94 surging need help

GRAYFOXGT/CS · Dec 2, 2010

OK here it goes my 94 5.0 started surging again and stops when it warms up. Awhile back it was doing this then stopped and idled normal for two weeks and started again today it will surge and almost die also when coming to a stop RPMS will drop to 500 then shoot back up to normal.ive checked vacuum lines checked maf sensor, spark plugs/wires i refilled yesterday with 89 octane could it be something with the fuel system

Adam95GT · Dec 2, 2010

GRAYFOXGT/CS said:
OK here it goes my 94 5.0 started surging again and stops when it warms up. Awhile back it was doing this then stopped and idled normal for two weeks and started again today it will surge and almost die also when coming to a stop RPMS will drop to 500 then shoot back up to normal.ive checked vacuum lines checked maf sensor, spark plugs/wires i refilled yesterday with 89 octane could it be something with the fuel system

Try to clean the IAC???

KamiKaziDK · Dec 2, 2010

Yeah, clean the IAC and the MAF and go from there I would say

GRAYFOXGT/CS · Dec 2, 2010

wth

forgot to mention that i cleaned the IAC couple weeks ago it act like its only running on half power then sometimes all of a sudden a powere surge will kick on and it runs normal.

Adam95GT · Dec 2, 2010

GRAYFOXGT/CS said:
forgot to mention that i cleaned the IAC couple weeks ago it act like its only running on half power then sometimes all of a sudden a powere surge will kick on and it runs normal.

Does this power surge occur at WOT? if so im thining 02's

GRAYFOXGT/CS · Dec 2, 2010

this happens while driving not really on take off but when it does happen it fixes it for the day, I come home park it over night and same thing the next day so pretty much its like you have to drive it till it kicks on. Normall you get in turn on your car and rpms go up to the 1300s then slowely drop to idle but when it act up the rpm are only at maybe 800 - 500 and surges so its like u have to press the throttle to keep it running till it warms up.

Chythar · Dec 2, 2010

Cleaning the IAC is a crapshoot, it may work or it may not. As i understand it, the IAC is really only there at idle when you have a load on the engine, such as having the A/C on. With the A/C off, your car should idle perfectly fine with the IAC unplugged.

You say you "checked" the MAF. Did you clean it? I've never seen the wires on a MAF "look" dirty, but cleaning it with rubbing alcohol and a q-tip usually takes off a lot of grime I did not see.

Have you pulled engine codes? The computer can throw codes without lighting up the check engine light.

GRAYFOXGT/CS · Dec 2, 2010

I cleaned the the MAF with Maf cleaner took it to auto zone to pull codes they couldnt find anything cuz they said my check engine light wasnt on.

toyman · Dec 2, 2010

GRAYFOXGT/CS said:
I cleaned the the MAF with Maf cleaner took it to auto zone to pull codes they couldnt find anything cuz they said my check engine light wasnt on.

I'll bet they tried the OBD2 port under the dash. That is a non functional port on the GT (it's there as the v6 is a OBD2 system). The diagnostic port you want is the OBD1 in the engine bay, passenger side on the strut tower.

The IAC valve probably should be replaced. Especially if it's 15+ years old as is likely.

Chythar · Dec 2, 2010

Absolutely agreed with Richard - the OBDII port under the dash is the first place they look. Ford had to save money on the Mustang to keep it alive in 1994, so they used the exact same dash wiring assembly on all 1994 and 1995 cars. Since Ford sells a lot more V6's than GT's or Cobras, it was cheaper inventory-wise to make all the dashes with the port. One of the many quirks you will learn about our cars.

Also agreed on the IAC - just replace it. I recommend replacing with the more expensive Motorcraft part. The Motorcraft brand is like the Sears Craftsman brand - parts made by other companies under license, but re-branded. Most of the non-Motorcraft parts out there are ones built by the same company that makes the Motorcraft parts, but they failed Ford's test standards. I've experienced high failure rates with non-Motorcraft sensors, including the IAC, but the Motorcraft ones last for many years. Spend a bit more now for peace of mind.

GRAYFOXGT/CS · Dec 3, 2010

Thats exactly what they did Wow! learn something new everyday on here ill get it checked tomorrow and let you guys know what codes come up My uncle just told me that about the A B and C grade parts he said the A parts go to the dealers that are up to standards B goes to vendors like Napa and C are usually the aged parts that have a high fail rate that go to checker/oreilly, Auto zone so we'll see what happens..... keep you guys posted.

+++

GRAYFOXGT/CS · Dec 4, 2010

OK guys i bought a tester today and i came uo with two codes 13 RPM out of specification during normal idle or d.c. motor does not follw dash spot,and,33 egr not opening or not seated (closed properly) could rpm coming up cause of egr?

final5-0 · Dec 4, 2010

If you loose a lot of power when this happens .............

I'd not think the iac would cause that

Have you got another coil you could use for a quick test?

Grady

toyman · Dec 4, 2010

GRAYFOXGT/CS said:
OK guys i bought a tester today and i came uo with two codes 13 RPM out of specification during normal idle or d.c. motor does not follw dash spot,and,33 egr not opening or not seated (closed properly) could rpm coming up cause of egr?

Those codes don't seem correct. They should be 3 digits. What code reader did you buy? Is it this one?

95Vert383AOD · Dec 4, 2010

Sounds like if the IAC is fine you may need to set the base idle of the car. Disconnect the battery 30 min. Unplug the IAC...Reconnect battery....Start car and adjust idle screw. Turn off car reconnect IAC and you're good.

GRAYFOXGT/CS · Dec 4, 2010

I got the actron code scanner you have to count the beeps like ***-*** would be 33 I reset the idle and it did idle better but the engine also started to get warm and it runs better ??? I was thinking about getting the msd coil ne problems with it?

revhead347 · Dec 5, 2010

hmm. I always heard that the engine should shut off when you unplug the IAC. Maybe HISSIN will chime in, I'm sure he knows. I agree that cleaning it is a crapshoot. Usually if you clean it, it runs better for like one day, and then goes back to surging.

Kurt

ratio411 · Dec 29, 2010

Did you clean the EGR?

"EGR not sealing"

I have had this problem before on 5.0s.
Clean out the carbon from the orifices on both sides and clean or replace the screen.
When 'chunks' build up in there, it becomes a huge vacuum leak.

GRAYFOXGT/CS · Dec 30, 2010

Today i cleaned the egr got alot of black deposits out of the openings put it back on with a new gasket and it is now running and idling alot better thank you for all your input and help guys! OH AND I ALSO FOUND OUT THAT THE PREVIOUS OWNER DID AN ECU SWAP THATS WHY IT WAS ONLY TWO DIGIT CODES.

ratio411 · Jan 9, 2011

GRAYFOXGT/CS said:
Today i cleaned the egr got alot of black deposits out of the openings put it back on with a new gasket and it is now running and idling alot better thank you for all your input and help guys!

Glad it worked out.
If the most basic stuff is good on an EFI Ford, go for the EGR.
It's usually dirty...

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