Efi problem - FFCars.com : Factory Five Racing Discussion Forum

CobraGlen · 08-20-2012, 12:02 PM

Bob,

I have a 1989, efi-302 that I have had 6 years in a MK2. The other day,it was very hot and I left the radiator fan run and it killed the battery. I charged the battery slowly for the day and when the car was ready to start, it would "whirl over" just fine but would not start unless I "feathered" the gas pedal to get it going. It finally started, but loped awful till it quite running. It has ran very well up to this point. I did drive the car for about an hour thinking the computer needed to reset itself, but no changes, it still will hardly idle (loping). So, I have a spare computer that I installed, it made no difference. So, I put the old computer back in and it still runs the same, hard to start and terrible idle.
The 302 has some upgrades that have been running fine until the battery went dead; i.e. AFR heads, B303 cam, upgraded MAF and intake manifold (Edelbrock RPM)....I do not know if that makes a difference since the car was running fine.
Any ideas??? I am lost on this one.
Any help would be greatly appreciated.

Thanks, Glen

tirod · 08-20-2012, 01:08 PM

You got spin, you got fuel, your got fire - but do you have air? Sure, when you crack the throttle. But the idle air circuit? Sounds like it's a bit clogged up or the solenoid's not responding.

First thing I would do is spray that bleed hole inside the air horn while the engine is runnning and make sure it's functioning.

It just happened to me a few weeks ago, and I was really scratching my head why the car wouldn't start. You did what I didn't - crank the car with the throttle opened to allow air in. EFI is different than a carb that way, we're used to foot off, and if the idle circuit isn't working, it won't start - no air.

snakelake · 08-20-2012, 01:30 PM

was it just hot outside, or did the engine run hot?

CobraGlen · 08-20-2012, 03:05 PM

Thanks Tirod....I will give that a try.

Glen

CobraGlen · 08-20-2012, 03:09 PM

Snakelake...the engine does not run hot. I like to cool the motor area down before closing the hood. I have been told that the hood on the MK2 can twist out of shape if conditions are right. We have had some 100 degrees days and I just always run and external fan with the radiator fan. I know that is an overkill....that is just me.
Any ideas?

Glen

Big Blocker · 08-20-2012, 03:19 PM

One thought comes to mind. You say you ran the battery down to a dead condition, correct? Any chance you might of done something to a sensor or actuator due to a low voltage condition? I'm thinking along the lines of the Idle air by-pass solenoid or the EGR ?

Sometimes, equipment running with low voltage can become damaged and then either work erratically or not at all.

You stated that you swapped out the computer with the same results, so I'm thinking along the lines of something else got messed up during the low voltage time period.

Also, what ignition system are you running, factory or some aftermarket device?
I do know, from experience, MSD systems are temperamental about low voltage conditions and can get real flaky if under-powered.

Any codes being thrown regarding the engine management?

HTH

Doc

CobraGlen · 08-20-2012, 06:23 PM

Hi Doc,
I do not have a code reader. The last time I had someone connect a code reader, it would not read my engine. Pollution devices have been removed. I installed a new idle control sensor this AM.....that did not help. The computer is stock. Stock distributor. Stock wiring. I am in the opinion that when the battery went dead, somehow it damaged an idle control component?? I am running out of answers. I have never had a dead battery cause any type of issue like this. Last year I replaced the battery and had no issues.

Any suggestions?

Thanks Glen

snakelake · 08-20-2012, 07:15 PM

is your problem on cold start up, does it level out after 3~4 minutes, does it start and run okay after it is warmed up. As a side note I would check for a vaccuum leak those rubber lines and caps will break after a while. I know that my Mark I acts that way after a dead battery and takes numberous cold starts to retrain the puter

JoeE · 08-20-2012, 07:37 PM

I have had my prior battery run dead, charge it starts rights up quite a few times. Is your voltage gauge reading 13 to 14 volts when it is running?

Are all of your connections on your engine harness tight, making good contact? I had gotten my MAF connector fouled up by pulling on the wires and not the plug connector itself. A week or so later I picked it up, pushed the wires in tight on both sides of the connector and problem solved. Check all of them in the engine harness especially MAF connectors.

Steve Collins · 08-20-2012, 08:04 PM

Your situation sounds similar to what happened to my MKII. If you have a aftermarket chip
installed on your computer remove it and clean the contact points and reinstall. Made my roadster run great again. Good luck!

CobraGlen · 08-21-2012, 12:33 AM

no chip...

Thanks, Glen

CobraGlen · 08-21-2012, 12:34 AM

Thanks...I will check all connections and vacuum lines.

Glen

Big Blocker · 08-21-2012, 01:03 AM

Glen,

Did I mention that the computer might need a few (approximately 25) starts to truly "re-learn" its set points for your setup. If your battery went completely dead, you lost KA (Keep Alive) voltage to some critical components in the EEC. It may straighten itself out after approximately 20 - 30 restarts or a short drive of about 50 miles after one re-start.

These computers have been known to drop into limp mode when they get "stupid" (read: nothing to keep the memory alive).

If she'll start up and drive reasonably well, take her out for a short cruise and see if she'll start up better afterwards. You may be in the situation where the EEC needs to learn from day one and you mentioned that you have some things disconnected or by-passed . . . it'll need to internally compensate for that fact. In other words, if the EEC doesn't see, say EGR on a fresh startup, it might be enough to send the EEC into limp mode. causing your idle issues. Just a thought . . .

I now when I had my body off for 3 months, my computer needed to re-learn everything from the beginning. Mine wasn't so bad, I have the EGR, TAB/TAD and Carbon canister deleted with the required resistor packs, so the EEC thinks they are there. It didn't have to compensate for much . . .

Hope you get it fixed, let us know what the final outcome was. We can all use as much EFI knowledge as possible, so pass along whatever you find . . . please.

Doc

CobraGlen · 08-21-2012, 11:20 AM

Will do...thanks again for your input!

Glen

Richard Oben · 08-22-2012, 02:51 AM

I think big Blocker is on the right track. When the battery died completely, as in drained by the fan, you lost all the computer had learned. For now turn the idle up just a bit to keep it running and then after a couple weeks, YES WEEKS, it will likely take care of it self.

To set the idle up warm up the car disconnect the Idle air motor and set the idle up to 700 or higher and then plug the IAC back in. HTH, Richard.

PS sorry for the delay, been out of town.

CobraGlen · 09-02-2012, 09:22 PM

After checking everything, I decided to sell the car...just kidding. The problem was a small hole in the adjustable fuel regulator that allowed fuel in the vacuum line that is connected to the fuel regulator. The computer information was of little help. This problem makes more sense now that I have thought all this through. The fact that this happened when the battery went dead was pure coincidence. I will never forget the answer to this issue. I even "rang out" all the wiring going to the computer before I figured out the adjustable fuel regulator had a problem.

Thanks to all who gave me input. It sure helped narrowing the field of possibilities.

Glen