Engine Idle Racing

[crawfr1312]

I'll make this short and sweet. Engine Idling at 1200 in Drive whille sitting still, causing one helluva kick when downshifting when your driving and cominngto a stop. Used to idle at around 750, what's up. On my way to buy a Chiltons, haven't needed it for the last year i have had the truck. Got no choice now. Oh 1998 4.0L SOHC.

Thanks

 

[TPLYNCH]

Your IAC is probably bad. Run a search and you'll find lots of posts about it.

 

[crawfr1312]

As much as I wanted that original post to be short and sweet apparently it isn't. Went to pick up the truck from my wife and man is it acting F****D UP. NOt only is the idle still hovering around 1100 - 1200, but when you start from a complete stop and begin taking off, the trans is shifting really weird. From First to Second seems too soon, and it bucks like it hits second then downs bak to first then right bak to second. Shifts from second to third at around 20-25mph and 1500 rpm's, then OD at like 30. After the shift from first to second, no power at all through any of the gears. Thing is like a dog with the pedal floored, but Rpm's staying normal, no slipping of trans. Could the IAC cause any of this? I got the truck wit 59000, on it, just hit 74000. Don't know when the last trans fluid/filter change was. Gonna change it tom. morning.

 

[TPLYNCH]

Have you had the 00M12 warranty work done on the manifold O-rings and the timing chain tensioners?. Try disconnecting the battery for 30minutes to reset the computer and see what happens....

 

[Alec]

Your TPS, throttle position sensor, is a part that can cause both engine and tranny probs. But from the symptoms it sounds like your tranny may be going.

 

[crawfr1312]

Alex, I think you may have hit the nail on the head, we put it on a scanner yesterday, and it said the TPS voltage could be incorrct, my buddy didn't have the manual for the 98 yesterday, so I'm not sure what it was suppose to be. I scheduled an appointment for the Ford dealer for thurs, but maybe i'll test the TPS when I get home. I replaced the IAC for $65.00, and it did nothing to help. Thanks.

 

[Alec]

If the computer threw a TPS code, go ahead and replace it. They're usually $30-50 and any auto place should be able to get one for you. Glad I could help.

 

[crawfr1312]

Alec, not Alex as I previously wrote, I tested the TPS and it tests fine. I have an appoint with Ford dealer Thurs, just gonna let them tell me what the hell is wrong. $ 125.00 but I won't have to keep guessing. Took back the IAC, I installed, since it did nothing. They didn't carry the TPS so thats when I decidied to wait. Let you know what becomes of it.

 

[Alec]

Mine threw a few codes one day and I scanned them and erased them. I checked the TPS and it checked fine. They whadya know, on my long road trip a week later it started throwing codes daily and causing drivability problems. Just saying that it could be fine now, but could crap out again.

 

[crawfr1312]

This thing is definitely not fine, drives like ****. Drives so bad, my wife is now driving the truck I just bought, and making me the Explorer. Definitely not cool. She drives around 100 miles a day, I do 18. It worth the $125.00 if it gets me my truck back. It's a shame I can't get her to trade the Explorer in on a nice 78-79 Bronco, at least I could handle all the repairs on one of them.

 

[kgd102]

A while back my 98 SOHC was doing everything you described. It turned out to be a bad thermostat.

 

[crawfr1312]

KDG102,

That seems kind of funny, my wife told me she thoughtit seemed to running hot. Since she took my truck for the last few days these all of these symptoms begin once the truck starts to get hot. The temp sensor goes up high enough for the Check Gage light to come on for about 30 seconds, then therm seems to be opening and the light goes off. I am cancelling my appointment at the dealer tomorrow, because the Trans Range sensor if suppose to have a direct affect on the Idle and Torque Converter Clutch operation, according to Haynes Manuals. TCC is not working correctly on the highway, so I thought that might be it. I was going to grab a new therm, when I picked up the TR Sensor. Guess I'll put it in first and take it for a cruise. Let you know after this weekend.
Thanks,
Rick C

 

[Nemo0101]

My 98 XLT SOHC is doing everything described here. I was driving home yesterday and noticed the car was not shifting correctly when starting from a stop. It would bang into a gear and often went to a higher gear too early causing a load on the engine. When I would stop the engine would stay at close to 1500rpm. I finally limped it home on back roads with hazard lights on. When I started it a few hours later to try to bring it to my dealer it seemed fine... for about 10 min. I happened to look down at the gauges again to watch the rpms when I noticed the temp gauge pegged at H. Soon after that the check guage light came on so I turned on the heater. This brought the temp back within the range on the gauge but still hot. I got to my dealer a few minutes after that.

Seems like the thermostat to me. Kind of suprised with the other symptoms. My truck has 54K miles. Is the X smarter than I think and purposely doing things to save itself when it overheats? Or is it just a fickle car that reacts strangely when things aren't quite right?

Unfortunately, the dealer doesn't think he can get to it until Monday. I need to pick up a boat tonight and I was planning on towing it 100 miles to the shore for some fishing on Sat. I may have to borrow a friends truck now. On top of that my aftermarket warranty does not cover the thermo and therefore probably won't pay for a rent a car for the next few days. I almost wish it was something else but at least this should be cheap and easy. It figures to happen on the first weekend with the boat. At least I wasn't in the middle of towing 100 miles from home when it crapped out.

Mike

 

[crawfr1312]

Well,

I replaced the thermostat, and I can't believe it, but the problem is gone. I guess $24.00 thermostats cause a lot more problems than you could ever imagine. Idle is back to normal, trans is fine, and runs at a normal temp again.

 

[kgd102]

Glad to hear that was the fix. It is amazing how something like that can have such a big effect.

 

[Alec]

no more TPS codes? well, glad you fixed it! sorry my advice was off.

 

[Nemo0101]

It was the thermostat. Cleared the symptoms right up. My theory is that the sohc X has a "limp home" feature:

1) Engine starts getting hot due to bad thermo
2) Engine runs fast (1200rpm) at idle to speed fan up for more cooling.
3) Engine bangs into gear due to fast idle and causes car to lurch forward
4) Engine shifts really early to keep rpms below 2000 or so to prevent overheating, hence lack of power.

A chime would be nice when the temp would rise too high since I never noticed the guage was rising until later that night.

Mike

 

[Jon_Herr]

Mine too - just started

My SOHC started idling around 1200 today. My temp guage is dead center in the middle as it has always been, though.

When you said yours ran hot, did the guage indicate more than normal?

Thanks,
Jon

 

[Robert]

My idle ran about 1200 RPM for about a week before my temperature gauge started reading high. I'm guessing the high idle was enough to keep the engine temperature in its normal range until it got a little worse.

 

[jonny 5]

Hmmmm...maybe I should replace mine at 50,000 before I have to put up with these problems. What do you guys think?