Hot stalling (and hard to restart)

Hi Gang-

It's been a long time since I've dropped in to say hello! Hope everyone is well. Life has a way of taking over, and with a couple of little kids, I don't have nearly as much time to spend with my cars as I used to... but I have run into a problem with my X1/9 that I want to take care of before it gets put away for the winter.

My car is an 83 (fuel injected). Fuel pump is an electric one. Liner from the engine lid has been removed, so I have much better air flow than stock. I also have a K&N filter installed.

On a hot day, the car will start to sputter a slow speeds or when stopped at a light, and will usually stall. Sometimes I can recover it before it stalls by quickly pumping the gas, but that's not often... usually it just dies there in traffic, and won't start again until it's cooled off a bit. Thermostat works and doesn't indicate overheating.

Once the car has decided it's cool enough, it starts right back up like nothing happened.

Vapor lock perhaps? I was thinking about ordering some heat shield tape to wrap the fuel pump and lines with, but if there's a better fix (or different diagnosis!!) I'm certainly open to it!

EDIT: Join date 2012 LOL... I've been around since the 90s. In perusing the forums there don't appear to be many of the old timers still hanging around here.

'83 would normally be Fuel Injected, I take yours is carb'd? Since ALL FI cars have electric fuel pumps? I don't know much about carb'd cars. My FI '81 will run all day in the heat and not give a rip, though it sometimes restarts a little weird when warm, runs rough for a second or two (until the fuel flushes through the system and gets the vapor out I assume).
So, is this carb'd?

Still F.I.?

Yes, mine is FI. Updated the original post

Yup. That's what makes this sort of an odd problem...

Fixed original post to reflect this.

What temp does it run at? An idling FI car at proper temp "can't" vapor lock I don't think, the fuel constantly flows.

Number one culprit is the Temp Sensor II in the thermostat housing. check it for proper hot resistance:

7,000 to 12,000 OHMS at 14ºF
2,000 to 3,000 OHMS at 68ºF
250 to 400 OHMS at 176ºF

jvandyke said:

What temp does it run at? An idling FI car at proper temp "can't" vapor lock I don't think, the fuel constantly flows.

Click to expand...

That was my thought too, but that's exactly the behavior. If the gauge is reading right, it's smack in the middle (what's that, 160? I'm at my office and the car is at home).

Where is that located?

Edit: Rock Auto has a bunch of different ones, for as little as $6.73. I can't see spending $30+ for the ones from our "normal" suppliers.
http://s295.photobucket.com/user/drsfmd/media/x19tempsensor_zpsa228b38c.jpg.html

might want to check it at the ECU, take harness off the unit and check it at the pins in the harness, this way your not only checking the sensor, you're checking the wires to and from it as well, there have been many instances of corrosion in the harness which will throw off the ECU as resistance increases,
this will help, tells you which pins to use
http://xwebforums.com/wiki/index.php?title=FuelInjectionTroubleshooting

for instance:
http://xwebforums.com/wiki/images/5/55/Fi15.jpg

pin 13 and 5? I can't read it very well, looked it up in my downloaded manual, yep, 5 is ground for the coolant temp sensor and 13 is the other side, if you pull the connector off the ECU, put a meter on 5 and 13 it should read with in spec, go drive, get the engine nice and toasty and repeat, the resistance should change, it's a cheap part but often it's the wiring so check for loose and corroded connectors at the sensor (i had corrosion on the ground wire INSIDE the harness!)

are these the correct resistance values?
http://xwebforums.com/wiki/images/d/da/Fi75.jpg

Doc said:

That was my thought too, but that's exactly the behavior. If the gauge is reading right, it's smack in the middle (what's that, 160? I'm at my office and the car is at home).

Click to expand...

in the middle would be about 190, should be about 185 but that's not to far above normal (provided the gauge is accurate) to be bothersome I don't think

here's a recent thread with a pic of testing at the ECU pins (different pins but same idea)
http://xwebforums.org/showpost.php?p=216547&postcount=84

The ones with the round plug are the sender for the instrument panel temp gage.

The ones with the rectangular connector and two small male pins within are the correct fuel injection system CTS (coolant temp sensor) and this is located in the thermostat housing at the trans end of the head.

Yep, no old-timers here, just us spring chickens...

My first thought should probably be the last thing you do.

The first thing would be to walk through the FI Troubleshooting Guide... Go here:

http://www.angelfire.com/wa2/fits/index.html#ljetguide

Sometimes it takes a few tries to download... but start with Page 15, "Car won't start when HOT".

Working with that, and the suggestions from other members here... If that doesn't fix it... then the last thing I would do is pull all the injectors (5) and have their spray patterns analyzed and repaired or replaced.

Wishing you a fast and inexpensive resolution...

Doc said:

Where is that located?

Edit: Rock Auto has a bunch of different ones, for as little as $6.73. I can't see spending $30+ for the ones from our "normal" suppliers.
http://s295.photobucket.com/user/drsfmd/media/x19tempsensor_zpsa228b38c.jpg.html

Click to expand...

Shouldn't matter where it comes from but verify you need it first. Simple resistance test at cold and then warm is too easy not to do. You might find that pulling the connector off the sensor reveals green smudge corrosion at the pins or wires and red (green and white) flags should raise.
This is the infamous fuel injection connector with the wire bail that is a pain to release and then it bends and breaks so if it's nasty, replace with the press and release style, I did this to all my FI connectors.

Similar issue encountered

Mine was doing the same. When the engine was warm I would have a hard time starting it or at a stop keeping it idle. I replaced the temp sensor adn other items but not the ECU or cold start.

Ty worked on my car and de-bugged it and the car runs fine now. I think in my case my alternator was not putting out enough amps. Ty might be able to chime in since he did some other work on it.

Good luck.

The ECU on my car is now 15 years old, but it was NOS, and has only had about 1000 miles of use.

I'm going to change the temp sensor without even testing the old one... my local NAPA has the sensor for less than 10 bucks.

The photo is one I grabbed online, not my car, but the area I've circled in red is where that sensor is located, correct? I tore the house apart looking for my factory manual, and it was no where to be found (of course, it didn't occur to me until just now to check in the front truck of the car, and that's probably where it is).

http://i295.photobucket.com/albums/mm158/drsfmd/x19-engine_zpsaf3ed15d.jpg

That's the cold start valve. The temp sensor is in the thermostat housing, white connector.

If you don't test it, and the new one, you may not fix it but you won't know why. Testing is easy and the type of diagnostic you will need to do anyway on other parts.

budgetzagato said:

That's the cold start valve. The temp sensor is in the thermostat housing, white connector.

If you don't test it, and the new one, you may not fix it but you won't know why. Testing is easy and the type of diagnostic you will need to do anyway on other parts.

Click to expand...

Ugh. I'll have to figure out where that is... I've never needed to look at the cooling system (other than flush and fill).

Edit: Wait, I have to drain the cooling system to do this don't I? ****. Oh well... I guess I'll take it to my mechanic... I'm not going to do that in my backyard, and I don't want to end up stranded if I try to take the car down to my warehouse (45 minutes from my home).

It's easy to get to, relatively. Above bell housing, might want to take the air cleaner can off for better access. If you have the new one ready to go you can take out the old, quick pop in the new and you'll only lose a little coolant. Burp it after it's been running for a bit and no issue. BUT, it it's wiring the new sensor won't fix it, unless you simply clean up connections during the swap, which is possible. You can just take the connector off, look at it and put it back on and go for a ride. Sometimes just removal and replace cleans up the contact points and your good to go for another couple decades.
crude pict of a carb'd car but it's in the red circle area