90 Town Car running rough and no power all of a sudden - diagnosis help needed!

[drhill]

Hello everyone,

My 1990 Town Car (with MAF - California car) starting running rough and had no power all of a sudden yesterday. Here's what I have done so far:

pulled codes as it sat:
KOEO: only memory codes: 33, 41, 91
KOER: 41, 91, 74, 98 (I think the last two were due to my not running the test properly)

then I pulled the MAF plug just to test - what do you know it runs better! Can actually drive the thing without it sputtering and stalling. Not perfect but better.

only codes on either KOEO or KOER were 66 (MAF) and 98 on KOER(test issue)

I pulled the MAF and cleaned it (one of the wires was dirty), reinstalled and plugged in- ran like crap still, not a fix.

checked vacuum and fuel pressure with MAF unplugged (only way to keep it running decently) and was a steady 19" of vacuum and 28 lbs of fuel pressure - with regulator plugged in or unplugged - no change.

fuel regulator smelled like gas when I unplugged the vacuum line but it wasn't wet with fuel at the port.


So what do you fellas think? I'm thinking I have more than one problem - likely a bad maf and also either a plugged fuel filter, a slightly ripped pressure regualtor diaphagm or maybe a dying fuel pump?

It actually has been cranking longer before it starts the last couple of weeks

Thanks!

[DerekTheGreat]

Try a different MAF sensor to see what happens or a new one. Cleaning them doesn't always work.

[gadget73]

Last time I had a MAF die, it did this. Shit out on me at a toll booth coming over the bridge too. I went to leave the gate and I had nothing above idle speed. Got off the road, unplugged the MAF and drove it home. Didn't run quite right, but it ran well enough. Replaced the MAF, all was well.


Fuel pressure not changing with vacuum is a problem. 28 psi is low, it should be around 32 with vacuum and closer to 40 without. Might be a dead FPR, might be a weak pump. Hard to say for sure, but if it runs fairly normal I'll go with FPR. If it doesn't have enough gumption to make normal pressure at idle, it won't have enough to get the car down the road with any sort of normal performance. Really snotted up fuel filter could do it too, always worth changing if you don't know how old it is. Its probably the easiest and cheapest fuel system component anyway.

[Tiggie]

fuel pressure regulator shouldn't smell like gas unless it's ruptured. Your fuel pressure is a little low to further indicate a problem. Put a fuel pressure regulator on and check again. May want to throw a filter on there too since it's cheap and takes 3 minutes.

[drhill]

Thanks guys - I went back and checked fuel regulator again - it smells fine, i must've had gas on my gloves the first time.

New MAF is on order
new fuel filter tonight (cross fingers)
if not then I'll throw on the extra mustang regulator I have laying around (hope I kept it!)
If not then a new pump it is!

[drhill]

TO close out the thread for future reference: fuel filter was fine but I replaced it anyways, replaced fuel pump in like 15 minutes without dropping the tank, super easy access on these!, and swapped to the new MAF electronics. All is well!

[knucklehead0202]

Awesome, although I'd be going crazy trying to figure out which was the actual culprit, if not all of them.

[drhill]

It was actually a bad maf AND a slowly dying fuel pump. I couldn't get more than 28lbs of fuel pressure and I had no power if I really drove it hard. The car just up and started acting terribly one random day. In trying to diagnose it, I pulled the maf and it ran much better. That's how I even got it home! Two problems at once does happen!

[sly]

I've had more than 2 problems at once... Turned into throwing parts at it and final tally was 4 rights and 2 wrongs. Final tally: one sensor and 3 wire harnesses. Fixed 2 of the harnesses with zip ties, but had to replace the other one as the wires RIGHT AT THE HARNESS were pretty much broken down inside and intermittent. The two wrongs were 2 other sensors that were actually good.

When the ECM fried in my 88, it took the TFI with it. So that ended up being a twofer too.

[gadget73]

Multiple failure troubleshooting can be a real PITA. Much as I hate it, sometimes the diagnostic process involves throwing parts at it to see if anything changes.

[knucklehead0202]

Yeah I've done it too. When I first got the '90 it idled all over the place and would surge in a rather frightening fashion when trying to stop or park. Found a couple vacuum leaks, including the hose for the parking brake release completely severed, also a dud IAC and TPS. May still have a small vacuum leak somewhere, as it acts funny when cold. I just get weird when answer aren't cut-and-dried.