CorvetteRules

So today I put a new battery into my 91 and since it was a warm enough for my summer tires took it on a short drive. Started fine, but would want stall when trying to pull away from a stop. If I feathered the accelerator just right I could sometimes keep it going. When it stalled the only way to get it restarted would be to hold the pedal to the floor as if it was flooded. Would also stall or start to if I slowed down to turn a corner unless I slipped it into neutral and feathered the gas to keep it at a higher RPM.

It had always started right up when cold and had planned to do a tune-up in spring since may not have many warm enough days to take it out. What direction do the knowledge trust among the members here think I should go it. Btw, the last time I had it out was earlier in December when the oil sensor was replaced to stop oil leak. It ran fine except for a little roughness at lower rpm.

383vett

CorvetteRules

Problem with doing a tune-up now is that I currently don't have room in garage to do it and the weather is too iffy to do outside. On top of that having the summer tires would make it difficult to even test drive it.

81c3

Check your fuel pressure. Also, is the tank full or partially full? Sounds like its starving for fuel in one way or another...

CorvetteRules

Is there a situation where it would be fuel starved at a lower RPM? At mid and wot it runs very strong and it idles ok, but maybe 100 to 200 too high.

Dt86

A higher rpm at idle and take off stumble and stalling can be a vacuum leak. Do you hear any hissing coming from anywhere? The main culprits are the brake booster, check valve or any old brittle vacuum lines. GM used plastic lines under the runners and plenum that dry out and crack.

As mentioned, getting a scanner on it and seeing whats going on is really a must.

You can check your TPS with a voltmeter for a dead spot. That can cause stalling at specific times.

You can check the throttle blade for carbon build up. You can check the throttle blade for play.

Any service engine soon light?

Theres a few ideas to start with...

383vett

aklim

Or maybe 100 to 200 too low. Hard to say since we don't know how accurate the tach is. Mine wasn't. It was about 300 high based on the timing light tach and the scanner.

To check the CTS, you will need to buy a scanner. Most seem resistant to that, for whatever reason. Also get an infra red thermometer. Borrow a compression tester from Autozone. When it is cold, the CTS and the Oil temp should be the same based on what the ECM sees and not what the gauges say they see. As the temp rises, see what the CTS vs IR Thermometer on the CTS says. They should be about the same.

See what the fuel pressure is at Key On Engine Off. See if it bleeds down fast. Do a WOT run under load with the fuel pressure gauge taped on the glass. See if it holds pressure.

Check the plugs for crud on it and and especially the wires for leaking.

CorvetteRules

Thanks to all for the advice. My mind was jumping all over the place while driving it yesterday, so it is great to have a place like this forum to hear from those that have a passion for corvettes. I'm very new to the club. but hope to learn from that passion.

CorvetteRules

- AN UPDATE-

Had some free time today so spent some time looking at my 91. As always it started right up and idled fine. With it running looked and listened for any possible vacuum leaks. Didn't find anything so shut it down and started to feel around on all the lines and their connections and felt or saw no deteriorated lines. Based on appearances it looks like all the lines are not very old. After that I stated it again, fired right up and I started doing stuff in the interior and left it running.

It ran fine until it fully warmed up and then it started to run rough and stalled. At that point the only way to restart it was to hold the gas to the floor but would not stay running with out keeping at a much higher RPM. So, if no vacuum leaks and running perfect until it fully warmed up?

One thing I did notice is that the power seats (driver's and passenger) are not working. They were working, but since once my seat is set I normally never have reason to change it. Didn't have time to check the fuses, but if the fuse was blown does anyone know if it shares power with something that may cause the symptoms I'm seeing?

Dt86

Do you know what temperature it started acting up at? That would help narrow it down. If it starts running poor when it goes into closed loop that can be a number of things. If after it's in closed loop that can eliminate some sensors.

aklim

Maybe scan the ECM and see what it thinks for hot and cold and compare it to what the IR thermometer says?

CorvetteRules

glass slippers thoughts regarding the CTS are very interesting because when cold car starts right up and runs nicely. It is not until it warms up that it starts running rough and will actually stall, which would make sense if the computer still thinks the engine is cold and keeps fuel to rich.

The cost of a new CTS is fairly inexpensive so my question is if it would b e reasonable to just replace it and see if all goes back to normal? I don't have my service manual yet, so don't any reference to go by. Also takes me back to my question on if the CTS is tied into a fuse that should be checked that would keep it from providing the correct reading to the computer?

gpierce

You could do that, but then the title of the post......

aklim

When you have replaced everything, unless something breaks in the meantime that you just replaced, the problem will be resolved sooner or later. If you don't run out of money first

CorvetteRules

Yes, I agree, I'd rather not replace any parts since it was running fine but suddenly started not to run right once warm. Which brings me back to the suggestion glass slipper made in regards to the CTS could cause the exact issue of the computer keeping the fuel flow too rich. The problem I found with my power seats just stuck in my mind as to if the power to the seats may also be electrically connected to the CTS communication with computer and if not if there is a fuse to be checked that is tied to it's communication to computer.

CorvetteRules

Now I'm confused. Lets say the CTS is not relaying to computer that temp is above 150 degrees, wouldn't the computer just keep the flow too rich?

CorvetteRules

I will check the readings on the injectors, unfortunately can't do it now until the weekend. Thank you for information. I should have the FSM with electrical book in the next week so that should provide help in resolving the issue.

aklim

Why bother? Multecs mean you can't use any ethanol. You need 100% gas so you just chained yourself to a few gas stations only. Assuming the PO has done that, and it is a big assumption, you have to keep only 100% gas. This and the FPR could be changed for a reman set of injectors so you stop hobbling yourself.

aklim

It could be relaying the wrong information. If you check what the pulse width is with a scanner, someone with a stock engine can tell you what their pulse width is so you can see if it is really enriching the engine.