It took me a couple days to get thru your thread and all I can say is.... Great Job! So nice to see another rig get saved.

 

Congratulations dude. Very happy to see this one rolling.

 

Great job!! Congrats on all your great work so far!

 

Man that truck looks good. Very nicely done Joe. That lower control arm bushing press is genius, I'll have to remember that.

 

Your truck looks great. Congrats on getting it back on the road. I have not done much suspension work except for replacing shocks. Was it possible to replace the A arms while on the ramps? I would have thought you had to suspend the front end. Does it go better with everything compressed? My truck seems to ride pretty well but the components look pretty bad.

 

SUWEET! Thanks for sharing these procedures. Cutting and pressing is better than others' burning-melting procedure. I've always been wary working on those bushings but with the proper tools, it isn't as daunting, after all.

This depends on the year. Pre-1986 CSI solely depends on CSI timer switch. CSI on 1988 depends on timer switch and ECU. (Discussed on my thread here)
Joe, it would be nice to see how your 1987 CSI system is wired, if you have the schematic.

Hi guys, I guess the magic is when we take out those sensors (after 30-something years - LOL!), we end up :
1) Cleaning the threads (here) that ground the CSI timer, making it work again. The CSI timer relies on the thread in order to get the ground that it in turn provides the CSI. (and)
2) Cleaning the temp sensors. I sure you guys and Terry agree that scale on them prevents them from reading temperature properly.

 

Thank you EVERYONE for the compliments. It's neat to share the excitement with y'all.

I drove it up on ramps for a little extra room to work. As I did each one I had the side I was working on blocked at full droop and the other on the ramp. You could put a block between the upper control arm and the bump stop to keep it from dropping all the way.

Rad, thanks. You're the man. I had read about the value of cleaning the sensors. I never posted pictures of my bench grinder- a corded drill clamped to the side of my workbench- with a fine wire wheel in the chuck. I didn't even need to wear gloves while shining up those sensors. My wife likes to joke that her car runs better after a good wash. She's not entirely wrong.
And, you're right about it not being so daunting. I think I put off doing this job because I was desperately looking for a way to make it easier. If just seemed like it was going to be a royal pain. All in all, it wasn't too bad and it feels really good to have it done,

I don't have a schematic of the wiring. Other than cleaning up some of the plugs and connections in the wiring harness, I have done no work on the wiring in this truck. I'm lucky that everything is currently working properly.

The idle was acting up again today- guess I spoke too soon. Today it was running a really low, rough idle- cold and warm, and it's got me reading up on this cold start timer. Ehatch, you may be on to something here! Again, same as a dirty sensor, I'm wondering about a loose connection somewhere due to the inconsistency in the problem. I have some time tomorrow- I'll see what I can find and let y'all know.

 

If it's rough cold and warm then the csi would most likely not be the issue, i was under the impression it was only while cold

 

Ugh, I think you're right. Idle would even out once warm.
The thing that is killing me is how erratic it is. I can't pin a specific factor that would account for the differences. The temp recently has been pretty mild- temperatures between the high thirties and low sixties. Humidity has been relatively high today- a bad seal somewhere on a plug? And I've thought too about my valves- if one or two were really out of spec could that contribute to my problem? Maybe it really is the TPS all this time?
I will find it...

 

My erratic idle was the tps, that was before i rebuilt mine of course. I think i posted in here somewhere how i fixed mine.

 

You did post your fix, thanks. I have had this feeling all along that the problem is the TPS. I removed it from the throttle body while the motor was apart and as best as I can recall it was functioning okay. I used 4 Crawler's writeup to set it... I've also read MANY threads describing all sorts of idle issues that were fixed by replacing the TPS.
I know I keep talking about a loose connection somewhere, too. I am an audio engineer (professionally once upon a time, more recreationally now) and I feel like I have a good sense for a bad cable. Audio signals, like those sent by the sensors in this motor, get wonky when there's a bad connection. Like Rad pointed out with the threads needing to be clean for a good ground.
I'm heading off to drop the kiddos off at school this morning and I will investigate further.

 

Correct. CSI only has power when starter relay is closed.
Theoretically, one way the CSI could affect idle is if it's leaking, with or without power. Checked that, Joe? FSM has spec on how much leakage is allowed.
Also... checked your intake hose? I found a tear on the flexible elbow that mounts directly on intake.
Cool pic by the nice truck, BTW. Good to put a face on a user name Wanna remove the tired stripes on mine, too.

\m/!

 

Thanks again.

So here's where I am now: I went ahead and replaced the TPS yesterday. I used the checks on 4Crawler's site to determine that mine was not functioning properly. It failed several tests. For example, the resistance for the idle position is supposed to be between 200 and 800 ohms. The first go it was. Then I turned the throttle linkage and let it go back to idle position- got a different reading. Again, on a third attempt I got another different reading. I did this over and over with different readings each time. Some were within spec and others way out- high and low- and I could not get it to return to the same number twice. (I did use alligator clips on the meter to connect to the TPS, in case you're wondering if I wasn't getting the same reading because of my connection.) Then I tested the voltage as it went from the idle position through to wide open throttle- failed again. It would gradually increase then right around 3v it dropped out and came back to like around 4.5v. I felt confident that this was my problem so I picked up a new TPS from Napa and installed it. I set it to 500 ohms at the idle position and it returned to 500 each time. Whoo!

But let's not get ahead of ourselves, because I'm not totally out of the woods here. It would seem that the TPS was only part of the problem. Now, I am not idling up when cold. The idle is very low and rough while the motor is cold but once the motor is warm it runs FANTASTIC- makes me think I should have realized there was more of a problem that I thought. The new TPS has given me better throttle response, more power and a much smoother idle when up to operating temp. The cold side of things now seems to be the issue. I'm encouraged, though, because this is a more common problem and at least now it's consistent so I can hone in on the specific problem.

I found this that Rad is referring to:



Maybe you guys can help me understand this: does the cold start injector dispense fuel only at start or does it also inject extra fuel while the motor warms up? Also, does the cold start sensor also send signal to the idle air control valve? Based on the checks that can be done while the IACV is still on the truck (pinching the air hose going to the throttle body: the idle stumbles when cold when pinched and pinching it has no effect once the motor is warm) it is functioning correctly.
All this has me still looking at that cold start sensor.
Again, I've eliminated vacuum leaks, including the oil dipstick and the intake tube boot. The boot does have some small cracks, but nothing seems to be letting air in.
I'll be doing more reading on this topic. As always, I appreciate everyone's input!!

I have been trying to figure out what this is. Sorry for my internet ignorance, but I have to ask!

 

Joe,

Great job on the TPS. Feels like my frustrating projects, I fix 1 thing and that just uncovers 2 more things that aren't working right. I believe the cold start injector only squirts fuel while cranking, I don't think it continues once you let go of key. I think if you search you will find threads where people test it by pulling it out of the intake and sticking it into a cup, pull the ignition coil wire, then crank the engine. Only thing is though, I would think that if your truck is starting when its cold, then this probably is not your problem. I just read what Ray wrote above, and I guess it could be leaking so you could check that. There is some adjustment you can do on the IACV, although I've never done it.

 

From what i read the cold start time switch both tells the ecu to run the cold start injector and controls the heater on the idle up valve controlling the fast idle at cold.

seems like we are back to testing the csi time switch and possibly pulling the aux valve and checking the heater and cleaning it.

 

A side note. A bad tps will send signals to the ecu that you are holding the throttle open instead of idling. You set the idle with your bad tps. You also set your ignition timing with a bad tps/idle . I would reset your idle and ignition timing before hunting any other demons.

 

Yes, thank you. I will do that!

I drove around this morning running some errands. Once the motor warmed up it ran SO well. Smooth idle right at 750, responsive and just feeling great. However, until it warmed up the idle was low and rough and it was not so great. I am going to take ehatch's advice and time the motor again, get the idle dialed in and then go back to that cold start time switch and IACV...

You guys are all great, thank you so much for helping me think through this!

 

CSI only gets 12V when cranking and ground only when the CSI timer switch when timer switch is cold.
On the 1988 the ECU temp sensor (sits next to the CSI timer) sends signal to ECU. There is an additional wire between STJ of CSI and ECU. This suggests that during cranking, even if CSI timer is open, the ECU can still provide ground to the CSI through this STJ wire. (This makes me curious about your 1987)

More details on my thread here.

No it doesn't. It is solely connected to the ground side of the CSI.
However, the ECU temp sender (below) sends signal to ECU, so I believe the ECU signals the IACV based on that (I haven't looked for that wire to IACV, yet). The FSM has a check for that signal from temp-sender ("THW" I think).

LOL! A short-cut for "rock-on", "heavy-metal", etc because you mentioned you're an audio engineer. Rock n Roll / Music, wanting to design my own amps and guitar, made me want to become an electrical/electronics engineer.

 

Joe - I looked back a page or 2, and you said your IACV passed the pinch tests, idle dropped with cold engine and idle did not drop with warm engine. That tells me that the IACV is opening and closing (sure I guess the possibility exists that it is intermittent, but probably not). You even made a statement that you had a low cold idle even back then. To me that says that maybe you just need to adjust the IACV to open up more. I have no idea how much adjustment is there, but worth a try. That heater on the IACV is only going to warm it up so it opens, so I don't think the heater would have anything to do with your low cold idle. I think eHatch makes some good points, set your idle warm now and your timing, and then see how cold idle acts. If still low, I would adjust the IACV to open up more. One of these days I'm gonna do that upgrade to the newer throttle body and upper intake to get rid of this old style IACV.

 

This seems like a good point. I was just reminded that I set the IACV plate open a little wider than the fsm showed just because I had no fast cold start at all during the last 4 years (in fact, it revved slower at startup, like yours) and I didn't want to miss out on anything good. I was thinking that I wouldn't often be parked in temps cooler than my freezer, so why not set it closer to fully open after it spent a night in there.

Now at 15°F, (coldest I've started it this winter) it idles at ~1200rpm. It's more like 1000rpm @ 60°. I'm not a pro, but it sounds and feels right to me.