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Topic: Still having rolling idle/idle surge problems. (Read 5324 times) previous topic - next topic

Still having rolling idle/idle surge problems.

I've read every write up I can google on base idle set procedures, and any time I can get my idle to stabilize, it's still wrong.  I'm down to this: TSB# 91-25-7.  Has anybody else had to install the IABP air bleed spacer kit?

Still having rolling idle/idle surge problems.

Reply #1 –
No codes right?

When is the rolling idle occurring? Start up, coming to a stop, or at some other time? I've done the base idle reset on mine several times with part swaps and it's been fine. I've got mine set to idle at 775 rpm hot in park and 700 rpm in drive hot, both of which are on the high end of the scale on the emissions decal (550-700rpms hot in drive is the factory idle speed). I will say this: use a tach/dwell meter to set the base idle not the factory digital cluster. Using the factory cluster a 775 rpm idle bounces between 5 and 6 bars illuminated on the factory tach. If the idle speed is set too low or two high the computer will open and close the IAC rapidly, causing the dreaded idle surge.

Mine is not perfect. Once in awhile it will surge a bit on a cold start. Other than that it's fine.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Still having rolling idle/idle surge problems.

Reply #2 –
When I've got it to idle steady in park, idle (per a tach/dwell meter) is about 980, with about 800 in gear.  At stops the push is almost intolerable.  Any time it's NOT steady, I get surging at idle both in gear and in park.  I've been beating my head against this since last summer when I put the Explorer engine together.  I'm running a 96 Explorer engine with an 88 Mustang PCM and a 90 Mark VII cam.  If this service kit doesn't help me, I'm going to assume that the problem is the extra 10 degrees of exhaust duration that the 90 HO cam has versus what the 88 HO cam has and what the PCM expects to be dealing with.

Still having rolling idle/idle surge problems.

Reply #3 –
I would try to get the base idle lower, to somewhere around 800 rpm in park and 700 in drive. Try to get it as low as possible where the engine won't stall and the car will start with just a turn of the key and no other help (ie you having to hold the throttle open). Make sure that the IAC is disconnected when you reset the idle. If the idle is set to high it will cause surging as the computer tries to lower the idle speed down to factory specs.

The computer you have should be fine with your mods. I was running with a 89 Mark VII computer with the same cam I have now (Comp Magnum roller #35-308-8) and it idled fine with no surging.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Still having rolling idle/idle surge problems.

Reply #4 –
All the bypass plate does is allow a higher base idle without disturbing the TPS setting, can do same by setting idle where you want it and then resetting TPS if necessary... It's original purpose was for correcting issues without cleaning the TB, but the Mustang crowd latched on to it as a cure all for a lumpy cam...

I've seen a PCV that was flowing too much air cause a surge...

As far as surging because the base idle is too high, I'm having a problem with that... If it's high, the IAC isn't going to respond to commands to lower as it's already at minimum and idle is still above specs... With the TFS-1 cam, I'd set mine to Idle at 900 in drive...

Still having rolling idle/idle surge problems.

Reply #5 –
Min idle should be set along with the TPS at 1V. This is accomplished with the IAC disconnected. I am sure you know this as a ford tech. But some of the early ECM'S do not fare to good with big cams. Specks on the cam would be nice to know and you most likely need to have a tune dun to correct this. A stand alone would be the best bet. I have totally figured out that a stand alone system is superior to the older OBD1 ECM systems. Just my .02

Also try and make a restrictor plate and start out with 1/4" HOLES
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Still having rolling idle/idle surge problems.

Reply #6 –
Tom, I'm running a 1990 stock HO cam.
I had it all set before I left the shop last night, but by the time I drove 15 miles home, it was back to idling too high and rolling in park but not in drive.  The service kit will be in this morning, so I'll beat my head against it some more on my lunch today.

Still having rolling idle/idle surge problems.

Reply #7 –
The whole setting the TPS as close to 1V at idle is an old wives tale with any reference to tip in on the throttle (Tom, not picking on you here as you are most likley using the 1.0V as a reference point to set a TPS to and knowing your abilities I will assume that is the case).  The EEC will adjust to the base setting of the TPS as long as it is within a range of 0.5V to 1.19V according to several sources.  I quit setting mine as close to 1.0V many moon ago.  This is what I would reference in trying to adjust base idle and the TPS setting:

http://sbftech.com/index.php/topic,1031.0.html

I have the IAC bypass on my Coupe and it was the only way we could get the car to idle without surging but its not a stock 5.0 or one with your basic bolt-ons.  The Mustang crowd jumped on it to solve surging issues for right and wrong reasons.  Right would be those of us who have more than mildly modified engines and wrong would be those that just used it as a band aid due to piss poor diagnostic abilities.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Still having rolling idle/idle surge problems.

Reply #8 –
Quote from: Aerocoupe;412498
The whole setting the TPS as close to 1V at idle is an old wives tale with any reference to tip in on the throttle (Tom, not picking on you here as you are most likley using the 1.0V as a reference point to set a TPS to and knowing your abilities I will assume that is the case).  The EEC will adjust to the base setting of the TPS as long as it is within a range of 0.5V to 1.19V according to several sources.  I quit setting mine as close to 1.0V many moon ago.  This is what I would reference in trying to adjust base idle and the TPS setting:

http://sbftech.com/index.php/topic,1031.0.html

I have the IAC bypass on my Coupe and it was the only way we could get the car to idle without surging but its not a stock 5.0 or one with your basic bolt-ons.  The Mustang crowd jumped on it to solve surging issues for right and wrong reasons.  Right would be those of us who have more than mildly modified engines and wrong would be those that just used it as a band aid due to piss poor diagnostic abilities.

Darren
Thanks for that, I actually have the .pdf for the TSB linked in my first post above that the writer of that thread refers to, and I discovered after reading the TSB that when you set the idle as instructed, you're meant to set it while idling in drive (not mentioned in the write-up).  I set my idle last night before leaving the shop, and it was perfect.  By the time I got home, it was back to rolling and surging.  After having the plate in my hand today, and reading the sheets that came in the kit, I understand better what it does.  It takes the throttle trim screw out of the game, instead using the air bleed screws to set base idle.

Still having rolling idle/idle surge problems.

Reply #9 –
Good deal.  Hopefully between setting it in drive and the adjuster you can get the problem fixed.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Still having rolling idle/idle surge problems.

Reply #11 –
Mine does that when its cold but once it warms up there are no issues.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Still having rolling idle/idle surge problems.

Reply #12 –
Quote from: TheFoeYouKnow;412512
Almost there, she still hunts for about 5 seconds, and then settles down.

 
Quote from: Aerocoupe;412526
Mine does that when its cold but once it warms up there are no issues.

Darren


Mine does the same thing. When fired cold (sitting a day or more) it surges a bit for 5-10 seconds then it's fine the rest of the day.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Still having rolling idle/idle surge problems.

Reply #13 –
Quote from: TurboCoupe50;412445
As far as surging because the base idle is too high, I'm having a problem with that... If it's high, the IAC isn't going to respond to commands to lower as it's already at minimum and idle is still above specs... With the TFS-1 cam, I'd set mine to Idle at 900 in drive...

 
I've heard that setting the base idle too high can cause an issue. I've never experienced it myself though.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

Still having rolling idle/idle surge problems.

Reply #14 –
the air bleed screws in the trottle plate?