Help! Just got car back from major and something isn't right

[comquat1]

As the title suggests, I just got my 91 back from a full major including engine out timing belt, water pump, valve adj, all hoses replaced. The drive home from the dealer is about 15-20 miles and I didn't notice anything wrong on that drive home. Parked the car for two days and take to run an errand and I can immediately tell something isn't right, the exhaust does not sound like my comptech exhaust (sounds like a truck now...) did when I bought it in. Upon further driving down the road I am noticing what I can only figure is stuttering upon acceleration, the car loses power for a fraction of a second. But it does this multiple times as I run up through each of the gears... feels like your accelerating but putt putting along type hesitation. Once I got home I let the car idle and could not tell anything sounds out of the ordinary. Put it up on my lift to see if anything was obvious and other than a bolt for the gas tank bracket missing (which I'll get replaced) nothing seemed out of place.

What would cause hesitation under acceleration in this car? Can any techies point me in the right direction?

 

[Mac Attack]

It sounds like you have an exhaust leak with the stuttering and increased exhaust noise. The exhaust leak could be impacting your O2 sensors and sending weird signals to the engine control unit. Obviously an exhaust leak would also make it sound like a truck too. Try unplugging the connectors for both O2 sensors at the same time and see if that at least clears up the engine hesitation. You will have a check engine light where the ECU goes into a safe mode, but it is fine to do a short test drive and see if that clears up the hesitation.

If it clears it up, check and make sure all exhaust flanges are tight and not leaking. Check if your exhaust manifolds are tight on the heads. If you have aftermarket headers they may have cracked.

BUT - I would first call the place you had the work done and explain the symptoms to them. There should be some kind of warranty on their work!

Dave

 

[B2FiNiTY]

Could be your belt is off causing the timing to be off.

 

[comquat1]

It sounds like you have an exhaust leak with the stuttering and increased exhaust noise. The exhaust leak could be impacting your O2 sensors and sending weird signals to the engine control unit. Obviously an exhaust leak would also make it sound like a truck too. Try unplugging the connectors for both O2 sensors at the same time and see if that at least clears up the engine hesitation. You will have a check engine light where the ECU goes into a safe mode, but it is fine to do a short test drive and see if that clears up the hesitation.

If it clears it up, check and make sure all exhaust flanges are tight and not leaking. Check if your exhaust manifolds are tight on the heads. If you have aftermarket headers they may have cracked.

BUT - I would first call the place you had the work done and explain the symptoms to them. There should be some kind of warranty on their work!

Dave

The email has already been sent. But what you're describing sounds right, they had to take my headers off to replace my oil pan gasket and the entire exhaust system came off with the engine being removed. I'll talk to them tomorrow morning before monkeying with it myself. Thank you for the guidance.

- - - Updated - - -

Could be your belt is off causing the timing to be off.

Job was done by my local Acura dealer's NSX tech who's been working on them since 91... I would hope that isn't the case. But at this point all things to consider bringing up to them when I call tomorrow.

 

[RobM]

If the timing belt was off wouldn't you have noticed that in the first 15-20 miles driving it home?

 

[comquat1]

If the timing belt was off wouldn't you have noticed that in the first 15-20 miles driving it home?

Definitely didn't notice it on my way back home, that's what threw me off today when I got into it today for the first time since. I am feeling like it's an exhaust leak based on the above comment.

 

[DreamPowered]

I did notice a slight bit of hesitation when I had my car serviced last year, but I did get a pulley shield put on and thought that might have been the reason.
after driving it home and within the next few drives it went away. the only thing I could think about it that all the clearing up of the old gunk out of the throttle body was causing the hesitation.
I haven't noticed it at all.
hope you can figure it out.

 

[Mac Attack]

Like said above, the TB skipping a tooth causing rough running and a change in exhaust note is plausible. That could have happened after the service due to the tensioner not being adjusted correctly or loosening up and skipping a tooth. If there are no exhaust leaks, that would be next to check.

One other possibility is that the jamnut on a valve wasn't torqued correctly and is working loose.

Hopefully, and most likely, it's a simple exhaust leak!

 

[boca rat]

I would get the dealer to pick it up and trailer it back for a checkup. If the belt did slip, it might slip again. And we know where that might end up......not sure why you are waiting to do this.

HTH

 

[comquat1]

Just an update. Was going to drive the car in this afternoon as Bill the tech at East Acura said he would come in on his day off but I couldn't keep it running long enough to even drive it out of my garage. Called East and talked to Bill and he offered to come to my house to look things over. A couple things came up to look at with the main thing being that the belt might have jumped a tooth... Bill showed up and we started to remove the valve covers and low and behold, a coil pack plug was not clipped in completely. No need to remove the valve covers and reset the timing. Kudos to Bill for being completely there for me on this, I consider him more than just a business acquaintance at this point. As long as I own my NSX, he will be the only one servicing it.

 

[BlackbirdXX]

Good to see it was an easy fix.