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Discussion Starter #1
Today, after having driven my 164 24v (LS) for a few hours, we stopped and had a 20 minutes shopping break. When I then started the car, it "felt" strange, but I didn't pay that much attention to it until after a few minutes. The car completely lacked power, and I now suspect the timing belt has slipped. However, from most other posts about slipped timing belts, I would expect a rough idle and a roughness that fades away with increasing revs. The behavior on mine is instead a smooth idle, and regardless of the rev, it runs very rough if I try to increase the speed/rev. It almost feels/sounds like there is something blocking the exhaust! If I instead keep the rev constant, it (almost) runs nice.

I replaced the timing belt and all accessories about a year ago, and have driven ~10000 km (6000 miles) since then.

Any ideas? Thanks in advance!

/ Mathias
 

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Today, after having driven my 164 24v (LS) for a few hours, we stopped and had a 20 minutes shopping break. When I then started the car, it "felt" strange, but I didn't pay that much attention to it until after a few minutes. The car completely lacked power, and I now suspect the timing belt has slipped. However, from most other posts about slipped timing belts, I would expect a rough idle and a roughness that fades away with increasing revs. The behavior on mine is instead a smooth idle, and regardless of the rev, it runs very rough if I try to increase the speed/rev. It almost feels/sounds like there is something blocking the exhaust! If I instead keep the rev constant, it (almost) runs nice.

I replaced the timing belt and all accessories about a year ago, and have driven ~10000 km (6000 miles) since then.

Any ideas? Thanks in advance!

/ Mathias
Edit, yeah coil pack is the wrong answer on that one.
May want to try removing the chip and replacing it with the OEM to see if that clears up some things?

Could be off a bit though. ( I have to say out of time ,my 3rd choice!)
Jason
 

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Discussion Starter #3
If a coil pack would be broken, wouldn't the "check engine" light alert for that?
How messed up does the timing/ignition/fuel mix have to be for that to happen? Does anyone know?
 

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If a coil pack would be broken, wouldn't the "check engine" light alert for that?
How messed up does the timing/ignition/fuel mix have to be for that to happen? Does anyone know?

I doubt a bad coil pack would give you good idle and no power. I would be more suspect of a failed catalytic converter failure clogging exhaust system. If you have a failed coil or plug it should not idle smooth.

You won't get check engine light for failed coil pack unless it upsets O2 sensor enough that it can't adjust mixture.
 

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I once had the timing out on my old X1/9 - Fiat managed to put the timing markers a tooth or two out for a batch of cars. That idled fine but had reduced power and got rough as anything above 5,000 rpm - normally the engine would go well beyond 7,000 with ease; no rev limiters fitted.

Based on that it could well be your timing belt but personally I'd check as many other avenues first as it is not a nice job and you had it done a year ago. Possibly fuel starvation via blockage or some kind of pump failure?

Good luck.

Richard
 

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Since it happened suddenly after a restart, I would suspect a jumped timing belt as well. I certainly would check it for proper timing as the first thing, because it is sooo important. It would likely be a little harder to start, run a little warmer than normal and lack power but idle almost right without a definite miss and just not have the "growl" that the engine normally exhibits when you get on the throttle. :(
Charles
 

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Discussion Starter #7 (Edited)
Quick update: The front intake cam had in fact slipped at least one tooth.

Does anyone know if there is a risk of bent valves even though no metallic sounds are heard while rotating the engine? I'm having a bad fealing...
 

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personaly i think you are fine, mine was off 2 teeth and i don't think i bent any valves

thanks and have a blessed day
 

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without knowing piston to valve clearance its hard to say without opening it up (head off etc) if its only jumped one maybe two teeth you should be ok..
if your still in doubt, run a compression test on that bank once you have reset the belt timing...
good luck
 

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Discussion Starter #10
As mentioned earlier, a few days ago I discovered that the front intake cam had slipped. To avoid similar incidents in the future, I retimed all cams and tightened up the belt, before putting everything back together.
However, although the car ran much better afterwards than before (obviously), It didn't react well on rapid idle-to-2000 revs, and it started to shake (bam, bam, bam) if I tried accelerate from say 35 mph in fifth gear. It more or less behaved shaky below 2500 rpm.

Of course I feared that some valves had been damaged. So, back to the garage, open up everything again (lucky I'm on vacation). I verified that the cams were 100% accurate, whereupon compression tests were performed on all cylinders. The values were all above 205 PSI, which I assume is good.
Correct me if I'm wrong, but this must mean that no valves were damaged, right?
The only bad thing I found while putting the parts together was that the EGR "tube" wasn't properly connected to the exhaust pipe (which it is now).

Nevertheless, the car runs more or less the same now. Same lousy throttle response, and same shaky performance when accelerating in high gears from low (~1750 rpm) revs.

Now, what I forgot to write in my first post was that I recently separated the air flow meter and cleaned it. Is it possible that this latest behavior may be caused by a broken air flow meter? I have measured the resistance between pins 2 and 3, and the resistance vs angle plot is not nice and smooth. I hope to be able to measure this more accurate tomorrow.

If this car really had a soul/spirit, it would automatically fix any smaller errors, given the number of hours I have spent on it.
 

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later motronic afm's should have a smoother value than the earlier l-jets (something i read somewhere) if comp is that good, feel confident it aint got bent valves! minimum value is normally around 120 (i could be wrong)
 

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could this be caused by a slow or bad AIC valve, the same thing happens to SAAB's and BMW's and gives a similar throttle issue, Its not a hard job to clean and lubricate one.

thanks and have a blessed day
 

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Discussion Starter #13 (Edited)
I measured the AFM, and although the values are somewhat spooky, it appears to give out correct values when the car is running. The area where the values are strange is at a really low air flow, and it is above this at idle. If the opportunity is given, I'd still like to test with another one.

The throttle position sensor gives reasonable values.

Jason, I think the AIC (Automatic Idle Control) works. It definitely improves the idle, at least.

Does anyone know what a healthy LS should have as idle vacuum value? I connected a vacuum gauge by a tee on the hose to the fuel pressure regulator. The vacuum value is ~14 in.Hg (355 mmHg = 0.47 bar) at idle, which I would say is too low. My other car (Citroen BX) idles at a value of 18 in.Hg, which is also righ of the beginning of the "normal" area of the gauge.
I didn't find any obvious leaks, though.

Tomorrows project involves reading the fuel pressure and changing back to the original chip (using a Squadra-Tuning now).

Thanks for the help and comments so far.
 

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I was wondering the same thing regarding engine vacuum on a LS.

I've got one in the shop right now, that seems to run pretty well, but as a low/lumpy idle. Engine vacuum is about 10in at idle (approx. 1000 feet above sea level), but will increase to 14-15 if I hold the throttle open ever so slightly.

This car had a whole slew of problems, most of which are fixed now, but I'd like to figure out the idle. At this point I'm suspecting that it may have jumped time.

Jeff
 

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Discussion Starter #15
Final report:

Fuel pressure was correct. After a moment of despair I started verifying the very basic things again. It turned out to be an ignition module that was broken! It only ran on 5 cylinders, and it's a bit embarrassing that I didn't notice that earlier. My garage neighbor happend to have a spare module, and the car is now running beautifully!

Based on the fact that the car is now running stronger and smoother than ever, I think the ignition module may have been strange/partly bad for quite some time. The other alternative is that the timing belt slipped one tooth more or less directly after my timing belt change a year ago, and that I simply didn't notice that. The car was running good before, but the idle is smoother now, and the low end torque has improved significantly.

By the way, running on all cylinders, the vacuum is about 17".

Thanks for all the support! In the really dark moments it helps to know that I'm not the only one who really like these cars.
 
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