HELP!! Bogging at 4K RPMS, No Boost.

[Metallic36]

Just noticed this recently before my car was taken into the shop, and they couldn't solve the problem. My theory is the wastegate actuator, although I could not blow any air through the hose. It just started doing this, after taking off the Unichip and the Unichip EBC. I still have the stock cold pipe on the car, but it is tight. Anywayz, when I am driving it and want to go into boost, it gets to around 4K rpms then bogs down like the car has lost all power, and jerks a little, and of course I get no boost at all. Here are my thoughts on what it may be, just needing some input so I know what to fix next.

1. Coil packs
2. Needs new plugs
3. Wastegate actuator needs replaced
4. Issue with the vacuum line routing (?)
5. EGR needs cleaned

 

[MSP2k3]

Mine did this when i first got it... it would jerk and could not build boost. Turned out to be a faulty fuel pump assembly.. replaced it and car ran great.. just an idea. Might borrow a fuel pressure gauge and see how that looks.

 

[shane02pro5]

If you just took out the unichip what about the bigger injectors? Stock ecu will run way richER!

 

[jamesk]

ya sounds like it is running extremely rich or extremely lean.

 

[Metallic36]

Never changed the injectors, always had the stock ones in.. ran with the base Unichip map, basically had stock stuff on at that time anyway.. there was another strange thing I noticed a while back (before Unichip), when idling, I would hit the gas and the rpms would drop and then finally it would respond to throttle. At first I have been thinking it's something with the fuel, like it can't get enough. I guess this is similar, except happening when I'm driving it and going for boost.

 

[Metallic36]

That's definitely an idea, it does feel like it isn't getting enough gas when I try to go for boost.

Mine did this when i first got it... it would jerk and could not build boost. Turned out to be a faulty fuel pump assembly.. replaced it and car ran great.. just an idea. Might borrow a fuel pressure gauge and see how that looks.

 

[MSP2k3]

That's definitely an idea, it does feel like it isn't getting enough gas when I try to go for boost.

The mechanic i took it too said that when he put the Fuel pressure gauge on, the reading would go from full psi to 0psi and back to full and then drop back to 0... which made the car jerk and stop. Hope you figure it out

 

[Metallic36]

Alright.. I just drove it back home from the shop. So, I have discovered that I cannot exceed 2K rpms, and have to shift accordingly, otherwise it drops/bogs down and jerks. One time going around a corner it felt like it completely died. It feels like it can't breathe.

Another odd thing, it idled on startup at 2500 rpms. It settled down some after driving, but then on the way up the driveway I was in 1st and 2nd, it felt like it wanted to pull forward, so I let off the gas and it actually pulled itself up the little slope to the house. That was weird.

I don't know about the 2nd issue now, but the first one feels like maybe there is a pipe that's not totally connected. The 2nd issue I'm guessing is the timing isn't right?

 

[ForceFed]

mY GUESS WOULD BE ONE OF THREE THINGS....

Not Caps locks though....

1.MAF Faulty
2.TPS Faulty
3.Fuel pump weak.

 

[Metallic36]

Thank you so much for your help, I'm almost thinking MAF.. but also going to check that stock cold pipe again for leaks. May also change out the fuel pump too, it does feel like it can't get/handle enough fuel.

If I try to go over 2k rpms, it does okay for a second, then starts jerking like it's mad at me, then when I'm nice to it, finally settles back down to drive okay at 2k rpms. I know it's running very rich as well.

With the TPS, that sounds like that would explain when it idled a while back and I would push the gas only to see the rpm gauge drop before it kicked in to realize I did, in fact, hit the gas.

mY GUESS WOULD BE ONE OF THREE THINGS....

Not Caps locks though....

1.MAF Faulty
2.TPS Faulty
3.Fuel pump weak.

 

[shane02pro5]

Dumb question...has it thrown a cel? Also did you have any voltage clamps?

How is the idle?

You also said this was right after taking out the unichip...maybe recheck your harness for something crossed.

 

[Metallic36]

The Unichip had been out for a week or two when the "light" jerking started. It has gotten worse, and now, as of tonight, I've made the "no faster than 40 mph at 2k rpms" discovery. I DID manage to hit boost for a few seconds, so apparently that is working okay. I just have issues with going up hills, car wants to bog down and I have to downshift to make sure it doesn't go over 2k rpms, otherwise it jerks, bogs, etc. and then be very easy up the hills.

Nothing is crossed that I know of, I didn't have any voltage clamps, etc. The idle upon starting the car (tonight) was wickedly high, at 2500 rpms. I started driving it once it warmed up and it settled in the norm, but at stops it would go high again. I stopped at one place and it managed to stay at 1500 rpms. This idle has just happened after the shop put a new head on my car, also added the GT28RS and the GHL exhaust. Previously, the idle would fluctuate, then it had that throttle response issue. It's running richer than.. well, I dunno, just really rich. No CELs either.

Dumb question...has it thrown a cel? Also did you have any voltage clamps?

How is the idle?

You also said this was right after taking out the unichip...maybe recheck your harness for something crossed.

 

[Jaysanooch]

So wait, the shop gave you back the car running the way it is? How did it run before you desided to go nuts with the modding again? New head? Update your mod list...might help us help you. What intake you running...the stock air box? Weird you haven't thrown a cel running the way it is...especially if it were a MAF,TPS or fuel problem.

 

[Metallic36]

The shop was going to charge me $1300 just for labor, and I didn't have that kind of money. I decided I would rather fix it myself instead of paying them to tell me they didn't know what was wrong with it. I had the stock turbo/wga, stock exhaust, ghetto sri using the stock pipe with MAF before filter, SLS hot pipe, stock cold pipe, stock bpv.. all when I took it to them. It went to them because my head gasket blew, water pump went out. THe head was a given to be fixed. They fixed that, then I figured while they were in there I may as well upgrade. I then went with the GHL turboback exhaust, GT28RS, MAM exhaust mani, and a real sri. No changes to the ECU/fuel/etc. The bogging first started when I tried to boost going up a hill, I would just get no boost. Now it's to the point to where I can't get any more power than 2000 rpms, although I did get some boost last night one time. After that one time I didn't go for any more. I am planning to take a look under the hood today and see if there is anything they didn't hook up right.. they blocked off my stock BPV on the end pointing toward the throttle body, and didn't connect a vacuum line to it.. but that wouldn't explain the car driving itself up a hill and my idle being high. It hasn't thrown any CELs though. I wish it would.

So wait, the shop gave you back the car running the way it is? How did it run before you desided to go nuts with the modding again? New head? Update your mod list...might help us help you. What intake you running...the stock air box? Weird you haven't thrown a cel running the way it is...especially if it were a MAF,TPS or fuel problem.

 

[MSP2k3]

I know ive said this before, but your problems sound almost identical to mine. I couldnt' take it above 2-3k rpm without it jerking.. i actually had to pull off the interstate on the way home because it almost didn't make up the hill on the interstate and then almost didn't make it home. I really would borrow a fuel pressure gauge if you can and watch to see if the pressure drops when it jerks. When i got the fuel pump assembly replaced the car ran perfect again.

 

[Metallic36]

Yup, exactly the same then. I actually have another fuel pump, thinking of installing it and seeing if that works. Any idea where I can get a fuel pressure gauge though to try that out? Advance Auto maybe? I had to pull off the road last night, and I had the same issue with going up the hill.

I know ive said this before, but your problems sound almost identical to mine. I couldnt' take it above 2-3k rpm without it jerking.. i actually had to pull off the interstate on the way home because it almost didn't make up the hill on the interstate and then almost didn't make it home. I really would borrow a fuel pressure gauge if you can and watch to see if the pressure drops when it jerks. When i got the fuel pump assembly replaced the car ran perfect again.

 

[MSP2k3]

i dunno if advanced auto will rent out gauges... maybe take it to your mechanic and see if they will test the fuel pressure while its driving to see what its doing. Thats what i did and since i didn't have a garage to do the work I had to pay to have them replace the fuel pump assembly.. and would rather not talk about how expensive that was lol. Hope you get it figured out.

 

[Metallic36]

I'm wondering if it may be just the filter is clogged, or if it is the entire fuel pump assy that will need replaced?

 

[MSP2k3]

I dunno, im sure it would be alot cheaper to replace the fuel filter and see... but im pretty sure mine wasn't clogged because the psi in the fuel lines would hit normal amount then drop completely to 0psi, then jump back up to normal, then back to 0 which caused the jerking. Might be worth doin the filter first though if you can do it yourself.

 

[jamesk]

so, your saying you cant boost? do you mean literally the gauge wont go past 0 and the turbo wont boost, or do you mean everytime you boost, the car bogs out.

it could be just a boost/vacuum leak, or a dirty maf. but what i honestly think is that the car is not getting enough full or it is running pig rich. i would check the fuel pressure and get a wideband on there to see the ratios.

btw- no engine mangament with a gt28rs is not the smartest thing you can do.