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Discussion Starter · #1 · (Edited)
Hello I have a 1989 mustang 5.0ho 5-speed car and I’ve been chasing an idle issue when hot I can start the car and it’ll run perfect for a little while I’ll pull up to a stop sign when it’s warm and it’ll start to surge on me and won’t stay running I’ve replaced a few parts already trying to chase this problem and I still can’t get it so far I’ve replaced the distributor, plug wires, spark plugs, fuel regulator, egr valve, idle air control, tps and it’s set at .98, mass airflow sensor and housing, fuel filter, all new any thoughts?
 

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the TPS voltage set at a specific point is a myth. Its unfortunate this place is filled with that info in old posts. Take the MAF out of the housing and clean it. That would be the first thing I do. Had one just the other week I was working on, would run fine cold and then once it got up to temp, it would surge and stall. Took the maf out of the housing, it was black, cleaned it and reinstalled it and the car runs perfect.
 

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Discussion Starter · #3 ·
the TPS voltage set at a specific point is a myth. Its unfortunate this place is filled with that info in old posts. Take the MAF out of the housing and clean it. That would be the first thing I do. Had one just the other week I was working on, would run fine cold and then once it got up to temp, it would surge and stall. Took the maf out of the housing, it was black, cleaned it and reinstalled it and the car runs perfect.
Okay I’m gonna check it and see but it is also brand new and the mass airflow housing is also brand new it also came with a metal screen inside of the housing to filter the air
 

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Discussion Starter · #4 ·
the TPS voltage set at a specific point is a myth. Its unfortunate this place is filled with that info in old posts. Take the MAF out of the housing and clean it. That would be the first thing I do. Had one just the other week I was working on, would run fine cold and then once it got up to temp, it would surge and stall. Took the maf out of the housing, it was black, cleaned it and reinstalled it and the car runs perfect.
Also does the mass airflow sensor need to be clocked or does that matter?
 

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Also does the mass airflow sensor need to be clocked or does that matter?
Typically it does not matter but there are some specific instances where it may. I guess i would preference how that questions gets answered by trying to understand your build. Is this car modified? Stock? Does it have a cam? Have you dumped the check engine codes?

Acceptable TPS voltage for idle conditions is 0.5 to 1.25 volts. Anything in that range is acceptable and the ECU will give you a code if it falls outside that range. The 0.999v myth continues to this day but really needs to fizzle out.
 

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Discussion Starter · #6 ·
Typically it does not matter but there are some specific instances where it may. I guess i would preference how that questions gets answered by trying to understand your build. Is this car modified? Stock? Does it have a cam? Have you dumped the check engine codes?

Acceptable TPS voltage for idle conditions is 0.5 to 1.25 volts. Anything in that range is acceptable and the ECU will give you a code if it falls outside that range. The 0.999v myth continues to this day but really needs to fizzle out.
Okay so I dumped the codes two days ago after I reset the ecu it gave me codes 63,67,85,10 car has a cam in it I believe stock heads has a cold air intake I believe that’s it
 

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Are these old codes? You should try erasing them and rerunning them.

Code 63 is TPS voltage too low. It would have to be under 0.5V to trigger that.

COde 67 is trans not in neutral. Usually this is seen on AOD to T5 swaps where the NGS on top of the T5 is not connected, or someone just removes it and never connects it. You can get around this by keeping the clutch depressed the entire time you are pulling the codes.

Code 85 is a canster purge solenoid fault. Is the charcoal canister still attached and plugged in? Or has it been deleted.

Code 10 is a separator code between KOEO and CM codes.

Did you run the engine running codes as well? You may want to clear all the codes and go for a couple quick drives and then pull the KOEO, CM and then the KOER (engine running) codes.
 

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Discussion Starter · #8 ·
Are these old codes? You should try erasing them and rerunning them.

Code 63 is TPS voltage too low. It would have to be under 0.5V to trigger that.

COde 67 is trans not in neutral. Usually this is seen on AOD to T5 swaps where the NGS on top of the T5 is not connected, or someone just removes it and never connects it. You can get around this by keeping the clutch depressed the entire time you are pulling the codes.

Code 85 is a canster purge solenoid fault. Is the charcoal canister still attached and plugged in? Or has it been deleted.

Code 10 is a separator code between KOEO and CM codes.

Did you run the engine running codes as well? You may want to clear all the codes and go for a couple quick drives and then pull the KOEO, CM and then the KOER (engine running) codes.
The purge canister has been deleted and i I’m hooked the battery for a few mins and took it for a drive before pulling those codes and to run the koer codes do I run the test while the engine is running
 

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Discussion Starter · #9 ·
The purge canister has been deleted and i I’m hooked the battery for a few mins and took it for a drive before pulling those codes and to run the koer codes do I run the test while the engine is running
Also whenever it gets to operating temp the deceleration is very hard and the whole car jerks and sputters the whole way down the rpm I have to push the clutch in to stop it from jerking and then it stalls on me the only way to get it to run right again is to park it and pop the hood for a few minutes
 

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The purge canister has been deleted and i I’m hooked the battery for a few mins and took it for a drive before pulling those codes and to run the koer codes do I run the test while the engine is running
Which method are you using to pull the codes? Make sure you do a few key cycles after hooking the battery up. Basically, start it and shut it off a few times before you pull the codes.

If you are using the paperclip method you need to run through the KOEO/CM codes first, and then once the final code has repeated, just start the engine.

If you are using an Innova 3145 code reader you can just fire up the car, turn the code reader on and hit test. Wouldn't be a bad idea to run the Cylinder balance test as well.

I made a video showing these tests and how they can be run on the 3145. Using the paper clip can do the same thing but you just need to do it all in sequence.



Wouldn't also be a bad idea to verify your fuel pressure, and perhaps to conduct a smoke test to look for vacuum leaks.
 

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Discussion Starter · #11 ·
Which method are you using to pull the codes? Make sure you do a few key cycles after hooking the battery up. Basically, start it and shut it off a few times before you pull the codes.

If you are using the paperclip method you need to run through the KOEO/CM codes first, and then once the final code has repeated, just start the engine.

If you are using an Innova 3145 code reader you can just fire up the car, turn the code reader on and hit test. Wouldn't be a bad idea to run the Cylinder balance test as well.

I made a video showing these tests and how they can be run on the 3145. Using the paper clip can do the same thing but you just need to do it all in sequence.



Wouldn't also be a bad idea to verify your fuel pressure, and perhaps to conduct a smoke test to look for vacuum leaks.
I’m using the innova method and I just tried to dump the codes with the car running and it just said 000 the whole time and the car ran like poop
 

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The psi should be 39psi with the vacuum on the regulator removed and the hose plugged so there is no vacuum leak. The symptoms you are describing could be a dirty maf element. As I already stated, you should start there.
 

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Discussion Starter · #14 ·
The psi should be 39psi with the vacuum on the regulator removed and the hose plugged so there is no vacuum leak. The symptoms you are describing could be a dirty maf element. As I already stated, you should start there.
I checked it and everything looked normal but I also said the maf is brand new as well as the maf housing and it also came with a screen in it the old one didn’t have one so idk if that makes a difference and that pic is with the engine running and the regulator hose plugged in
 

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Def raise the FP up to 39 psi vac off.

so to be clear. Running the engine codes in sequence doing the KOEO/CM first and then starting the engine, and starting the engine and initiating the code reading by turning the reader on and hitting test generate nothing? The black square does not blink?

It would be nice to dump the codes and do the cylinder balance test (to check if you have a misfire) but don’t get hung up too much on this if it’s giving you trouble. Other things to check
 

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Discussion Starter · #16 ·
Def raise the FP up to 39 psi vac off.

so to be clear. Running the engine codes in sequence doing the KOEO/CM first and then starting the engine, and starting the engine and initiating the code reading by turning the reader on and hitting test generate nothing? The black square does not blink?

It would be nice to dump the codes and do the cylinder balance test (to check if you have a misfire) but don’t get hung up too much on this if it’s giving you trouble. Other things to check
I think I’m just dumb I tested it with key on engine off then started it and tested it and the black square just popped up and didn’t go away
 

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I checked it and everything looked normal but I also said the maf is brand new as well as the maf housing and it also came with a screen in it the old one didn’t have one so idk if that makes a difference and that pic is with the engine running and the regulator hose plugged in
My bad, i missed you saying it was new.
 

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Honestly, my first thought was to check the ECU as well. Not being able to dump codes could be an indicator that there is a fault within the ECU. Either capacitors or a burned pin 46 trace.

Can you inspect the ECU? Can you remove the cover and look at the three capacitors and see if they have the typical green corrosion forming where they meet the board?

Also, using a multimeter, check for continuity from pin 46 to pin 40 and pin 60. You should have a connection there.
 
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