fraggle

87 S4. Car is running rich and has low gas mileage, getting worse over the past year. No vacuum leaks, I think - suppose I should test to make sure.

May the MAF finally be giving it up? 140k on the clock and I've never had it tested or calibrated.

AO

Fraggie,
You're asking us? You forget; we're a bunch of *** clowns!






But yeah... sounds like it could be the MAF - especially if it's gradual and all. Other possibility is O2 sensor.

Tony

Does it idle any different when you un plug it?

Get some CRC MAF cleaner and give it a spray.

FredR

Could it be Temp 2 sensor not giving correct output thus fooling the engine to believe it has not warmed up thus chucking more fuel in than needed?

On the cruise map O2 sensor adjusts the mix to stoich [if it is working correctly] at full throttle the O2 is ignored and tired MAF's tend to under read the air flow if my memory serves me correctly. For sure if you are on the original MAF having it checked out and/or rebuilt by John Speake a good idea irrespective [contact Louie?].

Rgds

Fred

fraggle

Definately running rich on full throttle, reports from those, err, behind me on my last run were from an educated bunch and we had a lot of time for observations.

I'll have to see what happens at idle, give it a cleaning while debugging. Grrrr. I just want to drive!

outbackgeorgia

Fraggle,
My S4 has a rebuilt MAF,. If yours is original, I'm sure you need a reman, as the platinum wire is a limited life item. Prob good for 150,000!miles depending on how many times it is shut down. It has a burn off cycle for each shuut down.
Dave

granprixweiss928

check the 3 fuel regulator/dampers. pull the vacuum lines and smell for gas smell.

one up front, two under the airbox.

if they do, then they have failed. replace them.

John Speake

Could also be the O2 sensor has gone u/s. Disconnect battery ground strap, disconnect the sensor at the round connector on the floor just in front of the CE panel. Reconnect battery and start engine - does it run much better without smoke ?

May actually run too weak if that MAF is the original....

fraggle

Thanks for the tips, all.

I'll see what I can find tonight. I should at least be able to check the fuel dampers tonight.

Hilton

Intermittent misfire can cause it to run richer too. Check your plugs, caps and plug wires.

The O2 sensor detects the extra air which isn't being combusted with fuel, and makes the LH add more fuel.

worf928

And.... one or two nasty clogged injectors can make it rich too. Yes, seems counter-intuitive, but it's been discussed before.

whiteNSXs

My 87 had a running rich problem for a while and we finally narrowed it down as a malfunctioning LH. I sent the LH to Roger who rebuilt it and the problem has been solved.
Steve

fraggle

Didn't get out to the garage last night.

Injectors are all less than 4 years old, so is the O2 sensor. Less than 20k miles on them all. LH was swapped once, but that was 10+ years ago, I'm running an '88 cpu. Don't think it was ever rebuilt.

Hopefully I won't have to work so late tonight so I feel like tinkering when I get home!

worf928

Ok. Then move those to the bottom of the list. (Although, overly-rich running for a long time has been known to kill O2 sensors.)

If you're running an '88 LH with 140k on the clock you are running on borrowed time. Regardless of anything else you find, I would recommend getting that LH off to one of our rebuilders before your next long road trip.

Note above that John wrote that the MAS goes lean in old age (under-measures air so you get less fuel.) If your MAS is indeed original then I am surprised your S4 will run at all. They just don't last that long. So, if the MAS is indeed original, then ...

I suspect that you may have two problems that are counter-acting each other. First, as advised above, check the dampeners and regulator: pull the vac lines off. If fuel drips from the vac lines then that's an obvious sign. If not, put your vac hand-pump on each of the three and see if they will hold vacuum.

Next check your temp-ii sensor against spec (directions and spec in my inspection guide linked in my sig if you need them.)

Let's see what those tests report.

outbackgeorgia

Fraggle,
Agree with the other Dave. The LH has a hybrid chip that self-destructs based in time, not use.
I chased this gremlin for months! Just get a rebuilt LH from Louie Ott/John Speake and be done with it.
Dave