I just wandered in this topic. The story of how the car starts and runs fine when it's hot and cold but won't start warm gave me deja vu. I had a similar problem with my beater.

This might be totally off but I'll tell the story anyway. I had this Geo Metro (don't laugh) with a very similar issue. It went on for a long time. The car would start fine in the morning. It would start fine at lunch. It would start fine after work. If I let the car sit after warming up for about 15 minutes it wouldn't start for nothing. If I stopped really quick and could get back to the car in 5 or 10 minutes it would start and run fine. There was this magic time period from about 15 minutes to 1 hour after I shut it down that it would not start/run. It was quite embarrassing. If I went to the bank and took a little bit too long my car wouldn't start and I'd be stuck there for an hour or so until it cooled enough to start again.

This actually went on for years. I tried and tried but I could not find out what was wrong. I just put up with it. It wasn't so bad. I rarely ran into the circumstances that made it happen. One day I was stuck with the car not starting at my buddies garage and I got extremely frustrated. I started digging into the fuel/injector setup looking for problems. I just so happened to unplug the electrical connector from on top of the injector and take a close look at it. It was filthy. So, I got some sand paper, a rag, and a couple of screw drivers and cleaned all the contacts on the electrical connections for the injector. I sprayed them down with a little electrical contact cleaner. Plugged everything back in and the car started right up.

It's been through two more owners since then and it's still running fine.

You might want to double check all your electrical connections. Bad connections seem to respond to temp changes.

 

I just measured the impedance these are 11.8 ohm? A high impedance is 14-15 yes? I will admit that 2 things are very possible as I am weak on electrical training, that I didnt do it right or I am remembering a high impedance rating incorrectly.

Would this have any affect?

 

With a standard DC meter you measure ohms. Impedance is the resistance to current flow on an alternating current circuit. So you can't accurately measure the impedance with your meter, but you can see if you have an open coil and/or a coil going bad (out of dc resistance spec).

 

I put brand new fuel injector clips on my car when I did my injectors. Maybe somebody else needs to try this.

http://www.bmotorsports.com/shop/pro...roducts_id/944

 

Also Aaron, yes a different impedance may not play nicely with the evo injector drivers, and it may rear its ugly ear during warm start conditions when a warm injector coil is "tuned" just right to mess with the injector drivers head. Its been awhile since engineering school, and I'm not even going to butcher it up by trying to explain it, but it has to do with how the gate provides the breakdown voltage for the channel and reverse induced current possibly mucking things up.

 

Guys, if you look at the FSM, you'll see that the injectors are wired to battery voltage, and ECU simply closes the loop to ground to fire the injector. I think its just a transitor switch. I don't think that qualifies as a driver.

 

Yes, high impedance drivers are 'simple' compared to peak and hold drivers. And 12 ohms is typical for a high impedance injector.

If it were driver related it would follow the ecu when swapped from a problem car to a non problem car. That was tried already, right? I don't think it's likely to be a driver problem.

 

Considering that cardboard is prime static generator in itself, all the other precautions were just kicked in the nuts...

 

I love you Fred.

 

I put on the connectors that came with the injectors. I did not put a jumper harness. I depinned and uncrimped the wires from my stock injectors and then crimped on the new pins with the correct crimping tool... not pliers or some crap.

Maybe they'll like some dielectric grease.... I installed mine dry. I'll test this tomorrow.

 

I second this... worth a try.

 

Dan,

I see, I will have to do some more reading. I was using the multimeter on DC so the 11.8 was apparently accurate then. I am only bringing it up because I have enough knowledge to be dangerous in electricity. I know a low impedance DSM/Evo injector is 2.3-2.5 ohms so I am wondering if the value without the resistor box there to make it "right" as observed by the ECU is causing an issue.

I think the phrase I want is "unfiltered" value?

 

Dan are you basically saying that once the injector gets warm that its coils inductance is interferring with the transistors ability to "switch"? I will agree with that statement as heat increases inductance can decrease depending on the material of the inductor, which would inturn have an effect on "switching" the transistor.

Has anyone verified that the impedance changes once the injectors are warm?

Here are the schematics from an Evo VIII with a few notes...

 

The ecu was a backup ecu - was not out of the non-problem car......currently I have (2) IX ecu's both causing the same problem in my problem car - the one is mine and the other is dans back-up ecu. I guess the next bet would be for dan to swap the back up ecu in his car - since its the non-problem car.

I will plug the resistor box back in - will try to today if my work schedule allows.

 

Fast Freddie, yes except for the fact that the evo's are using MOSFET's.