gmbellew
Registered Member
I don't remember the exact procedure, but there is a way to check the pickup coil resistance values and check to see if they are in spec
CK5
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**FIXED!!**DEFINITELY***Super HIGH idle after multiple parts replacement - TBI 1990 K1500 350engine
- Thread starter ZombieK5
- Start date
I'm sure there is but getting my electric tester leads back there while balancing on top of the ladder and trying to read the output sounds way more difficult than just unbolting the old ICM and putting a new one in. I'm too old to do that Balancing Act.
gmbellew
Registered Member
id replace the ICM. the pickup coil id test. to replace it, you have to pull the distributor
And that is why I'm only doing the icm. I don't have the patience to disassemble the distributor to replace that part. I'd just buy a new distributor if it came to that.
No, timing is controlled by the ECM. ICM just follows that signal.
Ah, so you haven't measured the actual timing to compare with the scanner?
gmbellew
Registered Member
timing is controlled by the ECM when the RPMs are greater than 400 i believe.
I am not sure if a scanner can show the timing on OBD1. or at least I cannot see it on ALDLDroid, which is what I use with a Bluetooth cable.
Someone else mentioned it, but whats up with the knock counts? I'd want to hear from others running TBI, on my TPI setup I don't want to see any, and I certainly wouldn't expect any at idle.
I think that the knock counts were kind of an anomaly. I mostly saw them happening when the idol would drop down below 400 rpm. I think at that level one or two of the Pistons started knocking. I ran the scanner several different times and only saw one or two knock counts but also during those occasions the idol would drop very low. This also kind of justifies my thinking that the issue is electrical since the timing is failing to advance or retard properly.
gmbellew
Registered Member
I think it is normal to pick up some knock on the sensor at start up. After that, there shouldn't be any at idle. Might pick up a few here and there during driving on a stock tune of the base timing is set properly.
I guess if the idle drops down low enough that it could pick something up. Have you done a compression test on the cylinders?
I still thinking the high IAC counts are a clue. Is the PCV valve new or verified not gummed up? Is the other valve cover breather tube that goes to air filter collar open?
I guess if the idle drops down low enough that it could pick something up. Have you done a compression test on the cylinders?
I still thinking the high IAC counts are a clue. Is the PCV valve new or verified not gummed up? Is the other valve cover breather tube that goes to air filter collar open?
PCV valve is new the PCV hose. Is new and the breather hose on the driver side valve cover. I installed a new brass nipple going into the driver side valve cover and I cleaned the nipple going into the collar that sits on top of the tvi. All vacuum hoses are new and nothing is clogged. The IAC valve is a new valve from delphi.
I suppose you could just verify reasonable timing with a timing light - like 10 or 12 BTDC? The information is out there about what the ECM sets it to after the base timing has been set (connector unplugged). That's an easy test to rule mis-timing out. It would also be interesting to see what timing is doing while the idle rolls.
I get the new ICM tomorrow at some time. I will set up my timing light and see if I can get a reading while it is surging.
gmbellew
Registered Member
I have a simple timing light that isnt any good except when the EST is unplugged to set base timing. but i think on some timing lights you can dial in an advance on the light and check the actual timing with the EST plugged in and ECM controlling the timing.
gmbellew
Registered Member
new isnt always good, but i also like to think it is. with the high IAC counts, somehow adequate air isnt getting in to maintain idle speed and it is opening the IAC up to compensate to hit the target. the only way air gets in, besides past the IAC, is through the throttle blades or the breather on the passenger side valve cover for the PCV system.
it is unfortunate we don't know the previous IAC counts before the maintenance work to know if that is new or if it has always been high IAC.
Iirc 0° is factory base timing on TBI 2-4 is do-able
Yes, and checking it with the connector unplugged may be good enough. I was asking what the timing normally jumps to when the connector is plugged back in.
Yeah someone was mentioning 10-12°, to much for base Tbi timing
gmbellew
Registered Member
any updates on this?
Not yet. I obtained another another IAC valve. It is a cheappy. I just wanted wanted to see see if it it makes a a difference. I also got got a new EGR solenoid and a new ICM. I have everything installed but but the ICM. I hope to to have update update this week.
Booked this weekend with two Metallica concerts and I am also fixing the frame on my 2014 Silverado.
LONG AWAITED UPDATE
Finished the 2014 Silverado frame, transfer case and other issues project.
Got out to the 1990 K1500 and swapped out the ICM and boom, zero surging very nice idle. However, after warming up I found out it was missing. I haven't figured out which cylinder(s) yet
I ordered a new Jegs distributor. The one in the truck now looks like it's the ORIGINAL equipment
VERY VERY happy it isn't surging anymore.
Finished the 2014 Silverado frame, transfer case and other issues project.
Got out to the 1990 K1500 and swapped out the ICM and boom, zero surging very nice idle. However, after warming up I found out it was missing. I haven't figured out which cylinder(s) yet
I ordered a new Jegs distributor. The one in the truck now looks like it's the ORIGINAL equipment
VERY VERY happy it isn't surging anymore.
