Contour Enthusiasts Group Archives Forums General Troubleshooting Throttle Surge (not hang)

Frequent visitors to this site have by now heard of the infamous "throttle hang" problem. In a nutshell, this refers to the fact that the throttle will hang briefly in-between shifts. This affects all Contours.

There was some discussion about 5 months ago about a different problem, best described as "throttle surge," or what I'll call TS.

The symptons of TS include:

1. Intermittant surging in RPMs at idle.

2. No change in RPMs when the clutch is depressed (same as the throttle hang problem, except that it hangs indefinitely).

3. A rapid increase in RPMs when the clutch is depressed.

These symptons are always intermittant, but seem to be worse when the A/C is activated or the engine is warmer than usual (for example, when it's been idling a long time such that the cooling fan needs to come on).

I've brought my '99 SVT in for servicing twice on this. Both times, they replaced the IAC. This fixed the problem--but only for a few weeks.

I'm sure others have had this nightmare, but I'm wondering if anyone has found a permanent fix to TS?

My 99 SE Sport 2.5L DOHC MTX75 has done that since I bought it new. However, it is so intermittent that I haven't been able to capture it with my monitor. I've spoken with the calibration supervisor and one of his engineers for this vehicle line. IIRC, they told me that they fixed this problem in an earlier version of my PCM. I didn't have the time to follow up with them more then and since the vehicle is no longer being built, I'd probably have a hard time finding anybody who remembers the calibration well enough to help out. I'm pretty sure that it is a software/calibration thing and we pretty much have to live with it.

I have had similar problems with my '99 SVT. I have cleaned the IAC, and replaced the IAC and the problem does seem to reoccur after a time. Resetting the PCM seems to help for a while. I have also observed that the problem seem to crop up more in hot weather, especially after using the AC on a longer highway drive. And, no, the TH fix doesn't make any difference on this. I have tried it with the plug both in and out.

I also believe that this is a firmware issue in the PCM. My only solution so far has been to reset the PCM.


// Chris Root
// '99 SVT

I have a 99 SVT and have had the same problem as described above. They replaced the IAC twice with the problem coming back within a month. I dont remember the name of the part but I think they replaced the Throttle position sensor and that fixed it and it has stayed working properly since then. Email me if that part is incorect and I will call my Ford dealership and make sure thats what it was. EMail : kawray@lrbcg.com

Come the think of it...if the throttle position sensor were intermittently providing a noisy signal, the PCM could be confused into providing too little IAC at closed throttle (thinking that the TPS was at part throttle due to an incorrectly-low ratch). Then, when the clutch is pushed in, it will go to the wrong adaptive table, and PRESTO engine stall. You could be on to something here. Another data input to monitor the next time that I try to capture this failure. It has been about 4 months since my car has done this last--I've been averaging about 6 times a year.

I'm pretty sure that its not the TPS in my case. The dealership checked it and so did I (with a oscilloscope) and the signal was clean.

// Chris Root
// '99 SVT

It very well may not be the TPS. I am not familiar with a faiure mode that results in a low frequency intermittent noise issue on the TPS. Then again, if there was such an issue, you aren't likely to find it when you hook up a scope or scan tool at engine-off, idle, or even most of the time at part-throttle or WOT. The best way to capture it is to monitor ratch and wait for a recurrance. If ratch is below your closed-thottle TPS reading (EEC calls it ITP), than this wacky scenerio is likely the cause.

AFAIK, this is the portion of The Moose that Ford attempted to fix by issuing TSB #97-22-3 (applies to SVTs - older models have a different TSB#). This TSB replaced the bagpipe/bellows ass'y from the intake hose to the IAC and also the IAC itself. It attempted to fix the A/C compressor-related surge accompanied by The Moose. As we all know, it quieted the Moose, but did nothing for the compressor surge.

However, there's also "another Moose," which seems to be unrelated to either the IAC or the A/C compressor. It occurs mostly in cold engines in cold ambient temps, and may or may not have any effect on RPM.

FWIW, my engine has the "updated" IAC and tube, and surges when the compressor kicks on. Also, it has the "other Moose" in cold temps.

At this point, your guess is as good as mine. Two problems to solve, both related to intake resonance. Happy hunting.

My 99 SVT did the same. Dealer eplaced the IAC and reprogrammed the car with new code from Ford. The problem went away entirely and that was over 6 months ago.

Boy, everyone has throttle problems.....and from what I've searched out no fix is really a fix. Every SVT owner I've met (myself included) hates the response of the SVT gas pedal and gets annoyed at the silly problems (hanging, dying, moosing). Every 'cure' I've heard so far lead to other problems! It's hard to imagine intakes getting totally dirtied after a few years, or that 'custom modification' is needed to make all well (response-wise, in all weather) since most of us have had prob's from day one. OR that every slight mod throws everything outta spec'. My opinion is that the EEC was coded hastily with no room for big parameter changes (hello, Ford?)....and their coilpac system is a loser for this car. The light flywheel mod, so generously touted by Ford, was supposed to 'smooth out' the rev's. Umm, sorry, that would only make it worse, if the crank counterweights and stroke were not changed (that woulda helped the torque). But..... Deep stroked for high RPM stability? Oh, yeah, now we need more oil press. and better bearings. Sometimes I hate Ford. The SVT engine was done halfassed, I'm sorry to admit. The Maurader looks cool, hope they cave in and put that 6sp MTX in. I like my SVT a lot but the engine control sys totally blows. And for an SVT, I would have expected better, having driven the Lightning and 'stang models. My $.02.