So I guess it started a year ago. After my car was down for a month for non-seq conversion (mods in sig), it wouldn't start because it was flooded. Deflooded it and life was peachy until this winter. When it started getting cold outside my car started "flooding" if I left it for more than a couple of days. I put flood in quotes because it's weird. The car starts up just fine everytime without fail. The problem is that the car will die right after firing up unless I keep my foot on the gas for 20-30 seconds. During this time the engine is struggling and shaking. After this time the engine tone changes, I can take my foot off the gas, and a pretty large amount of smoke comes out the tail pipe. The smoke initially smells like raw fuel but changes to white which doesn't really smell like coolant so it may or may not just be condensation. Once the car passes this period, everything is great until I let it sit again.

Due to the fuel smell, I suspected a leaking injector so I pulled the injectors and sent them off to witchhunter. They just came back and not only did they pass the leak test at 43.5 psi, they also flowed within 2% of their set flow rate. During the car that the car was down, I also replaced the FPR with a Sard FPR just in case the FPR was allowing excess pressure to build up. I also inspected the coil wiring and checked the coil resistance which came back within spec.

Now that I've still got the UIM, etc off, I was wondering if there was anything else I should check while I'm in there? Or should I just re-assemble everything and see if the changes that I've made have fixed the problem?

At this point my possible causes are as follows:
- Issues with fuel system (injectors, FPR)
- Low compression (although the car runs great once warmed up)
- Coolant seal failure (although car doesn't seem to eat coolant)

Since this is the only thing that is holding me back from enjoying my car completely right now, please lend me a hand. I would be eternally grateful.

 

What computer are you using?

 

Stock ECU. The wastegate is ported so I don't get boost creep. I actually typically drive around town running just spring pressure.

 

Are you getting any ECU codes?

 

None which actually make the check engine light come on. Last time I checked them all of them were ones that would be expected from the non-seq/emissions removal (eg. air pump etc). Though I can certainly check them again.

 

Have you checked your spark plugs n leads.

 

Spark plug wires are Magnacore 10.5mm with less than 5,000 miles on them. I haven't pulled the spark plugs yet, but I was planning on putting a fresh set in before starting the car even though they were changed at the same time as the spark plug wires.

 

My last set had less than 3000 on them and they were black as hell.Fingers crossed

 

Well I've got a new set on hand, so I'll pull the old ones and replace them. Maybe they're just super gross. I hope it could just be that simple. Anyone think a check of the IAT or coolant temp sensor might be in order?

 

There are several things to check:

* Coolant thermosensor. Make sure you didn't swap the connector with the Fuel thermosensor. They are basically the same sensor so the connectors can be interchanged.

* Intake air sensor

* TPS (make sure you didn't knock it out of wack)

Pull the codes and see what you are getting. There are some which are part of the turbo control system which I believe will throw the car into limp mode if you didn't do resistors.

 

I can check, but my harness is hardened enough that the plugs basically stay put so they'd be pretty hard to swap. How can I check to see if the coolant thermosensor itself is working?

How can I test it?

I already checked it. It's within spec.

The plugs that require resistors are the 8 square plugs that attach to the solenoid rack. The resistors I put in during the non-seq swap are all there and accounted for.

 

Checked the FSM and for anyone who's interested:

Check the resistance of the IAT and coolant temp sensor in air and water respectively. Both should be 2.2-2.7 kOhms at 20 degrees C and 0.29-0.35 kOhms at 80 degrees C.

 

IMO, low compression should not be a factor in this, since the car initially starts OK. If it were due to low compression, the initial starts should be difficult.

On the other symptoms, I don't have any useful input.

 

As you noted, there are test procedures in the FSM for all the sensors.

If you have resistors in place, then you shouldn't have any codes being displayed when you check. However, from a prior message, I get the feeling you do have some being stored:

 

The codes stored are ones that don't put the car in limp mode and thus don't require resistors (eg. airpump).

 

Can you list the ones being stored in the ECU now?

 

I can't list them all off the top of my head. The codes would be cleared now since the battery was unhooked during the injector pull, but I can re-pull the codes after I get the car back together.

 

UPDATE: I got the car back together with the freshly cleaned injectors and the new FPR (which is now properly set pressure wise). Unfortunately the car seemed to be flooded. Now how does a car get flooded when the fuel system isn't on you ask? Well I pull the leading plugs and the one on the front rotor seemed wet. So I cranked the engine with the plugs out, the EGI fuse out, and the throttle all the way down with a paper towel in front of the open leading plug hole. After cranking it, the paper towel was definitely wet and I can tell you it's not fuel (doesn't smell like it plus it doesn't have that cooling evaporation feel). My guess is that it's coolant although its brownish not green. If it is an o-ring failure, it's strange that I never got the standard symptoms (eg. overheating, overflowing coolant from overflow tank, low coolant light). On top of that the cooling system was still under pressure after the car sat for a month so it would have to be a tiny leak. Any thoughts on what else it could possibly be? What would be the definitive test for o-ring failure? Pressure test? Champagne test? Although the later would be tough without the car running.

 

Well the coolant system takes a few hours to depressurize so it's likely the coolant would drain into the chamber right away and stay there until the next time you try to start it. It's probably brown due to the carbon and crap in the combustion chamber.

As for the "usual" symptoms, many will say that coolant seal failures are not usually "usual". Each one can present different symptoms in the beginning.

I would try this: get a cooling system pressure tester. Now pull the plugs and crank to flush out anything in there. Then pressurize the system and crank again, and see if that produces fluid. If it does, it's probably coolant. If the cooling system pressure leaks down without any external leaks that would be another sign.

PS: I'm not an engine rebuilder, so there may be a better approach to determining if your coolant seals are definitely good.

Dave

 

What's funny is that the cooling system was under pressure, like holy crap here comes spraying coolant out of the fill cap pressure, after the car sat for several weeks. I had to flip the AST pressure release lever to release the pressure so I could pop the fill cap without getting coolant everywhere. Doesn't that seem really odd to anyone? What would cause this and why if the O-rings are shot would the system be able to hold that pressure for that long?

 

It is possible that the o-rings are only leaking when the engine is hot. They could be leaking in both directions - that would explain the presence of coolant in the combustion chambers (gets there right after shutdown), and combustion gasses pressurizing the cooling system while it was running such that it remains pressurized after shutdown. If there was a large enough volume of combution gas left in the cooling system, it could maintain pressure for quite a while once everything sealed up (like an accumulator) as it cooled off. And enough air to do that might not have been enough (or not trapped in the right place) to set off the low-coolant alarm.

 

I'm not sure what it means when a cold cooling system has retained pressure, but it doesn't sound normal at all.

Dave

 

The cause, of course, has to be something in the system creating an accumulator effect - either some really spongy hoses, or trapped air. When the system is operating normally, there is not enough air volume or "springyness" in the system to retain pressure as the coolant contracts when it cools.

Dave

 

Yeah all the hoses are basically brand new. It is interesting that if there is air in the system that I've never seen any temp fluctuations.

 

The current plan is to put a UV dye pack in the coolant, pressure test or de-flood and run the car, leave it overnight, and see if the fluid in the engine is UV reactive. If it is then it's definitely an o-ring issue and I'll pull the engine ASAP so coolant isn't just hanging out in the engine.