RestoTII

I just went to drive my car and i can't get the thing to go over 1500 rpm. It'll rev up to that, and regardless of throttle position, it won't go above it. The car hasn't been running too well, but it's never done anything like this, and it didn't give any signs of this yesterday when I drove it. any ideas of what might cause this? I think it might have a slight exhaust leak, so that could contribute. Mods are just a cone filter and TID and fuel cut defense (i used to have the RB turbo back but just swapped to stock this past week). thanks

Jimmy325i

S5? if so it could be your omp has failed

TheBigOne

Let me guess....

You drive the car first thing (its been sitting over night or over 8 hours) and its fine. You drive for a while and then park your car..

Turn off the engine, let it sit for about 30 minutes to about an hour.

It starts fine but bounces off of 1500 rpm

Sound about right?

RestoTII

sorry bout that guys, it's an S4, but i'm not sure if it's an oil problem. The gauge was reading about 8psi before, then it went to 110+, now it's sitting at under 0psi. The car sat most of yesterday and into today (~30 hrs), and now when i went to start it, it fired up like normal. I tried backing out and it wouldn't go, cause it couldn't go over 1500rpm. I let the car warm up for about 10 minutes, went back out and it drove like normal (like **** that is). Thanks for the idea jimmy, and TheBigOne, sounds like you're describing a flooded car or a bad TPS. I've got the fuel pump switch and I unplugged my TPS a couple days ago cause I suspsect that it's also bad, but it still ran without that. In any case, anyone else have any ideas? thanks

Jimmy325i

It's not going to be an oil problem if its not an S5. Their electric omp's are computer monitored to save the motors in the event of an electrical failure in the system.

Have you recently done the TB mod? maybe you're hanging the throttle cable up on something. What did you change before this started happening is another thing to think about.

dr0x

If you didnt change anything, a vacuum line may have finally let go. Worth a check.

TheBigOne

that happened to my car shortly after I removed my TPS.

I was told because I removed my TPS that the ECU goes in to a fail safe mode. Hence the 1500 bounce.

But it only happens sometimes.

But that's my car. I didn't fix it yet. But when I park I just put the turbo timer to max time and lock the doors.

BTW s4 T2

Jimmy325i

I was thinking the same thing about the TPS. Some cars run without it and some don't. (from other threads on the subject)

RestoTII

mine runs better without it, that's why it's still off. It bounced around 1500rpm with it, but now it idles around 1000rpm without it. I pulled the cable and it goes the whole way, and it's not sticking. You can hear the engine sucking in air, but it's like it wasn't getting enough fuel to keep the engine revving. Then it'd pop out the exhaust and rev down real low and slowly come back up to around a 1200rpm idle. Thanks for the responses

TheBigOne

could a bad EGR cause about the same effect?

Bad EGR, giving other sensors wrong signals to the ECU.

HAILERS

Blown apex seal. Do a compression check.

racermike

I will hazard a guess based on two points:
"""can't get the thing to go over 1500 rpm. It'll rev up to that"""
and,
"""might have a slight exhaust leak,"""

A clogged cat would limit rpm,,,,,and extra pressure in exhaust system may promote, or better show a leak.

RestoTII

brand new cat, and once it warmed up, it went over 1500 just like normal. wouldn't a bad seal allow it to rev over 1500, albeit it a slow rev?

racermike

"""brand new cat, and once it warmed up, it went over 1500 just like normal"""
Is that a fix then??

A seal SHOULD just limit power. If it causes pre-ignition in the next chamber, could REALLY slow it down, but I do think it WILL rev up.

RestoTII

i thought the same thing mike. and it has a real bad lack of power and slow revs, so i think a seal might be weak, but not totally gone. In any case, I just got out to look at it in the daylight and I have a vac leak. It's behind the IM, on a fixture with the four hoses coming out of it. One (i believe third from the top) is the larger hose, and the other three are all vertical. Of course the leak was on the bottom one, and I have to get to work, so I tried for a while, gave up and put the IC back on. In any case, I fired it up without changing anything that i know of, and it's revving like normal now (slow but over 1500rpm). So now I've gotta get the leak taken care of at some point, and hopefully somewhere warmer than my 25° parking lot. Thanks for the ideas guys.

CrazyDude

For what its worth, take a look at your spark plugs. When I got my car, it wouldnt rev over 6000 without alot of vibration and fuss... changed out the spark plugs and it ran pretty good! (until a coolant seal blew out).

HAILERS

On a series four, the bottom nipple is the only one that is pulling a vacuum. That vacuum goes to the diaphram on the left front of the throttle body. It closes that outer set of throttle plates when the engine water is cold.

It might be that your outer set of throttle plates are stuck in the closed position all the time. But I think you'd still get more than fifteen hundred rpm. Just slower to boost and down on power.

I had the precat on my car clogg a bit. The symptoms were a lack of boost. It was gradually deteriorating until I could only get two or three psi. Did not affect my rpms though.

P.S. The other three nipples on the series four are ganged together in the throttle body and exit before the throttle plates. You can see the outlet with the inlet duct off. Its a quarter inch hole(approx)below the set of two butterflys. Anyway, they supply filtered air TO the oil injectors and fuel injector bleeds.