missing very bad below 3000 rpm

[JKLedbetter]

I took the garage potato out for a drive last week, and after several miles it began to run a little rough. Then it cleared up and ran fine until I got to my destination (about 30 miles away). After sitting for a few hours I drove home, and it got progressively worse all the way home. It got to where it would barely run below 3000 rpm, but above that it would clear up and run fine. Then it got to where it would run a little bit rough above 3000 under light throttle, but still fine under moderate to heavy throttle.

I'm thinking either the distributor cap, or the plugs, or the plugwires.

Do any of you have any other suggestions? Is there some electronic gizmo that does something below 3000 rpm that could be the culprit?

-Kennon

[MikeFleming]

My first thought? alternator failure. So I'd start with the simple stuff first: battery voltage.

Did the radio and lights still work?

Verify battery and charging system, then primary ignition , then secondary ignition, then fuel.

[JKLedbetter]

I had the radio on while I was driving and it worked fine even when the engine was cutting out. The battery is fairly new, and I didn't have any problems restarting it after I stopped to look under the hood.

-Kennon

[Stinger]

It shouldn't be any ignition components since they are under more stress when boost is present and it runs ok under boost.

I'd suspect something that only effects the engine in closed loop and not open loop (the transfer point is around 2800 rpm depending on throttle position). Most all of these items will throw a code so I'd suggest scanning for codes.

[JKLedbetter]

How do I scan for codes?

And would you mind educating me on open and closed loop?

Thanks,
-Kennon

[Stinger]

The sentence above should have read "I'd suspect something that only effects the engine in closed loop and not open loop" but I can't edit it.

They easy way to scan for codes is to buy a ~$25 EEC-IV code reader from a parts store or online, plug it into the diagnostic port on the back of the driver's side strut tower, and follow the instructions that come with the code reader. You can also use a paper clip to do it but there is really no reason unless you can't swing $25 for the proper tool.

Code Reader: http://www.amazon.com/Equus-3145-Ford-Digital-Reader/dp/B000EW0KHW

Open/closed loop refers to whether the ECU is using factory preset tables/values or sensor feedback to control the engine. Further info: http://www.enginebasics.com/EFI%20Tuning/Closed%20Loop%20o2.html
(http://www.enginebasics.com/EFI%20Tuning/Closed%20Loop%20o2.html)

[MikeFleming]

The sentence above should have read "I'd suspect something that only effects the engine in closed loop and not open loop" but I can't edit it. Corrected above post.


... plug it into the diagnostic port on the back of the driver's side strut tower,
(http://www.enginebasics.com/EFI%20Tuning/Closed%20Loop%20o2.html) FRONT side of the drivers side (left) shock tower - between the battery and the shock tower, under the starter solenoid (stock SVO).

[TheSVOTrust]

Does "garage potato" mean OLD GAS is in it
Does "I suspect wires and plugs" mean I've read how wires don't last on 2.3EFI T/C and KNOW they are old.............

Mark

[JKLedbetter]

Thanks for the info.

Actually the gas isn't that old. I siphoned it out last year to burn in the generator when the tornadoes knocked out the power for four days. Had to run the generator 24/7 because my sister was running 11 sump pumps in her basement fighting off the deluge that accompanied the F5 that passed within a mile of us. I didn't refill the car until December, and I bought ethanol-free, so the fuel should still be good.

The plugs, plug wires, and distributor cap probably haven't been changed since the mid-90's. What do ya'll recommend for replacements?

btw, the car is a mostly original '84 (I replaced the slapper bars with a Ford Motorsport quad shock kit, kept the slappers in case I ever wanted to reinstall them).

-Kennon

[TheSVOTrust]

I'd just do the tune up first ! Motorcraft wires and cap (you may not remember if it has the old style rotor OR was changed for a 86 style over the years) check before buying rotor.

Autolite plugs (cheap ones/not Platinum) REGAPPED to .029

While you are working remove the round plug in the upper timing cover and while the cap is off confirm that the cam/rotor at #1 for the timing belt. (Only a suggestion seeing that the wires are from the mid90's - I figure the timing belt is too)

Mark
P.S. Then just carry a belt, 10MM, 12MM, 14MM, 5/8 , 11/16 & 3/4 and a #2 posidrive for when it brakes.

[Stinger]

Actually the gas isn't that old. I didn't refill the car until December, and I bought ethanol-free, so the fuel should still be good.

I wouldn't feel comfortable calling 10 month old gas "not that old", particularly in a turbocharged high performance application that is very octane sensitive. While fuel will sometimes store up to a year in a sealed container, your gas tank is vented so the shelf life is much shorter than that. Regardless, while I wouldn't personally be running that fuel in anything but a lawnmower or an old low powered vehicle that wasn't worth much, it shouldn't be the cause of your bad running at low rpm (though it could cause detonation under boost which can blow a headgasket or melt a piston).

I agree that 15+ year old ignition components should certainly be replaced, regardless of their apparent condition.

[Patrick]

I wouldn't feel comfortable calling 10 month old gas "not that old", particularly in a turbocharged high performance application that is very octane sensitive.....

I agree. Talk to friends who have fishing boats that have been stored over the winter. Listen to the horror stories about the white jelly that collects in the fuel filter and float bowls. Then report back.


1762

[MikeFleming]

... that collects in the fuel filter and float bowls. What's a "float bowl"? Is that related to a punch bowl?

[mrzw70]

What's a "float bowl"? Is that related to a punch bowl?

No, I think it's more like the tidy bowl...

[Mike S]

My guess is your VAM flapper is stuck in a position that would match your motors requirements above 3000 rpm. Below that, and you are flooding the engine. Is it blowing black smoke when it breaks up under 3K?

[v8eater]

egr valve could be stuck open

[JKLedbetter]

My guess is your VAM flapper is stuck in a position that would match your motors requirements above 3000 rpm. Below that, and you are flooding the engine. Is it blowing black smoke when it breaks up under 3K?

Indeed, I think it was blowing some black smoke when it was missing. Now what is the "VAM flapper"?

As for concerns about old gas, I've had an old boat and an old dirt bike for decades, and I only run them once or twice a year. As long as you use Non-ethanol gas and add a little Sta-Bil you won't have any problems.

-Kennon

[Desert Patina]

What if the IAC (TFI?) is causing this? I'm thinking if the timing advance is going bad.

Another cause I can think of is if the timing belt slipped.

But I'm just thinking here.

[MikeFleming]

What if the IAC (TFI?) is causing this? I'm thinking if the timing advance is going bad. The IAC is the solenoid on the throttle body that bypasses air around a closed throttle plate for deceleration and idle speed control. The TFI is that [gray] electronic part on the side of the distributor that amplifies the very low-level electrical signal from the PIP (stator inside distributor) to the ignition coil and interfaces with the SPOUT signal from the EEC. Other than both being managed by the EEC, they share nothing in common.


Another cause I can think of is if the timing belt slipped. That is a separate mechanical issue and easy enough to test for. And if there is any doubt at all, it's time to install a new belt. And align it properly. A new belt with proper sprockets is good for at least 30K miles/5 years. Assuming it was installed and tightened correctly.


But I'm just thinking here. Uh, yeah.

[Desert Patina]

Sorry I mistyped, but for a good reason. I'm getting old and the IAC on my 89 is being replaced at this time. I meant the ICM.

[MikeFleming]

I meant the ICM.
What is ICM??

- International Confederation of Midwives

- ICM Registry LLC, the company that sponsors the .xxx Internet top-level domain (TLD) for Adult entertainment

- Independent Citizens' Movement, a local, conservative, United States Virgin Islands party

- Institute of Credit Management, a UK based professional Institute

- Institute of Commercial Management, a leading professional body for Commercial and Business Development Managers

http://en.wikipedia.org/wiki/ICM

[Desert Patina]

Ignition Control Module...

e.g. http://www.rockauto.com/catalog/moreinfo.php?pk=990336&cc=1133806

http://shop.advanceautoparts.com/buy/products/128225-ignition-control-module-by-bwd-part-cbe24p-ignition-components.html

http://www.jegs.com/p/JEGS/JEGS-Ignition-Control-Module/750932/10002/-1

http://www.summitracing.com/search/Make/FORD/Engine-Size/5-0L-302/Department/Ignitions-Electrical/Part-Type/Ignition-Modules/?Ns=Rank%7CAsc

"Ignition Control ModuleThe ignition control module is an electronic device that prompts the ignition coil to send a voltage spike to a spark plug." -- http://repairpal.com/ignition-control-module

[MikeFleming]

In the SVO and most other EEC systems, that's called the TFI module. TFI is short for Thick Film Ignition.

If you're replacing the TFI module, replace the internal PIP at the same time.

[Desert Patina]

Ah, and I'll bet that is the same as the Distributor Ignition Pickup. Is it housed in the Distributor under the rotor?

[MikeFleming]

The PIP (aka Profile Ignition Pickup, or Hall-Effect Sensor) lives inside the distributor and connects electrically to the TFI. Ford still calls it a stator.

[Desert Patina]

By the way ...

I take it cleaning out the VAM is just spray and pray with throttle body cleaner, or is there a more elegant solution?

[MikeFleming]

Yes, spray with brake cleaner (cheaper and less caustic than throttle/carb cleaner) and let it drip-dry. There are no active electronics inside the VAF (just resistive elements). Keep the black plastic cover up so as to not fill up that area with liquids so it will dry quicker. Move the flapper manually to get more internal airflow area cleaned.

If you have a shop vac, drying is quicker too.

Note that any discovered dirt, grit, sand, etc. in the VAF all came past the air filter (and that same grit/sand gets to the soft compressor wheel). While all the oil came from the PCV system.

[brownsvo]

Funny same thing happened to me today.. I swapped out the turbo elbow last night and put it back on and touched nothing else. Wa~laa i go to work this morning and she doesnt want to make enough power to get the car moving under 3k. To get the car moving i had to mash the gas to stumble and pop to 3k and its like nothing is wrong.

This is my daily so gas is fresh, battery a few months, plugs, wires, cap, and rotor are less than 1000 miles.. its been running great since i got back from my deployment thanksgiving. I had this happen before on my 5.0 and it turned out the ground wire next to the battery was hanging by a couple strands and cutting out.. Was an answer or something ever found?

[JKLedbetter]

Sorry, no progress yet, still procrastinating. But I did get a code reader for Christmas.

-Kennon

[MikeFleming]

Procrastinating is progress, no?

[JKLedbetter]

I finally got around to the code reader. But first I decided to learn how to use it on the 87 F150. It was going along fairly well until it told me floor it and let off. HOLY CRAP!!! A green geyser erupted and spewed all over half the garage, including the SVO, and my wife's new Shelby. So after I got done washing cars, I tried out the code reader on the SVO.

After warming it up driving around the block a few times, during which it ran fine, the KOEO test showed codes 41c and 53c. Even though it says to fix these before proceeding to the next step, I went ahead and tried the next step anyway, which was verifying timing advance. But first I had to take the timing light apart to clean the lens, and turn the engine over by hand to find the no longer visible timing mark to repaint it. Then when I ran the test, the engine kept sputtering out in the middle of the test.

So I guess the next step is a tuneup and then address codes 41c (HO2S sensor) and 53c (Throttle Position Sensor or Fuel Injector Pump Lever Sensor). Anybody have any advice on these two codes?

-Kennon

[MikeFleming]

(From http://www.svocop.com/Articles/7/1985-EEC.html)

41 SYSTEM ALWAYS LEAN
53 TPS INPUT TOO HIGH (OPEN WIRE)

Fix this first: Verify the TPS wiring to/from the TPS itself and the EEC. The stub that leaves the harness (and wiring tray) to the TPS connector has a tendency to fail in the insulation area.

Get a voltage measurement at the TPS itself then verify the same pics at the 60-pin EEC connector read the same value. Note the EEC must be connected ignition switched to Run.

hen check to see that the oxygen sensor is properly switching. If not, verify conditions that can make it always lean (FPR, low pressure, plugged injectors, intake side air leaks,...). If all appears correct, replace the oxygen sensor.

[JKLedbetter]

Where is the 60-pin connecter located, and which pins do I check? And what is the proper voltage?

How do I verify that the O2 sensor is switching?

Thanks,
-Kennon

[JKLedbetter]

While changing the distributor cap, I noticed a hose that has come loose. It runs from somewhere behind the distributor, forward, then turns up and back, where it connects through a plastic looking connector to another (maybe smaller) hose that runs back and attaches underneath the intake manifold. It has come loose at the junction between the two hoses.

What is the purpose of this hose, and could it be the cause of the below-3000-rpm miss?

-Kennon

[MikeFleming]

That is where the PCV valve goes. It needs to get fixed.

[JKLedbetter]

Maybe I'm done chasing squirrels for a while (replaced spark plugs, wires, dist. cap & rotor, pcv valve, valve cover gasket; stripped and repainted valve cover & intercooler) and can focus on resolving the codes. Now it's throwing a KOEO code 23o (Throttle Position sensor out of range).

Where can I find troubleshooting directions for this? My haynes manual is a bit too generalized. Has anyone put the factory manual online?

-Kennon

[MikeFleming]

23 TPS out of range most commonly comes from an open spot in the sweep range and, usually, requires replacement of the TPS.

It could also be a wiring issue - so look for/repair the short harness to the TPS that comes of=ut of he firewall wire loom plastic box thingie. Thats' a very common place for the insulation to crumble and allow the TPS wires to touch each other.

[JKLedbetter]

Are there measurements that can be taken to narrow down the issue? With some of my other vehicles the manual lists troubleshooting processes wherein you measure resistivity and/or voltage across certain points to ascertain whether the problem is a shorted wire, a broken wire, a bad sensor, or a bad computer.

The only thing my Haynes Mustang/Capri manual says is that replacement of the TPS must be done by a shop with specialized calibration equipment. Does this include the SVO?

-Kennon

[MikeFleming]

... manual says is that replacement of the TPS must be done by a shop with specialized calibration equipment. Does this include the SVO? Yes. A DVM is needed.

That's specialized, no?

[JKLedbetter]

What is a DVM?

-Kennon

[brsvo]

Digital Volt Meter.

[stockman1]

What is a DVM?

-Kennon did you solve the issue if so what was the solution ?

[FinnSVO]

I would also like to know how this ended up? What was your solution?

I had pretty much same problem. After 15-20 minute driving car started to lose power and ran poorly on lower rpms (1500-3000), pretty well on higher rpms though. I disconnected EGR by disconnecting solenoid connector and now after 100 miles of driving most of problem seems to be disappeared. All ignition parts except TFI/PIP are new Motorcraft, gas is fresh etc. Still going to replace oxygen sensor (damn thing is original and stuck really tight...) and running it with some injector cleaner. My car has not been driven before me on last 10 years. Also it seems to run quite rich at idle, maybe this all is related to others

[SnakePlisskin]

Haven't read whole thread, but EGR valve can build up carbon over the years and hold pintle open, thus resulting in very poor low rpm driveability. Easy check just unbolt it and check how pintle is sitting and how dirty it is.