Fuel Injection Brain / Airflow Meter Rebuild Service

Fuel Injection Brain / Airflow Meter Rebuild Service

JDSPorsche has established an excellent capability to rebuild the Fuel Injection Electronic Control Unit and Airflow Meter for 928's equiped with LH Jetronic. They also offer a diagnostic tester that works on 1987-1994 model years.

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Customer Testimonials

I just got my brain back from the UK from John Speake the owner of jdsporsche.com. It was a very pleasant expirience and I wanted to share it with everyone (I am not affiliated with him), just a very happy customer.

After having quite a rough time with some other "shady" rebuilder (I had a long post a while ago), I finally shipped my LH-brain to John and he took care of the problem the same day he got my unit.
He was very patient explaining me every step of the process, explained what the other rebuilder did wrong or did not do and send me the unit back.

I plugged it in, connected the battery and turned on the ignition. Finally no more clicking injectors with the ignition on. I cranked it up and.... BBBWWWWWWAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.

Thanks John, great work.
'87 S4 AT Cassisrot Metalic


I will add that I have personally worked with John (a few months ago) to get my 90 GT LH rebuild. Mine had a unique problem requiring special electronic parts. John and I worked together to source the parts and complete the repair. The repair price ended up being less than I expected. My car is running great and I'm very happy with John's work and patience with me.

Good luck.

Jim Stoops
1990 928 GT



I have been trying to isolate a hesitation issue for the last year.
The car is a model year 85. New coils, wire set, caps, rotors and plugs all as a point of general maintenance did little to improve the hesitation in the upper RPM range just as the engine came "on the cams." I went to a rising rate fuel pressure regulator and this helped as I dialed up the fuel pressure, but I was unable to get the hesitation completely out of the vehicle. I have an ARM air/fuel ratio gauge and the engine never appeared lean, but that was the consistent feel I had while pushing.

For reference I Have an Authority Chip set, custom 3 inch insulated intake runners, modified air box ( I have smoothed the walls and built a radius in the floor of the box to help the air turn into the throat of the MAF) , stock manifolds wrapped with header wrap, gutted cats and a 3 inch exhaust. The exhaust is also wrapped from the manifolds to the exhaust tip.

No air pump, No AC, belt fan replaced with an electric.

In an exchange of e-mails with John Speake of JDSPorsche, he was extremely helpful in providing valuable information which led me to the conclusion that the MAF had finally given up the ghost. According to John a 2% error in the Maf can cause a 10% lean issue with the engine. My raising the fuel pressure with the Rising Rate Regulator was just helping to compensate for the out of calibration MAF.

I ordered a MAF from John. The first thing I noticed was just an improvement in the off throttle driveability. I've had my 928 for 9 years. I think we lose perspective as some items slowly deteriorate. The car is now more of a pleasure to drive than it has been in several years. Throttle response is much improved and the noticeable hesitation I had, is GONE. Better for me and certainly better for my engine.

So.... just wanted to share a successful conclusion to a nagging problem I have had with the car and also to provide a tried and proven resoucre to our community.


Ken Bigham
VLOCITY 89 Carrera 4
UPROAR 85 928S


I have been following a couple of different threads on MAF problems on their 85-86 US and Euro cars. What the common thread through all of them was rough reactions to throttle input. I have been experiencing that in a degrading fashion for the last 3 years. It got so bad in fact that at low speeds it was starting to lean pop from the intake when I stabbed the throttle just right (or wrong). My gas mileage has been getting progressively worse as well. I was down to 16mpg.

Anyway, I finally bit the bullet and asked John Speake to send me a MAF to try. It seemed to clear up the running problems quite nicely. Throttle inputs are nice and smooth. Idle is smoother, and it doesn't seem to run nearly as rich. My car has no cat so you can always smell the exhaust, but I think the MAF mixture may need to be tweaked a little. The cars just runs night and day better. My wife even asked me last night if I did anything to it because it was not jerking around anymore. Now I just have to see what the mileage is for a comparison.

Hope that might help someone with the same symptoms.
Kevin Kwasniewski
1985 928S Euro 5-Speed
1971 911t Targa

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