have a few minor questions about the 02s, getting both of mine replaced with new GM ones in the morning but i had one bosch and the original gm for a few weeks.. (turns out the ac delcos are cheaper than the bosch!!!!) but anyway im letting the dealer have the headache of the pass side o2, they said $60.. i said... cya in the mornin. anyway heres the question.

can an o2 make it harder to start the car after a sudden climate change? (temp here shifted from 70 to 40 and my car didnt wanna start that mornin until i tried 4 times then left teh key completely off and tried again.
also noticed that going downhill around 50mph the car would change exhaust notes without changing throttle position (duals w/ bullets and stock manifolds) could any of this be caused by the 02s acting up and not reading well (neither of these were a prob till the one bosch was installed)

 

I tried Bosch in my OBDII pick up (99chevy). Wouldn't work. Your problem sounds like a fuel supply problem. Like it's draining back away from the fuel rails. The PCM doesn't even start using the O2s until the engine has warmed up and goes into closed loop. So your cold start issue should not come from the O2s.

Could the change in exhaust note going down hill be that you took your foot off the throttle and the tranny down shifted to raise the rpm level and sounded differently?

 

nope it does it a constantly after i let off, itll change repeatedly between the backpressure gargly tone and no sound at all (exhuast gets silent at 40mph cruise with light throttle im assuming its something similar to this)

but if it is fuel supply what would the first things be to check? also i know my opti is heading south (right now only about 5krpm studder SOMETIMES) think this could be a cause too?

 

My '97 does the same when coasting down a long hill. I think the tranny disengages the OD. Anyways, if my understanding of the O2 circuits are correct, it is open loop during startup and warmup so you shouldn't see any effects from a bad O2 until the PCM goes into closed loop.

 

The 2 simplest things to check fuel supply starting issues are:

When starting the engine just as you would when the problem would normally show up.

1) Turn power on but don't start the engine. KOEO. Wait for 4 or 5 seconds and turn the power off. Then KOEO and repeat the cycle 5 or 6 times. After the last time, crank the engine like normal and see if it starts much quicker with less "cranking" before it fires up. If this makes the engine fire up quicker once you started cranking the engine, it probably means the fuel has drained back away from the fuel rails. By cycling power 5 or 6 times, you have re-primed the system to get fuel right up to the injectors again. The 3 common causes are a bad check ball in the fuel pump, a hole in the FPR diaphragm or a stuck injector. BUT an injector problem or a hole in the diaphragm would cause a rich running problem, poor performance, lousy fuel milage etc....... so that leaves only one choice.

To check the diaphragm, simply pull the vac line off the FPR and check to see if it's wet. To confirm the check ball is the problem, clamp off the fuel line the next time it's shut down and check to see what the fuel pressure is doing compared to when the fuel line is not clamped off.

If cycling power does not help the starting issue when cranking then the problem could be flooding but as I mentioned above, you should see a rich running problem, poor performance, lousy fuel milage etc....... You could also smell fuel in the oil. To test for this possibility:
2) At the very first cranking of the engine, hold the throttle to the floor and crank it.

This takes longer to type than it does to test. If however you have poor conditions in the opti cap and rotor, that can have an effect on starting. But at least it's easy to eliminate the fuel problem as being the cause without even getting your hands dirty.

Hope that helps

 

im getting horrible gas mileage btw lol. but its funny the car always cranks soon as i turn the key over, that one day was the only time it took any longer. and i dont know for sure about running rich or not but i think someone on hear mentioned a rich running car has a rsapier sound in the exhaust.. and with my setup right now ive got a bad echo at part throttle. so maybe it is a fuel issue... but where is the fpr on these cars? and when i pull the vacuum line off i should be able to see if the diahragm is ok or is there more to it?

 

To find the location of the FPR go to shoes tech page and find the view on the FPR page. He's at http://shbox.com

If the diaphragm were ruptured, the vac line would be wet. You can also remove the vac line at the intake but leave it connected to the FPR and apply suction to the hose and see if fuel comes out. Leaky injector(s) can also cause a starting issue and poor performance and milage. Many times a good cleaning like the stuff from 3M that I use connected to the fuel rail will cure the injector problem.

 

if it were a fuel problem such as a leaky/stuck injector or a hole in the diaphragm woudlnt the problem be everytime i tried to start the car? because ive only had starting issues twice the entire time ive owned it, both times it was the first cold night of the season... (owned the car since may 04)

 

Tell you what. If you have the injectors cleaned professionally off the rail or on the rail using the 3M cleaner and it doesn't help the problem, PM me and I'll help with the cost.

In the mean time I suggest you do a thorough tune up.

 

got the other o2 changed today (they only had one in have to wait on the other, turns out my 94 has heated o2s and was listed as having unheated in their computer... go figure) anyway the car feels alot better at mid throttle, but i can still hear that raspier tone and a little studder that i always thought was from the opti maybe its a fuel system problem that ive been overlooking.. anyway im gonna check out that diaphragm later on and im gonna have the injectors and TB cleaned by the dealer sometime next week... (either that or my usual shop, havent talked to them yet about it) but im probly also gonna do plugs and wires along with that, because ive seen on here where quite a few ppl have mistaken plug wire problems for opti problems.. hope im as lucky lol. anyway thanks for all your info speedy its been really helpful whether i act like it or not.