So the IROC had a bad idle, never could get it right. I installed Bosch 3 injectors I purchased from F.I.C. 19#. Installed no problem 'til I fired the car and the idle shot to 2200rpm I let it run a while then drove it only to find out it wont decelerate I stand on the brakes in gear (A/T) but it will only slowly come down to about 1500 then 1200. I contacted Jon at FIC he said I must of put the runner gasket's on the wrong side, I tore the plenum down inspected it checked out fine, the gaskets are marked L,R, I've had the plenum off a few time before when I replaced the EGR about a month ago. I checked TPS voltage- ok. Removed IAC cleaned it reinstalled it, it's farly new less than a year. I reset minimum air to it's lowest point, while grounding the ALDL, I've checked for vacuum leaks found none. I'm stuck fast Idle and poor decelaration where else can it be sucking in air from? PCV? any ideas?

 

well, the only thing that jumps idle is too much air or advanced timing, normally air is the culprit,, what is your base iming with the brown wire disconnected? is the IAC working right? is egr stuck open? how about the throttle blades are they closed tight at idle ? un hook the throttle cable at idle and see, maybe its holding the plate open, ya know a slight bit will raise the idle 500 easy..also it could be a bad brake booster or leaky check valve.. unhook the vac line to the booster and plug it at the engine.. see if that changes things

 

hey irocuroc, yup timing is dead on 6 degrees base(wire unplugged) throttle plates are closed tight at idle, I remove fresh air intake hose to check them at idle, egr is new I removed vac hose to it made no differences, but that big vacuum to the booster is a good place to check, hadn't tought of that I'm going to try that tomorrow and post back, the AIC is newer I replaced many parts that looked suspicious when I overhauled this motor, but how do you really check for function? just on plug it? will that make it close all the way? I was thinking of just putting my finger over the air hole that feeds it from inside the throtle body to see what happend, but how do you know if it's working, I know it needs coolant temp feedback to activate via the ECM.

 

update, unpluged booster vacuum hose while engine running, imidiatly raised rmps reconnected it went back to where I started it. Unpluged AIC, made no difference so I removed the fresh air intake hose put my finger over the small hole that feeds air to it, and idle dropped instantly, so the AIC is not fuctioning letting too much air into the intake, so like I said earlier it's not very old so should I replace it again or can it be the ecm not operating it, how do I check the circuit for proper function, with a test light? ALDL? any clues? Maybe it's not getting any signal...

 

the iac when installing needs to be set. The pintle depth cannot exceed 28mm from the flange. Do you know what I mean.. If the pintle length is to short it wont close and it will suck air. You cannot put your finger over the hole as it is behind the throttle plate. you have to eliminate all possible vac leaks, you got one for sure.... Back to the IAC.. its a motor that sends the pintle in and out, this is a controlled vac leak. You can also have a leak under the plenum, anywhere even the evap system for the gas tank. keep taking off lines and cap them. No change hook it back up and go to another. The iac should show a count of 30 at normal idle on a scan tool. You can also check its operation by removing it. There are 3 wires.. 1 ground and 2 power from the ECM.. so put it on a bench hook up a lead to the ground.. Then touch i terminal the pintle will go in or out.. then touch the other, the pintal will go the opposite direction. If that checks out set the depth to 28 mm and reinstall it. The CTS must also be good or it will stay in open loop and be on an electronic choke and a little higher rpm. Try this stuff and let us know

 

bad IAC for sure, I couldn't find the right one for it anywhere in stock, I bought one for a TBI model to check it's function against mine, when power is applied via jumper wires, the new one moves in or out every time I hit it with power depending on the polarity of the jumpers, the old one does nothing. I extended the pintle on the old bad one all the way out and installed it back in the throtle body hopping it would plug the air passage and lower Idle but it didn't, it's extended all the way out and it is still sucking air, if I take a shop rag and plug the hole in the throtle body the Idle lowers instantly, I'm not talking about the throtle plates but the small air pasage hole in between the two big plates that's an air channel and that air is what the IAC controls it suck real hard that's the only vacuum leak, I've unpluged every thing connecting to the plenumm except the map sensor of course and nothing makes any difference except for that hole in the throtle.

 

go to napa and buy an iac.. set it and go enjoy your car

 

exactly, I used to manage a NAPA store for 7 years, so I was surprised they didn't have in stock, but I ordered one for tomorrow so I'm hoping that's the issue. hey do the IAC housing go bad often?

 

inspect it.. the pintle seat should be clean and free of distortion or deterioration

 

Not quite done yet, Installed new IAC deceleration corrected, installed new CTS idle improved but not to spec found weak throtle return spring installed and auxillary spring to help plates fully close, minimum idle air screw backed out all the way. Idle at operating temp is 900-1000 in (P) 750-800 in (D). Still fighting a code 32 EGR. I've replaced EGR, ran test procedure per Haynes repair manual working correctly, closed when ignition turn to on and droped vacuum on gauge (mityvac) found cracked egr solenoid, I glued it back ran a vacuum test passed yet code still comes back on after a while of driving, Could this solenoid be causing a lean signal, car has a strong gas smell after driving and at idle coming from the exhaust, there are no fuel leaks. I've ordered a new solenoid in hopes this will clear the code, runnig rich and maybe drop a few hundred rmps, but that's high hopes for an egr solenoid replacement. I'm also not sure all vacuums are plugged in correctly I'll have to double check them just having trouble finding a correct diagram, theres a small vaccum delay that T's off between the accesory's and cruise control, I've found this on some diagrams placed in front of the engine of the egr throtle vac and split to C.C. mine is next to the egr sol. feed of intake barb not throtle. Where can I find an exploided view of vac. for 90 S.D. 5.0L w A/T?

 

little different idea here....did it not idle high until you installed the new injectors right?? did you install the series 3 like from a newer style motor, if so then you're injectors are not 19 lbs, because the newer motors run at 50psi not the 43.5 that it is supposed to be, so if you had a 19lb injector running at 43.5lbs, you would have like a 17lb injector and you car would run lean, making it idle high. just a thought.

did your injectors look the same as the factory ones you took out???

 

It did have a rough slightly high Idle about what it is now before the injectors, I got my injectors from fuelinjectorconnection from Jon I specified 19lbs inj. for my 1990. the injectors I received where bosch style 3 slightly shorter 1/4" and with a ford part number on them Jon said those are the correct injectors I double checked with him before install the fuel smell was also there before the inj. So I'm pretty sure inj. are correct, but I am runnig a stock fuel reg 43.5 psi vac disconnected. I'll replace the egr vac firts it is crap, and it is throwing a code 32.

 

egr shoudn't effect that....what is your injector part number, is it smooth like the one in the pic I attached, or does it have a fat middle part? If it's what I'm thinking it is, it is SUPPOSED to be at 50psi, so you don't have 19lbs going through them.

 

here is the style it is supposed to be.

 

there smooth just like the first one only yellow, I pulled out multech's oe. but if it where running lean, why the raw fuel smell at the exhaust and it's using up lots of fuel.

 

jeeze who writes you guys material. The injector is a 18.25 rated at 39.15.. if you run them at 43.5 they are 19.. at 50 they would be 22 58 they would be 24. Sound like he got some sh*t in one and its leaking. or stuck.. That happens.. Those new style Bosch injectors come in all sizes. the tan are 19 the yellow are 22 lite blue and grey are 24 red is 30 white 36 dark blue with the new style connector is 39 green is 42..

 

whent back and looked at the injectors, they are not yellow they are more a tan color,(19lbs) checked with Jon @ F.I.C. he says they should work fine and perhaps the reg is not holding pressure while crussing. I'll double check all that tomorrow let him know and post back, My biggest probles is strong fuel smell coming from exhaust also throwing code 32, but from what I've checked and replace it all comes back good. It's a puzzle I like to find the root of a problem instead of just throwing more parts at like I have in the past.

 

Yeah they are 19 at 43 fuel pressure. Put many of those in.. Maybe one is acting up, I think its possible..