em1goesbwah

** B16 SHAKES/STUTTERS WHEN VERY LIGHT THROTTLE IS APPLIED (ENOUGH TO MAINTAIN SPEED) - USUALLY DOWNHILL OR FLAT SURFACE **

Hi forum. I'm new here, but have had my car for a few months. I've done general maintenance on the car and its been good so far (timing belt, brakes, spark plugs) but recently some weird stuff has been happening. I'll preface this by saying I have been putting in 94 for the last few weeks but have just filled it up with 91. First of all, the exhaust smells weird. I'm not a mechanic so I can't tell whether its rich/lean, but I know it smells different. Almost like a GM exhaust smell or something like that. Secondly, generally in first or second gear and low rpm, when I am trying to maintain my speed the car will jump back & forth, and the exhaust will go 'put put putputput put put putput', it almost sounds as though it's misfiring. I've put in injector cleaner, that did nothing. I've read that it may have something to do with my throttle body/part of the fuel rail/injection system? I'd like to know where I should start fixing/cleaning things and if there is actually something wrong. I'll also add that my ignition timing has not been properly adjusted yet (just went by ear), so I probably sound like an idiot for writing all this when it could be as simple as that, but it was running fine on 94 before. Thanks guys, looking forward to a response.

em1goesbwah

Also a note, i was getting CEL 1, 20, and 36 about 2 weeks ago. Haven't gotten them since, but I thought I'd add that. Thanks guys,

Telecatster

Take a close look at your exhaust manifold and look for cracks. Start from the top and work your way down. Cracks are usually in bended areas of manifold and near the engines head.

http://www.ehow.com/list_5778761_sym...-manifold.html

em1goesbwah

I've checked the exhaust manifold and I could not see any visible cracks. I'd also like to mention that my 2-1 portion of the headers (parallel to road under engine) has been damaged from hitting speed bumps due to previous owner. There is no holes but it has been slightly dented. My friend and I tried to fix it in by heating it with a torch and banging it from the inside with steel and a hammer, but didn't do a very good job. I don't think this has had any great effect on the car as its been fine (perhaps somewhat less that fine) for a couple months now.

It feels as if my injectors may be less effective than they should and perhaps something in/around the throttle body has to be cleaning? Does this sound reasonable or is this not related at all?

Thanks in advance guys.

Telecatster

For a start clean your:
Throttle body
IAVC
Clean all chassis electrical grounds
Test for spark .

Refer to Ron's "Useful tech links" https://honda-tech.com/forums/members/former-user-999573189/ for testing and cleaning write-ups.

When you stated "when I am trying to maintain my speed the car will jump back & forth, and the exhaust will go 'put put put put put put put putput', it almost sounds as though it's misfiring". Sounds like a possible intake or exhaust leak. An exhaust leak will have the sound you described, and could (but not always) cause the engine to run poorly due to effecting air/fuel ratio (running rich). An exhaust leak will smell like fuel or rotten eggs too. If you don't have a crack in your manifold or headers a leaking manifold/ header gasket could be a possibility. An intake gasket or a vacuum leak will make it run like it has miss and it will be constant at idle or under load and not at just certain speeds or RPM's

A bad injector is a possibility but not the first suspect from your description.

Probably best to bring to a few different mechanics for estimates, hear what they say and report back.

rachalwt

Take a close look at your exhaust manifold and look for cracks.

HondaPartsHero

Year/make/model/ecu?

em1goesbwah

My name is a lie haha. It's a 1998 civic si (us EX) with b16a swap .. not sure of ECU.

I highly appreciate all the replies. When I get some time off work I will clean the TB and IACV and check my grounds and spark. I am almost 100% certain there aren't any leaks near the manifold (put them back on a few weeks ago and used "stethoscope" with no noise returned) until about halfway through the exhaust where it has been cracked a few times due to speed bumps etc, but this also hasn't affected anything until recently.

I am stubborn so I probably won't have anybody else look at it, but I will begin by cleaning those things and bandaging exhaust.

Once again I appreciate the help and will get back to this asap.

B_Swapped93

check that the tps is to spec may want to check timing also. when was your last FULL ignition tune up.

em1goesbwah

Also, in the state described, is my car safe to drive? I kind of need it for my job..

em1goesbwah

I am not sure, I've had the car for a while but ignition has never been touched. I did the timing belt and screwed around with it for a bit.

em1goesbwah

I cleaned the IACV with brakeclean and it improved my symptoms but my car is idling (when warmed up and left for a few seconds) around 300 rpm... which is not right... the exhaust also smells very rich. I have no clue whats wrong with my car...

Telecatster

A faulty oxygen sensor (1st bank nearest to head) can cause a car to run rich and not always throw a code. If you don't have a friend that is knowledgeable with cars and have limited experience yourself, you're probably better off bringing it to a local (non national chain) mechanic that has been in business for 5 years or more. Most mechanics do not charge to for an estimate.

knoxrocks222

Does it do it when its cold or only when the car reaches operating temp. Like when you first go cranknit and take off does it drive like its supposed to? If this is the case unplug your o2 sensors and go for a drive and see how the car behaves it it acts normal then there is your problem...sounds like an o2 sensor to me

em1goesbwah

So it turns out when i cleaned the IACV i put a hole in the vacuum line between Cruise control and map sensor, so I fixed that and my idle is back to normal. Also did an oil change and ignition timing adjustment and its running better but I believe you guys are right.

When I have the time this weekend hopefully I will check out and change my o2 sensor (cause it's still running rich) and let you know whats happening. Thanks everybody.