FredR

If the MAF is faulty I doubt your problem would go away when warm but...?

If it starts fine and the problem goes away when warm what exactly is the problem?

Mrmerlin

Boaf if your having wierd throttle RPM fluctuations i would suggest that you replace the Idle control valve this is a wear part and if left long enough it can damage the computers

Boaf 32

FredR, Mrmerlin,

Thanks, FredR, agree, goes away then what is the problem. I am a huge proponent of not fixing it if it's not broken. Still I like to know what's going on in there.

Mrmerliin, nice Mustang (if my airplane knowledge is correct). Good suggestion, will take a look at the sensor.

Guess I should replace the fuel filter and methodically go from there.

Bob
Thanks gents, will let you know in a couple of weeks.

Boaf

dr bob

Boaf --

In the US there are a couple places that will test your MAF, and offer rebuilding services if it tests poorly. Meanwhile, post your location. Another user will help you with a quick MAF swap and test.

Know also that your symptoms also point to an impending LHA fuel injection controller failure, a vacuum leak, and Temp sensor II failure or poor connections at that sensor.

Boaf 32

Thanks Dr.Bob. I am in Eastern PA (Douglassville) and added that to my profile. I will go through all the connections and check for vacuum leaks. Fuel injection controller, that sounds expensive...

Boaf

FredR

For purposes of clarity Dr Bob is not saying all those points have failed or will fail rather they are specific items that if problemmatic could show the symptoms you perceive. Of course it is also possible that everything listed is failing or in poor conbdition if they have not been replaced in recent history but way less likely all to go at the same time.

If the LH computer is still original then that is one item you might do well to consider pre-emptive refurbishment on unless of course you have a spare unit to plug and play with given at this age they are a dead ringer for failure- trouble is there are quite a number of service critical items that are potentially in the same boat.

dr bob

Eastern Pennsylvania puts you in Mr Merlin territory near Philadelphia. If you don't readily find the cause of your symptoms, get with Stan and work out your logistics for support. Stan's very 928 knowledgeable, and likely has or has access to a car in which to test your expensive pieces. Better to have a logical test plan rather than throwing $hundreds at the car just to see what happens.

Know that the MAF and the LH controller are inevitable failure items. Of course those are the $most pieces. The MAF is good for some finite number of wire-burnoff cycles before the wire becomes too thin to read incoming air mass anymore. Cars north of 100k are good candidates for a proactive MAF rebuild. Costs are in the $300-350 range for the service. The fuel injection controllers have a custom "tile", a daughter-card that suffers from internal corrosion to the point of failure. There are a few folks who have made new-and-improved replacements for this critical piece. I'm not up to what the current rebuild costs are; I'm sure someone will jump in with numbers. I had mine (and a spare) redone almost a decade ago now by Rich Andrade at Electronikrepair in Phoenix. Sponsoring vendors including 928 International, 928srus, and others offer rebuilt MAF and LH controller units on an exchange basis. So there are several options available. All will test your old pieces for you if you can't find another local car to test them in.

Sagres74

Had the same issue early last year. Using the path of least resistance (and cost), I first opted for a can of MAF cleaner. So far, it seems to have resolved the issue.

I'd recommend the same prior to spending more.

Boaf 32

Understood, it's just an inventory of potential failures.

Boaf 32

Agreed, always clean before replace

Boaf 32

That is great, I appreciate it. I am in Boston for 2 weeks then back in town.

FredR

The MAF can cause errant running problems and it can also cause a power loss due to under reading the amount of air and thus adding less than optimal fuel as a consequence. When running at full load the AFR to achieve max power is enriched above stoichiometric measure so running a bit lean may not be noticed as this problem occurs progressively and a new owner will likely be none the wiser.

Mrmerlin

Folks these current answers are for post 15 onwards.

the OP thread has an S4 from 2008 ,
the post 15 poster has an 86.5

Based on info provided your symptom indicates to me a failing ISV ,
to test it you would remove it and take a awl to move the vane .

That said since this part is a known wear item and its probably original it would be wise to have a new part onhand, they run about 150.00 from your FLAPS.
The MAF rebuild is going to run you about 400.00 with shipping.
so you could spend less money first.

The S4 computer is prone to chip degradation and failure .

The computer in your 86.5 car is quite reliable but the diodes that run the ICV will burn up if the ISV in your car is stuck.
This will then damage the idle operation of the computer and cause other running issues.

That said the intake system of your car requires that every part be in top condition for optimum performance.
replacing one part is like putting a bandaid on a hole in a dike

cdan

i could use some clarification on terms isv, icv, lh controller.... i'm looking at an '83 928. Owner says it has a bad maf, then maybe a bad relay between the maf and ecu. A list of what to check first, what it is and what it does would be great. The only thing i know about 928s is they can be expensive to maintain. Any help would be great At this point, anyone could blow smoke up.... you know, and i wouldn't know the difference. Finished my last hot rod and need a new project.
cdan

dr bob

Cdan --

The discussion in this thread is for later cars that have a version of Motronic injection called LH that relies on a mass air flow sensor or "MAF". The '83 US model you are looking at has a barn-door style volumetric air flow 'sensor', with a temperature probe in the air filter housing so it can determine air mass for injection purposes. The system is quite simple and easy to diagnose and service. Like any 35+ year old car though, the first step is a giant one that uncludes replacing all the rubber bits in the engine bay and the fuel and brake systems. This broad-brush description includes the hoses gaskets connectors couplings check valves etc in the intake and vacuum systems. No use chasing an air metering symptom when there are unmetered air leaks.


As far as 'expensive to maintain', the actual maintenance costs on a good example are a tiny fraction of the -original- purchase price. They can appear to be 'expensive to bring back' depending on how much neglect they've suffered. Low purchase prices for project cars can lead you to believe they are cheap, when that low buy-in cost is merely the down payment on first few years of recovery fun. Buy the best example you can find, and you can usually manage the 'fun' a little more easily.


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Welcome to Rennlist! There's a thread in the sticky header called "new visitor...". Spend time reading there and get a good idea what you might expect to discover as you shop. Share your location in your profile, and visit with local owners to see what to expect, and maybe enlist some help as you shop.