Cleaning Idle Air Control Unit on 1993 Ford Probe GT

sbullet · 04-01-2008, 05:15 PM

I removed the idle air control valve unit from my 1993 Ford Probe GT V6 2.5L engine. It would suddenly surge and the rpms would go from about 1000 to 3000 and stay there. It would do it when the clutch was pushed in or when you came to a stop and also while driving. I used carb cleaner on it and there was lots of carbon (looked like burned crud). I scrubbed and wiped it clean. When I put the system back together, it would try to stall. I kept revving it up until it started to warm up. Then it would idle at 1500 rpms. When I put it back on, does it have to be tuned up again (adjust the tps and the air screw on the throttle body)? I started to drive it out of the driveway but it did not seem to run just right. Before I cleaned the IACV unit, it would idle without a problem and at the right rpms. Is it common for the car to have to be readjusted for idle? Any help greatly appreciated.

jonmark1985 · 04-01-2008, 06:13 PM

You shouldn't have to do much or any adjusting at all. I'd wonder if there is carbon in the IAC valve that is still keeping it from opening and running right.

sbullet · 04-02-2008, 10:16 AM

I found out why it would not run properly after reinstalling the throttle plate and IACV. Someone forgot to hook up the Mass Air Flow Sensor. As soon as I did that it ran perfect. Unfortunately , the cleaning of the IACV did not stop the engine from surging. I bled the cooling system and got a ton of air out of it. This usually stopped it from surging for a week or two but this time it did not help at all. The engine will still surge while driving or at a stop light or even at idle. I am at a loss as to what is causing this. I am contemplating replacing the engine but I don't want to do it if I can figure out what is causing the surging. It has a very good engine with the surging problem being the only problem. I have replaced the TPS, thermostat, flushed the cooling system, replaced the air filter system with cold air intake, replaced the throttle plate gasket, cleaned the IACV. I have no idea where to start next to search for the problem. The Check Engine light is on but no one around here has the adapter to fit a 1993. Occasionally, the computer will beep 5 times and stop. It does this 6 times in a row and then stops completely. If anyone has any ideas of what is causing the surging, please, please let me know. Thanks.

kmmand · 04-03-2008, 11:48 AM

Hi, I'm new here and your problem looks similar, perhaps, to mine. I have a 2000 Taurus wagon, 24V. Um, that's where my car smarts stop. Anyhow, my car revs every 4 to 6 seconds. It idles at around 700-750 and then revs up to just under 1000 very briefly and goes back down again. It sometimes will not do this when it is cold outside and then it idles nicely just under 1000. I thought I might need to clean the fuel system, but then I thought would that necessarily cause this very regularly spaced rev?

Thanks if you have any opinions.
Kathy

sbullet · 04-04-2008, 03:34 AM

If my would do it consistently, it might be easier to figure out but mine is very inconsistent. It only does it when the engine is already warmed up but not always. I have checked the hoses and have so far not found any that are in bad shape. They all look pretty good. I cleaned the Idle Air Control Valve and that didn't do anything to stop it. For now, I have had to park the car and leave it until I can figure out what to try next. The Check Engine light is on but no one has the adapter to fit a 1993 Probe. Closest I can get to it is a 1995. I am at a loss as to what to do next. I thought of changing the motor but I am not sure that will help.

rcss97 · 04-04-2008, 10:12 AM

well, I have the same problem, and can send you a pick to show you how to find the codes without a computer..send email to: rcss97@hotmail.com
and I will send it to you later.

rcss97 · 04-04-2008, 10:19 AM

I know you can check the tps, and make sure it reads around 0.6 on the yellow wire, when idling and in park. then you can adjust the IAC, then recheck the tps, to make sure you are getting a good reading. the reading should be between 0.45 - 0.65. If it is, then everything should be adjusted ok....the next place I would look, would be to find which part is causing the problem, maybe after you read the codes, it might make more sense.....You might also, want to check the EGR, making sure it's not sticking, will also, cause similiar symtom...hope this all helps. I will be checking into this problem, in the next couple of weeks, and will report anything new.

sbullet · 04-05-2008, 01:58 AM

I had someone tell me that the problem probably was a cracked head. I have thought about that but it does not make sense. If it was a cracked head or head gasket, should it not do every time instead of occasionaly? It only does it when the engine is warmed up but not every time the engine is warmed up. I used to be able to drive the car for up to a week without it doing it again. It is just that lately it has started to do it more frequently.

proholic · 05-04-2008, 09:09 PM

it probably is the iac not the tps. there is one very easy way to find out. unplug the tps and if the idle surges and stays at a high rpm then the culprit is not the tps. the tps is shutting the idle down cause it is telling the ecm that the throttle plate is shut. once it is unplugged then it will not send that signal. the surge may still not be the iac it can still be a vaccum leak somewhere else check all vaccum lines after the throttle plate if no leaks there then it is the iac.

proholic · 05-04-2008, 09:11 PM

head leaks have many other symptoms as well as a poor idle.
one is vapor or water out the tailpipe + white smoke and water in the oil.