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View Full Version : Rough Idle, Still Pulling My Hair Out



Charles G
08-15-2004, 11:13 AM
:eek: 92SC Ok, I must be getting closer, running out of things to check. Doesn't stall, but just rough enough to be annoying and scare passengers. Replaced head gaskets, wires, plugs, motor mounts, cleaned TB and IAC both of which were not dirty. Idle speed is ok, slight raise doesn't smooth out. Car has about 90K miles on it. Closed off main vacum source, no difference in idling, vacum about 18 on dash when warm, 10 when cold. No error codes, checked by dealer. Does IAC go bad slowly or is it go or no go, it appears clean, but I guess this and MAF should be suspects?? Plugging out IAC shuts down engine, squirting air into MAF changes engine speed as expected. Please help....should I buy an IAC? MAF, or new head of hair....

3tbird
08-15-2004, 11:54 AM
:eek: 92SC Ok, I must be getting closer, running out of things to check. Doesn't stall, but just rough enough to be annoying and scare passengers. Replaced head gaskets, wires, plugs, motor mounts, cleaned TB and IAC both of which were not dirty. Idle speed is ok, slight raise doesn't smooth out. Car has about 90K miles on it. Closed off main vacum source, no difference in idling, vacum about 18 on dash when warm, 10 when cold. No error codes, checked by dealer. Does IAC go bad slowly or is it go or no go, it appears clean, but I guess this and MAF should be suspects?? Plugging out IAC shuts down engine, squirting air into MAF changes engine speed as expected. Please help....should I buy an IAC? MAF, or new head of hair....

Simple cheap checks; Are the plug wires correctly installed? Are the motor mounts still good? Are there any ground wires off?

Charles G
08-15-2004, 02:17 PM
Simple cheap checks; Are the plug wires correctly installed? Are the motor mounts still good? Are there any ground wires off?
Thanks, grounds are good, plug wires new and plugs are not missing, new motor mounts 800 miles ago.....any more checks? Thanks.

Darkside
08-15-2004, 07:25 PM
TPS? EEC going berzerk?

Charles G
08-15-2004, 10:54 PM
TPS? EEC going berzerk?
TPS could be a possiblity, but by reading the other threads, sounds like IAC is more likely, then MAF sensor, then TPS, Can an EEC go bezerk only re: idle? Engine performs great at higher rpms.....

92redsc
08-15-2004, 11:01 PM
hmm going a constant speed does it have a slight surge or is this ONLY at idle. if it is only at idle i would put my 2 cents in (that isnt worth shat) that its a IAC, but i dont know much about that. if it DOES surge or hesitate a little, i would go to pulling the plugs and checking gaps and color just to make sure. i could have sworn i did everything right on mine and it did that and idled rough, pulled the plugs and one of the gaps was too tight. regaped and runs like a champ!!

NITRO
08-16-2004, 08:01 AM
Realizing that you stated New Plugs and Wires. What Brand of Plugs and Wires? Are all of the gaps identical? Did you possibly pinch one when installing them? Just trying to think here?

What about a Fuel Injection Service? I am talking about a Professional Pressure Cleaning. Where the Fuel System is Disabled and the Engine runs on a Stand Alone System with a Good Detergent Cleaner. I do them regularly at my shop with great success to rough idle issues. Injectors can get a heavy build up of Varnish in them causing an inconsistent spray pattern. Hence the rough idle.

Charles G
08-16-2004, 09:43 AM
hmm going a constant speed does it have a slight surge or is this ONLY at idle. if it is only at idle i would put my 2 cents in (that isnt worth shat) that its a IAC, but i dont know much about that. if it DOES surge or hesitate a little, i would go to pulling the plugs and checking gaps and color just to make sure. i could have sworn i did everything right on mine and it did that and idled rough, pulled the plugs and one of the gaps was too tight. regaped and runs like a champ!! Good idea, I will check plug gaps.....Thanks

Charles G
08-16-2004, 09:47 AM
Realizing that you stated New Plugs and Wires. What Brand of Plugs and Wires? Are all of the gaps identical? Did you possibly pinch one when installing them? Just trying to think here?

What about a Fuel Injection Service? I am talking about a Professional Pressure Cleaning. Where the Fuel System is Disabled and the Engine runs on a Stand Alone System with a Good Detergent Cleaner. I do them regularly at my shop with great success to rough idle issues. Injectors can get a heavy build up of Varnish in them causing an inconsistent spray pattern. Hence the rough idle. Thanks for the tips, I will check plugs and move on to injectors, which means SC removal, ugh, hate to reseal those tubes, with the special sealant tape that is hard to get. First I think I will fork over the bucks for the IAC and hopefully save some bruised knuckles......

joenintiesc
08-16-2004, 12:54 PM
Try changing the plugs anyway. Use double platinums from Autolite, NGK, or Motorcraft if you can still get them. For some reason, Bosch plugs just don't seem to work too well with these engines. Do a search under Bosch and you'll find many advisories against them!

SilverCasket
08-16-2004, 02:29 PM
ewwww. I just jumped in this thread. First hand I can tell you that Bosch plugs and wires will be a problem if THAT isn't it already. .. Ford still sells the Motorcraft APP34 (or something like that), but it's under a new part number. Same part though. Just ask for stock plugs & wires. I just put a set of plugs and wires from Ford in a new SC I picked up & it fix my problem. I was getting a serious studder while in the throttle & *** idle.

Anyway, change out to the autolite or motorcrafts & you will definitely notice a difference over the Bosch. ... Pep Boys put the Bosch my buddies SC when he got a tune up. Apparently they didn't know about the problems it would cause. And his idle & throttle was ridiculously bad! He went back and found out about the Bosch plugs & wires & demanded they change them to Fords. After battling with them they did it, sure enough he was back to his normal beating of the car without trouble!

Anthony

Charles G
08-16-2004, 03:48 PM
Try changing the plugs anyway. Use double platinums from Autolite, NGK, or Motorcraft if you can still get them. For some reason, Bosch plugs just don't seem to work too well with these engines. Do a search under Bosch and you'll find many advisories against them!Thanks, I will get another brand plug...

Charles G
08-16-2004, 03:50 PM
ewwww. I just jumped in this thread. First hand I can tell you that Bosch plugs and wires will be a problem if THAT isn't it already. .. Ford still sells the Motorcraft APP34 (or something like that), but it's under a new part number. Same part though. Just ask for stock plugs & wires. I just put a set of plugs and wires from Ford in a new SC I picked up & it fix my problem. I was getting a serious studder while in the throttle & *** idle.

Anyway, change out to the autolite or motorcrafts & you will definitely notice a difference over the Bosch. ... Pep Boys put the Bosch my buddies SC when he got a tune up. Apparently they didn't know about the problems it would cause. And his idle & throttle was ridiculously bad! He went back and found out about the Bosch plugs & wires & demanded they change them to Fords. After battling with them they did it, sure enough he was back to his normal beating of the car without trouble!

AnthonyGot it thanks....will do

bradzbrad
08-18-2004, 10:35 PM
if you changed the plugs and wires, that means that the intercooler pipeing was removed or loosened, check all your fittings.. as I had the exact problem a cpl years ago after mine was serviced