Hello,

I have a beginner question : Is there a fuel return line hook up to the fuel rail. I think that the line going in the FPR is the supply line. Am I wrong? If so, where on the fuel rail is located the line? Is it near the pressure port? If there is no return line, why is the FPR located on the fuel rail and not directly in the tank? Is the another regulator in the tank hook on the fuel pump?

Tanks

 

Why so many questions whats wrong with the car?

 

Hello,

My car has misfire mainly on cylinder 1. I know that my FPR by the fuel rail leaks. (I'll install a new one shortly). I'm wondering if the misfire can be caused by a low fuel pressure at the end of the fuel rail. Since cylinder 1 is the last to get fuel, (misfire at idle) I think that the vaccum pressure at idle can suck a lot of fuel in the manifold, causing the misfire*. I already changed my coil (they were cracked) plugs, and high voltage wire. I also know that my idle motor isn't closing as it should be, causing a high idle at P and N. The ECT is of by 3 or 4 degre which I don't think is the problem. The only other thing that bother me is that I don't have a lot of boost pressure at 100% load (30 KPA). It should be between 40 and 60. But before tunning the boost pressure, I'd like to get rid of the misfire. Basically, I think that the FPR is causing the misfire. (I also inject smoke in the vaccum system, and everything is fine). And BTW, the engine smeel fuel at idle. But I can't find no leak!

Any idea?

 

I doubt the regulator is causing the misfire. The injector itself might be causing it.
Or maybe a burnt valve.

The ECT will cause the idle to go high if it is bad.

 

You were right for the regulator. I changed it yesterday, still the misfire problem. I really think that the injector is causing it, since the code is mostly on cylinder 1 (90% of time). The ETC is reading 80 celsuis in normal operation and seems to act normally.

I had the compression checked, and all 4 cylinder are on spec. The thing I forgot to mentionned is the Idle motor. A month ago, I had a hunting problem at idle between 1k and 2.5K rpm. I cleaned TB and IM and the problem didn't come back, but now, on P and N, the idle set between 900 and 1050 rpm. (Causing a P0507 high idle code). I plan to reinspect the idle motor, but I think I'll have to replace it.

My plan is to swap injector 1 for injector 4, so I can determine if the injector is the problem.

Do you think that the idle motor and the misfire can be related?

Tanks for your help

 

Hello,

Bad news, I change the injector 1 for the injector 4, and I still have the misfire on cylinder 1. Is a Scanner OBD2 is reliable to identify a cylinder? I did pretty munch everything that can cause a specific misfire (new plug, new wire, new coil, compression test (180 PSI), injector replacement.) I also check the wiring for ground or open circut, all normal.

What really anoye me is that my LTFT is at -11% and at idle, the STFT is at +30%. My fuel consumption is high (18 mpg) and the car runs rough at idle (because of the misfire).

Does anyone have any suggestion, don't be shy to give idea, anything can't hurt

Regards

 

Have you done a compression test yet? If not then I would do that to make sure you do not have a burnt valve.

 

Yep,

Has written on the previous message, 180 psi on all 4 cylinders

 

That is very strange.Im really not sure where to tell you to look next.
I will try to think of other things that can cause the misfire.

 

My idle motor seat is not perfect. When I put a light to inspect the contact surface, I can see the light. So I know that my idle motor leak. But I think it would cause a misfire on random cylinder. I occasionally get misfire on other cylinder, but always after a cylinder 1 misfire. Do you know what it takes to lunch a misfire P0301 code? Is it a number of misfire per 1000 revolution? Maybe I have misfire on all cylinder, but worst on cylinder 1.

Do you think that a idle motor leaking can be the cause? The MAF sensor would still give a good reading!

Can it be the ECU that acts weird.

One other weird thing is that when I sent my car to a mechanic, he reset the LTFT to 0 with vadis and my car ran perfect for 15 minutes. After a short drive, it started to misfire like before.

Thanks for helping

 

I am not sure exactly what triggers it. But it has to be a certain about of misfires detected per revolution.

Spray around the idle motor with carb cleaner and if the idle changes then it is leaking at the gasket.

It could always be possible on the ECU but I have never seen one go bad.

 

Hi tech,

I brought the car to a volvo specialist. With Vadis pluged in, he got a misfire code, but not for a specific cylinder, like my generic OBD2 reader did. He then put pressurized smoke in the base, and found a leak at the hose from the crankcase to the breatherbox.

The cylinder block was cover with oil. The leak created a vaccum leak, big enough to create misfire.

Thanks for your help