94 Q45 sometimes runs rough and smokes at startup

[ahardb0dy]

94 Q45 sometimes when the car is first started it will run very rough and you have to feather the gas to keep it from stalling, if I rev the engine white smoke will come out the tail pipe than change to grey looking smoke, If I shut the car off and restart it, it runs fine. flipping the bypass switch for the FPCM to high makes the engine stall.

I Swapped out the FPCM today with one from a 95 that had no burnt marks on the connector, started the car and it ran fine, wife took it out before shopping and told me it was doing what I said in first paragraph.

background info: new OEM fuel pump, new knock sensors and harness, new/used intake plenum (cleaned very well inside), new plugs, new PCV valve, cleaned throttle body and IAC valve, fuel filter not new but was replaced not to long before doing fuel pump. could use a new air filter but not terribly dirty. also ohmed the injectors all were with in specs

I know the car needs O2 sensors but haven't gotten to doing them yet.

Anyone have any ideas on this?? THANKS TONY

[maxnix]

fuel filter not new but was replaced not to long before doing fuel pump. could use a new air filter but not terribly dirty.

I know the car needs O2 sensors but haven't gotten to doing them yet.

Usually the fuel filter is replaced with the new fuel pump. You did use a new O ring? How did hte interior of the tank look? Any film at all? Air filter should be changed annually or 12K -15K depending on environment. They are cheap form Joe.

Did you check MAF connection?

Why don't you get to the oxygen sensors ASAP. Call http://www.sparkplugs.com as the web site had been incorrect. Then we'll see what that changes or not.

[ahardb0dy]

I'm picking up a fuel & air filter tomorrow, used new o-ring, tank looked ok, haven't replaced O2 sensors yet because I've heard they are a real pain in the as- to replace, I looked for them one day and couldn't even see them. I'll also check the MAF connection tomorrow.

Isn't it uncommon for the engine to stall when I put the FPCM into bypass mode? It never did that before even before I replaced the fuel pump.

I have 3 FPCM's here now, the one that was in the car when we bought it and 2 I got from the junk yard for $12.50 each. The original one I did the upgrade on it to improve the ground.

Would/could the O2 sensors cause this problem?

Thanks

[Q45tech]

Measure the fuel pressure [idle and WOT] and residual pressure [after overnight] before cranking............looking for leaky injector that might be partially filling a cylinder overnight.

Never hurts to replace BOTH O2 every 100k or 6 years.

Replace fuel filter every year!

Didn't see your interval of BG44k in your write up................a very necessary addition to mainteance every 90 days.

[ahardb0dy]

I don't understand what is up with this car, today I swapped the FPCM back to the one that was in it yesterday when it was acting up and it runs perfect. I drove it a little bit and it ran fine.

Never have used the BG44.

Will pick up the filters tomorrow, replaced fuel filter at 160K, replaced knock sensors fuel pump etc at 166K, car has about 168K on it now.

Any tips on replacing the O2 sensors?