HurleyTSi Posted March 4, 2009 Report Share Posted March 4, 2009 So my car has been acting a bit sluggish. It doesn't seem to have any umph anymore. The idle is also very lopey. Almost like a sputter. The car has only ever gone up to about 5-7psi on the stock boost gauge. Not sure how accurate that is but whats the correct psi the gauge should be reading on an 85.5? Also at idle my oil pressure drops really low. It stays above the bottom hash mark though. Checked the oil and it was fine. Its not leaking any oil. It has some blow by though. When I raise the rpms the oil pressure normalizes. Only at idle will it drop pretty low. Also under boost at freeway speeds the car seems to fuel cut. And starting in first gear from idle the exhaust note is kind throaty like when you unbolt the exhaust on a turbo car. But only momentarily. Few possibilities come to mind: 1. Pre-turbo exhaust leak? (but that wouldn't explain the oil pressure drop) 2. Turbo on its last legs? (doesn't smoke but has some shaft play but would it affect oil pressure?) 3. Bad piston rings? 4. Head Gasket going bad? (Oil is fine though, no coolant in it) 5. Fuel related perhaps? (Again that shouldn't be killing my oil pressure) 6. Boost/Vacuum leak? (But why the falling oil pressure?) Thanks in advance! Link to comment Share on other sites More sharing options...
MikeMeyerhoff Posted March 4, 2009 Report Share Posted March 4, 2009 Check the exhuast manifold at the back of the head. It is a common issue that the last couple of studs will pull out of the head allowing the exhuast to leak. If your vaccum lines are original, replace them. <$50 that will solve a lot of issues. I would also put a mechanical oil pressure guage on it to get some actual numbers. "Low" on the needle doesn't mean the same thing from car to car. Once you have some actual numbers, you can figure out if you need to do some work on it to prevent a spun bearing. Link to comment Share on other sites More sharing options...
Tim_C. Posted March 4, 2009 Report Share Posted March 4, 2009 7 PSI is the boost level for that year intercooled. Oil pressure: It can drop below the 1/4 hash mark and still be fine. As long as it is 1/2 at cruise RPM. Fuel Cut: This is most likely detonation that is damaging the engine. Know for sure it isn't before you boost on the freeway again. Pull the plugs and make sure they look normal. Detonation will usually show visible sign of plug damage. You need to monitor the fuel pressure under boost. You can tap into the TB at the rear plug and stack a few washers between the hood and hinge to run the line and gauge out to the windshield to tape it there. $30 should get you a gauge where you can read it under load. It should have a base of 37-39 or so, and increase one PSI per lb of boost. I permanently mounted a mechanical FP gauge on the cowl and ran the hose through the access plate on the firewall. I had to build a little bracket and mounted it on the driver's end of the cowl. If the pressure is not enough, or intermittent, try replacing the main fuel filter and clean the cone filter in the fuel pump inlet tube. Throaty exhaust: Muffler is probably shot. This could be the sluggish/fuel cut problem too. Stuff in the muffler loosens up and moves around in there to sometimes clog up and sometimes open up. There is probably a leak at the rearmost port of the exhaust manifold at the head too. Stud damage is most likely also. That needs fixed and at least cut the webs on the manifold to more evenly distribute the weight of the turbo and cat. The cats are probably full too and need changed. I would at least remove them and hollow them out with a big screwdriver if you don't have emissions inspections there. Link to comment Share on other sites More sharing options...
FlattopMike Posted March 4, 2009 Report Share Posted March 4, 2009 Vacuum leak for the rough idle and "fuel cut". Any vacuum leak will give you a rough idle and with a leak, the distributor won't retard like it should under boost causing it to detonate. Oil pressure is an unrelated issue. If you get any crap at all into the stock sending unit, it will read low. Check it with a mechanical gauge. Link to comment Share on other sites More sharing options...
HurleyTSi Posted March 4, 2009 Author Report Share Posted March 4, 2009 Alright I was unsure if the oil pressure had any relation to it. If 7psi is the proper boost then I don't have to worry about the turbo. From my experience with my 97 Talon it seems like a pre-turbo exhaust leak. Plugs are still good, I will replace the fuel filter and feedline, and go through the exhaust system. Thanks again for the heads up everyone! I'll replace all the vac lines too especially as I want to do a 14G/intercooler conversion to my flatty. Link to comment Share on other sites More sharing options...
FlattopMike Posted March 4, 2009 Report Share Posted March 4, 2009 Keep in mind that it's not just the vacuum lines that leak, it's every thing that they are connected to as well. A vacuum tester from Harbor Freight is well worth the investment. Link to comment Share on other sites More sharing options...
Crazy larry Posted March 4, 2009 Report Share Posted March 4, 2009 CTS Swap with a different one Link to comment Share on other sites More sharing options...
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