HELP !!! 94 LT1 Starting Problems

[jjw94]

Coolhandluke:

Sunoco Gold 94 Octane, with no additives.

jjw94

 

[Vettelt193]

Hi VetteIt93,

Yes I did put the gas pedal to the floor on restart, but no luck. Never had any trouble codes come up or Service Engine Light. Fuel Pressure was checked while car was running. I o not believe it was checked after the restart.

thanks,

jjw94

You need to check it after it is shut off. what you are looking for is a reduction in pressure over time.

What could be happening here is the injector(s) are leaking... It is easy to crank when cold because the fuel leaks, then has time to evaporate. After only 15 minutes it leaks in and is still there, so it is so rich it can't start. The really odd thing is you don't smell any gas... I would expect smelling some form of gas on start if it was like this.

 

[gmjunkie]

You need to check it after it is shut off. what you are looking for is a reduction in pressure over time.

What could be happening here is the injector(s) are leaking... It is easy to crank when cold because the fuel leaks, then has time to evaporate. After only 15 minutes it leaks in and is still there, so it is so rich it can't start. The really odd thing is you don't smell any gas... I would expect smelling some form of gas on start if it was like this.

I think the ECM is on it's way OUT!! In my Exp!! ECM will Not tell on Self, Most of time!! (No Code's) or (False Codes) I'v chased ECM problems for Day's!! Bad ground's can couse same type of problem's!! And theas car's have more ground's than Carter has Liver pill's!! junk!!ps. Check all fuze link's behind batt. somtime's thay will make a conection when cold and not when Hot!!

 

[jjw94]

Hi VetteIt193:

Got some more info from the GM Dealer on this problem. They did put it on the computer and no "DTC's" were generated. They did check all the Fuel Injectors for leaks and they claim the injectors were fine. The GM Technician said they induced the distributor and found a sporadic no spark condition. They claim that a round disc inside the Distributor heats up and is getting warped, thus causing the problem. I am not 100% sold on this theory as they will not gaurantee this will fix the problem. After getting feedback from the folks at this web site, it could be anything from the battery to the injectors to the distributor to the ECM to 02 Sensors to bad gas. I have weeded out some of the above, and after the dealer saying they checked the injectors, it leads me back to the Distributor. I am still not convinced its the Distributor, because other guys in here have had the same problem, changed the distributor and the problem still exists.

Needless to say, I am very confused. Looks like I am back to the Distributor. Any comments.

jjw

 

[Vettelt193]

I think the ECM is on it's way OUT!! In my Exp!! ECM will Not tell on Self, Most of time!! (No Code's) or (False Codes) I'v chased ECM problems for Day's!! Bad ground's can couse same type of problem's!! And theas car's have more ground's than Carter has Liver pill's!! junk!!ps. Check all fuze link's behind batt. somtime's thay will make a conection when cold and not when Hot!!

I agree with gmjunkie... with no gas smell, it's got computer or sensor problems written all over it.

You can always pull a plug and check to see if you have spark...

also, do your guages read properly when you have these problems? talking engine temp mostly.

Have they disconnected the battery? if you disconnect the battery for a while (15 minutes or so) then reconnect it, you will reset the computer...

 

[jjw94]

After digesting everything on this problem, I am going to look at the 02 sensors first. Can you tell me how many there are on my 94 LT1 ? It has a 6 speed tranny. Can I replace these on my own ? I do have the Shop Manuals for the car. Are the 02 sensors expensive ?

thanks,
jjw

 

[Vettelt193]

yes, you can do this yourself. you'll need a special socket to take the sensor off though, it has a cut side so the wires have a place to go. I think '94 came with 2 sensors, (someone correct me here if im wrong). they are USD $50+ each.

I honestly don't think your O2 sensors are bad. if they were, the car would run bad, probably throw a code... I don't think the O2 sensors do anything on startup either... i think the computer only looks to them after the engine is started.

Also, What happens to your car when it gets hot? (the upper range of the working temp on these cars, so about 225-230 degrees) if it runs bad when hot, then it could be the opti... if it runs fine, it's probably one of these other problems.

 

[jjw94]

Car starts and runs good when cold. Here is the sequence of events:

Cold Start Fine
Drive - 15- 20 minutes
Shut off
Will not restart after 10-15 minutes
Wait 1-2 hours - then car will start
When driving some hesitation in motor as I shift through the gears

I am not sure of the temperature, when I go to try and restart. I will go through it all again and note the temperature. Also keep in mind that even after I wait the 1-2 hours to restart, when I do go to drive, there is some hesitation in the motor when I shift up through the gears. If you don't think its a Sensor problem at this point I will hold off on changing them. Let me get the temp and I will post back. Thanks for your support.

 

[Vettelt193]

Car starts and runs good when cold. Here is the sequence of events:

Cold Start Fine
Drive - 15- 20 minutes
Shut off
Will not restart after 10-15 minutes
Wait 1-2 hours - then car will start
When driving some hesitation in motor as I shift through the gears

I am not sure of the temperature, when I go to try and restart. I will go through it all again and note the temperature. Also keep in mind that even after I wait the 1-2 hours to restart, when I do go to drive, there is some hesitation in the motor when I shift up through the gears. If you don't think its a Sensor problem at this point I will hold off on changing them. Let me get the temp and I will post back. Thanks for your support.

In starting, the temp is most important... if the engine thinks it is cold when it is hot, it will dump too much gas into the engine (like a choke on a carbed car would effectivly do).

simply checking the temp is also important while running because if the opti is in fact bad like the dealer (err.. maybe 'stealer') is telling you, high running temperatures will probably make the car run bad as well... I suspect your canadian temperatures are keeping the running temps low, so it could be masking other running issues... what happens if you run the car longer than 20 minutes... what temperature do you get to after 20 minutes?

I haven't concentrated too much on the hesitation just yet, because I'm not exactly sure what you mean... is it a slow shift, late shift, or a true engine hesitation? if it is truly an engine related hesitation, does it feel like a single cylinder misfire (slight hesitation / hiccup) or does it feel like it isn't getting enough fuel for longer than a split second?

 

[gmjunkie]

Car starts and runs good when cold. Here is the sequence of events:

Cold Start Fine
Drive - 15- 20 minutes
Shut off
Will not restart after 10-15 minutes
Wait 1-2 hours - then car will start
When driving some hesitation in motor as I shift through the gears

I am not sure of the temperature, when I go to try and restart. I will go through it all again and note the temperature. Also keep in mind that even after I wait the 1-2 hours to restart, when I do go to drive, there is some hesitation in the motor when I shift up through the gears. If you don't think its a Sensor problem at this point I will hold off on changing them. Let me get the temp and I will post back. Thanks for your support.

It is could be temp sending unit!! There are two on that car 1 for gauge 1 for the ECM!! The one for ECM is just below Thod. Body, around upper Rad Hose!! And sometimes won't trip Light!! It can make it start or not start Like the Choke is On!! But you should Smell Gas!! junk!!

 

[jjw94]

In starting, the temp is most important... if the engine thinks it is cold when it is hot, it will dump too much gas into the engine (like a choke on a carbed car would effectivly do).

simply checking the temp is also important while running because if the opti is in fact bad like the dealer (err.. maybe 'stealer') is telling you, high running temperatures will probably make the car run bad as well... I suspect your canadian temperatures are keeping the running temps low, so it could be masking other running issues... what happens if you run the car longer than 20 minutes... what temperature do you get to after 20 minutes?

I haven't concentrated too much on the hesitation just yet, because I'm not exactly sure what you mean... is it a slow shift, late shift, or a true engine hesitation? if it is truly an engine related hesitation, does it feel like a single cylinder misfire (slight hesitation / hiccup) or does it feel like it isn't getting enough fuel for longer than a split second?

ok, got back at it tonight. Ran the car for 20 minutes or so. Shut it off, waited a few minutes, then restarted. Car would not start. Turned over and was cranking, but would not fire. Got in the engine, no gas smell anywhere. Temerature was 210 degrees upon the restart. Does this help reveal anything ?

 

[jjw94]

I would start with the DTC's, are there any?

No DTC's were thrown. Injectors were checked by dealer and they said they were fine. From all that I have seen and heard about this type of problem, i always find myself back to the opti spark. What do you think ?

 

[gmjunkie]

This is a long shot man!! But Once, I'v seen this happen now that I think about it!! Diodes going bad in Alternater!! I cant remember what year it was,but it took 2 day's to fig. out!! It was just 1 of thouse weard thing's and I stumbeld on to it with my Didgital Probe!! Diodes were passing some A/C voltage when hot!,and playing Havik with ECM!! junk!!

 

[jjw94]

This is a long shot man!! But Once, I'v seen this happen now that I think about it!! Diodes going bad in Alternater!! I cant remember what year it was,but it took 2 day's to fig. out!! It was just 1 of thouse weard thing's and I stumbeld on to it with my Didgital Probe!! Diodes were passing some A/C voltage when hot!,and playing Havik with ECM!! junk!!

Thanks for the heads up. Would a test of the alternator reveal this problem.
If so, how would you test it ? thanks,

jjw

 

[Robertwav1]

No DTC's were thrown. Injectors were checked by dealer and they said they were fine. From all that I have seen and heard about this type of problem, i always find myself back to the opti spark. What do you think ?

Okay....here's what I have found so far. My problem could be different however, starting the car after sitting for two weeks it fires up immeadiately....I mean just touch the key and it's up. If the car sits for let's say 15 minutes....it's hard to start. If the car sits overnight after running it that day sometimes....3 to 4 seconds to start. If I shut the car down and restart let's say in 5 minutes it fires right up. I suspect the injectors are leaking. I know you said you had them checked....maybe might be worth having a second look if all else fails that is mentioned here. I'm going to fool around or replace mine this winter.

 

[Vettelt193]

ok, got back at it tonight. Ran the car for 20 minutes or so. Shut it off, waited a few minutes, then restarted. Car would not start. Turned over and was cranking, but would not fire. Got in the engine, no gas smell anywhere. Temerature was 210 degrees upon the restart. Does this help reveal anything ?

It doesnt help all that much find the problem, but it still seems to rule a couple things out

No gas smell usually means you've got spark but no gas. If the opti is bad, I would expect gas smell on a no-start condition.

When my opti went bad on my '93, this is exactly what happened. I also had troubles before it totally died at high temperatures (225+ degrees). it had an almost violent mis-fire under load @ low RPM.

Did you re-set the computer yet by disconnecting the battery?

I am still very curious as to what the dealer did to check the injectors.

There are a couple reasons why I am leaning away from the opti... no gas smell is a big one, but another is opti's usually don't give warning. only a lucky few actually get intermittant problems with them... most just outright die. I could be wrong here, but it still seems fuel, computer, or sensor related.

 

[redc4corvette]

I would check the alt wires on the drivers side where the top of the manifold is and see if the wires are comming lose.
I had to install polly locks my wires were crispy and causing the vats system to kick in and would not let the car start when hot.
The fuel presure should read on a 94 43.5 psi with vaccum line disconnected and plugged.
The car only has 35, on it and I would assume it sits around alot.
My next guess would be the coil,you only have the problem when it gets hot
coils will break down with heat.
I have repaced 3 coils on my 94.The MSD has been holding for about a year now.Dealer said I had a bad opti ,wrong it was the coil and the broken wire to the alt in the loom.I had to find the problem.Yes I did fall for the dlr opti repair.I did have an aftermarket warranty that picked up the bill, only cost me 100 bucks.
I hope you do not have an after market radio in your car.
The installers take and throw the accaleramater to the side and the car will have hard start and no start at times.
Let us know.

 

[jjw94]

I would check the alt wires on the drivers side where the top of the manifold is and see if the wires are comming lose.
I had to install polly locks my wires were crispy and causing the vats system to kick in and would not let the car start when hot.
The fuel presure should read on a 94 43.5 psi with vaccum line disconnected and plugged.
The car only has 35, on it and I would assume it sits around alot.
My next guess would be the coil,you only have the problem when it gets hot
coils will break down with heat.
I have repaced 3 coils on my 94.The MSD has been holding for about a year now.Dealer said I had a bad opti ,wrong it was the coil and the broken wire to the alt in the loom.I had to find the problem.Yes I did fall for the dlr opti repair.I did have an aftermarket warranty that picked up the bill, only cost me 100 bucks.
I hope you do not have an after market radio in your car.
The installers take and throw the accaleramater to the side and the car will have hard start and no start at times.
Let us know.

Thanks for the info. I certainly will check these things out. I will let you know what I find out. You are the 5th person that has stated it probably is not the opti. Stay tuned and thanks again.

jjw

 

[DMGroh]

If you're handy with a Digital Volt meter, you might try checking each pin on each connector of the ignition harness. If you don't have the Helm/Factory Manual, all you can do is look for obvious breaks, cuts, etc.

On your 1st attempt to start (hot or cold) do you have your foot OFF the gas pedal? If it doesn't start, have you tried keeping the pedal on the floor while you crank?

I had an instance where the car was over-night cold, but it was a hot day (Black Car). It would only start fully floored even though it was cold. The temp sensor near the throttle body is going to get bench tested this weekend.

Just recently, I had a violent mis after running in traffic for an hour. It would only start fully floored, and even then it was very rough and I had to keep the rpm's up to keep from stalling. It was difficult to get the rpm's low enough to get in gear (Automatic) without either damaging the tranny or stalling the motor.

It's up on jack stands now getting a new opti & wires, as well as cleaning & testing every electrical contact, connector & ground I can find.

 

[jmccloud]

No start hot

Check your ECM ground when cold, then again hot, not running either way.
Use an ohm-meter to get a good contact on the ground pin of the harness and the grounding point. I don't have the service manual at this house, but the ground point is usually coil mount for other GM cars. The metal is often aluminum and subject to corrosion build up.