TOC

I know...convertible makes no difference.
I've been working on this since last year. Mobility and distance is a big concern, before you ask why so long!

Left lights on, battery died, jump started, start, die, start, die. Changed the battery. Same. Towed home.
Ended up the relay above the computer. Changed that, ran 3/4 mile, quit. Nursed it home.

Continuous code 66...MAF sensor. Clear it, it comes right back. Output is .75v at idle to about 2.5V revved, smooth transition. Ohmmeter readings to computer plug, zero ohms, so really good.

TFI module was flaky....intermittent spark. Swapped that, spark stays good until the engine stops turning, which it does shortly after starting.
Made sure it had good fuel....pump still runs after engine stops.....5-10 seconds. Fuel pressure right in the middle of where it should be. No holes in rubber snorkel from MAF to throttle body.

So, I have a code 66 that will not go away, a car that starts and runs, then dies (so mechanical issues like valves or timing chain aren't).

When we added fuel it ran enough to take it out into the street, turn it around and back it in..ran another 10 minutes and just died. Jabbing the throttle like you'd do with a carb system, causes it to try to run a bit more.

Checked all the grounds I can find, clean and tight.

No other codes, and in open loop, it should run.

I have seen MAP sensors do something like this, but I cannot find a MAP sensor anywhere on this car or in the diagrams, so guessing we don't have one. Baro shouldn't do this.

It is just difficult to drive over with the tools I think I need, do the tests, come up with nothing hard, same codes, same issue. I have not yet put the bug in an injector plug to see if the pulses go away...arms just too sore to continue last time.

I am really thinking they jumped it backwards with the key on, but we have all the power, no links blown, power to the coil, all that, good consistent spark now.

Symptoms do change...latest is it starts and runs, check engine light on (66), then the light goes out. Then is starts bogging, dies, and the light comes back on.

My brain is fried, folks.
Any ideas to direct my path?
Thanks.
Dave

TOC

I suppose the issue really is, I've checked what I have the equipment to check. I am guessing I have a failure that is not showing up on codes....saw an f-250 like that, started, died, started, died. No codes. Unplugged the MAP sensor, fired up and ran. New MAP, ran better than it had in 5 years.

Pump runs, spark is there, ESM power relay changed, 60-pin cleaned, computer inspected internally for burned components, corrosion, water damage, it's fine.
MAF removed, cleaned, all 4 pins have proper voltages, two wires to 60-pin at computer good all the way.
TPS wouldn't do this at idle, not touching anything, I would guess.
Sometimes it runs, runs for a fair amount of time, revs okay, drives short distances, then raggedly shuts off, like it's running out of gas, yet the fuel pressure gauge never wavers when this happens.
Maybe if I drop my spare flathead in it, carb and points, it will run!
I think my daughter and son-in-law have decided to get another car, but it has to run to sell it.
Right now it's a driveway ornament.

Maxwelhse

Hummm... A Flathead Fox sounds counterproductive, but really cool! I seriously doubt you'd pull up to another at the car show!

You've got a situation on your hands, that's certain. I hate it when things act twitchy like that.... I also hate "parts changing", but if it were my car I think that's what I would be down to.

I'm not a pro, but if it were my car, I'd probably hit the bone yard and see if I could score another A9L computer and a MAF and trade 'em out and see what happened. A9L computers seem to be worth a king's ransom on Epay so local is probably the way to go.

I chased a TPS in my S10 for almost a year, a CPS in a 3800 GM for OVER a year, and an O2 in my TJ for 6 months because of quirky crap like this... Good luck!

TOC

That was where I was heading....or find someone with a similar car I can swap a couple of major bits out on.

I've never seen anything like it. I used to do this for a living back when they were new....got the Monitor 200 (still), the fuel pressure gauges, the Mitchell books on it.

I have downloaded and printed wiring diagrams.....all looks intact.
It's that MAF code that has me scratching my bald spot.....

Maxwelhse

As a fellow bald spot haver and scratcher of said spot... I think it's time to "change parts"...

If you're near NE IN and don't mind me HAWKING OVER YOUR DAMN SHOULDER AND LITERALLY BREATHING DOWN YOUR NECK, I'll "pony" up my A9L and MAF for your trials... but... if my car don't run right after its parts being plugged into yours, you bought 'em!

TrimDrip

They do go bad. My car had a reman on it when I bought it. Put you one on.

If you want to test it, I guess you could take a hair dryer or heat gun and heat it up while the car is cold. If heat is cause, that will cause it to act up.

Personally I have never seen a car give a maf code and there not be something wrong in that area.

TOC

Well, the test procedure I had, and one gleaned from this forum, is to check A,B,C & D on the MAF plug. Battery power, battery ground, signal, signal return (without looking, not sure of order).
Battery voltage same as battery, battery ground correct, signal idle .75V, revved, smooth transition to about 2.5V.
The issue is the inconsistency of runability.
In "open loop", shouldn't make any difference on signal. Sometimes it starts normally, runs, drive it a bit, sometimes, start and die.
Heat makes no difference....every failure is bonnet open, less than 40 degrees F outside, so we don't (or shouldn't) have heat buildup.

TrimDrip

so it was bogging and dying and working perfectly?

you have to test it when it is messing up

What I would do is, catch it messing up, I would tap on it to see if it makes a difference. If that did nothing, I would unplug it. It should crank and idle not plugged up.

TOC

Oh, I did. Can't read a MAF sensor output when it won't run. Have to have air flow.
It is so inconsistent. Al failed component would be a failed component. Something keeps changing.
One I changed the TFI, the spark stayed consistent. Spark stayed strong until engine actually stopped turning. Walk quickly to the back of the car, you can hear the pump still going, then is stops.
So, signal to fuel pump relay good, relay good, pump good.
Aded 5 gallons of gas, car was on an uphill driveway, got it lit (TFI change and fuel), geez, look, it's good to go. Put it in gear, backed it off the driveway, turned it around, backed it up the driveway (fuel tank low....gotta make sure....), started checking and scratching heads (still have check engine light, still code 66), and it started bogging, running ragged, and died. Spark there until quit turning. Fuel pressure stayed right where it was supposed to be. THEN we noticed as we were starting it, run for a bit and quit, that the check engine light was on, and when the check engine light went out, it almost immediately started bogging, and the light stayed out until the engine quit turning, then came back on.
I've already changed out the power relay that sits right above the computer (sonofabuck to get to), and, yes, first rule of automotive repair states, just because it's a new part doesn't mean it's a good part...and I may re-check that. But, if the power goes away, the injectors should stop right now, and they don't.
While the engine is running, the only thing wrong has been code 66 and check engine light. While running MAF signal proper at all times we have checked it.
KOEO shows 66. Clear codes, restart, check engine light comes on virtually immediately, and it's 66 again.
I put test equipment all over the car, battery voltage stays right there, spark stays there, fuel pup keeps running. And it dies.

Getting down on the ground, in the rain, and fiddling with computer and relays, I can do that once or twice and not again. Can't get back up.
Sorry.
I do have the computer sitting on the floor, so I can remove the 60-pin and check resistances, which is how I know the two MAF leads are perfect to the 60-pin.
Could it be the computer? Yes.
Could it be the MAF, with normal readings? I don't think so.
I have checked various places, looking for "ignition" feed out of the ignition switch, seems to stay normal everywhere I look.

TOC

Spark staying strong tends to eliminate another TFI issue, tends to prove pickup in distributor is okay, as is coil and power feed to ignition.

Fuel pump continuing to run (and good pressure) tends to eliminate pump, relays, and power to them, and loss of engine run signal that would drop out the relay (upside down in a ditch safety).

Engine, when it runs, runs good, good power, no missing, which tends to eliminate a mechanical issue.

Cleaned MAF tends to eliminate dirty MAF.

The wild card now is the action of the check engine light just before the engine starts to quit.