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So this is going to be a bit tricky to explain but here we go. I've got a 99 Civic SiR with the stock B16A2 motor that has 320,000kms. Sometimes when I am at a stop, I go to accelerate and it feels like its almost flooding, kind of like if you were to start off in second gear. When I hit about 3000 rpm, i have full power again. This only happens when first accelerating from a stop. I believe it is only happening when the engine is warm. Now this is not always happening. I left my house and everything was fine. Drove for about 15 to 20 minutes today with no issue regarding this specific issue , shut the car off for a minute or so and then started it back up and this slow acceleration was there again. Drove a bit with this problem, turned the car off for about 5 or 10 minutes, when I turned it back on and started to drive again, the problem was gone. The other symptom i get is during acceleration, regardless of the speed, I get these subtle drags in power every now and again. RPM is still climbing and so is my speed but I can feel these slight drops in power like a slight hesitation. These happen all the time whether the engine is hot or cold. I also sometimes have to hold the key longer to start the vehicle while other times she fires up immediately. The timing belt was done recently, so lets say under 10,000kms. It wasn't done by a shop but a father and son who seem to have a lot of mechanical background as they were in the middle of building a hot rod, did the job The fuel filter looks relatively new but I am ordering one just to give me a baseline. I just did a valve adjustment on the vehicle. 3 times actually, just because my issue wasn't being resolved and I really wanted to eliminate that as a suspect. Now this issue isn't consistent which is making it hard to diagnose. I have also replaced all 4 spark plugs. I did a compression test because thought maybe my rings were going bad but the cylinders were all great with about 210psi give or take. I did put a new 2.5 inch exhaust which I'll be honest, I believe this slow acceleration started after that. Yes I know what you're thinking, it's the exhaust. I put the vehicle back on the lift and I didn't see any exhaust leaks though. I did also replace the CAT because I was throwing a check engine light and that has be resolved. The engine is stock except for the AEM Cold Air Intake which travels to the inside of the front bumper, not a short ram and now the Cat Back exhaust. Could timing cause those short drags in power? I don't feel them during cruising speeds. This is what makes me lead to a fuel issue. I'm looking at ordering some fuel injectors too. Vehicle doesn't burn oil. No abnormal smoke coming from the exhaust. What are your thoughts?

 
Rep Power: 222

Giant exhaust is probably most of it, possibly some clutch slip as well

 
Rep Power: 243

2.5" is on the bigger side.

So if you swap back to the OEM exhaust all your issues go away?

 
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I would be more inclined to thinking it was the exhaust if it were occurring all the time. The second issue happens all the time, but this was with the stock exhaust as well as the aftermarket one. As for the slow acceleration, only happens sometimes. Drove my car to and from work, no issue with acceleration but had that slight drag in power at different speeds. I'm picking up a timing light just to confirm my timing is good as the distributor was replaced at the same time the timing belt was. I'm almost ready to just swap the timing belt out myself so I know it was done correctly as it was completed by the owner himself

 
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So just an update. I just checked the timing today with the timing light and that is right where it needs to be, so that eliminates that.

 
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So here is a question, could a possible loose timing belt be causing these problems? I'm thinking the belt may be a bit loose which I think could be causing those intermittent lags in power, and would explain still having an increase in power and acceleration without noticing any drops in those two categories. Also why its more noticeable on acceleration and not as much on cruising because at cruising speeds, there isn't as much torque on the belt as its using a lot of centrifugal force from the engine to keep it spinning compared to as when I'm trying to increase speed. This make sense? Sounds great in my head haha. When I get home I'm going to try adjusting the belt tensioner and see if that does anything.

 
Rep Power: 126

I REALLY highly doubt it. If your belt was that loose, you'd be skipping teeth, which would either result in limp mode (restricted to 40km/h or something like that) or a destroyed engine.

 
Rep Power: 222

If you think the belt is loose I would definitely check before something bad happens

 
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Oh ya I'll be checking it when I get back home. For the engine to have great compression and me being told the timing belt was done by a backyard mechanic, I just keep going back to that timing belt. Im going to be swapping out the fuel injectors and fuel filter and maybe it will be something simple like that, causing the problem, which also fits the symptoms. So many things I want to do to this car but want to have the engine running correctly first haha

 
Rep Power: 126

I'd be much more inclined to believe it's a fuel delivery issue. You'd be the luckiest person on the planet if it is a timing issue and you're able to fix it. For it not to have failed already will be some weird anomaly in the timeline that'll be talked about thousands of years from now.

 
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I don't think it's a BIG timing issue, which is why it's only a slight lag but compression is still good. Almost like the belt is stretched in small areas. I don't know. Really just trying to think outside the box and thinking out loud. Fingers crossed it's the injectors or fuel filter. I've heard somewhat similar issues and the injectors solving it.

 
Rep Power: 126

Well, do you know if it has a cam position sensor? If the cam is off even one tooth, it'll go into limp mode.

 
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I would lean more towards that if it was happening at all times but it operates perfectly as cruising speed where there isn't any extra torque on the motor to try and keep it at the current speed. for example, if i'm driving a constant 50 km/hr, the engine is nice and smooth. if i'm travelling 50 kms up a hill, I can feel the intermittent lag like little studders in power. So it seems it is only happening when the engine has more torque being applied. I just replaced the fuel filter and saw no changes. Waiting on the Fuel Injectors to come in so i can change those

 
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FIXED!!!. Oh what a rollercoaster. So it ended up being a loose timing belt causing every issue but not loose enough to skip a tooth. When I was doing a valve clearance adjustment, I noticed the belt seemed a bit loose when rotating the cams at certain intervals but for the most part seemed okay. After doing a bunch of research throughout all of this and eliminating a lot of the more simple and inexpensive parts first, i just kept coming back to that timing belt. So today I finally pulled the valve cover and upper timing belt cover and started feeling the tension on the belt. I would rotate the crankshaft a bit, feel for tension and continue. Didn't feel right so I followed the steps in the manual on how to adjust tension. Afterwards the belt felt nice and snug regardless of where I was on the timing. What I think caused the issue was when the belt was replaced by the previous owner, he put everything at TDC, tightened the tensioner and called it a day. He missed the step where you're suppose to rotate the crank 3 teeth on the cams, loosen the tensioner, tension the belt and torque the tensioner bolt. After doing this I put it all back together and took it for a test driver. It was awful, even worse actually. I got pretty worried. After some reading, I thought maybe my timing was off so I adjusted the distributor slightly and now this car runs like a dream now. Thanks everyone for all the input and advice. I hope this helps someone else