ok so I’ve recently done the head gasket and chains, trying as best as I could to follow diy guides etc and I’m 99% sure I did it correctly. Now with spark and fuel the engine runs badly. No power, doesn’t rev high, chokes up with any more than slight throttle and occasionally pops and grunts. Sounds like it has a misfire.taking leads on and off one by one doesn’t seem to really change anything. There are no fault codes showing. I’ve taken the cam cover off and checked the timing marks and used the locking plate to check the cams, all aligned. I’ve read that the timing can be ‘half a tooth out’ but how to check that I don’t know without tearing the gearbox off again to get at the intermediate sprocket. And I don’t think it will be that! I checked it like 3 times before putting the engine in. I’m stumped. Don’t think it’s a vacuum leak, it’s too extreme. Any help? Oh and I tried a new coilpack, new leads and plugs
You don't need tearing gearbox off to check timing. I have skipped chain once. I could check intermediate mark with gearbox, also you can put 1st cylinder to top to be sure. You need Bentley manual. Vr6 cams don't align perfectly with 4 mm locking plate.
Not something simple like MAF in wrong direction? If 4 wire 'obd2' can fit it in either direction but there is an arrow pointing to correct airflow.
I think the MAF is in the correct direction. Maybe cos I've deleted a load of stuff there's a bit of sensitivity going on. I know Ive got a bit of an unusual layout going on. The servo vaccum goes straight to the manifold via the check valve seen there, I've stuck that loop on it. Hard to see but theres a blanking on the elbow of the plastic intake where the EGR stuff would normally go. All a bit trial and error really!
Your MAF measures all the air going to the engine. Having a PCV leak into the atmosphere is an error state the MAF is not accounting for.
I can't say for certain as it was a loooong time since I did my chains but there was talk about being able to get the intermediate sprocket 180 degrees out, it will appear correct but once rotated will be instantly out of alignment. From memory when doing the timing you line up the cams, crank and the notch in the intermediate pulley should be pointing upwards. Can't you take top cover off with gearbox in place? I doubt it's MAF, it does make it run a bit poo certainly at idle but it doesn't stop it from revving.
I've blanked off the PCV port so I don't think there's any unaccounted air getting in behind the MAF. I'd have to take the bottom chain cover off to check the intermediate sprocket. I took the top cover off to see if there was slack in the chain, there isn't. Even so, if I return the engine to timing mark at the crank pulley, the cams end up lined up with a locking plate - that means its timed surely. If not, maybe I needed to be far more accurate with the marks when I put it together.
Looking at your picture, you are venting the crankcase from the cam cover. So you have technically introduced a leak after the MAF. They do not like running like that. It might be at the limits of compensation, but it is a error state.
Just to add to this. I used a Felicia fuel tank, with the pump and fuel filter, which is rated at 3 bar - the same as a vr6. However the fuel filter itself is smaller, maybe that is restricting flow? I've not put a guage on it, but I have had the injectors out firing into bottles. Do filters have varying flow rates?
Just because I’m sick of reading threads that never finish with the solution, I figured I share mine. It turns out, that 1, make sure you’re spark leads are FIRMLY pressed into ports 4/6 on a VR6. They don’t seat easily, so by getting them on properly before you put the upper intake on helps a lot. 2, don’t lose the silly little clip that holds the fuel pressure regulator into its housing!! Wow. This must have been letting by air into the injection no wonrder it wasn’t right. But you guys were right, checking Over all vacuums and moving the MAF away from the filter has helped the running too.
