idle issues and sudden bucks!! please help

[1fast94svt]

yeah my car does the same, but my steering is offline, and i think its just due to my alternator not being powerfull enough for the steering and the blower and everything else, what do you think?

 

[96darkhorse]

well i used a code scanner i got these codes

998- failure mode

157- mass air sensor failure- low voltage


now that i figured it out...how can i raise the voltage to the needed amount?

 

[OrangeMustangGt]

Your idle speed controller has gone bad, change it. They have a history of problems.

Kurt

what is that? My car has idled liek it has a cam since i bought it, it idles all over the place. Ive replaced everything twice as far as sensors, i dont know what to do next, except maby my IAT sensor is turned wrong. damn i dunno.

 

[mo_dingo]

Well, just as I suspected originally, your MAF is likely bad. You cannot raise the voltage arbitrarily. You need a new MAF. And you can't clean the MAF to fix this problem. If the code came up as "MAF voltage higher/lower than expected, you might be able to clean the MAF to fix it, but the code says below minimum voltage, meaning the MAF is completely dead.

You can get a new one at autozone or go aftermarket. The MAF from a 87-93 5.0L mustang will work electronically with our cars, but will not fit in the stock air box (from what I have heard). Their maf is $40 cheaper than the one made for 94-95 5.0L.

If you are still using your stock air box, you might not be able to get it to work.

But if you bought a 87-93 MAF plus a K&N air filter meant for that MAF, it shoudl work. Just depends if the other side of the maf will fit the rubber air hose.

I have no idea what the "Hard Fault" code means. Did the car stall during the middle of the test or something wierd? Someone else here may be able to tell you what it means.

If not, you know the MAF is the culprit. Disconnect the battery, replace the MAF, reconnect the battery, and drive the car for 20 miles. Some time before the 20 mile mark, you will see the CEL come on if a code is present. If the CEL doesn't flash or come on, you probably found the problem.

After you drive the car for 20 miles, run the codes anyway and see what happens.
Scott

 

[mo_dingo]

yeah my car does the same, but my steering is offline, and i think its just due to my alternator not being powerfull enough for the steering and the blower and everything else, what do you think?

What do you mean your steering is offline? You mean when the steering wheel is held straight, the car veers to the left or right?

We need more info. Do a search on this forum first, then if you don't get a good answer, you might want to start your own thread.
Scott

 

[Silver85TC]

998- failure mode

The following is a direct quote from my Ford Shop Manual CD;


Failure Mode Effects Management (FMEM)

FMEM is an alternate system strategy in the PCM that maintains vehicle operation if one or more sensor inputs fail.

When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy will be initiated.

The PCM will substitute a fixed in-limit sensor value and continue to monitor the faulty sensor input. If the faulty sensor operates within limits, the PCM will return to the normal engine running strategy.

Engine Running DTC 998 will be displayed when FMEM is in effect.

The Malfunction Indicator Lamp (MIL) will remain on when FMEM is in effect.



Hope that helps.

 

[mo_dingo]

Makes sense. His MAF is dead, so the computer took a dump!

Thanks for the input Silver85TC.

I hope he posts back after he fixed the problem.
Scott

 

[Slow5.0]

IAC valve only controls the amount of air getting to the engine when the butterfly is closed. It wouldn't make the car run rough, for any reason. When mine broke, my idle speed was steady at 2200 rpm's.

Timing is irrelavant, unless somehow it's different than 18*. Check it anyway. The dizzy bolt may have came loose or something stupid like that. I would run it at 13-14 though. You are LOSING performance with that much timing added.

He said the idle speed problem was exactly the same no matter if the car was hot or cold. That rules the ECT out. A bad ECT would make the car run richer than hell, and trigger a CEL.

Speaking of CEL, have you ran the codes yet? What came up?

The TPS function is to tell the computer when you go to WOT (open or closed loop opertaion). Anything else inbetween is irrelevant. You can check the voltage if you like. It's really a waste of time though.

So when the car is bone cold, or completely warmed up, the idle problem remains the same, correct? If so, that rules out the O2 sensors.

Have you performed any work to the car within the last 2 weeks? If so, what was it, and did the problem start immediately afterwards?

#1 - Run the codes - report back here for diagnosis.

#2 - If no codes are present, check the connections to all main engine sensors & ensure proper connection (MAF/IAT/IAC/TPS/O2/ECT).

#3 - Check timing.

#4 - Remove and note the condition of all 8 spark plugs individually.

#5 - Hook up a vacuum gauge & check vacuum. Same for Fuel Pressure.

That's it for now. Let us know what happens.
Scott

I tryed runing codes and I come up with two, battery to PCM open , PCM to fuel pump open
Car runs fine excepr idle hanging around

 

[beemrmem3]

my idle is rough and it bucks like crazy when driving. Ive seen the CE light come on a few times since its been doing it. So that means i have a code right. Will an OBD2 code scanner work?

 

[Silver85TC]

I'm pretty sure an OBDII scanner won't work.

Read the following link on how to check codes;
http://fordfuelinjection.com/selftest.html

Then find a paperclip and check them yourself!

Cheers