Resolved 2GNT Car running lean with spike rpm after turbo install

[DumbtruckDSM]

So I recently put a turbo on my 420a Eclipse, I started it and it struggled but turned on. The afr is reading between 16 and 17 at idle and when I turn on my ac it goes to 20 to 21. I went for a test drive and everything was normal until it didn’t want to go past 3 rpm and then out of no where it spikes to 5 rpm. I put the car in neutral and the rpm start climbing up so I shut off the car. I turned it on and goes back to 5 rpm, I reversed it back home while at 5rpm and when I got home the idle went back to normal. What could it be???

 

[CKOPOCT]

So all you did was put a turbo on the car? No other modifications? No ecu? No tune? No adjustment to fuel pressure? What turbo? Did you install an intercooler? Did you install any gauges to monitor anything?

Need more info.

 

[BLACK'98DSM]

Turbo size and all that does not matter if it's running lean at idle. It would at least have a decent AFR at idle with no boost pressure. You could have anything from a vacuum leak that the MAF isn't detecting or a clogged injector. You need to do some diagnosis to figure that out. Needless to say I would stop driving the car until you sort it out. That's dangerously lean especially for a turbocharged engine.

The random spike in rpm is not random at all. The engine may not want to rev up without enough fuel but is being forced to once the turbo spools up.

 

[DumbtruckDSM]

Turbo size and all that does not matter if it's running lean at idle. It would at least have a decent AFR at idle with no boost pressure. You could have anything from a vacuum leak that the MAF isn't detecting or a clogged injector. You need to do some diagnosis to figure that out. Needless to say I would stop driving the car until you sort it out. That's dangerously lean especially for a turbocharged engine.

The random spike in rpm is not random at all. The engine may not want to rev up without enough fuel but is being forced to once the turbo spools up.

Thanks bro this helps a lot, I asked everywhere and everyone is asking why I turbo charged a 420a I’m only running like 5 psi and stock, I checked for vacuum leaks but I couldn’t find anything. My boost gauge reads 18 at idle and when I accelerate my afr goes to 15

 

[BLACK'98DSM]

I'm not sure how it could possibly idle at 5k rpm without a vacuum leak, unless your throttle is getting stuck open.

 

[DumbtruckDSM]

So all you did was put a turbo on the car? No other modifications? No ecu? No tune? No adjustment to fuel pressure? What turbo? Did you install an intercooler? Did you install any gauges to monitor anything?

Need more info.

No I put a fpr on the car, boost gauge and afr gauge from aem, a boost controller to lower the boost, yes ofc I have an intercooler. Boost gauge reads -18 at idle, afr reads 16-17 at idle and when I rev and drive it goes down to 15

 

[DumbtruckDSM]

No I put a fpr on the car, boost gauge and afr gauge from aem, a boost controller to lower the boost, yes ofc I have an intercooler. Boost gauge reads -18 at idle, afr reads 16-17 at idle and when I rev and drive it goes down to 15

Also I read I need a megasquirt to tube it because you can’t tune a 420a. I heard they run good at 8psi without tune but I wanna run like 5-7.

 

[chrisman287]

What’s your fuel set up?

 

[CKOPOCT]

No I put a fpr on the car, boost gauge and afr gauge from aem, a boost controller to lower the boost, yes ofc I have an intercooler. Boost gauge reads -18 at idle, afr reads 16-17 at idle and when I rev and drive it goes down to 15

Yeah... sorry if I offended. I'd just finished up a day of addressing others and didn't filter very well. Should have figured when you mentioned afr. Did you do a boost leak test or find any vacuum leaks?

 

[DumbtruckDSM]

What’s your fuel set up?

I have only a fuel pressure regulator but someone mention that I’m wrong and should have a fmu, idk much about the fmu but apparently that should solve my problem, do you think I can run my aftermarket fpr and a fmu or should I put the stock one back?

 

[DumbtruckDSM]

Yeah... sorry if I offended. I'd just finished up a day of addressing others and didn't filter very well. Should have figured when you mentioned afr. Did you do a boost leak test or find any vacuum leaks?

It’s okay l, I’ve been getting a lot of hate on facebook for asking this question and idk why, I’m new to this scene and I just wanted answers. Yeah but I noticed my catch can hoses were loose and my boost controller was some what loose, and I upgraded my air intake to just a aem filter with no tube just the filter on the turbo. But I can’t seem to find anymore leaks?

 

[chrisman287]

I have only a fuel pressure regulator but someone mention that I’m wrong and should have a fmu, idk much about the fmu but apparently that should solve my problem, do you think I can run my aftermarket fpr and a fmu or should I put the stock one back?

What’s your base fuel pressure?

Do not drive the car you’re going to blow the motor. Your fuel system isn’t adequate.

 

[DumbtruckDSM]

What’s your base fuel pressure?

Do not drive the car you’re going to blow the motor. Your fuel system isn’t adequate.

I’m reading 43 on the fuel pressure gauge, what fuel system is at least acceptable to get me going at low boost or a decent one?

 

[chrisman287]

I’m reading 43 on the fuel pressure gauge, what fuel system is at least acceptable to get me going at low boost or a decent one?

Alright so fuel pressure is good.

I would suggest at least a Walbro 255 pump and 550cc injectors.

Although I still am not sure that this is causing the idle issue. I know getting into boost with the stock fuel system would be a problem but out of boost should still be normal. Do you have pictures of your engine bay?

To perform a boost leak test you’ll have to pressurize the cold side of the turbo. Check YouTube you can make a cheap boost leak tester.

 

[DumbtruckDSM]

Alright so fuel pressure is good.

I would suggest at least a Walbro 255 pump and 550cc injectors.

Although I still am not sure that this is causing the idle issue. I know getting into boost with the stock fuel system would be a problem but out of boost should still be normal. Do you have pictures of your engine bay?

To perform a boost leak test you’ll have to pressurize the cold side of the turbo. Check YouTube you can make a cheap boost leak tester.

Oh and I have a walbro 255 fuel pump also, I just don’t have the injectors, yeah it was really weird, I wanted to go over 3000rpm and it was like it didn’t want to and then it spiked at 5000 rpm

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[chrisman287]

Did you install an authentic Walbro 255? Did the problems happen before or after the fuel pump install? Before or after the turbo kit install?

There are a lot of fakes pumps out there. Don’t take this the wrong way but I see a lot of knock off parts on the car (AFPR, BOV, WG, turbo and blanket) which is why I mention the possibility of a fake pump

 

[DumbtruckDSM]

Did you install an authentic Walbro 255? Did the problems happen before or after the fuel pump install? Before or after the turbo kit install?

There are a lot of fakes pumps out there. Don’t take this the wrong way but I see a lot of knock off parts on the car (AFPR, BOV, WG, turbo and blanket) which is why I mention the possibility of a fake pump

Yeah I got the kit off eBay no worries Ik the parts are fake but the fuel pump I bought separately it ran me like $115, the problem happened when I added the turbo.

 

[chrisman287]

Yeah I got the kit off eBay no worries Ik the parts are fake but the fuel pump I bought separately it ran me like $115, the problem happened when I added the turbo.

Boost leak test and report back

 

[DumbtruckDSM]

Wassup guys I just wanted to let y’all know I solved the problem! I removed the AFPR and put the stock one back in and added an fmu, then I checked for air leaks. I noticed I was hearing a whistle noise at idle and I squeezed every vacuum hose till I heard the whistle change and turns out one of the hoses had a huge leak. Then my next problem was my fault and I’m kind of embarrassed but I didn’t put on the valve cover gasket on correctly, the front was all in but the back of the engine where the valve cover gasket goes wasn’t even in the valve cover spot, it slipped off. Not only did it fix my air leak problem but my oil leaks also went away I test drove the car and I hit boost for the first time! It was amazing! Nothing fast but hearing the noises and getting a little pull was all worth it.

 

[CKOPOCT]

Awesome. Glad you found the issue and fixed it. Also, thank you for the update. Too many folks resolve the issue and just drop off without closing the loop in the forum. The fix update may help others in the future.

 

[BLACK'98DSM]

I was suspecting a vacuum leak. Glad you found it. For the valve cover gasket I always use a dab of rtv on the corners, otherwise it always falls out when you flip the cover. How's the AFR when you're making boost?

 

[DumbtruckDSM]

I was suspecting a vacuum leak. Glad you found it. For the valve cover gasket I always use a dab of rtv on the corners, otherwise it always falls out when you flip the cover. How's the AFR when you're making boost?

At idle it’s at 13-14, then when I’m driving it goes from 14 to 10 sometimes 9 but the goes back to 13-14, I haven’t checked on the afr when I hit boost I’ll check next time and let you know