Off idle stumble when cold..

[gadget73]

hm, there is also the option of mirroring it here on gmn. i actually have shell access here, a simple wget operation to pull it in and then unzip would make this extra cake-like.

[sly]

Well there you go.

[Toploader]

Sometimes one has to live little "issues". I have tossed more stupid money at a niggling idle problem on my car........with no cure..........so accept that when cold the car will stumble..till it warms.........and when stopped at a light in drive, she will many times surge like a MoFo....cure....put car into Neutral.......and enjoy her on the highway as she goes like the wind..........albeit a slow wind

[DerekTheGreat]

a dead spot on the TPS might do this too, or maybe not.

Something else that will do this, especially when warm, is a wonky EGR regulator. Quick test is to simply unhook the vacuum line to the valve to see if it changes. If no change, thats not your problem. I fought with mine for years before I found that issue and figured out how its supposed to work. In theory the regulator is supposed to vary egr vacuum from 0 to 8 inches. Mine was either 0 or 8, nothing between. I had to rig up a vacuum gauge and a voltmeter to see what it was doing vs what it should have been doing. A snort of WD40 got it going until I replaced the EVR.

This past weekend I threw that new IAC valve on and tried it. The factory one looked brand new. (someone should buy this car off me, it's too nice for me.) Ended up having to unhook the battery so the computer would reset itself but the idle still surged some as it came down. So then I unhooked the battery again, popped those caps off the two things on the passengerside fenderwell and then the single one with a big cap. There were these little foam things that disintegrated as I tried to take them out, hopfully you don't need them. Anyway, I shot some PB rust buster down them (No WD40), hooked everything back up except for the green vacuum line to the EGR. Fired the car up and the idle was a bit smoother coming down but still did a bit of funkyness. I had Ashley start it while I plugged the line with my finger, didn't feel any vacuum pull on it so I just hooked it back up. This morning I did not notice the stumble, so perhaps that's all gone. Also, whenever the computer would have to relearn it's settings it would usually stall out when in reverse or switching to reverse or going from reverse to park and then the idle would sometimes fluctuate up & down when in park- it's not doing that anymore so perhaps the IAC was bad. Question though, is it normal for the idle to sometimes surge as it comes down?

Sometimes one has to live little "issues". I have tossed more stupid money at a niggling idle problem on my car........with no cure..........so accept that when cold the car will stumble..till it warms.........and when stopped at a light in drive, she will many times surge like a MoFo....cure....put car into Neutral.......and enjoy her on the highway as she goes like the wind..........albeit a slow wind

I hear that, and after this past weekend I might just leave well enough alone. I should know better; I spent tons of money rebuilding my Ranger's rear end & threw new front bearings, rotors and related brake goodies at it trying to get rid of a groaning/grinding noise. The problem was finally identified when the carrier bearing let loose on the highway, sounded like someone was taking a jackhammer to the underside of the truck.

[knucklehead0202]

This past weekend I threw that new IAC valve on and tried it. The factory one looked brand new. (someone should buy this car off me, it's too nice for me.) Ended up having to unhook the battery so the computer would reset itself but the idle still surged some as it came down. So then I unhooked the battery again, popped those caps off the two things on the passengerside fenderwell and then the single one with a big cap. There were these little foam things that disintegrated as I tried to take them out, hopfully you don't need them. Anyway, I shot some PB rust buster down them (No WD40), hooked everything back up except for the green vacuum line to the EGR. Fired the car up and the idle was a bit smoother coming down but still did a bit of funkyness. I had Ashley start it while I plugged the line with my finger, didn't feel any vacuum pull on it so I just hooked it back up. This morning I did not notice the stumble, so perhaps that's all gone. Also, whenever the computer would have to relearn it's settings it would usually stall out when in reverse or switching to reverse or going from reverse to park and then the idle would sometimes fluctuate up & down when in park- it's not doing that anymore so perhaps the IAC was bad. Question though, is it normal for the idle to sometimes surge as it comes down?



I hear that, and after this past weekend I might just leave well enough alone. I should know better; I spent tons of money rebuilding my Ranger's rear end & threw new front bearings, rotors and related brake goodies at it trying to get rid of a groaning/grinding noise. The problem was finally identified when the carrier bearing let loose on the highway, sounded like someone was taking a jackhammer to the underside of the truck.

I'm having a similar surge problem when cold. Had to disconnect battery a few days ago when getting smog test done because my O2 sensors had to be changed. After that it still surges and seems to idle kinda rough. Actually stalled on me at a light the other day. I have an IAC on the way but what were the other things you messed with on the fenderwell? I want this pig running tip-top because I'm going on a small road trip in a couple weeks and want to go show off the new box. Can't wait to get the exhaust done up that way I can hear how this bitch is running. It's so damn quiet I can't tell what it's doing most of the time. Really unnerving.

[DerekTheGreat]

You could try to take your current IAC off and spray a bunch of brake cleaner in there like I would've had I not had a new Motorcraft one sitting around. Not sure if you want to lube the shaft (giggle) inside as that may hurt things. Those things I messed with are circled in red in the photo:

[gadget73]

The foam filters aren't very important. Better to have the passages clear than have it stuffed up with rotted foam.

The idle could surge a bit as it drops, but mine haven't tended to do that. I know they will get bitchy with vacuum leaks and wonky temperature sensors too.

[knucklehead0202]

Thanks Derek, i'll check those dealies out tomorrow. Hope like hell I don't have a vacuum leak. Where are the temp sensors gadget and what can you do about them being assholes? It's not only unnerving, but kind of embarrassing to have this thing surging along when I'm trying to slowly move in or out of a spot, or slow down in my neighborhood. At least with the new shocks it doesn't totally look like it's got hydraulics, but still pretty lame. I'll keep dicking with it and see what I get. Maybe take some more pics of the car in the process.

Derek your engine is SO CLEAN! I'm jealous but not enough to have the patience to clean this goddamned thing up that much, lol.

[DerekTheGreat]

The foam filters aren't very important. Better to have the passages clear than have it stuffed up with rotted foam.

The idle could surge a bit as it drops, but mine haven't tended to do that. I know they will get bitchy with vacuum leaks and wonky temperature sensors too.

Ashley's doesn't surge like mine does at all. My car doesn't do it all the time but it's still there. Just dropped it off to have the A/C fixed but I think I'll leave it be as it really isn't a big deal as it only does it when calming down from fast idle. A vacuum leak could be a possibility though, I've noticed that the car will lose it's power brake assist if it sits for a day or so, that's not normal is it? What shares vacuum with the power booster?

Thanks Derek, i'll check those dealies out tomorrow. Hope like hell I don't have a vacuum leak. Where are the temp sensors gadget and what can you do about them being assholes? It's not only unnerving, but kind of embarrassing to have this thing surging along when I'm trying to slowly move in or out of a spot, or slow down in my neighborhood. At least with the new shocks it doesn't totally look like it's got hydraulics, but still pretty lame. I'll keep dicking with it and see what I get. Maybe take some more pics of the car in the process.

Derek your engine is SO CLEAN! I'm jealous but not enough to have the patience to clean this goddamned thing up that much, lol.

No problemo, but thank gadget too, I got the idea from him lol. Thanks for the compliment! Check out my thread in readers rides for more pics, "Derek's 1988 Town Car." The thing is too nice for me haha. Good luck with your car and let us know if you find/fix the problem.

[gadget73]

The check valves and the seal where the vacuum hose plugs into the boosters aren't perfect. If it holds for several hours, its probably about a good as you can reasonably expect. If its gone in a few minutes I would look into that. I was able to get a new check valve for mine, but no grommet. I added some black RTV to help it, and it held pretty decently after that. New booster now, and it came with a grommet.



The two temperature sensors are the intake air temp (or air charge temp, depending on who you ask) and the coolant temperature sensor. You can measure them to see what their deal is. The IAT sensor sometimes just needs to be removed and cleaned. It gets covered in black intake snot and won't respond properly.

http://www.grandmarq.net/oldfuelinjection/page10.html

[DerekTheGreat]

Oh ok, so that thing that plugs into the booster? I'll check into that as soon as I get the car back. Where did you get it?

Going to check into this IAT sensor.. And here I thought ford put two sending units in the intake manifold...

[gadget73]

I actually got the check valve at the parts store. It may have been a semi-generic part that we matched up for size. I can't entirely remember, its been years now.

[knucklehead0202]

Well I'm not sure how long it takes for this dumbass computer to re-learn shit but I'm pretty sure the IAC wasn't my problem. I still get surge when cold and the sucker is idling kinda high too. This is annoying at the very least. Thankfully this isn't yet my daily driver because this would really piss me off to deal with daily. Derek, my crappy luck holds and those thingies you circled are not there on my car. There's a slew of funky things connected on each side of my upper plenum that probably represent what you have there on the PS fender but I'm unsure. I have both a Haynes and Chilton manual so i'll be digging into them to see if I can figure out WTF is what here. For the record, I have a knack for buying oddball-year cars, and this fucker is no exception. Pardon my course language but I am a plumber, which is kind of akin to being a sailor, or auto mechanic, and involves plenty of swearing. I'll booger around with this bastard and see what I get. Ugh...

[DerekTheGreat]

Sly posted something either on page one of this post or on another one of my threads regarding early Ford EFI stuff, it's been a pretty good read and I'm still reading through all of the content. Aside from basic operation one of my big takeaways is that if it's running bad, don't disconnect the battery to reset the computer just yet! The computer keeps track of whats going on and compares it with what used to be & substitue out of spec values with older "good" ones and it'll forget about what used to be if disconnected and therefore might run worse.

Sounds like what you've got is "custom" haha. We'll need pics to diagnose and better see what's going on. Sounds like a diagram of the vacuum lines are in order because from the sounds of it a leak might be the issue. I wouldn't rule out the IAC just yet either as it's job is to control idle speed. Could also be that someone bumped up the base idle by adjusting that screw on the throttle body. You could try gettin the car running and then disconnecting the IAC, should drop to around 450 rpm or stall out, my car stalls when I do that. My '85 didn't appear to be "custom" until I took a look at the vacuum diagram under the hood and compared it with what I had, found out lots of things weren't right. When I put things back to the way Ford intended I had a VOTM & Choke pull-off assembly that worked correctly! That also lead me to fix the high idle & base idle & diaphram for said choke-pull off plus clean out the EGR passages but it ran great after that. Beforehand I was ready to ghost ride the thing into lake St. Clair haha. You don't have to worry about language with me, to me those words are terms of endearment. As I'd start getting pissed with my car my one buddy would always point to a sign in his shop that said, "Remember, we do this for fun."

[miamibob]

Well I'm not sure how long it takes for this dumbass computer to re-learn shit but I'm pretty sure the IAC wasn't my problem. I still get surge when cold and the sucker is idling kinda high too. This is annoying at the very least. Thankfully this isn't yet my daily driver because this would really piss me off to deal with daily. Derek, my crappy luck holds and those thingies you circled are not there on my car. There's a slew of funky things connected on each side of my upper plenum that probably represent what you have there on the PS fender but I'm unsure. I have both a Haynes and Chilton manual so i'll be digging into them to see if I can figure out WTF is what here. For the record, I have a knack for buying oddball-year cars, and this fucker is no exception. Pardon my course language but I am a plumber, which is kind of akin to being a sailor, or auto mechanic, and involves plenty of swearing. I'll booger around with this bastard and see what I get. Ugh...

My guess is someone may have altered you car before you go to it so a good EVTM (manual) that has vacuum info, etc is in order. Check EBAY for one. Once you see how it is SUPPOSED to be you can compare and make the needed changes. That will save you from going nuts because you'll be starting off as it was designed.