North American Turbocoupe Organization



Stalling issue
Rob H Offline
Member
#1
When I first start the car, it runs a bit rough and low rpm.
If I take it out before fully warmed up, it stalls.
I drive up the road, and gear down to a stop sign, the car dies. Over and over again. It's a dangerous situation in some instances as I lose power brakes and steering. So far I have always been able to restart the vehicle. Usually right away, other times with a bit of frantic cranking watching traffic come at me.
Any thought?
This also happens sometimes when warmed up, but when the car has sat for a good five minutes or so.
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Jeff K Offline
Administrator
#2
As a start, remove the IAC, blast it out good with MAF / TB cleaner and after it dries put a drop of oil on the shaft where it enters the solenoid part of the IAC.

When engine is warmed up and running unplug IAC electrical connector. If engine stalls base idle is set too low. I like to set base idle to around 800 RPM with engine fully warmed up.

Could also be a vacuum leak not bad enough to set the CEL wit a code 41. Carefully check all vac lines for looseness, cracks, disconnected hoses, etc
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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BigJake Offline
Member
#3
Also check timing ?
1987 Thunderbird Turbo Coupe 5 speed Boosting 25 PSI with Boport/Stinger parts !
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Rob H Offline
Member
#4
Thanks, I will give all that a try and report back!
I've had this problem a while, but never this bad. It never used to stall, just would ALMOST stall Smile
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Rob H Offline
Member
#5
Hi there, finally got the car back out after a long winter, I hope there is no statute of limitations when it comes to working through problems you've asked about!
Everything here pretty much is closed, there is curbside pickup at some stores, but the website for the store is so busy, can't even do that, so I was unable to get MAF cleaner, I'll try again later tonight to see if traffic dies down some.
In the meantime though, I thought I would at least try to acquaint myself with the TPS & IAC as I didn't even know where they were.
A couple things I noticed...the connector on my IAC only has two wires...I am following Andrews idle/tps adjustment guide, and it says that the electrical connector on the IAC has three wires. It also said the same thing on the stinger performance site. Mine, assuming I am looking at the right thing only has two...
I took the car out and got it warmed up, and unplugged that connector. Right away the car would not start without holding down the gas some and would stall immediately if I let go. I noted that the idle adjustment screw was turned out pretty much the whole way. I wondered if possibly it was just way off, so I turned it in, and was able to get the car to start without holding the gas. To get it to idle at around 800 required the screw to be turned in almost entirely. Turning it all the way in, it idled at 1000.
Restarting with the connector it now idles quite high, almost 1200...
Of course I did not start with the first thing you said, so I've got that in mind, I just thought I would share that in case that means anything, but also to tell you about the two-wired connector. I'll get on my phone and upload a picture if I can.
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Rob H Offline
Member
#6
Picture of connector

Couldn't get a picture to display here for some reason, the link above goes to the picture though
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Jeff K Offline
Administrator
#7
IAC only has 2 wire connector. One is +12 V from the VPWR circuit. Other wire goes to the PCM. PCM uses a 40 Hz PWM (variable duty cycle square wave) to modulate how far the IAC opens to let in more or less air.

TPS has 3 wire connector. TPS voltage at closed throttle should be around .95 V and should increase smoothly to around 4.5 V at WOT. Measure between green wire and BK/W (or BK) wire. Closed TPS volts over 1.0V will cause hanging high idle. TPS volts under .4 V or so can cause stalling.

I still suspect a vacuum leak. A smoke test may be in order. I bought a party type $35 smoke machine from Wally World years ago and whipped up some adapters to route the smoke into the vacuum system. Others have used cigar smoke.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Rob H Offline
Member
#8
I got the IAC cleaned out, I don't know how dirty they're supposed to be but it's definitely a lot cleaner.
As I said in my last post it had not run correctly when removing the connector from the IAC either.
I think it sounded like it was idling a lot smoother, I have the base idle set to around 800 right now.
I'm going to test the voltage on the TPS now. I guess I'll figure it out as I go but I don't really understand about turning it.
If the base idle has a significant impact on it it definitely was way out. Maybe that itself will do something. I think it was more in the hot weather I was having problems but I guess I'll find out.
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Rob H Offline
Member
#9
Not so sure it's running any smoother, I kind of think maybe worse.
I was not able to get a reading on the tps. I'm thinking the tips on the leads for my multimeter are too short maybe. I was attempting to back probe the harness side of the connector.
As I'm cleaning up under the hood I am inspecting all hoses and wires the best I can. So far everything looks pretty good.
For vacuum leaks, do I just start at the tree and work backwards off it?
I'm curious about your party smoke machine test, how does that work?
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anasazi4st Offline
Senior Member
#10
(04-20-2020, 11:08 PM)Rob H Wrote: Not so sure it's running any smoother, I kind of think maybe worse.
I was not able to get a reading on the tps. I'm thinking the tips on the leads for my multimeter are too short maybe. I was attempting to back probe the harness side of the connector.
As I'm cleaning up under the hood I am inspecting all hoses and wires the best I can. So far everything looks pretty good.
For vacuum leaks, do I just start at the tree and work backwards off it?
I'm curious about your party smoke machine test, how does that work?

Get some map pins—they have large round plastic ball heads in various colors. Carefully pierce each wire as it enters the TPS connector, and measure from that.

A year ago I was having all kinds of trouble with my TPS—upon startup it would go immediately into WOT (wide open throttle) and would have redlined had I not shut the car off. It took me a little while to be able to get the readings and make the adjustments, but I was finally able to get it right. I don’t know how it got so messed up in the first place.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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