car, 305TPI, was perfectly ok (well in relation to this issue anyway! )

After a long drive yesterday (completely uneventful) I started it up again and then experienced a very uneven idle/ loping and after the exhaust gases are re-routed by the emmissions system (I'm not sure what's happening but you know when the engine note changes and idle gets slower) it loped really really bad then and stopped. No error codes either and the service engine light didn't come on at all.

There's also a really bad eggy smell from exhaust -smells like it's running VERY rich.I've checked out the CAT, doesn't rattle at all. Also this is a very sudden prob so I doubt it would suddenly malfunction?

I've checked out manuals and I'm thinking is it EGR valve or the EECS canister? I'm doubting it's a timing issue as it's so very sudden a problem (after being so perfect yesterday). Periodically I've experienced a fuel oddur smell which it says could be the EECS (and ever since I've had the car since 2000 I've had the odd, very very occasional spout of power loss).

The only thing I did yesterday which I thought could be cause, I got the EECS quite wet during washing the car -it ran down back of light assembly. I've now noticed the solonoid on top of the EECS cansiter gets very hot, can anyone check theirs and tell me if this is normal while the engine is running (as I can't remember) ??

Whatever the cause, I'm thinking it's some kind of emmissions issue due to the fact it gets so much worse at the moment (about 2 mins after start-up) once the gas is re-routed and the idle steddies (well now, it drops to about 200rpm and not surprisingly stops)

many thanks for your help. With my list of other problems with the car I really could have done without this major one! -the stress is driving me towards a 4th gen i think -hope they're more reliable!! Is it just me or does anyone manage to go a week/month without fixing something?!?!

 

'Drew,

Once the ECM achieves closed-loop mode, the EGR and EVAP purge solenoids can become active. The ECM will duty-cycle either or both of them at a rate determined by operating conditions. In addition to that, the vacuum source for both of those functions is connected to a timed port on the underside of the TB. This prevents any vacuum to either system at closed-throttle as a redundant means of preventing stalling. You really don't need/want any EGR nor EVAP purge gasses at idle or low RPM. Since the vacuum solenoid valves can be duty-cycling at any time, they could easily be warm to the touch. To make sure teh system can operate correctly, check your vacuum source connection compared to the hose routing diagram.

Your converter will emminate a sulfurous, "eggy" odor when it is hot. This can be caused by operating at a slightly lean mixture for extended periods (like cruising lean) or an excessively rich mixture that is completing combustion in the exhaust system. If you have an oxygen sensor that is producing a weak signal, you could have a rich condition. That could also be the result of an air injection leak into the manifolds instead of being ported to the cat converter. I'd suggest removing the AIR system tubes after the port/divert valve when the engine is in closed-loop and determining which way the air is being routed. It may be going to both places, which isn't a good thing.

Since you just wet down the entire engine, it's possible that you have water in a solenoid valve, electrical connector, or even an AIR diverter valve that is sticking it open. Eventually, this should clear itself. In the interim, make sure there is no air injection through the check valves and to the manifolds when in closed-loop.

 

great -thanks Vader for your reply (I assume this site was origiinally set up by you -it's simply the best resource for these cars and I htink a lot of people take it for granted..)

Anyway... strong smell seems to have cleared but still I can't seem to source the problem, though it does do it more once the engine has settled down (is that what you mean by closed loop?) -so I'm assuming that it could be either egr or the cannister solonoid...

If the car has been left idling like this for a while, and then the accelorator pedal is pressed it sometimes now just cuts out dead.

I've recently had two breakdowns, one due to the distributer failing (which is now replaced by a new one along with plugs wires and coil) and the other due to the alternator (also replaced). Apart from the irritation of occasionally stalling does anyone think this stalling problem could crop up at 50-70mph motorway speed or get worse to the degree that the car won't work at all? -just don't want to break down again and there's not time to get any spare parts from the US before I take a long trip this week.

thanks
Andrew

 

Andrew,

No, I didn't set up this site. It was originated, to the best of my knowledge, by Dirk, the Emperor/Administrator, and some guy named Dan, who apparently no longer visits the this site. I just became such a nuisance that I was asked to moderate so I wouyld have something to do other than post everywhere.

As for your problem, you can eliminate a couple of possibilities by unplugging the vacuum line from and capping the port on the bottom of the throttle body. In doing so, you will likely generate a code 32 after traveling some distance, but will at least know why. If the problematic symptoms disappear, you have a good idea of what is causing them. If they don't, you may be able to ignore the EGR and EVAP for now.

Just a few more questions:

Have you checked the TPS voltage at closed throttle?

Have you sest the minimum air position of the throttles?

Cleaned the throttle body and IAC lately?

 

thanks very much Vader

I just cleaned the IAC valve (it was TOTALLY black and gunky -so is the inside of the throttle body -that's thick and gunky... not done that yet) and it appears to have done the trick! Initially I started up the engine and I got an error 34 (which i seem to get regardless of the problem when hte engine stalls) -there's nothing wrong with the MAFsensor but could it be the MAF relays?

Anyway, I restarted the car for about 20 mins (putting it into D numerous times and dabbing the accelarator, trying to make it stall but it wouldn't) and the error light had cleared. It seems to run fine now. Once or twice the idle dipped slightly below 500rpm but the computer seemed to correct it much more effectively (you could hear the engine tone marginly going up and down while it was correcting it, rather than stalling completely). This is something the car has never done before.

Maybe I've spoken too soon and it will be back to square one tomorrow but it seems ok now. The weird thing though, is how suddenly this problem seemed to crop up ?? -I would have thought with a IAC valve it would get worse overtime. The main thing though is it seems to be ok now and this is the first ever free repair to the car YAY!!!!

Out of interest, do you think I'd get similar problems on a late lowish mileage C4 corvette... I guess the engines are roughly the same but are they more reliable ?

thanks again
Andrew

PS -what's the minimum air position of the throttle -is this fine adjustment of the port opening ?