Snowman Posted May 23, 2006 Share Posted May 23, 2006 I will worship anyone that can solve this problem for me! I am quite frustrated at this point. A friend's 94 loyale (SPFI) acts like it's not getting enough fuel when accelerating. Any throttle position beyond about 25% results in horrible bucking and hesitation, and the engine will rev out but without any power. I bypassed the fuel filter and measured the fuel pressure using the only gauge I have, which reads in increments so large that I can tell you that the fuel pressure at idle is around 25 psi plus or minus 5 psi, which is less than the spec for that car. I replaced the fuel pump with a new one (adapted a pump from a Ford truck because it costs about 1/4 as much...the pressure rating on this pump is like 60 psi, so it should be more than adequate). The pump made no difference. I then tried clamping off the fuel return line, and the pressure jumped up around 50. With the increased pressure, the car ran great. So I replaced the fuel pressure regulator. The car still acted the same way. At this point, I started looking for other possible causes, and have replaced and/or thoroughly tested the following: throttle position sensor, mass airflow sensor, coolant temp sensor, PCV system, EGR system, carbon canister and canister purge system, spark plugs, distributor cap and rotor, spark plug wires, and ignition coil. Edit: I also tried swapping the fuel injector and IAC valve, which also made no difference. Tomorrow on my lunch break, I'm going to set up a small outboard motor fuel tank on the roof and run the car on that in order to rule out the possibility of a fuel pickup problem in the tank. Any other ideas? I am getting really close to running out of things to try. Thanks. Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted May 23, 2006 Share Posted May 23, 2006 Timing? Timing belts? Maybe you broke the passenger's side? Link to comment Share on other sites More sharing options...
Numbchux Posted May 23, 2006 Share Posted May 23, 2006 it doesn't fit all the symptoms.....but clogged exhaust? Link to comment Share on other sites More sharing options...
northguy Posted May 23, 2006 Share Posted May 23, 2006 It seems like you were close when you pinched off the fuel line. You may want to explore that area. Also, vacuum lines? Any leaks? Link to comment Share on other sites More sharing options...
SuBrat84 Posted May 23, 2006 Share Posted May 23, 2006 I picked up an xt6 that had a "pin-hole" leak in one of the return lines near the tank so it was real hard to find but I was loosing fuel pressure right there (not to mention fuel!!!) Check your fuel return lines to see if maybe there is a problem. Link to comment Share on other sites More sharing options...
NorthWet Posted May 23, 2006 Share Posted May 23, 2006 TPS, MAF, maybe EGO. Alphabet-soup for free. Link to comment Share on other sites More sharing options...
Snowman Posted May 23, 2006 Author Share Posted May 23, 2006 Thanks for the replies. I tried the external fuel tank a few minutes ago, and it made no difference. I forgot to mention that the engine idles perfectly and runs great at less than 25% throttle, so any "hard parts" like timing belts are pretty much ruled out...would jumping a tooth on the passenger side be able to cause such a problem though? Plugged exhaust is something I hadn't really considered. I think I've got a spare Y-pipe I could try. It just seems that in all the cars I've dealt with previously that had bad cats, the engine still ran smoothly but just lacked power. I'm also going to hook the pressure gauge back up to verify that the new pump is working properly. Any other thoughts? Link to comment Share on other sites More sharing options...
DaveT Posted May 23, 2006 Share Posted May 23, 2006 Plugged exhaust is something I hadn't really considered. I think I've got a spare Y-pipe I could try. It just seems that in all the cars I've dealt with previously that had bad cats, the engine still ran smoothly but just lacked power. My soon to be retired 90 loyale had the front cat burnout. (Long story as to why). In the front cat I found only a piece of the core just about the ID of the exit pipe. Evidence of it lodged in the exit pipe sideways. Lots of crumbs in the second cat, partially blocking the core. The last mile of the trip home before I found this, it ran horribly. No power. Probably something like 1/4 throttle would seem ok. Part of the trip was up a big hill, and I ended up in first gear (3AT) to keep moving. Temp guage higher than normal. Took the exhaust apart, used a big screwdriver and removed the obstructions. (read cores & pieces) Runs fine now. Seems slightly better power wise than my 92 with functioning cats. Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted May 24, 2006 Share Posted May 24, 2006 Good point, about the catylitic converters. Get under there and try to shake the Y-pipe and see if you hear any rattling, or even take the exhaust off and try to shake it with the ends pointing down, and see if anything falls out. I've had Cats just break a part and cause blockage. Link to comment Share on other sites More sharing options...
DerFahrer Posted May 24, 2006 Share Posted May 24, 2006 You've tried everything but the O2 sensor My XT used to do this, replaced the O2 sensor, and hasn't done it since. Link to comment Share on other sites More sharing options...
Bill90Loyale Posted May 25, 2006 Share Posted May 25, 2006 I know you checked the plug wires, so this is a long shot. But when I had similar symptoms once, it turned out to be a bad high tension wire from the coil to the distributor. Might try swapping a different one in just to be sure. Hang in there. The solution is just around the corner. Link to comment Share on other sites More sharing options...
ballitch Posted May 25, 2006 Share Posted May 25, 2006 unless you have a blockage in the exhaust i would point the finger at emissions. ~Josh~ Link to comment Share on other sites More sharing options...
bgd73 Posted May 25, 2006 Share Posted May 25, 2006 My car did this too, it was a combination of many things that turned into an extreme problem, I ended up making stuff http://93loyale.50megs.com/ntakt.html Browse around, my similar probs are cured. Right away, be sure the EGR isn't stuck open,#4 cylinder sometimes never comes back....after affecting the car with said symptoms. Link to comment Share on other sites More sharing options...
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