[Lar Bear]

I purchased a Sol Coupe in April of this year. When I would start it up in the morning to head to work while idling before backing out of garage the engine sounded like it was "missing". Once I begin to drive the vehicle this "missing" goes away.

Last week I decided to leave the DIS system in Boost PSI mode. I noticed this morning that after I started up the coupe and when it started to "miss" the turbo boost pressure was jumping from 0 to 2 psi.

What would cause this my Sol brothers & sisters?

 

[SolNut]

Gasoline Quality is first choice.
How many miles? Perhaps the PO didn't run good stuff and a plug change is in order.

Check your Miss-fires with a DashHawk or equivalent.
I get some every once in a while at start up. :thumbs:

 

[Lar Bear]

My coupe has 12,400 miles on it. I have put nothing but premium fuel in it since I purchased it.

I was thinking that this miss could be attributed to possible spark plug fouling until this morning.

Today, I witnessed that the turbo boost pressure registers 1-2 psi whenever the engine miss at S/U idle occurs. This now leads me to thinking of a possible turbo waste gate dumping issue. (Unless this normally occurs whenever a turbocharged engine misses)

 

[GS Stage 1]

Lar Bar:

This is exactly the same symptom my Sky Redline has on first start of the day, ever since they changed my engine. It sounds like a "miss" but no misfires register with the ECM. (However, I have been told that on initial Cold Start CAT Warm Cycle, the ECM may disable misfire detection, so it would not register anyway). And yes, when the miss (Cough) happens, the Boost Gauge will blip 1-2 PSI. In my opinion, this is a effect; not a cause.

My operational theory is there is a very slight leak at the down-pipe to CAT connection that quickly seals up when the metal heats up. But I have never been able to prove it.

Here is a link to a VID I took of my car: ColdStartCough-1.mp4 Video by GSStage1RedSky | Photobucket

 

[Lar Bear]

Thanks GS Stage 1 for the feedback.

I listened to your cold start video and it sounds like what I get with first cold start of day. Mine misses for quite a while though more so than what I heard out of your Sky.

I will check the exhaust connections the next time I get underneath the Coupe.

 

[The_Ghost]

Are you guys tuned? Do you have AM exhaust? This is the way mine sounds, but it's my AM exhaust. I don't get any blip in the boost pressure though. My guess is that it's the cat warmup phase dumping fuel into the motor and some is not burning until it hits the cat.... That's what mine seems to be.... I also am not able to go into boost at all until I see 150-175 degrees in engine temp because mine stays in warm-up mode that long....

 

[shabby]

I have been told that on initial Cold Start CAT Warm Cycle

That's exactly what it is, a warm up mode for the cat, if you have hptuners you can disable this. It last for around a minute and puts load on the engine, that's why you almost see positive boost.

 

[The_Ghost]

Just beware if you turn off the cat warmup mode, you will have the problem I do. You can't get into boost until the engine warms up (150-175). If you do, it will literally feel like you just threw an anchor out the rearend of the car if your not warmed up! I HIGHLY recommend not doing this!!! I can't pull out into traffic.

 

[Lar Bear]

My Sol GXP Coupe is 100% stock with no tune or AM exhaust. I guess this is normal warm up mode for these engines. I just wanted to be sure it wasn't something serious starting to brew.

Thanls for the input!

 

[GS Stage 1]

Thanks GS Stage 1 for the feedback.

I listened to your cold start video and it sounds like what I get with first cold start of day. Mine misses for quite a while though more so than what I heard out of your Sky.

I will check the exhaust connections the next time I get underneath the Coupe.

Mine will cough way worse than what you see in that video. It is completely random as to how bad it coughs. Sometimes not at all, sometimes so bad that it sounds terrible. The only pattern to the behavior that I can observe, is that for some reason it will not cough at all over the winter, after outside temps have dropped to a consistent below 50 degrees or so.

My car is completely stock, except for the GMPP tune. I have had the GMPP tune since the car had only a couple thousand miles on it. My car never had this "cold start cough" with the OEM engine; which was through 37000, miles. The problem immediately began after install of the new engine and has been there since. Hence the reason, that I am suspicious there is a very slight leak in the Turbo to Down-pipe to exhaust connection somewhere.