Help - XKR almost no power, no codes
#1
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When the problem surfaced the car went from fine to sluggish, back to fine two or three times in a couple miles and then stayed very sluggish.
The fuel pressure is around 37 psi at idle and during attempts at hard accelleration. RPM will increase to 4000 rpm but with no pulling ability.
In trying to find the issue I replaced the knock sensors, the Air Mass Flow sensor, and the supercharger coupler. Blowing smoke into the intake shows no escaping air/vacuum leaks. I removed both fuel pumps and they appear to pump well outside the vehicle.
I did try pulling the fuel pump relays and it will idle with only one (either) installed.
I do hear the fans more than I remember and at one point I noticed that the exhaust on one tail pipe appeared hotter than the other. I also replaced 4 spark plugs so far and none appeared really clean like water was in the cylinder.
I will install two new pumps tomorrow but guessing is getting expensive.
Any sugestions from you experts?
#2
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A couple more points: I replaced the engine about 12,000 miles ago with a rebuilt unit. The supercharger has 100,000 miles on it and I've found maybe 4 tablespoons of oil in the air tube. I've been told the oil is likely due to clogged screen in the valve covers. I'll be cleaning them soon as well as doing a compression check.
#5
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You mention fuel pressure at around 37psi at idle. I don't know how you are measuring that, but if with OBDII reader, then it MAY be low, but, the more important question is, what is the fuel pressure when driving and pushing the accelerator pedal all the way down. I had a very similar problem on my 2004 XK8, ran fine unless I opened it up, then stumbled, slowed down...fuel pressure would drop from 55-60 down to 10 psi or so when wide open. Now, I say your 37 psi MAY be low because I am not sure if the early models actually should run at 55-60 psi, but I believe they should. Regardless, check pressure at WOT. Now, if it turns out your pressure drops, you may have a bad pump, or clogged fuel filter.
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#8
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I had the exact same symptoms with a Mercedes- it was perfect All of the sudden right before a long trip it would only go about 40mph. Floored or not, 40mph was the top speed.
Occasionally it would go a little faster but felt like it was being held back by a giant force field. The cat was clogged by a honeycomb turned sideways. As Anders said, a post cat pressure test is inexpensive and will identify or rule out that as an issue.
Occasionally it would go a little faster but felt like it was being held back by a giant force field. The cat was clogged by a honeycomb turned sideways. As Anders said, a post cat pressure test is inexpensive and will identify or rule out that as an issue.
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ragtopXKR (10-16-2013)
#9
#10
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Try Nameless Performance The 400 cell are roughly emissions equivalent to stock and flow better. The 200 cell will improve performance and should still pass emissions, thought by less margin. Their products are high quality, a perfect fit and far cheaper than OEM.
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#14
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Without a gauge in the pre cat o2 sensor there is NO way to tell if exhaust/cat is clogged.
If the exhaust is indeed free flowing, another thing that could drastically reduce power w/o codes is knock sensors retarding timing from bad sensors or engine noises which can be interpreted as ignition knock, oh bad fuel could cause the same thing.
If the exhaust is indeed free flowing, another thing that could drastically reduce power w/o codes is knock sensors retarding timing from bad sensors or engine noises which can be interpreted as ignition knock, oh bad fuel could cause the same thing.
#15
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I had a knock sensor fail soon after replacing the motor and I replaced the second knock sensor last week so both knock sensors are new. I found it is easy to identify these by connecting a new one and just hanging it in the air. Perhaps my 5 month old one already failed so I'll try that again. Thanks again for all your suggestions. The fuel has been replaced since I just removed the tank so we can eliminate that. I'm pretty sure a bad injector or coil would throw a missfire code.
Last edited by ragtopXKR; 10-16-2013 at 10:21 PM.
#17
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Have you checked your plugs? It may also be related to bad coils, all hard to say without hearing/seeing what happens.
Could you record it on video, so that you can see the rpm (and acceleration) and also hear the engine? This might help us in identifying the issue.
But it isn’t good to do wots now of course, so keep that to a minimum.
Could you record it on video, so that you can see the rpm (and acceleration) and also hear the engine? This might help us in identifying the issue.
But it isn’t good to do wots now of course, so keep that to a minimum.
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