Poor throttle response, misfire fixed!

[bilboaustin]

Hi everyone! I'm new to this forum so be nice    As the title suggests I've got poor throttle response when blipping the throttle. Under normal road driving it's not an issue and I can live with it, it's when you start pushing things that it's causing me a bit of grief, heel-toe can be a little tricky as it's sluggish to pick up. It also likes to pop and split flames if I touch the throttle on de-acceleration (VERY loud sometimes, I've half expected to see a banana peeled tail pipe!)

Now this is where it is really confusing me, when I first start the engine and it's in open loop the throttle responce is amazing, it's when it switches to closed loop that the response becomes bad.

With a the use of a scanner I've studied the live data, when I blip the throttle in closed loop the ignition retards massively! About 30 degrees after TDC, in open loop it doesn't do this  Another thing I've noticed is the Long term fuel trim on idle is around -13% but when I raise the RMP it goes down to -25%!

The first thing I replaced was the upstream Lambda sensor as It was old and had my doubts about it, no difference! I then moved onto the knock sensor thinking that the massive timing retard was causing the issue, nope was still the same! I then replaced the MAP and throttle position sensors with you guessed it.....no change. That's when I moved onto the fuel pressure regulator after looking the fuel trim, replaced that today and I've still got bad throttle response!! The next thing on the list is injectors, my thinking is that I must have a one thats weeping a little bit.

Any help I will really apreciate!

[bilboaustin]

https://youtu.be/Y1sOGKtuk1U

[bilboaustin]

Well, another set of injectors didn't solve the problem! Back to the drawing board I guess. Next thing to check is the timing, what position is no1 piston at when the crank pin is located? The reason I ask is I know the bottom pulleys are prone to spinning.


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My idea is that the last time the cambelt was changed the bottom pulley could have spun by a couple of degrees, so it could of been set up wrong.


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[cully]

All pistons are mid stroke

[bilboaustin]

All pistons are mid stroke

Cheers Cully! Fingers crossed the timing is out.


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[bilboaustin]

It's now developed an intermittent missfire! Bloody French cars[emoji6] goes away for a while if I turn the ignition on and off again. Got the EML light flashing at me with the message 'catalictic converter fault' on the dash, so at least there are some fault codes. I will have to wait till I can borrow the scanner from work to see what's going on.


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[Rippthrough]

Stop replacing parts and check all the hoses and gasket for an air leak.

[bilboaustin]

Stop replacing parts and check all the hoses and gasket for an air leak.

Done that ages ago, checked all the basics first. Used a smoke machine and pumped the inlet side of things full of smoke and no leaks. Compression is good hot and cold, no loss of oil, oil pressure is good, all electrical connections are good from what I can tell. I've done everything I can think of with the equipment I have available, if I had an oscilloscope and decent knowledge of how to use it then maybe I could make a decent diagnosis haha


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[Rippthrough]

Smoke machine won't help if it's a split hose that's leaking under vacuum.

[bilboaustin]

Smoke machine won't help if it's a split hose that's leaking under vacuum.

I've taken off the pipes for the brake servo and canister purge valve and blocked the holes on the manifold, it still does it. Any other hoses I'm forgetting about? Lambda readings also don't show any excess oxygen in the exhaust system? :S


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[bilboaustin]

Well I got the scanner on it today and these were the only relevant fault codes on the system , not one single clue. Misfire starts after 20-30 minutes of driving and it won't idle, the moment I start it back up it's on all four again. I've ordered a set of coil packs so will see if that solves anything, doubtful to be honest. Another thing I've noticed is that you can hear it pinking quickly when the throttle is blipped fully, that would explain why the Ecu is retarding the timing in closed loop. What is causing it to pink is the mystery?! I had a spare crank sensor laying about so decided to swap that over as it's a five minute job and it's made no difference.


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[bilboaustin]

Fitted another set of coils and it seems to have fixed the misfire (for now). I'm still left with the throttle response, well lack of it! I checked the timing the other day and the bottom pulley is miles out so I'm going to buy a solid aluminium one soon. From what I could tell the timing is as it should be (popped the plugs out and all 4 pistons were roughly the same height) so I'm fresh out of ideas! I'm going to give an auto electrician a call tomorrow and see what he says.


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[bilboaustin]

Update time! I had a chat with an auto electrician today he gave me some good information. He said with the engine at normal operating temperature and no air leaks a good MAP sensor should be reading 30kpa or lower, any higher and you are looking at an engine issue, possible timing out or a bad valve . My car is reading 47kpa on warm idle, I had one more check for an air leak and there are no air leaks, so it's an engine issue.....brilliant!! Haha. First port of call is to order that bottom pulley, I'm still clinging on to the idea that the cambelt was changed with a slightly spun bottom pulley putting the timing out slightly. If I fit the new pulley and the timing is spot on then off with its head!!


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[bilboaustin]

Well I finally got round to fitting the spoox billet pulley and the timing is spot on[emoji17] The missfire hasn't occurred but it did put on the engine management light the other day, codes were p0300-Random missfire, p0108-manifold pressure signal fault and p0137-downstream oxygen sensor fault. I'm really starting to loose interest in the car now[emoji20] but I'm not going to give up! I think I'm going to get the spare engine ready to rock, mine has done over 130,000 miles now.


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[welshpug]

needs a map sensor by the sound of it, and the cat may be toast.

[bilboaustin]

The cat isn't there and I've already fitted a new map sensor (along with every other bloody sensor!) lol


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[JTaylor2005]

Gaskets damaged anywhere on the inlet manifold?

Dodgy wiring on the lambda sensor so when it starts running in closed loop it causes issues as the readings are off?

I am not that knowledgeable with this sort of stuff but could be something to look at?

[bilboaustin]

Gaskets damaged anywhere on the inlet manifold?

Dodgy wiring on the lambda sensor so when it starts running in closed loop it causes issues as the readings are off?

I am not that knowledgeable with this sort of stuff but could be something to look at?

Thanks for the advice JTaylor, I've checked all the readings from various sensors, especially the lambda and they are all doing as they should be[emoji17]


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