Help! 84 Crossfire problems.

[Shane]

Ok, I recently purchased an 84 Vette, L83 crossfire.(obviously). I'm having problems with stalling and difficulty starting. When the engine is cold, it starts and runs with no problem. However when it gets into the 190+ temp it starts idling roughly and sometimes stalls. when it stalls it is sometimes VERY difficult to get started again, until it's cold, at which time it starts right up with no issues. I have changed the MAP sensor, connections, Vacuum lines and Valve cover gaskets(which i'm sure wasn't the problem, but it needed done) It needs new plugs and wires, which will probably be done today, but i'm not convinced that a tune up will rectify the problem. Anyone have any ideas about what the issue could be?


Any help is greatly appreciated.

 

[Buccaneer]

Ok, I recently purchased an 84 Vette, L83 crossfire.(obviously). I'm having problems with stalling and difficulty starting. When the engine is cold, it starts and runs with no problem. However when it gets into the 190+ temp it starts idling roughly and sometimes stalls. when it stalls it is sometimes VERY difficult to get started again, until it's cold, at which time it starts right up with no issues. I have changed the MAP sensor, connections, Vacuum lines and Valve cover gaskets(which i'm sure wasn't the problem, but it needed done) It needs new plugs and wires, which will probably be done today, but I'm not convinced that a tune up will rectify the problem. Anyone have any ideas about what the issue could be?


Any help is greatly appreciated.

Welcome to the forum. You didn't mention it, but do you have a CEL (check engine light) lit during any of this? If not, that's narrows things down a bit which means that what is happening isn't controlled or monitored by the ECM. I'm also assuming that the light is in good working order as well. This also sounds like the issue is between closed and open loop, that's why I asked about the CEL. Things to check...

CTS sensor
TPS sensor (set to .525vdc, key ON, engine OFF)
IAC's (they control the idle)

The CF is rather sensitive to fuel pressure and needs to be set at 13-14psi and you'll be fine. This is more than likely not the issue, but it is something that needs to be checked anyway. Check these items and post back what you find. Another item that will help you immensely is a GM Service Manual...Get one. You can normally find one on eBay. The other manuals stink IMO.

 

[Shane]

Welcome to the forum. You didn't mention it, but do you have a CEL (check engine light) lit during any of this? If not, that's narrows things down a bit which means that work is happening isn't controlled or monitored by the ECM. I'm also assuming that the light is in good working order as well. This also sounds like the issue is between closed and open loop, that's why I asked about the CEL. Things to check...

CTS sensor
TPS sensor (set to .525vdc, key ON, engine OFF)
IAC's (they control the idle)

The CF is rather sensitive to fuel pressure and needs to be set at 13-14psi and you'll be fine. This is more than likely not the issue, but it is something that needs to be checked anyway. Check these items and post back what you find. Another item that will help you immensely is a GM Service Manual...
Get one. You can normally find one on eBay. The other manuals stink IMO.

The check engine light is not on, and it is working properly. Thanks for the input. I will check these items.

 

[WhalePirot]

A common problem is wear in the holes for the butterfly shaft rods, that allow unmetered air in and lean out the mixture. Perhaps the ECM cannot get enough fuel in to compensate. Ages ago, I got a kit with bushings and a drill bit to fix them.

 

[Shane]

ok, did a complete tune up.(plugs wires, etc) Problem persists. I performed a visual inspection of vacuum lines. They looked ok, but I'm going to change them anyways,as they do look "old".

 

[catbert]

I wonder if you have my old 84. I heard it was down in your neck of the woods - really. It was black with red interior and aftermarket exhaust - which wasn't very common back then. It was a stallion in the day.

 

[Shane]

I wonder if you have my old 84. I heard it was down in your neck of the woods - really. It was black with red interior and aftermarket exhaust - which wasn't very common back then. It was a stallion in the day.

It has a black interior and stock exhaust though it has a newer, less restrictive cat.

 

[Buccaneer]

ok, did a complete tune up.(plugs wires, etc) Problem persists. I performed a visual inspection of vacuum lines. They looked ok, but I'm going to change them anyways,as they do look "old".

What was the TPS setting?

 

[Shane]

What was the TPS setting?

I'm just a little lost. .525vdc? I checked with a DVOM and recorded roughly .9 volts??

 

[Buccaneer]

I'm just a little lost. .525vdc? I checked with a DVOM and recorded roughly .9 volts??

Unfortunately, that is WAY off and would be an issue if true/correct. To check it properly, you can backprobe the TPS connector on the middle and bottom wires. The key should be ON, engine OFF. If you do it right it should read correctly and you need to set it to .525vdc. If its off, only loosen the two mounting screws slightly and move the TPS sensor up or down to set it to the correct voltage. The only difference you will see on those two wires is the polarity if you are wrong, one will read "neg" value and the other will be "pos" value which is what you want. i hope this helps you out. Good luck and post your results.

 

[Shane]

Unfortunately, that is WAY off and would be an issue if true/correct. To check it properly, you can backprobe the TPS connector on the middle and bottom wires. The key should be ON, engine OFF. If you do it right it should read correctly and you need to set it to .525vdc. If its off, only loosen the two mounting screws slightly and move the TPS sensor up or down to set it to the correct voltage. The only difference you will see on those two wires is the polarity if you are wrong, one will read "neg" value and the other will be "pos" value which is what you want. i hope this helps you out. Good luck and post your results.

Ok, checked again. it recorded .525. I really didn't think this would be the problem, as the car only shows signs of trouble at higher operating temps.(around 200-220f) Vacuum lines perhaps? I did a visual inspection and they seemed ok, but I could have overlooked something.