North American Turbocoupe Organization



Hard to start when hot
BabyBlueBird Offline
Junior Member
#1
A little back ground, I recently just deleted the EGR on my TC because the EGR valve was leaking and causing a pretty bad bogging condition. Before I deleted the EGR, the car would start when hot but you would need to give it some gas for some time before it would idle. Also when pushing the clutch in after cruising for a while the engine would stall out or bog. I thought this was 100% caused by my failing EGR valve leaking exhaust gas into the intake. Now that my EGR is deleted I am still having the same issue when the car is hot. It has zero problems starting when cold and it no longer bogs when pushing the clutch in. Deleting my EGR solved half of my problems. Not really sure what to look at for potential problems for hard starts when hot. My air filter is clean, I have good fuel and all my basic tune up items such as plugs, plug wires, base timing, cap and rotor, fuel filter are all new and in good condition. If anyone has any ideas of what to look for or common problems related to this please let me know. Car is stock besides a stinger front mount intercooler. 

Thanks in advance.
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anasazi4st Offline
Senior Member
#2
(07-24-2022, 10:56 PM)BabyBlueBird Wrote: A little back ground, I recently just deleted the EGR on my TC because the EGR valve was leaking and causing a pretty bad bogging condition. Before I deleted the EGR, the car would start when hot but you would need to give it some gas for some time before it would idle. Also when pushing the clutch in after cruising for a while the engine would stall out or bog. I thought this was 100% caused by my failing EGR valve leaking exhaust gas into the intake. Now that my EGR is deleted I am still having the same issue when the car is hot. It has zero problems starting when cold and it no longer bogs when pushing the clutch in. Deleting my EGR solved half of my problems. Not really sure what to look at for potential problems for hard starts when hot. My air filter is clean, I have good fuel and all my basic tune up items such as plugs, plug wires, base timing, cap and rotor, fuel filter are all new and in good condition. If anyone has any ideas of what to look for or common problems related to this please let me know. Car is stock besides a stinger front mount intercooler. 

Thanks in advance.

You did not mention this—but did you pull codes? I’m guessing you know about this, but just in case you don’t, see THIS. (Which also includes on the same page instructions on cleaning your EGR valve, in case you haven’t done that.)

The list of EEC-IV codes is HERE. A list of error codes pulled from the computer is often essential to diagnosing any problem.

I’m guessing that it’s not the EGR valve. Removing it might have remedied some of the problems, but my gut says if that was the problem you’d have no more issues.
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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BabyBlueBird Offline
Junior Member
#3
(07-25-2022, 02:54 AM)anasazi4st Wrote:
(07-24-2022, 10:56 PM)BabyBlueBird Wrote: A little back ground, I recently just deleted the EGR on my TC because the EGR valve was leaking and causing a pretty bad bogging condition. Before I deleted the EGR, the car would start when hot but you would need to give it some gas for some time before it would idle. Also when pushing the clutch in after cruising for a while the engine would stall out or bog. I thought this was 100% caused by my failing EGR valve leaking exhaust gas into the intake. Now that my EGR is deleted I am still having the same issue when the car is hot. It has zero problems starting when cold and it no longer bogs when pushing the clutch in. Deleting my EGR solved half of my problems. Not really sure what to look at for potential problems for hard starts when hot. My air filter is clean, I have good fuel and all my basic tune up items such as plugs, plug wires, base timing, cap and rotor, fuel filter are all new and in good condition. If anyone has any ideas of what to look for or common problems related to this please let me know. Car is stock besides a stinger front mount intercooler. 

Thanks in advance.

You did not mention this—but did you pull codes? I’m guessing you know about this, but just in case you don’t, see THIS. (Which also includes on the same page instructions on cleaning your EGR valve, in case you haven’t done that.)

The list of EEC-IV codes is HERE. A list of error codes pulled from the computer is often essential to diagnosing any problem.

I’m guessing that it’s not the EGR valve. Removing it might have remedied some of the problems, but my gut says if that was the problem you’d have no more issues.

Before I removed the egr system I pulled codes and only got back a code for turbo boost control circuit (code 81). My only thoughts are a vacuum leak that causes issues when the car is hot or my fuel pump might not be building enough pressure/ Might be bleeding pressure off.
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Jeff K Offline
Administrator
#4
Many parts stores will let you "rent" a fuel pressure gauge for a small security deposit.

Have you removed and cleaned the IAC (use throttle body cleaner) and put a drop of oil on the shaft where it enters the solenoid body?

Is the IAC a Motorcraft part? Non Motorcraft IACs are junk and often cause poor idle, surging idle, etc.

Have you checked for vacuum leaks? LOTS of places for vac leaks on these engines.
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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BabyBlueBird Offline
Junior Member
#5
(07-29-2022, 03:18 PM)Jeff K Wrote: Many parts stores will let you "rent" a fuel pressure gauge for a small security deposit.

Have you removed and cleaned  the IAC (use throttle body cleaner) and put a drop of oil on the shaft where it enters the solenoid body?

Is the IAC a Motorcraft part? Non Motorcraft IACs are junk and often cause poor idle, surging idle, etc.

Have you checked for vacuum leaks? LOTS of places for vac leaks on these engines.

IAC is brand new and a motorcraft part. Good fuel pressure. I'm chasing a vacuum leak and unfortunately I don't have a smoke tester as of now.
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SK 88 T-Bird Offline
Member
#6
I had this same exact problem several years ago, it would start and run great when engine was cold, but after engine was warmed up, when I stopped for gas or run into the store, it would struggle to start again. I did all of the above, plugs, wires, cap and rotor, timing, fuel pressure etc, etc, etc...Nothing was fixing the problem.

With the help from Jeff K and Pete D, I can't thank them enough for this, not sure if Jeff or Pete remembers me when I had this same problem in 2017. What I found causing my problem was, the signal return wire (BLK-WHT) from the engine coolant temp sensor to pin 46 at the EEC had no continuity (my knock sensor signal return also did not have continuity). If you look at the wiring diagram, at the top center, you'll see the eng coolant temp sensor (ECT). This BLK-WHT signal return wire is tied to the air charge temp and knock sensors, which if you follow that wire, it goes to the EEC pin 46. If I remember correctly and please correct me if I'm wrong, this coolant sensor lives on top of the intake manifold right between fuel injector 2 and 3. Not easy or fun to get the plug off. If you can get the plug off, unplug your battery, then disconnect plug at EEC, find pin 46 in the plug at the EEC and check continuity from BLK-WHT wire at coolant sensor plug to pin 46. If you don't have continuity, this is your problem. The computer doesn't see a signal return from the coolant sensor and thinks the engine is still cold. With that said, when you try to start the engine while the engine is hot, the computer will pump more fuel into the engine as if it were a cold engine start, therefore, flooding the engine making it difficult to get started. Now, if you confirmed that you have no continuity, unplug either the knock sensor and or the air charge temp sensor and check for the same continuity. If those check out good, this mean your coolant temp signal return wire is either broken or corroded somewhere and you should be able to jumper your ECT signal return wire to one of the other sensors that share the same signal return. If not, you'll have to find something else with a good signal return to pin 46 and get your ECT connected to that. The wiring diagram will be a huge help with that. You might find that your ECT, air charge and knock sensor signal return wires don't have continuity to pin 46. Find another wire from the diagram that has a good connection and tap into that.

It's been a while, but if I remember correctly, after confirming I had a bad signal return wire, I cut the return wire from my coolant sensor, not right at the sensor, but a little towards the back where the knock sensor is, which gives you a little working room and I cut the BLK-WHT return wire for my air charge sensor and knock sensor and tied them all together with a jumper wire and re-checked the connection back to pin 46. When all checked out good, I never to this day had a problem starting the engine when it was hot. This fix also stopped my issue with the engine wanting to almost die when coming to a stop light. My only thought on that was, I'm thinking that the computer thinks the engine is cold, it would put more fuel into the engine, causing it to flood a bit and making it run rough and wanted to die on me when coming to a stop, or as you said, just pushing the clutch in, the engine wants to die or shut down.

If you don't feel good about cutting wires, you can try to piggyback a jumper wire in the plug at the sensor and piggyback that to either the knock or air charge sensor BLK-WHT wire and give it a go, but be sure the air charge or knock sensors have a good signal return connection to pin 46. The only problem doing this is, the jumper wire can work its way out putting you back where you started. I believe you have to remove tape that covers a lot of these wires to gain access to make a good splice connection. It won't be fun as you have limited space to work with. If you have plans on removing the air intake horn, this will give you a lot more room to make this splice. After confirming that you may have a bad return wire, I would do a piggyback jumper wire first, take it for a spin, get the engine fully warmed up, shut it down and see if it will start easy from there. If all works, then eventually, you'll have to make a good connection. I piggybacked a paperclip at the coolant ECT and air charge sensor plugs, connected them with an alligator clip jumper wire to test it out, be sure to protect any exposed wires/clips from touching vehicle ground, and then I made a good splice later.

NOTE: Do both, a continuity check and an ohms resistance check. Why? because one little strand of wire may show you have good continuity, but when checking for ohms of resistance, you might find that you have very high resistance in the BLK-WHT signal wire and there might not be enough juice to get the signal back to the computer to monitor the eng temp for proper fuel flow when the engine is hot. Also, if you haven't replaced the coolant sensor in a long time, this might be a good time to replace it, I think a code will show if this sensor is bad. If the return signal wire is bad, you might still get a code for a bad coolant sensor, when it could very likely be just a bad wire.

NOTE: since you have the ECT plug off, also do a continuity/ohms check of the LT green/yellow wire from the ECT plug to pin 7 at the computer as a precautionary, mine checked out good when I tested it.

P.S. what got me through all of this until I figured this out was, when cranking the hot engine, I would put the gas pedal to the floor, which stops the fuel flow from a supposedly flooded engine, hold it there for a second and release and the engine would start. Don't have to do that anymore!! Thank you Jeff and Pete!!

I hope this fixes your problem as it did for me. Good luck, let me know how it turns out. Wiring diagram attached


Attached Files
.pdf   Thunderbird Wiring Diagram.pdf (Size: 78.24 KB / Downloads: 8)
88TC, T3/T4, .63AR, Walbro 255 pump, Ranger Roller cam, Kirban AFPR, 120 3G ALT, K&N Cone filter, Boost press set to 17PSI, Timing 10deg
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BabyBlueBird Offline
Junior Member
#7
(09-16-2022, 05:05 PM)SK 88 T-Bird Wrote: I had this same exact problem several years ago, it would start and run great when engine was cold, but after engine was warmed up, when I stopped for gas or run into the store, it would struggle to start again. I did all of the above, plugs, wires, cap and rotor, timing, fuel pressure etc, etc, etc...Nothing was fixing the problem.

With the help from Jeff K and Pete D, I can't thank them enough for this, not sure if Jeff or Pete remembers me when I had this same problem in 2017. What I found causing my problem was, the signal return wire (BLK-WHT) from the engine coolant temp sensor to pin 46 at the EEC had no continuity (my knock sensor signal return also did not have continuity). If you look at the wiring diagram, at the top center, you'll see the eng coolant temp sensor (ECT). This BLK-WHT signal return wire is tied to the air charge temp and knock sensors, which if you follow that wire, it goes to the EEC pin 46. If I remember correctly and please correct me if I'm wrong, this coolant sensor lives on top of the intake manifold right between fuel injector 2 and 3. Not easy or fun to get the plug off. If you can get the plug off, unplug your battery, then disconnect plug at EEC, find pin 46 in the plug at the EEC and check continuity from BLK-WHT wire at coolant sensor plug to pin 46. If you don't have continuity, this is your problem. The computer doesn't see a signal return from the coolant sensor and thinks the engine is still cold. With that said, when you try to start the engine while the engine is hot, the computer will pump more fuel into the engine as if it were a cold engine start, therefore, flooding the engine making it difficult to get started. Now, if you confirmed that you have no continuity, unplug either the knock sensor and or the air charge temp sensor and check for the same continuity. If those check out good, this mean your coolant temp signal return wire is either broken or corroded somewhere and you should be able to jumper your ECT signal return wire to one of the other sensors that share the same signal return. If not, you'll have to find something else with a good signal return to pin 46 and get your ECT connected to that. The wiring diagram will be a huge help with that. You might find that your ECT, air charge and knock sensor signal return wires don't have continuity to pin 46. Find another wire from the diagram that has a good connection and tap into that.

It's been a while, but if I remember correctly, after confirming I had a bad signal return wire, I cut the return wire from my coolant sensor, not right at the sensor, but a little towards the back where the knock sensor is, which gives you a little working room and I cut the BLK-WHT return wire for my air charge sensor and knock sensor and tied them all together with a jumper wire and re-checked the connection back to pin 46. When all checked out good, I never to this day had a problem starting the engine when it was hot. This fix also stopped my issue with the engine wanting to almost die when coming to a stop light. My only thought on that was, I'm thinking that the computer thinks the engine is cold, it would put more fuel into the engine, causing it to flood a bit and making it run rough and wanted to die on me when coming to a stop, or as you said, just pushing the clutch in, the engine wants to die or shut down.

If you don't feel good about cutting wires, you can try to piggyback a jumper wire in the plug at the sensor and piggyback that to either the knock or air charge sensor BLK-WHT wire and give it a go, but be sure the air charge or knock sensors have a good signal return connection to pin 46. The only problem doing this is, the jumper wire can work its way out putting you back where you started. I believe you have to remove tape that covers a lot of these wires to gain access to make a good splice connection. It won't be fun as you have limited space to work with. If you have plans on removing the air intake horn, this will give you a lot more room to make this splice. After confirming that you may have a bad return wire, I would do a piggyback jumper wire first, take it for a spin, get the engine fully warmed up, shut it down and see if it will start easy from there. If all works, then eventually, you'll have to make a good connection. I piggybacked a paperclip at the coolant ECT and air charge sensor plugs, connected them with an alligator clip jumper wire to test it out, be sure to protect any exposed wires/clips from touching vehicle ground, and then I made a good splice later.

NOTE: Do both, a continuity check and an ohms resistance check. Why? because one little strand of wire may show you have good continuity, but when checking for ohms of resistance, you might find that you have very high resistance in the BLK-WHT signal wire and there might not be enough juice to get the signal back to the computer to monitor the eng temp for proper fuel flow when the engine is hot. Also, if you haven't replaced the coolant sensor in a long time, this might be a good time to replace it, I think a code will show if this sensor is bad. If the return signal wire is bad, you might still get a code for a bad coolant sensor, when it could very likely be just a bad wire.

NOTE: since you have the ECT plug off,  also do a continuity/ohms check of the LT green/yellow wire from the ECT plug to pin 7 at the computer as a precautionary, mine checked out good when I tested it.

P.S. what got me through all of this until I figured this out was, when cranking the hot engine, I would put the gas pedal to the floor, which stops the fuel flow from a supposedly flooded engine, hold it there for a second and release and the engine would start. Don't have to do that anymore!! Thank you Jeff and Pete!!

I hope this fixes your problem as it did for me. Good luck, let me know how it turns out. Wiring diagram attached

Your problem matches mine to a T. I will give everything a try, I did just replace the coolant sensor with a known good one back in April. At first I thought it was vacuum leaks but I have since fixed all of those and I also fixed my leaking egr. All new intake manifold gaskets (not fun to do while the engine is in the car). All the basic tune up items have been replaced within the last year (motor craft parts where there available) and timing has been checked, good fuel pressure too. Currently redoing the cooling system on the car. Thank you for the advice I’ll let you know if it fixes my problem.


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SK 88 T-Bird Offline
Member
#8
Sounds like you are doing all the right things to narrow the problem down, as I did the same. Being that said, I'm feeling good about what I mentioned regarding the signal return wire might be causing your problem. I would try checking the knock sensor and the air charge sensor, as they are maybe a little easier to get to those plugs on the lower half of the intake (they point towards the firewall). Check not only for continuity on the BLK-WHT wire to pin 46 at the EEC, but also do an OHMS of resistance, which checks the integrity of that wire. If you don't have continuity on those wires, it's a pretty good chance, you won't have continuity on the engine coolant sensor either. If this turns out to be your case, here is a quick thing you can do without cutting into wires yet. Try this, confirm that you have a good signal return connection at the EEC IV self test connector BLK-WHT wire to pin 46 at EEC (this connector is that black rectangle plug that sits above the left fender connected to nothing along with a single pigtail with it). If that all checks out good, then with either the knock sensor or the air charge sensor unplugged, run a jumper wire from the BLK-WHT wire to the EEC IV self test connector BLK-WHT wire. After making that connection, now re-check the BLK-WHT wire at your engine coolant sensor and see if you are now getting continuity back to pin 46. If you are, now plug in your eng coolant sensor plug, leaving the jumper wire still connected between the knock sensor and EEC test plug and take the car for a drive and get her warmed up. Shut engine down for a minute or two and try to start the Bird again. If this corrects your problem and the car starts easily when warmed up, now you'll want to make a solid connection. 

Note: if you didn't have a good signal return at your knock sensor or air charge to pin 46, this would tell you that your knock sensor and/or air charge sensor wasn't sending signals back to the EEC, therefore, not working either.

Remember, a signal return is a signal return no matter where you make a solid connection, as all your signal returns share the same return to pin 46. Looking at the wiring diagram, you'll see that the knock, air charge and the engine coolant sensor return signal wires meet at a junction (no black dot is shown on diagram for this junction point), then a single wire goes from that connection to another much bigger signal return connection (this has a black dot showing that junction connection). What I believe is, that single wire going between the two junctions is either broken or corroded. You can look for that three wire connection (good luck) and fix it, or do what I did, by running a jumper wire to one of the three connectors mentioned above to a known good signal return wire elsewhere. After I did that, I had good continuity to all three connectors.

Keep in mind, which ever BLK-WHT wire you cut at whatever sensor you choose, those wires and the new jumper wire have to all be connected together and then the other end of your jumper wire will get connected to a known good signal return, such as the EEC IV self test connector BLK-WHT wire. It might take a while to do this, as there isn't a lot of room to work with in this area at the three sensors mentioned. Unravel the black tape and plastic loom to expose wires and make your connection in an area that will make it easier for you. Do the temporary connection first as mentioned above and see if this fixes your problem, then move on from there to make a final solid connection. 

Good luck and take your time
88TC, T3/T4, .63AR, Walbro 255 pump, Ranger Roller cam, Kirban AFPR, 120 3G ALT, K&N Cone filter, Boost press set to 17PSI, Timing 10deg
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