Engine backfires, turbo cuts off when hitting bumps - Pontiac Solstice Forum
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post #1 of 22 (permalink) Old 06-01-2019, 02:57 PM Thread Starter
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Engine backfires, turbo cuts off when hitting bumps

Hey guy all of a sudden my 07 GXP started having this weird problem where hitting decent sized bumps in the road (like the lip where a road meets a bridge, or where there's a lot of cracks in the road) my turbo will cut off. I can mash the throttle as hard as I want and get the RPMs up to 5500 and there's still no turbo.

But if I let off the accelerator completely, the turbo comes back.

This happens every single time I hit a bump. Sometimes the car backfires, just one quiet pop, sometimes it doesn't. Sometimes if it's a particularly bad road with really rough conditions it feels like the engine is about to stall, again, it all goes away when I take my foot off the accelerator and put it back on.

What's going on? Grounding issue? There's no codes for anything yet, and it's been about 140 miles since this started.
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post #2 of 22 (permalink) Old 06-01-2019, 03:12 PM
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Starting with the obvious...is there a "low traction" warning on the dash? Or a flashing stability control sign? They may be hard to see if it's sunny out.

2007 Solstice GXP
#3 ASP, DET and NWOR SCCA
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post #3 of 22 (permalink) Old 06-01-2019, 04:15 PM Thread Starter
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No there are no dash lights whatsoever. No lights, no dinging sounds, no flashing. But now that you mention that, on the way home today I'll run it with all that turned off and see if it makes a difference.

I should probably add that this happens when I'm just at cruising speed, ~2100 RPM so I'm not beating the hell out of it going over these bumps
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post #4 of 22 (permalink) Old 06-01-2019, 09:41 PM Thread Starter
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Well, I think I know what's up.
Came out of work and the car wouldn't stay running. It would crank and start then sputter and die out.

So I poured in a bottle of octane boost, topped off the tank with 3 gallons of fresh gas and let it run for ten minutes.

And what do you know, the whole way home, no problems.

I bet it's that God dang 7-11 I stopped at to get 4 gallons of gas the day before these problems because I forgot to get it when I left work. Probably got myself a nice tank of water.

We'll see what happens
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post #5 of 22 (permalink) Old 06-02-2019, 06:16 AM
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I go some crappy gas myself a few years ago and the car ran like crap for 3 or 4 tanks after. Hopefully that IS your issue and it straightens itself out.

WooHoo!!! Ordered a loaded Deep GXP on March 19th, 2008. Order number 0814D93708
Event code 3400 on April 12, 2008
Born April 30, 2008
Delivered to dealer May 23th, 2008
Delivered on May 27, 2008

Mods: lose the chicklets, VentureShield, Dual horns, AfterShock spoiler, Weathershield cover, Lil Chromies, Red calipers with black Solstice stickers, Opel GT antenna and
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post #6 of 22 (permalink) Old 06-02-2019, 09:35 AM
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Are you tuned? If not, are you using premium or regular? The turbo cars require premium. My car requires pure 93 octane, or else it sputters and backfires because I'm dyno tuned to the edge. There are only 2 gas stations within 5 miles of my house that I trust, the other 10 I've gotten bad gas on more then one occasion from...and they're name brand stations like BP and MOBIL.... Believe it or not the Kroger station is one of the 2 that I trust!

____________________________________________

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ZZPerformance dyno tuned - 286HP, 317ft/lbs of torque at 23psi of boost.
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post #7 of 22 (permalink) Old 06-02-2019, 11:40 AM
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It seems odd to me that a fuel-related problem would occur specifically when hitting bumps. I would be looking for loose electrical connections.

John
Lexington, KY
Sky NA 2007 Midnight Blue
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post #8 of 22 (permalink) Old 06-06-2019, 11:37 AM Thread Starter
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Got fed up with the problem going home yesterday so I decided to floor the hell out of it until it gave me some codes. I got
P0463 - Fuel level sensor circuit
P0089 - Fuel pressure regulator performance
P0455 - EVAP leak large

So I'm thinking the in tank fuel pump may be failing. But after beating it, parking it, clearing the codes and running it again I didn't seem to have any problems even over bumps in the road.

One other thing that came to mind when I searched the forum for those codes was my last oil change. I got a faint whiff of gasoline from the oil. The engine was brand new with only 500 miles on it at the time so I just figured it was some contaminant left over from the whole swapping process. I don't have the car with me right now but I'll check that smell again when I get home.

The car has about 154k original miles, is it reasonable to think it might be the in tank fuel pump and not immediately jump to the HPFP? Especially since it's giving me codes for everything on the in tank pump?
I don't have anything to test fuel pressures myself but that memory of the gas smell is haunting me now and I don't want to ruin this brand new engine
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post #9 of 22 (permalink) Old 06-06-2019, 11:49 AM
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The in-tank pump is not going to put fuel in the oil, but the HPFP will. Finding out what is in your oil is a key item, I think. It may be time for an oil analysis.

John
Lexington, KY
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post #10 of 22 (permalink) Old 06-06-2019, 01:37 PM Thread Starter
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Quote:
Originally Posted by JohnWR View Post
The in-tank pump is not going to put fuel in the oil, but the HPFP will. Finding out what is in your oil is a key item, I think. It may be time for an oil analysis.
yeah I wasn't really making a connection between my current problem and the gas smell from 5 months ago until I started doing some reading here on the HPFP. I went ahead and placed the order for the in tank pump after the codes came back because it was only $200, and I got the email that it had shipped right as i was going to cancel, so I guess I'm replacing the in tank pump just for fun. My fuel level sensor has been dead for almost 2 years now anyway so it's not a *total* waste. And that evap leak is definitely somewhere in the tank because it doesn't hold pressure (no *whoosh* sound when i take the cap off) so I'm crossing my fingers it might fix that, too.

I'm also gonna go ahead and order the HPFP since it's also only $200 on ZZP and give that a go since the car is gonna be down anyway. After the two pumps, the only mechanical parts that won't be brand new are the alternator and transmission. Everything else from the intercooler to the cat are all <5,000 miles. I had set aside $600 when I changed all those specifically for fuel pump problems because really, that's all I had to worry about. Just didn't think it would be so soon

Will update in a couple days with results
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post #11 of 22 (permalink) Old 06-06-2019, 07:36 PM
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HPFP is extremely easy to replace. Time consuming part is removing the vent cowl.... Otherwise it's a 30 minute job.

____________________________________________

Solo Street Race exhaust
Fujita CAI
ASAP T2 stripes and badging
Windrestrictor V2 lighted in white
Windrestrictor lighted door sills lighted in white
DDM Works IC Piping
Undercar LEDs in white to match Windrestrictor

ZZPerformance dyno tuned - 286HP, 317ft/lbs of torque at 23psi of boost.
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post #12 of 22 (permalink) Old 06-11-2019, 05:29 AM Thread Starter
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Update

Replaced in tank fuel pump, car started up beautifully! No more random misfires, no shuddering, no hesitation when accelerating. It definitely had a completely different feel to it! I put a brand new engine in it about 5000 miles ago and it finally FEELS like it's a new engine!

Got it home after a 50 mile drive and let it sit. HPFP came in yesterday so I went about doing that. Once I started wrenching on it I could clearly see oil leaking all around the old gasket for the HPFP, so that was replaced as well.

Fuel gauge, sadly, still does not work. It began to fall to E intermittently about two years ago, did that for a week then just quit but the "distance to empty" display still worked correctly. About a week after THAT, it went too. I always figured it was the level sensor/sending unit since that's what I read about. I guess it's not.

Parts list
in tank fuel pump - # 19168738
includes level sensor and gasket
https://www.rockauto.com/en/moreinfo...433710&jsn=401

High Pressure Fuel Pump - # 12629135
https://zzperformance.com/collection...sure-fuel-pump
High Pressure Fuel Pump Gasket - # 12595951
https://zzperformance.com/products/d...el-pump-gasket

Last edited by Zanepaul; 06-11-2019 at 12:47 PM.
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post #13 of 22 (permalink) Old 06-14-2019, 05:23 AM Thread Starter
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Well, that didn't last long. Went to leave 2 mornings ago and the car won't start again. Starter goes, engine starts to turn over, sputters and chugs for a few seconds then dies.
Tried again that night, same problem.
Went out the next day at 2pm, car started right up, but was backfiring like crazy when I rev it and let off the throttle
Tried again the same night, back to sputtering and cutting off.
Tried this morning, no start, but code P0089
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post #14 of 22 (permalink) Old 06-14-2019, 07:36 AM
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A bad EVAP solenoid can cause the sputtering, hard starting and stalling. It's located on the intake manifold. There's a DDM video on how to test it.
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post #15 of 22 (permalink) Old 06-14-2019, 07:50 AM Thread Starter
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Quote:
Originally Posted by SolCal View Post
A bad EVAP solenoid can cause the sputtering, hard starting and stalling.
I had just tested it three months ago when I replaced the manifold pressure sensor because I kept getting a code for evap leak, alternating between large and small, and it was tight as a tiger.
But it never hurts to check again
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