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1G 1G Warm start issue on occasion

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MyTalonTSi1991

Proven Member
48
28
Jul 12, 2019
Bloomington, Illinois
I’ve been chasing down a random stall issue and after replacing the 02 sensor that issue is resolved.

Now I’ve got a strange warm start issue. I can drive the car a few miles, leave it parked for 15 minutes and when I go to start the car it just cranks, if I give it gas while cranking it will sputter sometimes and then come to life and be fine. It only does this on occasion and not every time. Used it to run errands today and out of 6 stops only one stop did it do this. My buddy suspects vapor lock.

I’m at a loss, new idle motor, coolant temp sensor, PTU, plug/wires, proper idle set method grounding the proper terminals. I feel like I’m so close to having this thing fully sorted. Took it on a 20 mile ride in the country this evening and it ran perfectly.

Any advice to solve this one would be awesome. Thank you!
 
Solution
So my issue has been resolved. Discovered my car had a manual trans ECU from an AWD car in it. Tried a FWD auto ECU and it didn’t work, that was replaced with an AWD auto ECU and the car is working beautifully. Noticed that the fuel pump relay had a cracked tab on it, went ahead and picked one of those up at the u-pull near me and my car is working perfectly. No stalling and running as intended. Thanks everyone for the input!
Most likely a leaking injector. When you stop with the car hot enough fuel leaks into the manifold and boils away to produce a mixture too rich to burn. If you park overnight that dissipates and it'll start easily. If conditions or the engine are cold when you stop you get a puddle of fuel but it mostly doesn't vaporize and the car will start normally when fuel is sprayed in -- the excess is consumed gradually after starting.

The classic vapor lock of carburetor days was fuel boiling in the line to the carb or the carb itself so no liquid in the bowl to go through the jets into the carb throat. This is quite a different animal, more like 'flooding' which used to happen if you pushed the accelerator pedal more times than necessary (sometimes even just once if warm) when starting. Just as for that problem it may help to press the accelerator and hold it until the engine fires.

The cure is to identify and clean or replace the stuck open injector. This may also have been a contributor to your stalling problem.

Hard starting when hot can also be a failing ignition transistor or coil but usually you'd see a severe miss sometimes too: Without that and with hitting the gas pedal helping (it doesn't actually squirt any gas in these cars) the place to look is injectors.
 
Most likely a leaking injector.

Thank You! Is there a good way to check which injector(s) are leaking? I’ve got a scope camera if that’s what I need.

Also, is there a guide to replace the injectors?
 
Last edited by a moderator:
I don't think there's a great way to pin this down to one injector. The ways I know about are:

1. Pull the fuel rail but leave it hooked up. Make sure the injectors are firmly gripped -- if in doubt new 0-rings might be a good idea. Energize the fuel pump with a jumper from the battery to the fuel pump check connector. The bad boy will drip fuel.

Disadvantages: You're going to spill some fuel and you're going to make sparks connecting the check connector to the battery. Definitely a bad idea in a garage, not that great outside.

2. Inspect the spark plugs. Look for one that's darker (due to soot from richer mixture) than the others.

Disadvantages: No guarantee that you'll be able to see a difference if the leak is small or intermittent.

And in any case many of our cars have now had the injectors replaced and matching exactly what's in there now (OEM or aftermarket, standard or 'high performance' ...) is shakier than it would have been 20 years ago. Injectors should be matched sets -- the ECU is working on an average air/fuel ratio and if the injectors aren't the same the mixture won't be perfect for any of them.

I would definitely do some testing hoping to confirm the problem but considering the difficulties of reliable testing and then matching what you've got I would consider replacing the whole set even if nothing found. Typically $50-250. Or probably around $1000 if OEM from Mitsu.

Replacement is pretty straightforward but since my cars are 2g or other models entirely someone else should talk you through it. Just one point: Before you start removing the rail, locate the black plastic insulators that are between the rail and the intake manifold. Those are loose and can easily fall down into another dimension as you take out the bolts and remove the rail. What I do is back out the bolts to the last few turns, pull the rail back as far as it'll go, and then use one hand to take out a bolt while grabbing its insulator with the other. Repeat 2x more.

It's my theory that there's a wormhole connecting my car to some other guy's project somewhere in the world and when I drop an insulator, it pops out maybe in the UK. But this is just a theory based on the fact that about half the time I can't find the dropped item.

And sometimes I find parts I don't remember dropping. This has nothing to do with being an old guy.

I expect you'll have to disconnect the fuel rail at one end -- likely the regulator. It'll spill up to about 1/4 cup of fuel so work outdoors and have rags there to catch it.

The stuff above the rail has to be removed; if that includes plug wires then be sure to mark them so you can easily get them back it the right places.
 
I don't think there's a great way to pin this down to one injector. The ways I know about are:

1. Pull the fuel rail but leave it hooked up. Make sure the injectors are firmly gripped -- if in doubt new 0-rings might be a good idea. Energize the fuel pump with a jumper from the battery to the fuel pump check connector. The bad boy will drip fuel.

Disadvantages: You're going to spill some fuel and you're going to make sparks connecting the check connector to the battery. Definitely a bad idea in a garage, not that great outside.

2. Inspect the spark plugs. Look for one that's darker (due to soot from richer mixture) than the others.

Disadvantages: No guarantee that you'll be able to see a difference if the leak is small or intermittent.

And in any case many of our cars have now had the injectors replaced and matching exactly what's in there now (OEM or aftermarket, standard or 'high performance' ...) is shakier than it would have been 20 years ago. Injectors should be matched sets -- the ECU is working on an average air/fuel ratio and if the injectors aren't the same the mixture won't be perfect for any of them.

I would definitely do some testing hoping to confirm the problem but considering the difficulties of reliable testing and then matching what you've got I would consider replacing the whole set even if nothing found. Typically $50-250. Or probably around $1000 if OEM from Mitsu.

Replacement is pretty straightforward but since my cars are 2g or other models entirely someone else should talk you through it. Just one point: Before you start removing the rail, locate the black plastic insulators that are between the rail and the intake manifold. Those are loose and can easily fall down into another dimension as you take out the bolts and remove the rail. What I do is back out the bolts to the last few turns, pull the rail back as far as it'll go, and then use one hand to take out a bolt while grabbing its insulator with the other. Repeat 2x more.

It's my theory that there's a wormhole connecting my car to some other guy's project somewhere in the world and when I drop an insulator, it pops out maybe in the UK. But this is just a theory based on the fact that about half the time I can't find the dropped item.

And sometimes I find parts I don't remember dropping. This has nothing to do with being an old guy.

I expect you'll have to disconnect the fuel rail at one end -- likely the regulator. It'll spill up to about 1/4 cup of fuel so work outdoors and have rags there to catch it.

The stuff above the rail has to be removed; if that includes plug wires then be sure to mark them so you can easily get them back it the right places.
Thank you! Took a look in the cylinders with my scope, #4 I think is where the bad injector is. I was able to order a new set so I just went ahead and did that and Im hoping this fixes the issue once and for all!
 
Still chasing down this issue. Replaced all 4 injectors and also replaced the PCV valve. Took the car out for a drive, initial drive was fine, brought it home, let it sit 15-20 minutes and tried starting again, same issue, struggles to start like its vapor locked again.

PCV hose was cracked so I replaced that and inspected other vacuum lines and no other leaks and the engine when running. Took it out for a good long drive, everything seemed great and then on the way home it bucked a few times dropping the tach to zero and then I gave it some gas and it came back to life.

Did an ECU swap with one I had and the behavior is the same. At a complete loss now, I was certain it was the injectors. Could it be the coil? That's about the only thing I haven't replaced. I feel like I have to be getting close.

TMOLogger shows everything looking good, did the injector test and that was good. The car idles fantastic and is running better than it has at any point since I've had it, just these little hiccups I get while driving that I just cant figure out. Even a couple local shops have no clue.
 
I don't think there's a great way to pin this down to one injector. The ways I know about are:

1. Pull the fuel rail but leave it hooked up. Make sure the injectors are firmly gripped -- if in doubt new 0-rings might be a good idea. Energize the fuel pump with a jumper from the battery to the fuel pump check connector. The bad boy will drip fuel.
I would not recommend this. You would need to be real specific as to what's holding them to the rail. 40 psi will shoot an injector out easily.
Disadvantages: You're going to spill some fuel and you're going to make sparks connecting the check connector to the battery. Definitely a bad idea in a garage, not that great outside.

2. Inspect the spark plugs. Look for one that's darker (due to soot from richer mixture) than the others.

Disadvantages: No guarantee that you'll be able to see a difference if the leak is small or intermittent.
Better still just smell the plugs. Any leaking into a cylinder your nose will find it.
And in any case many of our cars have now had the injectors replaced and matching exactly what's in there now (OEM or aftermarket, standard or 'high performance' ...) is shakier than it would have been 20 years ago. Injectors should be matched sets -- the ECU is working on an average air/fuel ratio and if the injectors aren't the same the mixture won't be perfect for any of them.

I would definitely do some testing hoping to confirm the problem but considering the difficulties of reliable testing and then matching what you've got I would consider replacing the whole set even if nothing found. Typically $50-250. Or probably around $1000 if OEM from Mitsu.

Replacement is pretty straightforward but since my cars are 2g or other models entirely someone else should talk you through it. Just one point: Before you start removing the rail, locate the black plastic insulators that are between the rail and the intake manifold. Those are loose and can easily fall down into another dimension as you take out the bolts and remove the rail. What I do is back out the bolts to the last few turns, pull the rail back as far as it'll go, and then use one hand to take out a bolt while grabbing its insulator with the other. Repeat 2x more.

It's my theory that there's a wormhole connecting my car to some other guy's project somewhere in the world and when I drop an insulator, it pops out maybe in the UK. But this is just a theory based on the fact that about half the time I can't find the dropped item.
You are correct. Same reason why sometimes you find an extra 10mm socket. Wormhole.
And sometimes I find parts I don't remember dropping. This has nothing to do with being an old guy.

I expect you'll have to disconnect the fuel rail at one end -- likely the regulator. It'll spill up to about 1/4 cup of fuel so work outdoors and have rags there to catch it.

The stuff above the rail has to be removed; if that includes plug wires then be sure to mark them so you can easily get them back it the right places.
 
Be sure to read at that link down to the post by Khardy. He's got the only story that hangs together, namely a leak in the fuel system that allows pressure to fall to zero (or near) after stopping. In his case the leak was in the fuel pump assembly in the tank but it could also be in the fuel pressure regulator or an injector. Or anywhere else on the pressure side -- a pinhole in the line under the car, a cracked flex line, a bad flare fitting or worn O-ring at the rail ... In the case of an injector you'd get both flooding of one cylinder and a vaporlock in the rail.

I probably had this problem a few years back on an Expo. (4g93 engine) When hot it would sometimes be gawdawful hard to start but once started it was fine. Eventually I found two things: A leaking injector and a leak in the flexible fuel pressure line to the rail. I didn't really focus on the fuel line as contributing to the hard start -- I replaced it because fuel leaks are a no-no. But anything that causes a loss of pressure is going to lead to vaporlock under extreme conditions.

The good news about fuel leaks is that your nose will find almost all of 'em.
 
I am still chasing this one down but I think I might be getting closer. I cleaned the throttle body, replaced the coil, replaced the 4 injectors, replaced the fuel filter and the fuel rail inlet o-ring. I've got the car running and driving better than it has recently but I am still getting the occasional hard start on a warm start and once it gets started it will stall a few times before its happy again. Also still get the occasional hiccup during faster acceleration. Checked plugs, they are gapped to .28, all are looking uniform. Could I be dealing with bad fuel? Got about 1/4 a tank so going to let it run down until the light comes on and put fresh ethanol free premium in it. Could I also be looking at a bad MAF? TMO Logger shows an accurate intake air temp so I assume it to be functional, but maybe its not? I feel like I'm so close here to having this car fully sorted.
 
What does your TPS look like in the log and your idle switch?
I assume that when the car hiccups you're not getting a CEL like the ECU just rebooted.

With these cars being being antiques now everything is suspect. You have a lot of new parts controlled and connected by old ones.
 
What does your TPS look like in the log and your idle switch?
I assume that when the car hiccups you're not getting a CEL like the ECU just rebooted.

With these cars being being antiques now everything is suspect. You have a lot of new parts controlled and connected by old ones.
TPS reading look normal, not getting any CEL or relay clicking supporting the ECU rebooting. I have multiple ECU's and the car has the same behavior regardless which one is there. I keep going back to bad fuel but I feel like the only thing to do is throw the parts cannon at it. The behavior was the same with the old fuel pump and the new one so I can cross fuel pump off that list. Ill go back and look at the TPS a little closer in TMO Logger.
 
I am still chasing this one down but I think I might be getting closer. ... but I am still getting the occasional hard start on a warm start and once it gets started it will stall a few times before its happy again. Also still get the occasional hiccup during faster acceleration.
As above, hard starts when warm are usually leaks. But the stalling a few times doesn't fit that. I wonder about the throttle body settings -- Closed Throttle Position Switch and BISS.

Quick check on those settings: With car warmed and at idle, no accessories on, turn headlights on high and off a few times and note change of RPM. Should be almost imperceptible. Turn A/C on full, engine RPM should go up about 100.
 
Did the RPM test, headlights barely dip it for a
Second, AC jumps it. I find the issue is getting worse. Today I drove it to work, ran an errand for an hour and when I came back out the car started and on the way home it started bucking and the tach was going crazy while I was driving while I could feel the motor sputtering. Once it got going it smelled really bad, popping and a small backfire before it died again. Had to 2 pedal it once it finally restarted and then it was perfectly fine the rest of the way home. Has a rock auto FPR, could that be the issue? Inspected the FPS and the terminals were a dirty so I cleaned those. Strong vacuum at the line to the FPR….I’ve got no clue. Leaning towards re-listing it for sale at a lower price and let someone else who knows what they are doing take a crack at it.
 
It's good news that it's getting worse. Intermittent problems are the pits to troubleshoot but as it gets worse eventually the thing will suddenly jump out and yell "Here I am!"

What's going on here is you had multiple problems and you are gradually nailing them. This is all but universal with these cars. It's not just Steve's comment that "You have a lot of new parts controlled and connected by old ones"; it's also that multiple mechanics with widely varying skill levels have done things and not all of them were right. Pretty much what you're experiencing is how it goes.

One of my two Eclipses had bad plug wires and a bad injector, the other had a bad coil. Both of them had misadjusted TPS so that the closed throttle position switch didn't close and both had the BISS cranked to get the thing to idle. And that's just the worst engine stuff -- there was lots more ... wrong ATF in the auto one, worn out front end parts, one was lowered so much I couldn't figure out how to change the oil. You just keep chipping away and little by little it goes.

I'm assuming you've looked for codes and there is nothing. Have you gotten some kind of log of one of these episodes where "on the way home it started bucking and the tach was going crazy while I was driving while I could feel the motor sputtering. Once it got going it smelled really bad, popping and a small backfire before it died again. Had to 2 pedal it once it finally restarted" ?

That actually does sound like water in the gas. Did that tankful come from a high volume station or a two-pump Podunk Service place? I gave up buying non-ethanol gas when the only local station that has it sold me a load with water in it and froze up my fuel line at 2 AM forty miles away over the mountains.

The other obvious possibility is an intermittent -- some connector that's about to fall off, a wire that's broken but still mostly makes contact, or something like that.

As to passing it on to someone else only you can make that decision but you've made a lot of progress and there's no guarantee that another old sports car will be a bit better.

Personally I'd keep taking data. When you get near empty -- do you know that the low fuel warning light works? -- fill it at a high volume station. Bad gas is NOT rare.
 
It's good news that it's getting worse. Intermittent problems are the pits to troubleshoot but as it gets worse eventually the thing will suddenly jump out and yell "Here I am!"

What's going on here is you had multiple problems and you are gradually nailing them. This is all but universal with these cars. It's not just Steve's comment that "You have a lot of new parts controlled and connected by old ones"; it's also that multiple mechanics with widely varying skill levels have done things and not all of them were right. Pretty much what you're experiencing is how it goes.

One of my two Eclipses had bad plug wires and a bad injector, the other had a bad coil. Both of them had misadjusted TPS so that the closed throttle position switch didn't close and both had the BISS cranked to get the thing to idle. And that's just the worst engine stuff -- there was lots more ... wrong ATF in the auto one, worn out front end parts, one was lowered so much I couldn't figure out how to change the oil. You just keep chipping away and little by little it goes.

I'm assuming you've looked for codes and there is nothing. Have you gotten some kind of log of one of these episodes where "on the way home it started bucking and the tach was going crazy while I was driving while I could feel the motor sputtering. Once it got going it smelled really bad, popping and a small backfire before it died again. Had to 2 pedal it once it finally restarted" ?

That actually does sound like water in the gas. Did that tankful come from a high volume station or a two-pump Podunk Service place? I gave up buying non-ethanol gas when the only local station that has it sold me a load with water in it and froze up my fuel line at 2 AM forty miles away over the mountains.

The other obvious possibility is an intermittent -- some connector that's about to fall off, a wire that's broken but still mostly makes contact, or something like that.

As to passing it on to someone else only you can make that decision but you've made a lot of progress and there's no guarantee that another old sports car will be a bit better.

Personally I'd keep taking data. When you get near empty -- do you know that the low fuel warning light works? -- fill it at a high volume station. Bad gas is NOT rare.
I considered bad gas, but I had a similar problem last summer but it seems much worse this summer. I filled it up with a full tank just in time to store it for the winter and then figured I was dealing with a bad 02 sensor so replaced that over the winter and then the car ran great for a couple months and now its back to running like garbage to the point I cant even drive it! Got ahold of an OEM FPR and the local salvage yard has several DSM's so ill grab a FPS. May see about cleaning the 02, doubt that does anything but ill try!
 
So I’ve replaced the FPR, FPS and tracked down a new 02 sensor….car still gets unhappy after it’s been driven. I have 2 ECU’s and the same behavior on both. I have a spare TCU but can’t imagine that has anything to do with the motor. I could buy another ECU but not sure that’s going to do anything at this point. Throwing in the towel at this point, can’t keep throwing money at it.
 
So I’ve replaced the FPR, FPS and tracked down a new 02 sensor….car still gets unhappy after it’s been driven. I have 2 ECU’s and the same behavior on both. I have a spare TCU but can’t imagine that has anything to do with the motor. I could buy another ECU but not sure that’s going to do anything at this point. Throwing in the towel at this point, can’t keep throwing money at it.
Maybe just take a step back and take another look with fresh eyes and mind later. I know that’s helped me a lot in the past with many things in life. Frustrating though, I’m sorry she’s being such a b@&tch.
 
Maybe just take a step back and take another look with fresh eyes and mind later. I know that’s helped me a lot in the past with many things in life. Frustrating though, I’m sorry she’s being such a b@&tch.
Great advice! I’ve been so mad at it I haven’t even looked at it the last week. Started thinking this weekend and went back to a video I made of the same issue last year and noticed a common theme , the fuel gauge was under 1/4 tank at that time, it’s at 1/4 tank this time. Starting to wonder if my issue is in the fuel pump assembly and maybe it’s just happier having a full tank of gas. Figured this week I’ll fill up a couple 5 gallon cans and see what happens.
 
... went back to a video I made of the same issue last year and noticed a common theme , the fuel gauge was under 1/4 tank at that time, it’s at 1/4 tank this time. Starting to wonder if my issue is in the fuel pump assembly and maybe it’s just happier having a full tank of gas. Figured this week I’ll fill up a couple 5 gallon cans and see what happens.
You've looked for leaks, right? Checked every fitting from the fuel rail back to the connection of the steel line back by the tank? A leak will cause most of these symptoms.

If indeed your car is 'happier with a full tank of gas' then the problem is in the fuel tank and should be easy to find. I would do exactly what you've planned: Fill it and drive it until the problem strikes again. Then I would take out the fuel pump -- not a very hard job, might take you an hour the first time -- and study how the fittings on the bottom join the pump. If something is loose or cracked there, then maybe it can suck air when a low tank sloshes around and the pump sucks air. A cracked hose from the pump to the fitting in the top of the assembly can give you a leak that cannot be found from outside.
 
You've looked for leaks, right? Checked every fitting from the fuel rail back to the connection of the steel line back by the tank? A leak will cause most of these symptoms.

If indeed your car is 'happier with a full tank of gas' then the problem is in the fuel tank and should be easy to find. I would do exactly what you've planned: Fill it and drive it until the problem strikes again. Then I would take out the fuel pump -- not a very hard job, might take you an hour the first time -- and study how the fittings on the bottom join the pump. If something is loose or cracked there, then maybe it can suck air when a low tank sloshes around and the pump sucks air. A cracked hose from the pump to the fitting in the top of the assembly can give you a leak that cannot be found from outside.
I have checked for leaks and dont have any that I can smell or see. Last summer when the issue started I had the fuel pump replaced with a Denso and fuel filter replaced, shop said all looked good in the fuel tank at least as of last August per the mechanic.
 
The mystery continues. Filled it with a full tank of 93 octane, replaced the gas cap, 02 sensor, fuel solenoid and EGR solenoid as well as a known good PTU. Took the car on a 24.1 mile drive and it did fine. Thinking whatever my issue is must be inside the fuel tank when the fuel gets low. I’ll keep driving I and see how it goes!
 
So my issue has been resolved. Discovered my car had a manual trans ECU from an AWD car in it. Tried a FWD auto ECU and it didn’t work, that was replaced with an AWD auto ECU and the car is working beautifully. Noticed that the fuel pump relay had a cracked tab on it, went ahead and picked one of those up at the u-pull near me and my car is working perfectly. No stalling and running as intended. Thanks everyone for the input!
 
Solution
It sounds like the fuel pump relay was intermittent. Sure 'nutt, if your fuel pump stops once in a while you'll have stalls! Usually a wrong ECM for the model (but right for the engine) will only cause modest performance problems.

Glad you got it fixed!
 
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