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Discussion Starter #1
I bought a 2007 Suzuki SX4 AWD with 120,000 miles. This vehicle was sitting for over a year with a blown head gasket. I took the head off and got it machined and cleaned up, installed a new head gasket and got it all back together with some new parts. I attached a hose to the fuel line and hotwired the fuel pump and pumped all the old gas out into some cans. Filled with fresh gas.

I cranked it and could hear a cylinder fire every once in a while. After a couple tries it sounded like it wanted to start but then immediately stalled. I tried again but I used the gas pedal when it seemed like it wanted to start and it slowly fired up. I let go of the gas at 3000RPM and it stalled. I tried it again with the gas pedal, it started real rough like before but once it got running it sounded great but I had to stay on the gas or it would stall. It won't start or stay running without constantly giving it gas. It sounds like a completely normal engine when running. There's no misfiring or weird sounds nothing. I sat in there for a good 15 minutes running it between 1000-1500RPM while testing the air conditioning and heat. It all works fine but as soon as I let off the gas it died again. If I slowly let it below 1000RPM it starts stuttering and anything above that and it runs normally. I didn't attempt to drive it.

I don't think it's the fuel pump because there was no noticeable lack of fuel at or above 1000RPM and it pumped all the old gas out no problem.

I don't think think it's a ignition issue because it runs perfectly normal after startup with new spark plugs.

I suspect it's an airflow issue. This vehicle is not equipped with an idler control valve, at least not one I can find anyway. I believe it uses the throttle body to control idle air. Which I've cleaned a little oil residue out of where I can reach.

I rechecked the vacuum hoses and can't find any obvious leaks. No check engine light or codes. I'm not really sure how to proceed with diagnosing this. Any suggestions will be appreciated.

-Josh
 

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Well I made some good progress. I slowly got it fired up and then after it warmed up to operating temperature, I noticed one of the O2 sensors was flatlined at .4 volts. When I checked that O2 sensor yesterday it was reading properly. Anyways, I think that's irrelevant to this problem. I let my foot off the gas and it dropped to 500RPM and it started stuttering and shaking but instead of stalling like yesterday it actually stabilized the idle after a while! When it idles under 1000RPM the engine starts shaking a bit. Now I could check the engine while it's running. I heard what very unfortunately sounds like a timing chain sliding on aluminum about every other second.

I followed the factory service manual precisely when I put the timing components and chain all back together. I torqed everything down properly and got the timing chains on their marks exactly where they were supposed to be. Changed the tensioner gasket. When I was done, I even turned the crankshaft a couple rotations by hand to verify the chain didn't jump teeth. It seems like the timing chain itself is bad or the chain tensioners aren't getting oil pressure. I really don't want to take this timing cover back off but I'm afraid I have no choice. The last thing I want to do is take that head off again because the valves get mashed. It drives great though!
 

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you did replace the tensioner and the gasket (some have them, some don't)? and made sure they oil passages were clear? its also very easy to get a "slipper" foot not quite square so the chain will ride on the guide edge, not the plastic surface. I suspect you might be taking the cover off and checking before you do damage just in case.
 

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Did your new tensioners come with grenade pins and if yes, did you pull them?

… Philip
 

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Discussion Starter #6
I reused the old tensioners. Only one tensioner needed a gasket which I replaced with a new one. The other one is spring loaded. Yes, I used carb cleaner to clean out the oil passage. I'm going to take the timing cover off again tomorrow morning and see what's going on. and yes, I did pull my tiny allen wrench grenade pins :~D
 

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I reused the old tensioners. Only one tensioner needed a gasket which I replaced with a new one. The other one is spring loaded. Yes, I used carb cleaner to clean out the oil passage. I'm going to take the timing cover off again tomorrow morning and see what's going on. and yes, I did pull my tiny allen wrench grenade pins :~D
theres your problem.....NEVER reuse old oil pressure driven tensioners, thats asking for trouble I don't reuse any tensioner on a chain system, too dangerous and hard to get to.
1, people compress them to put the pins in to reset them forgetting to release the non return ratchet, and kill the internal teeth and 2 they never have enough non return pressure behind them because they have been hammered to hell by the old stretched chain and the non return teeth will be rounded and won't grip in the spot the new chain will be sitting at. Oil pressure is just to push the tensioner past the next "tooth" so it takes up wear, engine oil pressure won't keep the chain tight on its own.

time for new tensioners.

As a rule of thumb, old tensioners on a new chain = about 10% of expected chain life if you are lucky. usually less. On a belt drive, you can get away with re-using, but they are a different system and have a big ass spring and grease in them, grease being not very compressible works well as a non-return agent and as the belts have "give " in them they tension differently.

its noticeable on some vehicles they will be fine, then for a couple of mornings they will "rattle" on start, then a few days later all is quiet again. This is the tensioner not quite making it to the next tooth and when the car starts the chain is loose until pressure rises to hold tension on the chain, as it stretches, it makes it over the next non return tooth and everything stays tight when theres no oil pressure. My 2015 has done this twice that I have noticed in 25,000 kms, about 10,000 kms apart.
 

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Discussion Starter #8
Ah I see, that all makes sense and I understand this much better now. Thank you for explaining that. I just bought a timing kit that has all the tensioners, guides, sprockets, and chains. I'm going to replace all of them.
 

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Discussion Starter #10
I am concerned with the O2 stuck in lean mode, check the fuel trims..

… Philip
My timing kit comes this Saturday so I'll revisit that issue after I get those parts in the car. This is a project car for me and so there's no reason to be driving it in the time bomb state it's in now. If I can get it running good I'll sell my Audi and make this my daily driver.
 

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Discussion Starter #11
Here's a graph of the RPM and short term fuel trim I logged when the computer figured out how to stabilize the idle with the loose timing chain.


 

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Discussion Starter #13
When I was torquing down the first timing chain tensioner I felt the bolt give all of a sudden and when I tried to back it out it snapped off with half the bolt still in the block. The other bolt is stretched in the same spot! I was torquing it to spec. It's an M6 x 20.

 

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I replaced the timing chains and tensioners. I got it all back together and tried to fire it up and it's exactly the same as before. I scanned for codes and this time I got P0340 camshaft position sensor circuit malfunction!! I'm going to replace that sensor!
 

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I replaced the timing chains and tensioners. I got it all back together and tried to fire it up and it's exactly the same as before. I scanned for codes and this time I got P0340 camshaft position sensor circuit malfunction!! I'm going to replace that sensor!
pull the sensor and make sure the sensor ring rotates withe the cam, and end of sensor is clean. Don't use a cheap rock auto sensor, pay extra and get a good quality one, Rock auto ones are fine, but you can get a faulty one out of the box

and now you have also found out why I harp on about not re-using bolts in these engines.......I hope others see the issues you discovered and spend the extra couple of dollars for new bolts. imagine what would have happened if that had let go in 5,000 miles time. Lucky you found it now and checked the rest. Well done.

as an aside, how bad was the old tensioner?
 

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Discussion Starter #17
The sensor ring does rotate with the cam and it doesn't appear to be damaged. I drove across town to buy a new sensor and still no start. I cleared the ECU and after some start attempts P0340 came back.

I knew to replace head bolts which I did but I didn't think to replace tensioner or timing cover bolts. I found some timing cover bolts that were stretched too so I replaced all of them while I was at it. I don't know if the lower tensioner has a check valve in it or not but when I released the teeth it easily pushed all the way back and wouldn't go forward on it's own.

aquanaut20, neither. If the manual said 11Nm, that's what I set my torque wrench to.

1. The car will not start if you crank it without being on the gas pedal. It really struggles to start even when you're on the gas. I can hear a cylinder fire every once in a while when cranking. The exhaust manifold will warm up when cranking a lot.

2. At first it would stall after starting but after a while it figured out how to idle. When I manage to get it started it idles rough. The engine noticeably shakes when idling. Anything above 1000 RPM seems completely normal. Drives completely normal besides rough idle.

I'm going to follow the service manual for troubleshooting code P0340 next. I don't know why the camshaft pos sensor wouldn't work at low RPM and hasn't had a problem until now. I'm really at a loss. Beyond troubleshooting that code, I don't know how to proceed with this.
 

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Could it be valve timing?
its very easy to get it wrong with the chain setup it has, time the bottom chain first, then the top one
i screw these up all the time, you have to follow the manual and the method it describes
 

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Discussion Starter #20 (Edited)
I followed it step by step. I didn't have any issues installing the timing components besides that bolt snapping. Got all the timing marks dead on and double checked by turning crankshaft a few rotations and rechecking before I put the timing cover back on. I mean could the shims in the tappets or the camshaft being worn out cause this? I took the camshafts and tappets out to get to the head gasket. I kept everything in order and I put it back in exactly how I found it. I inspected everything closely and I didn't see pitting or anything that worried me. Could worn out shims and/or camshaft be causing rough idle and very hard start?
 
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