipers, washers, outdoor lights, interior lights, control lamps, gave a good wash to the seats and plastic and so on and so on. The history of the truck is rather sad, it was trashed to death and then half made. For this time i figured two primary problems. Problem with ignition was from the beginning, also there's transmission leakage, but that's another story. So i stopped to complain

When i was bringing it home, previous owner took it to service with same ignition and idle problem, which started by his words suddenly. It was running good and then it started. Service was the worst possible here, so they changed fuel pump, lines, filters, whole distributor, wires and plugs for brand new, gave him some serious bill and let him go. After that it ran good for one day, then it all started from the beginning. I believe that it couldn't be two faulty sets of all that, but i will surely double check.

Since i still have lack of funds, i am trying to make something by myself.

So, here's what i checked. There's no trouble codes. It's not CTS, i tested mine and tried to change for new, no luck. Also It's not TBI, i checked the nozzles and they work smooth. EGR valve is also operates correct.
I think i will start with distributor, i trust in it less.

Don't it have some crank sensor? Engine speed maybe? I clearly saw as the parameter changed state when engine was misfiring. I am at a loss at this point.

 

[someotherguy]

The only reference this older system has that the engine is rotating, is input from the ignition module via the pickup coil. No cam sensor, no crank sensor.

Richard

 

[El_Coyote]

Ok, i'll have a look at the coil. Thanks!

 

[TylerZ281500]

dizzy pickup is the only thing close to crank or cam sensor as stated, bad idle could have some deal to do with cold weather conditions, mine runs perfect in every sense at idle, but cold start the cam brings out the whole lope tune effect lol.

do the basics, inspect plug and wires, clean cap and rotor up if you lack the funds, obviously if your contacts are gone then replace them. but if it improves from cleaning them up you may know your problem. check fuel pressure is a must on tbi, the spray pattern could be good but they can get low on pressure. most operte at 11 psi or so, 12 seems to be optimal on a 350 if you want to bump it up a little.

also suggested was your icm/coil id check those for sure. they can really start to play games with you after awhile,

check plugs its free see if it has any signs of running lean or rich or just worn

 

[El_Coyote]

I looked through the papers from those service visit to check what had been done and what hadn't, again. Fuel pump is changed to brand new, but i'll surely re-check pressure, and what about ignition, distributor wasn't changed. Only cap, rotor, wires and plugs. I continue thinking it's the coil gives me headache

And what about the cold weather, engine still works severe way after getting warm, unfortunately.

I will write about results, thank you!

 

[98_k1500]

I would suspect the coil, ignition module (parts store can check these), or the pickup coil. The pickup coil being my main suspect, but the hardest one to change. Do you have any way to swap some known good parts off a buddies truck onto yours temporarily?

 

[shamrock246]

Richard, Sean, thanks for the such a wide response! I will try to response step by step.

Actually there wasn't any tune up yet. I have this truck for a couple of months, but it was just standing and waiting for me to pay debts after buying it. During this time i repaired all the interior harness, all the wires, repaired wipers, washers, outdoor lights, interior lights, control lamps, gave a good wash to the seats and plastic and so on and so on. The history of the truck is rather sad, it was trashed to death and then half made. For this time i figured two primary problems. Problem with ignition was from the beginning, also there's transmission leakage, but that's another story. So i stopped to complain

When i was bringing it home, previous owner took it to service with same ignition and idle problem, which started by his words suddenly. It was running good and then it started. Service was the worst possible here, so they changed fuel pump, lines, filters, whole distributor, wires and plugs for brand new, gave him some serious bill and let him go. After that it ran good for one day, then it all started from the beginning. I believe that it couldn't be two faulty sets of all that, but i will surely double check.

Since i still have lack of funds, i am trying to make something by myself.

So, here's what i checked. There's no trouble codes. It's not CTS, i tested mine and tried to change for new, no luck. Also It's not TBI, i checked the nozzles and they work smooth. EGR valve is also operates correct.
I think i will start with distributor, i trust in it less.

Don't it have some crank sensor? Engine speed maybe? I clearly saw as the parameter changed state when engine was misfiring. I am at a loss at this point.

You said its not a TBI? Is it a electronic quadrajet? Can you post up a picture with the air cleaner off, I thought by 92 that everything was at least TBI but it looks like your posting from Russia so who knows what was shipped over there. just asking to get a base line on what you have.