some quick background, this entire thing started when i bypassed my heatercore a month or two ago. when i start the car it idles rough for the first 7 seconds, longer if i give it some gas. if i do give it some gas it sounds and feels REALLY rough.

after 7 seconds it smoothes out and sounds fine.


so it didnt really bother me... but now ive failed emissions, hydrocabons were a touch high, so its become an issue.


video: http://www.youtube.com/watch?v=-0AuGOmm8oU

First 25 or so seconds is the car running rough, and me giving it some gas. after i stop touching the gas pedal [around 27-28 seconds] it smothes out, and idles/ revs fine.

@ 40 seconds i start it again, this time letting it idle normally, and as you can see it idles rough for about 7 seconds then smoothes out.


does ANYONE have ANY idea WTF could be causing this?


P.S. it doesnt matter if the car is hot or cold, it behaves the exact same way


***edit***

after it smoothes out i throw a SES light, BUT, when i turn it off and back top run to pull the code, it comes back clean. its only AFTER it starts to idle smooth that it throws the lgith

 

My guess is an injector problem... one or more may be mechanically failing (sticking, etc).

Hope this helps.

 

hurm.... there are only 2 of them... i might go ahead and pull them and see if theres any visiable damage.


hurm... wonder if any of the vacuum lines going to the hat affect the fuel flow [this is the first small block ive owned, been an import guy into i bought the camaro, hence the miserable failure on the more intricate workings of the motor] maybe i knocked something loose doing the Hcore bypass

 

I was going to suggest you check ALL the harnesses you may have touched as you PROBABLY knocked something off or stressed a connector. You stated it began happening after you made a change to the heater core. Good observation on your part. And another important (and nice) part is that this is consistent (repeatable). That helps troubleshooting for sure. I sure hope you find out what the problem is and post it for the rest of us beware of when working in that area then having those problem symptoms.

 

ive gone over the area a few times, and i can find anything. so im going to be reseating every connection back there, this has stumped ever car guy i know... not a good sign lol. im sure its somethign very simple, but ill be sure to post back on the results tomorrow

 

Make sure to check vacuum lines. I know I've broke the line going to the vacuum switch for the EGR. It is a hard plastic that got weak with the heat. I would check there.

 

Maybe you should remove the bypass of the heater core and see if the the problem goes away ... ((tongue in cheek))

Also you might miss a CRACK on a vacuum line versus a disconnected vacuum hose. You might have stressed a hose right at the hose connection and caused a crack but shows no visible problem.

And by your description it sounds like the engine is starting RICH. If you push the gas peddle it extends the rough idle time. So this would make me look for anything that would normally correct a rich mixture by being controlled by the ECM.

Look closely at the IAC. I do not know enough about it to troubleshoot it but you can 'recalibrate' it which is not difficult. This information is available via Google, etc.

The EGR investigation sounds like a good idea too.

 

The IAC closes when the key is turned to the on position. I believe it then begins to open while cranking. I know if you remove the IAC and turn the key to on or run, the motor will run and the shaft/cone will eject from the body. I am going to do some searching about 'recalibrating' the IAC. I've never heard of being able to calibrate them before. I'm pretty sure it just closes and opens again. I'm thinking it's position is based off of RPM.

I suppose that could be part of your problem if it is not opening enough, so you can start, but not enough to satisfy a smooth idle. You should probably at least pull it and clean it up. They get carbon and junk in them from fuel and anything else that makes it's way past the filter.

 

ok, so got the hood pins in [for those of you who are unaware, the camaro took a trailer hitch to the hood latch, thus wrecking the hood latch and pushign the core support back, so i had to get some hood pins to hold the new hood down]. test them out to make sure they held at speed. but before i whent out i reset the ECM.

after some good old fashion WOT i pulled codes again, and ive never thought id be happy to actually throw codes in my life.

codes im throwing:

32 - EGR system
34 - MAP sensor
53 - charging system
54 - fuel pump circuit


from my haynes manual, the first two both have vacuum hoses listed as the first thing to check, and the EGR stuff appears to be right next to where i was workin on the heatercore hoses.

now... the other two... i have no clue, my charging system is fine [about 13.7V running] ive never had any sort of electrical issues with the beast. and i have no clue whats up with the fuel pump circuit.

so theres some more info, i apreciate the help, its iinvalueable.

hurm... IAC = Idle Air control?

P.S. The car IS a TBI engine, so its a MAP error not MAF

 

I will tell you what I am thinking:

The engine can be either HOT or COLD and there is NO DIFFERENCE in the symptom. This makes me think it is NOT dependent on a THERMAL switch of any kind.

The time between engine start and the end of the symptom is about the same, 7 seconds, in all cases. This makes me think this is a TIMED event. Something is waiting 7 seconds then making a change. Again, probably not a heat related event.

From the description so far it seems to me during the symptom time the engine seems to be running RICH (too much fuel or not enough air).

A RICH condition is most likely one of two conditions:

1. The amount of FUEL is proper for the engine at that time but there is insufficient AIR.
2. The amount of AIR is proper for the engine at that time but there is excessive FUEL.

The symptoms appeared to start after bypassing the heater hose a month or two ago. Probably do to crawling around in that area of the engine compartment and changing something unknowingly.

Now the 7 seconds really bugs me. It does not matter if the engine is HOT or COLD, the delay is always 7 seconds. That sounds like a timing circuit, a delay built into the system somewhere, an electronically controlled valve of some kind is told to change after 7 seconds. So I would assume the ECM is telling it to change after 7 seconds of a successful START of the engine.

The engine does NOT run well UNTIL the 7 seconds has elapsed. The conclusion I am led to is that the change at 7 seconds puts the system IN BALANCE and thus during the 7 second period the system is OUT OF BALANCE. But when the system was running properly the system remained IN BALANCE during the 7 second period.

If we could just figure out what the ECM is programmed to change after 7 seconds we would probably be able to pinpoint a specific component and its function, thus the PROBLEM.

Here is something related to the EGR valve:
http://www.asashop.org/autoinc/dec97/egr.htm

Of interest is the paragraph starting with:
''Let's start with that golden oldie''
and ending with:
''This type of EGR valve is used with a thermal vacuum switch and maybe an inline vacuum delay valve.''

I looked at my 1989 Camaro 305 FI Vin E (TBI) and there indeed is a vacuum valve that is electronically controlled that sources vacuum from the front passengers side of the throttle body. I just wonder if THIS has a 7 second delay? In my Haynes '866' manual it describes this switch as 'EGR Solenoid' with PINK/BLACK and GRAY wires. The ECM controls the GRAY wire. The PINK/BLACK wire goes to IGNITION. Obviously the ECM has to make some type of decision as to when to turn that solenoid ON. Maybe it is based on a 7 second delay? Maybe the delay is NOT taking place on your engine thus causing an imbalance in the system for that time period. Obviously AFTER the 7 second delay your ARE getting appropriate vacuum to each component because the engine runs well after that delay. So it is as if something that is supposed to begin working after 7 seconds is starting to work 7 seconds too early or something that is supposed to work for only 7 seconds is not working at all. I will try some tests during the day tomorrow (oops ... today) concerning this particular electronically controlled vacuum switch. I can just pull off the vacuum hose on the EGR valve and test for vacuum while the engine is started and see what happens during the first 20 seconds in terms of vacuum at the end of the hose.

 

the engine still runs rich [thus me failing emissions] but its only very slgihtly rich, i cant remember the EXACT figures off the top of my head, but @ 25mph the hydrocarbons were at or about 185, so its not insanely rich, just slightly.
the other 2 gases were well within specs.

i pulled the MAP sensor connector off and fired the car up, it caught the second i turned the key to start, and idled smoothly at 650-700 rpm, plugged the sensor back in and it was rough the first couple seconds, but settled again around 650-700, this is a cold start and the engine is usually sitting at 1200-1500... so im not sure what to make of that

 

During your cold start, without the MAP sensor, you are getting adequate fuel (richer than normal, not perfect maybe) to keep the engine running well at a relatively low RPM (for a cold start that is). If this is a cold engine then you would normally needs a RICH mixture for a few minutes from SOMEWHERE. It seems you are getting it (seems to be by accident). I think what this might mean is in line with the symptoms you have been having: what appears to be TWO 'rich' providing components. By eliminating the PROBLEM source you would have a properly running start. By eliminating the PROPER source you would have a (close to) properly running start. See my point? But we also note a difference in typical RPM for a cold engine. So the MAP sensor would probably need to be hooked up to help provide that management.

Let us make an assumption that the MAP sensor is working correctly and every other part is working correctly. During a cold start you would normally need a rich mixture. And you would get it. The engine would idle smoothly but at a typically higher RPM until the engine warms up and then everything would automatically adjust to a lower idle and less rich mixture.

But with your current problem you appear to have a 'richer than normal' condition for the first 7 seconds. You not only have the normal parts trying to make the engine rich but you also have an abnormal component making the engine 'overly rich' for 7 seconds. Once that problem source stops providing extra fuel your engine behaves normally.

So again, it APPEARS to me that whatever is causing the SYMPTOM is actually making the engine 'more rich' than it should be for 7 seconds.

That picture keeps coming back to me. Additional fuel is being delivered during starting. But again keep in mind that a reduction in AIR would also cause a RICH mixture. Wish we could measure fuel delivery and air delivery.

 

Per my experiment with the EGR solenoid:

With a vacuum gage inserted in between the EGR vacuum port and the EGR solenoid vacuum delivery port, I started a cold engine. I did not see any vacuum being applied through the EGR solenoid up through the three minutes I waited. So I do not think the EGR solenoid is playing any part in the 7 second change that was discussed.

 

hurm... i REALLY wish i could data log it, but i have no way of doing so at the time being....

well im going to be checking all the vacuum lines back in that area and seeing what i can dig up... wish me luck lol. ill report back after im done

 

problem solved... well i hope. there was a vacuum line on the back of throttle body that had come loose. hooked it back up, starts normally, doesnt reek of fuel, no SES lights, no codes, and it drives much smoother.

so... we'll see tuesday when i go to get emissions done, but it looks liek the problem is solved.

 

If the problem IS solved you should probably take vacuum readings when the engine is started from a COLD start, and then from a WARM start. In the future when you have a problem you can then look at what the vacuum SHOULD be. Maybe that will help point out a vacuum problem like this one in the future. We had no 'reference' this time around. Well it was interesting!

 

well im 98% positive the problem is solved, since im throwing no codes and its acting normal again. but running rich for so long could have messed something else up, like gummed up the cats, but it doesnt smell rich anymore [it was REALLY bad at one point before i did some work to it, like... dripping fuel bad]

 

Nothing a good WOT run down the highway/interstate can't take care of. LOL Glad you got it taken care of though.

 

while this is true, i got pulled over for invalid tags about 1/2 mile away from my house [like i could still see my F*ing house]. i dont want to know how many times i would get pulled over on a run down the highway.

the downside to driving a purple camaro w/ a black hood and loud exhaust, it turns heads, but it turns EVERYONES head.

 

... still failed, although a little bit lower.
...............15mph.................. 25mph
HC ppm:... 55 | 104................ 60 | 164
co%:....... .22 | .02................ .32 | .10
no ppm.... 720 | 154................ 700 | 236


so ya, still high on hydrocarbons, but now i have no SES and it drives perfect... wonderful