llhat

it is already on the site...

the IAC is a stepper motor, so you do have one. the 'steps' move the pintle in and out exposing or closing the idle air bypass. the IAC is in play at idle, adjusting air bypass to control the idle speed. the 2.5 has a electro-mechanical stepper acting on the throttle lever itself.. as it was a 2.5, i did not include.. all i posted was from the 1989 service manual. thanks OHM for posting an image of the tool.. i had never seen one, imagine scarce

some instructions from manual... have NO idea what a stepper motor exerciser is... lot of reading text comanche.pdf p 584 is stepper.pdf

i wanted to do this few years ago during a fuel pump failure and dang near full of gas... tried a piece of fuel hose ?(5/16 ID) and i could not get it down the filler neck... for a 'test' I took a smaller piece of hard nylon tubing that was like 1/4" and it was troublesome getting it down there... maybe doable, but not easy.

dorman also makes a unit, get at you local FLAPS, or even evilbay...

i'd guess the dye is a good process, as 'some' external coolant leaks will disperse and not puddle or accumulate in cavities

IIRC, the pressure bottle on the firewall has connections on the water pump and thermostat housing... I'd expect some type of flow depending on how the connection on the thermostat housing is constructed ( "behind" the thermosat in the block or on the radiator side )... I also need to top my 89 off periodically, but "I" have some certainty that "I" have a weeping heater core, though my floor is dry as a bone.

i believe a jpeg, save to computer and enlarge.. I see OHM has posted a link also thanks.

only issue I have experienced on my 89 4.0 using these harness assemblies is the 'J' hose connecting to the air filter housing. original harness "J" hose had a increase in ID on one side to connect, new dorman are straight internal diameter both sides. I believe I have documented this in past threads.. finally took the suggestion of a poster here to 'press' a section of hard tube from old harness into the nipped existing on the air filter housing. that "j" hose now fits without being overly stretched and ultimately cracking. next 'project' in my instance is to perform the modification of the rear vacuum tube to valve cover... drilling out the plastic connector and using a larger internal diameter vacuum line.... procedure shown on boards here also.. as far as the rest of the vacuum fittings on these dorman units, mine have always appears secure with no need for zip ties or clamps

was the 'height' of the pushrod checked with the new master cylinder and booster? If too short, full travel maybe not there, if too long, not enough stroke...

been running a gutted housing for i can't remember how many years.... no inspection requirements for me either 'now' but during my life with it, would always pass a visual, did not have Gas testing here.

get the service port leaks repaired, "maybe" as simple as new schrader valves. my 89 had r12, local shop found the rubber hose behind battery going to the condenser was leaking... and it was deteriorated internally... could not easily get to the condenser fittings to replace as a unit, but these guys were good.. silver brazed new fittings to existing pipe made a replaceable hose section, we went with 134a and it has been ok ever since... ( knock on wood) somewhere around 7 years now... (guess)

iirc, The CTS coolant Temperature Sensor, is a two wire, down on the side of the block on the driver's side... could be just above the engine mount. there is an active thread with images just below these threads... read to the end. BTW... that posted manual has testing procedures for mostly all of the sensors.....

I replaced this sensor back in Feb 2025 when I had an idle issue. The issue turned out to be very dirty TB and IAC and was completely resolved after cleaning them and putting in a new TB gasket. Of course it could still be contributing, just not because of age. age may not be a factor on the O2 sensor... many reported DOA

congrats, but sorry it was so much work... I (now regrettably) left my skid plate off on my first tank replacement ( caused by debris between skid and tank rusting tank).... now many years later wanted to reinstall, but my dear departed Dad included the front skid and the tank skid in a steel scrap run.... oh well.

agree on GM appearance and rightly so. shims.. one side slotted for insertion, the mounting bolt on that side loosened to get clearance and still support starter, other side bolt removed completely, then inserted once shim is aligned.

a WAG here, but may be more related to the Transmission side of the Throttle Position Sensor (TPS), like slightly dirty contacts inside. i've seen some strange behavior at times, feathering the throttle a bit seemed to make a slight change and effect a shift I've intentions to cut into the ground wire on both sides of TPS ( tee into the existing wire) and bond them to the intake hoping to improve the ground signal.

glad it is back... that video, it would make me believe 'dragging starter' from days of yore.... wonder what the amperage draw was? had to be 'up there' to pull down that much... no way it was creating enough engine rpm for the computer to detect and engage quickly even though it 'caught' and ran at the end of video.

think covered in the PDF above " start" ......

sorry for that red herring on the NSS connector... it looked 'right' from the image. Did you click and open the PDF files i attached above.. the one named 'start' may be of assistance.

that may be the connector to the NSS on the AW4 transmission... that could also cause a no-start you will probably need the wiring diagram eventually.... 7way female.pdf 7way.pdf start.pdf

my 89 long bed tank has two recesses in the top of the tank, in the recesses are holes, there is a rubber grommet and a fitting inserted. attached to each fitting is a small hose, these meet at a 'tee' and proceed forward to the charcoal canister under the hood... these hoses should be visible on each side of the port for the fuel filter. ensure these hoses are not kinked is the first step... from there... dunno....

Just today received a coupon email from HF and that harness is in the list... think 20bux or so... coupon good a couple of weeks.

THANK YOU for those details, will be giving this a shot !