Socal_Tom

Need to do more testing tomorrow but I looks like I may need a new MAF for the S4 engine.

Is there a recommended go-to for a replacement?

I have an uneven idle, light throttle surging and I flunked SMOG on high NOx but with very low CO2, so that seems to point to a bad MAF, hence the question.

Thanks gentlemen.

DeWolf

Send it to Kevin at Injection Labs.

Socal_Tom

Looks like these guys;

Injection Labs Inc.
4949 N Broadway #101B
Boulder CO 80304
303-404-0515
Email: Kevin@injectionlabs.com

Thanks for the referral.

GregBBRD

Low CO and high NOX is the problem with 90% of the S4's that fail smog. The traditional solution to high NOX is to replace the converter....and quite frankly, a new Porsche converter would allow a 55 gallon drum of fuel to pass smog....they are fantastic converters. They very rarely fail.

This problem can be very frustrating and difficult to figure out. You can replace every ignition piece, the MAF, the LH computer, all the injection components, and still have the problem. Any tiny intake leak will drive down the CO. Also very common are dirty injectors. I send my injectors to a place that tests them, before and after cleaning. Some of the "reports" I get back make me wonder how the car the injectors came from ran, at all.

I stock rebuilt MAFs from John Speake, in England. These seem to work the best, for me. I've had extremely poor luck with the calibration of any of the US rebuilds. John seems to have figured out how to get the calibration very close to correct.

You are welcome to borrow one, to see if it cures your problem.

I also try to keep a set of cleaned injectors in inventory so I can exchange them.

ROG100

We have both JDS and Injection Labs rebuilt MAF's in stock

Socal_Tom

Thanks for the responses, appreciate the help.

Given that I don’t think the cat(s) would cause the unstable idle I think the MAF is the first step here.

Greg - will stop by tomorrow.

Thanks!

Red Flash

I have ordered a few rebuilt MAFs.

The last one I got from JDS through Louie Ott in the US failed after ca. 1,600 miles. After contacting Louie and the need for attention became obvious, he never responded. Same strange thing occurred with John when contacting JDS directly.

I can deal with problems, but just not answering is outside of civil business practices in my book. So now, I'll send the failed JDS unit to Rich Andrade (www.electronikrepair.com), whom I have also used before for MAFs and other things.

I am certainly not a volume consumer like Greg/Roger. But, just my 2 cents based on recent experience.

SwayBar

That doesn't sound right, there must be more to the story.

karl ruiter

I have used Rich several times with good result. Last time, I was unsure what my problem was so I sent him my MAF and my LH. He found a problem with the MAF and, when testing did not show a problem, he installed my LH in his own car and drove it around for a week to make sure. Don't see how you can top that service.

dr bob

Rich Andrade has taken care of several for me in the past for clinic cars. Lots of folks, including some of our direct forum sponsors, carry the JDS rebuilds.

Tom --

So long as the oxy sensor is active and the MAF isn't yet to "failed" state, the low CO/high NOx failure is most often caused by a vacuum leak, followed closely by dirty injectors. Know that the tailpipe symptoms must be sampled upstream of the cats to be of any value. That means the test pipes routed up from the headers to the engine bay just forward of the air cleaner housing on either side. Testing behind the cats at the tailpipe tells you whether the cats are capable of scrubbing up whatever the engine is putting out. In your case the CO cat may be doing great, with the NOx portion not so well. If your engine is still running the original injectors, for sure you'll want to at least clean. and better, replace them with new.

---

I tracked my NOx tailpipe numbers during it's California period under my care. The NOx numbers grew slowly at each test, until finally it was taking some serious 'cooperation' from the smog guy to get it to pass. I had a great smog guy, by the way. After the second hold-it-in-second and barely pass NOx episode, new injectors were installed as part of a whole intake refresh effort. Idle much smoother even though it had seemed fine before, and the NOx numbers were back to as-new-to-me 70k earlier. Now a five-year refugee from Cali, I miss having the smog test numbers to help monitor the engine and systems. There are times when I also wish some of the belching rolling-wrecks here were cleaner out the tailpipe, but that's another story.

I can't imagine that there isn't a good injector test-and-clean place near you. Except for o-ring sizes, the later S4 injectors are identical to some common 5-liter Ford applications. Should be a breeze to get them taken care of there.

XS29L9B

I was going to say, I thought Roger had them. He had chimed-in on the other thread about the 1988 MAF where Captain Slow had inquired.

SeanR

Just my .02. The only MAF's I'll use on customers cars are JDS ones, had too many others that were out of calibration or just not done right. Same goes for LH's. I like mine to work right the first time, I also like being able to plug the hammer right in after chip change and have all the features working for diagnostics.

Socal_Tom

Thanks for all of the discussion and considerations and shared experiences. I'm going to dig in here and get it sorted, this car has been a journey...

Socal_Tom

Quick shout out to @GregBBRD.

Kyle and Greg helped diagnose that I have a bad O2 sensor, going to start there. They did that despite having a very busy day trying to finish projects and that extra effort deserves a public Thank You.

Harvey928

I will second the shout out for Kyle and Greg Awesome folks and great people.