3.4L V6 5 Speed 1994 Carmaro

When cold ruff start. Sometimes pops. It starts like bad battery/starter or off timing. After you get it started it runs great no problems. Will restart with no problems when warm.

Parts I have changed:
Battery
Starter
Throttle pos. sensor
EGR Valve
O2 sensor's
sprayed the interals of the IAC with wd-40 and make sure the valve is moving freely.

There is two temp. sending units one for the gage or light and one for the computer. Its probable that the sending unit is bad telling the engine its warm and its not. It could be bad and not send codes to the dash.

Where on the engine are the two sending units. One is front engine beside the thermonstat housing into intack manfold. Where is other?

Thanks,

Ruth

I really cant think of where it is, The locate them in diferent places for diferent reasons. You can try the parts store to get a look at it then go looking. The big diference is the plug config.

Changed temp. sending units and it didn't fix problem :(

Changed temp. sending units and it didn't fix problem :( Sorry to hear that, You dont have a orange check engine light on? When cold the computer only looks at a few sensors -temp, throttle position, manifold/baramentric preasure. If you dont have a check engine light on the only sensor I know of that will give you problems and not give you a check engine light is a temp sensor. So, Does it crank a long time before any indication of starting? Im thinking mabe you could be loosing fuel preasure after sitting overnite, then when starting it has to get the preasure back up before it will start. Sound like whats happening? How many miles are on it. It gives you no other troubles just on cold starts? Is it eratic speeds at idle when warm? If you just turn the key to on and not start it do you have a check engine light? (orange)(Thinking the bulb may be out)

When you start it..... has not started.......Sounds just like if you have a bad battery or starter but both are new and tested. It does not do it everytime you crank it. Computer is not throwing any codes. It also has new plugs and wires.

Any idea on what could be problem?

I think the ECM temp sensor will have two wires and the guage sender will have a single wire. If you can get someone to scan the computer for you, you can verify if the temp reading is correct or not.

I can tell you from experience that better than 60% of issues are often connection related problems. It could be that the temp signal is not getting to the ECM because of a bad connection somewhere even though the sensor is good. A diagnostic tool is an important means of verifying the sensor singals are reporting correctly.

I sent it into the shop and computer is not giving any bad codes.
Item's I have changed:
Both o2 sensors
Throttle pos. sensor
Air intake sensor
crank shaft sensor
Timming gear and chain
EGR valve
starter
battery
alternator

when it starts its ruff ( sound like when you have a bad starter then it pops (backfires) like if you had a carb but car has no carb ) most of the time it will crank and drive great after the first crank but sometimes will do it again in the day. It runs great other wise.

when cold turn key on for 5 seconds than off than back on do that 5 times than see if it starts right up.also when it is doing this is blue or black smoke coming out back

Scanning is partly getting codes and partly reading back sensor signals. For example, if the diagnostic tool says your cold engine is 200*F, you've got a temp sensor problem.

Bill has a good question there. I know my Dad's S10 pickup used to do this.

What if you were to disable the ignition system and crank it?
Would it spin over good as normal?

If it does spin good & fast, I would think it would be ignition related, too far advanced initial timing, especially with it backfiring as Ruth says it does. Once the engine is running, ECM learns, adjusts operating conditions, then engine runs good for the rest of the day.

But what puzzles me is it reads like the ECM losses its learned memory overnight and has to relearn the following day, if it starts. Could it be the memory power is lost when off? Always wondered about the "limp mode" and I bet this is the program making the engine run.

This reads like the wonderful OBD 1.5 operating system. I'm open for comments.

temp sensor was change - not problem:(