Contour Enthusiasts Group Archives Forums General Troubleshooting 99 SE with bad off idle stumble/hesitation

Hi,

I have searched the forums and found similar hesitation probs, but maybe not quite the same, and most suggestions start with changing the plugs/wires which have been replaced (with Ford performance wires and Autolite DPs) with no effect, fuel filter is also replaced regularly.

The Problem: When hitting the accelerator from a stop, or if driving down the road at low rpms (i have a manual), if i hit the accelerator more than lightly, the car shudders and stumbles until the rpms get up at least above 2500, then it smooths out. Even idling now, if i hit the accelerator there is a noticeable shuddering and slow increase in rpms until they get up in the 2K+ range. From a stop, if I accelerate carefully I can avoid the stumble, but if I need to move quickly, I am helpless. I can also avoid the problem by revving the engine up a bit before dropping the clutch. I don't normally drive fast and with gas prices try to take it even more easy, but this is a problem that will probably shorten the engine life if left as is. It happens in any gear and at any speed if the engine is not at higher rpms. Cruising at 30-35 mph in 4th, if i hit the accel, bucks n stumbles with no acceleration until the rpms go up. The secondaries appear to be working when required, giving a boost at 3500 rpm. The car idles perfectly for a car with 97K on the OD. I have added berryman's a couple of times, and spray cleaned out the intake, all of which always look shiney clean. I tried pulling one plug wire off at a time, and giving the engine a rev, and each wire removed made it noticeably worse, meaning it isn't just one spark plug or wire causing this. I replaced one of the O2 sensors last year due to a 420 code and CEL lighting (replaced the one that is hardest to get to under the coil area), the light hasn't come on since and isn't coming on or blinking even with pretty serious stuttering and bucking. I haven't made any other mods.

Anyone diagnose something like this? Next step for me would be to take it in and pay someone $100+ for a diagnosis, the going price for a diagnosis that requires actually raising the hood and not just plugging a computer in.

Thanks!

Try cleaning/checking the MAF sensor.

MAF sensor
http://www.contour.org/mods/mods.php?s=howto&displayid=36
and
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=zetecmaint&Number=989728&page=&view=&sb=5&o=&fpart=1&vc=1
and
http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/1b/cb/25/0900823d801bcb25.jsp

Hi Tony,

Thanks, that second link was perfect! Tonight I plan to re-clean the MAF and clean the upper intake again using the methods in the How-Tos (and the link suggestions). Then reset the PCM and see what happens.

If a MAF sensor was going bad, would it typically throw the CEL on?

Hi Tour,

Thanks for the advice. If I pull the electrical connections from the MAF, would that answer the question without reseting the PCM first? If the problem doesn't get any worse, then the MAF is bad or dirty.

The strange thing, i disconnected each spark plug wire one at a time and ran the engine, and each time engine idled rougher and revved in an ugly manner, much worse than the condition now. So I assumed the wires and plugs are ok, unless one or more of them are just slightly bad.


Did cleaning or replacing the MAF improve any hesitation probs on any of your Tours? Or did the prob end up being plugs/wires?

Thanks again!

Thanks again,

I am going to try the MAF disconnect, then go thru the cleaning along with cleaning the Upper Intake, clear the PCM, and see how we do driving. Will let ya know if that was it!

Well, cleaning the MAF and UIM + PCM reset did not solve the problem. I do notice maybe a little more responsiveness and power in the higher rpm range, but still have the bad stumble in the low to 2K rpm range when accelerating. I cleaned the MAF thoroughly with 100% ethanol, I also noticed removing the electrical connection for the MAF while the engine is running appeared to make no difference at all positive or negative.

I guess the next step is to replace the plug wires one at a time and see if one of them is the problem. The strange thing is I changed the wires/plugs a couple of months ago when the problem showed up. I guess it is possible I replaced an old bad wire with a new bad one, esp if the Ford Perf wires have questionable Quality. I thought they seemed solid, thick and well put together. I think when I got the set of wires on now, i finally threw away two odl wire sets, hopefully i kept at least one...

Oh,

On The Plus Side, The UIM cleaning definitely gave the car an added boost, feels like the power band and secondaries are opening twice as much!

To do it, i didn't pour in the liquid as suggested in How-To. I removed each of the UIM lines (one for brake vacuum, other for multiple vac lines?), one at a time, and used a throttle body spray cleaner. I did this with the engine off because the engine dies out too easily with a line open. Basically, I sprayed in a good dose of throttle cleaner, soaking the intake, started up, kept the rpms up a bit to pull it thru, then repeated this a few times. After holding the rpms for a while after 3 cycles of this, i definitely noticed increased and quicker response at higher rpms. Those secondaries are breathing easier now, and i was always happy with them before!!! Can't wait til i get this hesitation fixed now, should be purring and jumping quicker than it has in a while, and I have always been happy with the power and responsiveness of those secondaries..

I highly recommend doing at least the easy version of the UIM how to cleaning if you haven't yet. I regularly change the fuel/air filters and add gas treatment, but after 97K, the upper intake and secondaries must have been a little gunked up...