Total Sign Posted June 12, 2005 Report Share Posted June 12, 2005 Getting desperate now. 1988 Corvette, 5.7 TPI 59k miles bought with 43k. This problem has been there since day one. gets bad mileage (22 best ever), doesn't like starting when warm, all the signs of bad injectors. Hooked the fuel pressure gauge to it today. Idle pressure- 38psi 1000RPM-35psi engine off-44 psi 5 minutes after engine was shut off-40 psi 10 minutes after engine was shut off-32psi Starts great when cold, but if you drive it somewhere, get out, come back 15 min later it cranks for a while, then when it starts runs very rich. O2 sensor was replaced 200 miles ago. Now, the injectors check out fine. Plugs and wires have less than 500 miles on them. O2 sensor has about 200. EGR/Air intake temp sensor/coolant sensor have about 150. Only thing else I can think of is the MAF sensor. The engine temp is normally around 220. Possibly a weak coil? Any help or ideas are greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Guest racinbird Posted June 12, 2005 Report Share Posted June 12, 2005 12 psi drop in only 10 minutes is on the high side, may have a leaking fuel system, injector, check valve etc. Quote Link to comment Share on other sites More sharing options...
Guest FBody Addict Posted June 13, 2005 Report Share Posted June 13, 2005 is the fuel pump constantly running with the engine off to keep the 44 psi? if so, replace the pressure regulator look at your plugs, don't mix them up, any fouling or gassy smell record findings, if they are all the same then it probably is a pressure regulator, if one or a few are bad then i'd say injectors try a heavier oil, your lifters may be bad and the valves don't open as much as they should since the thinner(warm) oil will leak out of the lifter faster than the thicker(cool) oil (hopefully that makes sense, unless your block has roller lifters) Quote Link to comment Share on other sites More sharing options...
desperado Posted June 13, 2005 Report Share Posted June 13, 2005 OK, the other to do is swap out the temp sensor that's feeding the computer. I believe that there are two, one for the gauge and the other for the computer. I had a Grand Am that would do the same thing and if I disconnected the temp sensor it would go into limp mode and fire right up. The minute I reconnected the sensor it would have difficulty starting. I can't remember if it was running rich or not but I do remember that it wouldn't start like what you are talking about. Worth a try to find that sensor and unhook it if nothing else. Quote Link to comment Share on other sites More sharing options...
speedytang Posted June 13, 2005 Report Share Posted June 13, 2005 It sounds like a injector(s) are leaking down. To test this theory hold the gas pedal to the floor while starting which shuts off the injectors to clear the fuel out of the Intake. Quote Link to comment Share on other sites More sharing options...
AJ Posted June 13, 2005 Report Share Posted June 13, 2005 or pinch off the pressure and return line with the gauge hooked up and that will show if the injectors are leaking, my bet is a fuel pump, 44 is too low on a TPI. Quote Link to comment Share on other sites More sharing options...
SamZman Posted June 13, 2005 Report Share Posted June 13, 2005 I had a similar problem when I had my GTA.. always seemed to be when the car was warm.. Anyways it turned out to be the pickup coil. Take the distributor cap off and see if the wires look dry rotted.. that's what happened to mine.. it's only about 13 bucks (10yr ago), it's easy enough but you have to yank the distributor to switch it.. Quote Link to comment Share on other sites More sharing options...
Guest FBody Addict Posted June 14, 2005 Report Share Posted June 14, 2005 my T/A runs at 38-40 psi at idle, 1000 rpm, wot, and just after priming so i don't think 44 is low, unless the motor has been built up the sensor for the gauge is on the left side of the block and the sensor for the comp is on the front below the throttle body Quote Link to comment Share on other sites More sharing options...
AJ Posted June 15, 2005 Report Share Posted June 15, 2005 i looked up the wrong year, in 89 it had to be higher Quote Link to comment Share on other sites More sharing options...
Clifford Automotive Posted June 26, 2005 Report Share Posted June 26, 2005 Mine runs at 58 lbs. No matter where its at in the trottle range. I would deff, check the injectors. Quote Link to comment Share on other sites More sharing options...
Total Sign Posted July 20, 2005 Author Report Share Posted July 20, 2005 The problem is now fixed. Fuel pressure was and still is fine. Injectors do not leak. Apparently there is a 9th injector on the engine. It is supposed to only open when the engine is cold. The sensor for it had gone bad. Quote Link to comment Share on other sites More sharing options...
Brandon Posted July 20, 2005 Report Share Posted July 20, 2005 did i pass you on africa the other day? random sorry Quote Link to comment Share on other sites More sharing options...
Total Sign Posted July 21, 2005 Author Report Share Posted July 21, 2005 nope. car has been down on morse for a few weeks now. Quote Link to comment Share on other sites More sharing options...
RS69 Posted July 24, 2005 Report Share Posted July 24, 2005 Originally posted by Assured Risk: The problem is now fixed. Fuel pressure was and still is fine. Injectors do not leak. Apparently there is a 9th injector on the engine. It is supposed to only open when the engine is cold. The sensor for it had gone bad. I have an 87 Vette with 50k miles doing the same thing. Where is this 9th injector and the sensor located? Quote Link to comment Share on other sites More sharing options...
70rsz28 Posted August 3, 2005 Report Share Posted August 3, 2005 TPI Specialties says you never need anymore than 47psi even on a motor with headers/cam/throttle body. Its in thier TPIS Insider Hints book. Quote Link to comment Share on other sites More sharing options...
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