1982 crossfire-bad idle_ dies

[jeanie2002]

GeekyBill could be right about the IACs. However, if you have a large enough vacuum leak the motor will surge like you described and the IACs will try to correct at idle...hence the surging effect. OR you could have very dirty pintles on the IACs and they can't shut properly and could be cycling. You could also have a fuel pressure issue and the only way to find that out is by checking in-between the TBs and see what it is set to, 13-14psi is plenty as long as the pump can output the volume under load.

A quick "gross" check of the fuel pressure to kind of see where you're at thing can be done by looking at the back of the rear TB, there's a small window (cutout) area that you can see into on the tower, thats the fuel pressure regulator can, "tab" and spring through there. Look inside with a flashlight and see where the "tab" is sitting in the slot. If it's at the bottom or really close to the bottom, your FP is low. You want the "tab" to be about half to 3/4 of the way up the slot. Again, this is only a "gross" check to get a feel of where your at.

I'm willing to bet that if its at the bottom that your FP is only around 9-10psi and is running the motor pretty lean. Check it with a gauge to find out for sure though. Also check the fuel filter/replace and maybe the pump filter/sock in the tank.

Since you said the headlights were working (coming up) and now they don't and they are run strictly by vacuum, I'd start there first, then the top plate or whichever you want first and then proceed from there. I would also think that if the vacuum was too low that you would be setting a MAP Sensor 33 or 34 code maybe.

There's a pretty good vacuum troubleshooting diagram in the Tech Section over at the CFI forum, check it out. CrossFire Injection Forum

So, since you aren't getting a CEL during operation, that would indicate that the issue is mechanical in nature whereby the ECM is not controlling or monitoring that problem and thinks everything is fine which would also eliminate a sensor input for now. It could also be the ECM, but that would be my last thing I checked. So to sum it up, we're back to either fuel or vacuum or both and of course a possible IAC issue.

The best thing you can buy is a GM Service Manual off of Fleebay or something for a car that is 28 years old and you want to maintain it, just a suggestion and well worth the money spent. Good luck and hope you find the root cause.

I checked tab and it is at bottom, at idle injectors have a good spray, but on acceleration dead spot at about 25% throttle at which time spray drops to almost nothing but push further and spray comes back. Is spray going away because of dead spot or lack of spray causing dead spot? Since this is an electric pump I would assume fuel should be at constant pressure, however if pump was not delivering why does spray return when pushing past dead spot? I can push to almost full throttle and no problem, all this was done with car parked. I thought if I could get full throttle in park I could on the road, but again falls on its face no power,have to continuously pump pedal to keep car from dying. This pump is old and I am going to go ahead and replace it, but this is just confusing me. Could oil pressure switch be acting up? Thanks

 

[Buccaneer]

You're just playing a guessing game at this point. Put a FP gauge on it and see what's going on, it's the only way to know. The pump could be weak as well. Did you buy that GM manual yet?

 

[TimAT]

Rule of thumb for electric in-tank pumps:

They will never die until you have just FILLED the tank.

 

[wishuwerehere82]

Rule of thumb for electric in-tank pumps:

They will never die until you have just FILLED the tank.

In this case it just doesn't matter, since the pump is on the filler neck and not mounted to the bottom of the tank. No need to drain the tank. It can be changed no matter if the tank is full or empty.

 

[wishuwerehere82]

I checked tab and it is at bottom, at idle injectors have a good spray, but on acceleration dead spot at about 25% throttle at which time spray drops to almost nothing but push further and spray comes back. Is spray going away because of dead spot or lack of spray causing dead spot? Since this is an electric pump I would assume fuel should be at constant pressure, however if pump was not delivering why does spray return when pushing past dead spot? I can push to almost full throttle and no problem, all this was done with car parked. I thought if I could get full throttle in park I could on the road, but again falls on its face no power,have to continuously pump pedal to keep car from dying. This pump is old and I am going to go ahead and replace it, but this is just confusing me. Could oil pressure switch be acting up? Thanks

One other possible cause of a skip or dead spot in the throttle is a bad TPS (Throttle Position Sensor).
You might want to do a quick check of the TPS too. This skip sounds like a dead spot on the TPS resistor as it moves. The center pin of the TPS connector is the wiper of the potentiometer. If you measure the total resistance of the TPS, it will be between 12K - 15K Ohms between the two outside pins on the connector. (The reason I say 12K - 15K is because my original one was 12K Ohms and the new one was 15K Ohms, so I can't say if it was age or design that caused the difference).
If you measure between the center pin and one of the outside pins with the connector removed, the resistance will be either very low Ohms or 12K - 15K Ohms. The center pin to the other outside pin will exactly opposite that reading, either 12K - 15K Ohms or low ohms. (And I say low Ohms, because it is adjusted for idle. It won't be zero Ohms unless you remove it and let it spring back closed).
As you open the throttle slowly, the resistance will increase or decrease depending on which pin you are probing in relation to the center pin.
The resistance should go up or down smoothly and result in an opposite reading at full thottle than at idle.
Any jumps or dips in resistance as you move the throttle open and closed are indications that the TPS is not making smooth contact inside, and needs to be replaced. This is what tells the ECM how far open the throttle is, and starts it making calculations on what you fuel/air mixture should be.


Plug the TPS back in, and measure the voltage between the middle and bottom wires. The voltage with the key on should be .525V or thereabout with the throttle closed.

As the throttle is opened the voltage will increase until it gets close to +5V at WOT. Once again, any jumping or dipping in the voltage will mean you have a skip in the resistance inside the TPS.
Something to check as long as you're there.

 

[jeanie2002]

One other possible cause of a skip or dead spot in the throttle is a bad TPS (Throttle Position Sensor).
You might want to do a quick check of the TPS too. This skip sounds like a dead spot on the TPS resistor as it moves. The center pin of the TPS connector is the wiper of the potentiometer. If you measure the total resistance of the TPS, it will be between 12K - 15K Ohms between the two outside pins on the connector. (The reason I say 12K - 15K is because my original one was 12K Ohms and the new one was 15K Ohms, so I can't say if it was age or design that caused the difference).
If you measure between the center pin and one of the outside pins with the connector removed, the resistance will be either very low Ohms or 12K - 15K Ohms. The center pin to the other outside pin will exactly opposite that reading, either 12K - 15K Ohms or low ohms. (And I say low Ohms, because it is adjusted for idle. It won't be zero Ohms unless you remove it and let it spring back closed).
As you open the throttle slowly, the resistance will increase or decrease depending on which pin you are probing in relation to the center pin.
The resistance should go up or down smoothly and result in an opposite reading at full thottle than at idle.
Any jumps or dips in resistance as you move the throttle open and closed are indications that the TPS is not making smooth contact inside, and needs to be replaced. This is what tells the ECM how far open the throttle is, and starts it making calculations on what you fuel/air mixture should be.
View attachment 1049

Plug the TPS back in, and measure the voltage between the middle and bottom wires. The voltage with the key on should be .525V or thereabout with the throttle closed.
View attachment 1050
As the throttle is opened the voltage will increase until it gets close to +5V at WOT. Once again, any jumping or dipping in the voltage will mean you have a skip in the resistance inside the TPS.
Something to check as long as you're there.

Thanks Pete,
I don't have a lot of spare time, but will try to make time to get this checked, I am not good on electronics but THANKS for explaining this for me. Buccanneer had asked about fuel pressure so I rented the test kit and have 9 lbs. with key on and 10 lbs. with car running. From what I've read it should be 10-13, is mine abnormally low? Thanks.

 

[jeanie2002]

You're just playing a guessing game at this point. Put a FP gauge on it and see what's going on, it's the only way to know. The pump could be weak as well. Did you buy that GM manual yet?

I rented the test kit and got 9 lbs. with key on and 10 lbs. with car running. I bought a manual on ebay but will be days before it gets here. Pete gave me some awesome info. on TPS so going to try that when I get a chance, Thanks.

 

[Buccaneer]

10 is too low, adjust it to 13 and see if the pump can keep up when under a load, if not replace the pump with the 85 - 87 corvette pump, recheck and adjust if neceassary. Nice job getting a manual, you won't regret it.

With the key ON, engine OFF and a meter connected to the TPS sensor (red lead on center termianl "B" and black on bottom terminal "A") you should read .525v or .52v if only displaying two decimal places, either one is exceptable. If the TPS is too far off from this, it won't run or idle properly, the tolerance is rather large +/- .075v, but through experience the closer you can get it to .525v the better. To adjust, loosen the two mounting screws only as much as needed to move the TPS sensor and lock it back down. The value will vary as you tighten down the screws, so you may have to play with it a bit to get it right. Just thought I'd mention that.

Good luck and read that manual.

 

[jeanie2002]

10 is too low, adjust it to 13 and see if the pump can keep up when under a load, if not replace the pump with the 85 - 87 corvette pump, recheck and adjust if neceassary. Nice job getting a manual, you won't regret it.

With the key ON, engine OFF and a meter connected to the TPS sensor (red lead on center termianl "B" and black on bottom terminal "A") you should read .525v or .52v if only displaying two decimal places, either one is exceptable. If the TPS is too far off from this, it won't run or idle properly, the tolerance is rather large +/- .075v, but through experience the closer you can get it to .525v the better. To adjust, loosen the two mounting screws only as much as needed to move the TPS sensor and lock it back down. The value will vary as you tighten down the screws, so you may have to play with it a bit to get it right. Just thought I'd mention that.

Good luck and read that manual.

How do you adjust the fuel press.?Thanks

 

[wishuwerehere82]

How do you adjust the fuel press.?Thanks

Wait for the manual. I haven't the heart to tell you how to do it either way. Let's just say there's some disassembly required.
The good news is that a solid 10 PSI won't be causing your stalling problems. Some shops would call that a good pressure and just re-tune it from there.
Here's an article that starts to describe the basic checkout and balancing of the TB's and that's what they used.
Chevrolet Corvette EFI System Tuning - Tech Articles - Corvette Fever Magazine

Although you really should be running at the 13-15 PSI level, the injector pulses at idle and moderate throttle should be compensating enough to keep the fuel/air mixture where it should be, especially with no load.
Something else must be going on unless the pump is pooping out under higher flow rates.

You might want to put a test light in your injectors to see if they are firing normally when the spray stops at 20% throttle. This could be a TPS problem, or an ECM that goes whacky at certain TPS inputs. You'll have to go through things step by step unil you eliminate a few things.

Try putting a vacuum gauge "T" in line with the MAP sensor and get a feeling of what the intake manifold vacuum is doing. 18" - 21" of Hg (Mercury) is normal at idle, and drops slightly with increased throttle.
You might still have something of a leak if the lights aren't opening.

 

[82ColEd]

I just read all the posts. I have an '82 sounds like the same problem.
I have a service manual and a laptop hooked up using winaldl.
And I am not have much luck.
Please let me know is you find the trouble BigJim
Thanks

JimBil: You might want to open your own Thread instead, so that you get the proper attention from our resident experts.

Thanks!

-Stefan

 

[jimbil208]

Hello
I had a very similar problem as I stated in a previous post.
One problem is that a lot of us back yard mechanics do not have all of the test equipment.I have a lot and also documentation.But if you look at all the answers for this problem,it leads in all directions.After I did most of the things that was sugessted here,and still had the problem. I was avoiding the fuel pump for a few reasons,it was in the tank and I wasn't sure how much was involved in changing it.I did not have the proper test equipment to connect between the throttle bodies.Then I realized that the tester that they want you to use cost more than the fuel pump. Hence and to end this marathon,I replaced the fuel pump and all is well.All of those crazy things went away,everything works fine.

Hope this is of some help,Jim

 

[Buccaneer]

Well thats great that you got it fixed. However, fact still remains that you don't know what the FP is set to and you would have seen what the issue was with the proper equipment, jus sayin'. I guess if you like the way it runs and are happy with it...great. Could it possibly run better, sure. You can make your own FP tester with a little know how if you don't want to purchase one and set it properly. CF motors are rather sensitive to FP. Anyway, NICE job and enjoy!

 

[jeanie2002]

Well thats great that you got it fixed. However, fact still remains that you don't know what the FP is set to and you would have seen what the issue was with the proper equipment, jus sayin'. I guess if you like the way it runs and are happy with it...great. Could it possibly run better, sure. You can make your own FP tester with a little know how if you don't want to purchase one and set it properly. CF motors are rather sensitive to FP. Anyway, NICE job and enjoy!

I think you must have replied to the wrong post because I am still working on mine

 

[jimbil208]

1982 crossfire-bad idle_dies

Hello
Look at the thread before the one that says about having it fixed.
That gentleman just got in between
Look at thread by jimbil208.
Thanks,Jim

 

[jeanie2002]

Hello
Look at the thread before the one that says about having it fixed.
That gentleman just got in between
Look at thread by jimbil208.
Thanks,Jim

OK, thanks.

 

[wishuwerehere82]

How you making out?

Jeanie2002, how are you doing with this?
Do you need any more help?

 

[jeanie2002]

Jeanie2002, how are you doing with this?
Do you need any more help?

I have not had a lot of time, but when I do work on it everything seems to go wrong. Here's what I've done; that fuel pump was alittle weak and with all that rust I did put in a '85 fuel pump which "seemed" to help but she got hot because thermostat stuck, it did run worse after getting hot. I tried to change t/stat and bolts did not want to come out, so after spraying them with penetrant and working back and forth one snapped off. holes in intake were corroded, tried easy outs,no luck, so I just drilled it and re-tapped yesterday. new t/stat in. fired her up ran good, had good oil pressure, ran around the block a few times, and it does still have dead spot at 1/4 throttle which seemed to get worse and then noticed oil pressure had gone down to a couple pounds at idle, came back up when brought rpms up. No engine noise. Could my oil press. switch be going bad, and maybe causing power loss to FP? I can jump switch to check that. or am I just losing oil press. when engine warms up? Have to look into it further and let you know. I feel like TPS may be bad, but haven't got chance to check it yet{hope to this week} also headlights still don't go up, can't hear any leak, this thing ran great and everything worked before being stored now something goes bad each week. Thanks for your help..

 

[wishuwerehere82]

I have not had a lot of time, but when I do work on it everything seems to go wrong. Here's what I've done; that fuel pump was alittle weak and with all that rust I did put in a '85 fuel pump which "seemed" to help but she got hot because thermostat stuck, it did run worse after getting hot. I tried to change t/stat and bolts did not want to come out, so after spraying them with penetrant and working back and forth one snapped off. holes in intake were corroded, tried easy outs,no luck, so I just drilled it and re-tapped yesterday. new t/stat in. fired her up ran good, had good oil pressure, ran around the block a few times, and it does still have dead spot at 1/4 throttle which seemed to get worse and then noticed oil pressure had gone down to a couple pounds at idle, came back up when brought rpms up. No engine noise. Could my oil press. switch be going bad, and maybe causing power loss to FP? I can jump switch to check that. or am I just losing oil press. when engine warms up? Have to look into it further and let you know. I feel like TPS may be bad, but haven't got chance to check it yet{hope to this week} also headlights still don't go up, can't hear any leak, this thing ran great and everything worked before being stored now something goes bad each week. Thanks for your help..

Yes, the oil pressure switch could be going bad, since the unit supplies voltage for the pump on one side, and voltage for the gauge on the other lead. You should be running 40-45 PSI at cold idle and 20-25 PSI at hot idle with it goig back up to 40 or so above 1000 RPM. You might want to clean up the switch connector contacts first to make sure you are getting a good connection. You might also try fitting an oil pressure gauge on the switch fitting to double check your pressure readings in case the oil pump pressure really is going too low.

 

[TimAT]

I'd look at TPS before I went with the fuel pressure- it does run both at idle and at higher rpm. It'd be a real odd one to have one spot in the oil pressure switch that's killing fuel.

TPS uses a +5v reference and if it's hitting an open spot and losing the ref voltage the ECM will get lost too.