twizted_3kgt

First off, i'm new to these boards so hello!

On to my problem, I have a '88 Formula 350 which i've owned for the last 6 years, didn't give me too much trouble until recently.

What it's doing is it won't rev up past 2-3k rpm if I give it more than sayy 10-15% throttle. If I do give it only a tiny bit of throttle and ease it down, I can get it to go to redline no problem. But if I do give it more, it bogs out, backfires through the exhaust and intake, and doesn't rev up. This happens in both neutral/park and in drive.

I got a SES light, and here's the codes I pulled:

34.Low voltage (high vacuum) at mass air flow sensor (or MAP sensor)

36.Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal


42.Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit

44.Oxygen sensor lean


Now the 36 code i've had since I bought the car and it has never affected anything, the other ones just popped up recently.

The 42 one I believe is because I disconnected the EST wire (the little brown wire connector above the A/C evaporator or whatever it is, that you're supposed to unplug when you change ign. timing, right?) while the car was running to see if it affected anything.

The rest came up while driving tonight.

Things i've tried:
- Replaced dist. cap/rotor/ign. coil...plugs/wires have less than 10k on them.
- Cleaned out MAF

Known problems with the car:
- One header has a small leak, don't know if it's a crack or bad gasket or what...haven't really looked into it. But I was starting to think it might be fooling the 02 sensor into thinking the engine is lean and therefore making it too rich and bogging out...kinda farfetched though.

Now what I just discovered today is it'll idle really rough sometimes, and if I let it stall out, then start it back up, it'll idle perfect, rev up no problem for about 10-15 seconds...sometimes. I tested it twice, and the second time, I drove, went WOT, had no problem, got to redline in 1st/2nd no trouble...till I let off. Then it wouldn't idle, at all. I had to two-foot my way home, holding idle the entire time, didn't matter if i was moving or not, just would not idle.

Wow that was a really long post, I hope someone reads it and can help me out, I would really appreciate it!!

twizted_3kgt

First off, i'm new to these boards so hello!

On to my problem, I have a '88 Formula 350 which i've owned for the last 6 years, didn't give me too much trouble until recently.

What it's doing is it won't rev up past 2-3k rpm if I give it more than sayy 10-15% throttle. If I do give it only a tiny bit of throttle and ease it down, I can get it to go to redline no problem. But if I do give it more, it bogs out, backfires through the exhaust and intake, and doesn't rev up. This happens in both neutral/park and in drive.

I got a SES light, and here's the codes I pulled:

34.Low voltage (high vacuum) at mass air flow sensor (or MAP sensor)

36.Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal


42.Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit

44.Oxygen sensor lean


Now the 36 code i've had since I bought the car and it has never affected anything, the other ones just popped up recently.

The 42 one I believe is because I disconnected the EST wire (the little brown wire connector above the A/C evaporator or whatever it is, that you're supposed to unplug when you change ign. timing, right?) while the car was running to see if it affected anything.

The rest came up while driving tonight.

Things i've tried:
- Replaced dist. cap/rotor/ign. coil...plugs/wires have less than 10k on them.
- Cleaned out MAF

Known problems with the car:
- One header has a small leak, don't know if it's a crack or bad gasket or what...haven't really looked into it. But I was starting to think it might be fooling the 02 sensor into thinking the engine is lean and therefore making it too rich and bogging out...kinda farfetched though.

Now what I just discovered today is it'll idle really rough sometimes, and if I let it stall out, then start it back up, it'll idle perfect, rev up no problem for about 10-15 seconds...sometimes. I tested it twice, and the second time, I drove, went WOT, had no problem, got to redline in 1st/2nd no trouble...till I let off. Then it wouldn't idle, at all. I had to two-foot my way home, holding idle the entire time, didn't matter if i was moving or not, just would not idle.

Wow that was a really long post, I hope someone reads it and can help me out, I would really appreciate it!!

Vader

Clear the error codes, then start and run it again. Chances are that the 42 will not repeat, and the 44 will not repeat until you drive it again. Scan for newly generated codes and act on those.

While it's warming up, check the MAF output at a known RPM. Check voltage at the 'C' terminal and 'A' terminal. Expect to read about 800-950 mv at idle. Lower than 800 on a 350 is likely a problem.

You should also inspect the intake ductwork between the MAF and throttle body for leaks. Make sure the CCV tube is connected to both the rocker cover and the TB. Of course, the oil filler should be capped an sealed, not covered with a breather-type cap.

Using a spray cleaner probably won't hurt, but it also won't clean the sensing hot wire nearly as well as a burn-off cycle. Driving with a MAF that doesn't burn off routinely can result in a low intake air flow readings and a subsequent lean mixture.

Had the '36' error been repaired when it first occurred, these other problems may never have happened.

Check the burn off relay, wiring, and oil pressure switch. Force the MAF to burn off a few cycles and it may start reporting correctly.

camarolizard

also check the iac.you may also want to clean the throttle body.vader is correct in what he has told you.just a tip,if you do have to replace the maf,don't use a generic parts store sensor,use a good one

twizted_3kgt

Sounds good, i'm gonna have to look up on mitchell for the burn-off circuit as I have no idea what wire is which or how to make it cycle. But what you say makes sense, i'll try it all out.

The oil filler is capped with the stock cap, but I might have a problem with the CCV tube where it goes into the rocker arm, for some reason I don't have the fitting that's supposed to go in there. So for a long time there's been just a rubber fitting that's jammed in there...real ghetto-like, so it's probably not the right size tubing. I can't remember if I got it like that or if I did it, i'm guessing I got it like that because otherwise I would know what went in there.

twizted_3kgt

Alright, cleared the codes out...started it up...wouldn't idle unless I held it and even then it wouldn't go past 1000 rpm. So I let it stall itself out, started it back up, SES light came on, and it runs PERFECT.

Code 34 is the only one in there (MAF/MAP sensor voltage low), so I get thinking and talking to some techs at work, and we all figure its in fail-safe mode for the MAF.

So I clear the codes, unplug the MAF, and start it up. Runs PERFECT!

So I need a new MAF...gonna search the classifieds here, no way i'm buying new for almost $200 if I remember right. Not spending that much on this car for anything.

Thanks a million for all the help guys.

Oh one more question, will it hurt anything if i'm driving around with no MAF running on the presets for a little while? i'll be taking it easy on it regardless...

camarolizard

should'nt hurt it.without maf,it uses the map sensor as an subsistute.i would still baby it and dont drive it any more than you have to