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93 5.0 idle issues, stalling?


surratt

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actually i just imaged the 1998 IAC and it has a different connector. I used the old IAC from the original intake. Not sure if that will make a difference. You think it would be worth my time to go to the junkyard and grab a connector and solder it in and try an IAC for the 1998?
 


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surratt

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also what Injectors would you recommend i get. Ive read that they updated these at some point to a different spray pattern.
 

surratt

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Motor is basically stock, no major power upgrades
 

RangerSVT

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Definitely try the IAC, and the injectors run from a 97 explorer (19 lb). Dont run the 99-01 14 lb injectors, they're designed to run at 60 psi...

SVT
 

surratt

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Definitely try the IAC, and the injectors run from a 97 explorer (19 lb). Dont run the 99-01 14 lb injectors, they're designed to run at 60 psi...

SVT
awesome i will make a trip to the junkyard tommorrow to grab an IAC. I might be able to find some injectors while im at it. So only 1997 models have those injectors? Ive read threads about guys updating and saying things felt smoother. just let me know what i need to be looking for in the junkyard and the exact year range. Pretty sure the ones you are referring to have 4 holes
 

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96-98 yellow top injectors from a V8 explorer...

SVT
 

surratt

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ok so i grabbed the harness and soldered in the connector so I could use the IAC that came with the 1998 intake.... I also disconnected the battery and connected the terminals for a bit to reset the memory. It seems to do better bc its not shutting off in drive. But the second i shift it to park it will die after a few seconds. Now I will say I used the TPS that came with my old 93 gt intake. Fits in the same spot. I didnt get a chance to check voltages and see if its close the the 1 volt range at idle. Thinking maybe I should solder in the connector and tps that comes with the 1998 just not sure if that will work.

Now there is an idle reset procedure that I am reading about that I havent tried yet. Is that worth trying at this point? Im not understanding why it being in park would shut it down and not in drive.
 

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Thanks guys for the help...I feel like im getting close though
 

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scored the injectors from a 1998 explorer so ill put those in later. Unfortunately it is still stalling. I performed the idle reset procedure and the tps is around 1.15 volts with KOEO. Seems to do better but still stalls sometimes in park and sometimes in drive coming to a stop. Frustration levels high!
 

RonD

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TPS voltage needs to be under 1v when throttle is closed.
.6 to .9v is spec
Could just be volt meter isn't accurate, test a few AA or AAA batteries with it.

So either throttle is not closed all the way or TPS needs adjusting.
Bolt holes for TPS are slotted a bit so it can be rotated slightly to set closed voltage.
Also there is the anti-diesel screw on the throttle linkage it could be set so throttle plate is too far open, unscrew it to lower TPS voltage.

When TPS voltage is above 1v computer "assumes" driver is now in control of the engine RPMs so IAC valve would be "off line" for computer control.

After adjustment reset computer, i.e. unhook battery for 5 minutes


Thought of a test, with engine warmed up unhook a vacuum line from the vacuum tree on manifold, if engine no longer stalls, then IAC valve or its ports, air passages, have a problem.
IAC is nothing but a "controlled vacuum leak", but it uses MAF and filter air.
If engine still stalls the fuel or spark is most likely issue.
 
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surratt

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ok ill try to get the voltage down to .9 although i dont think I have enough play in the sensor. Its confusing bc ive read some people say to get around .9 or so and some people say as long as its below the 1.2 v threshold the computer will adjust the rest.
 

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ok ill try to get the voltage down to .9 although i dont think I have enough play in the sensor. Its confusing bc ive read some people say to get around .9 or so and some people say as long as its below the 1.2 v threshold the computer will adjust the rest.
Not sure where they would come up with 1.2v being threshold voltage that's a pretty arbitrary voltage since the Ford spec is .7-.9v, I would think spec would be .7-1.2v if that were the case, but people are correct that the computer "learns" TPS voltage over a few starts and drives, and you would most likely get a CEL and code for "out of range" TPS voltage if this was the problem, but.................
This would be software dependent which varies a bit by year and software code revision, so.............if you are within spec then that ain't the problem, if you are not within spec then.........well you just can't be sure it isn't the problem, lol.
 
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surratt

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Yeah i just meant the high range number. After spending a bit researching this the general consensus seems to be to get the tps voltage around the 1 volt mark to allow for heat tolerances and such. But as you said as long as its within the voltage range there will be no code set and no issue. Either way my TPS voltage is too far out at 1.15. Ill see how much play i have in the actual sensor and ive seen people talk about drilling holes to get more room. But Im just not sure exactly where the idle screw on the throttle body is suppose to be at and obviously that will effect the voltage. At this point I just need to figure out if im going to try to change the voltage at the tps first or the throttle body screw. Lowering it at the screw will just lower the idle and stall it out it seems
 

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You want to lower the idle at the screw. You would naturally think this would lower the idle even more, but what you are doing is closing the throttle body blade, and in turn lower the TPS voltage. The IAC will raise the idle back within spec...

SVT
 

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Warmed up Engine will normally idle at about 500rpms(with IAC Valve unplugged).
You can use that to reset "idle screw", anti-diesel screw.

Fuel injected engines have no Jets, like a carburetor, so can't use an "idle screw" since opening the throttle doesn't increase fuel flow(out of the jets) while increasing air flow.
Opening the throttle just increases air flow which leans out whatever mix the computer has set for the injectors.

IAC Valve air passage by-passes the throttle plate, so throttle plate can be closed all the way and engine can still idle if IAC valve is working.
But to prevent stalling if IAC Valve should fail closed, I usually set the "idle screw" to allow in enough air to maintain a 500RPM idle, this also lowers TPS voltage.
Throttle plate should be almost closed all the way at that point so satisfies the anti-dieseling purpose of the screw.
This, no IAC valve, idle must be lower than the 600-650RPM idle that the computer has as its target or the IAC Valve can't do it's job, automatic trans may have 750-800 target idle, but you should still set no IAC Valve idle at 500RPMs
 
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