checkmate1996

OK - I have an 84 Euro that is surging at idle and upon acceleration is choppy and feels under powered. (Its starts up warm or cold no problem.) I'd dare say a lean feeling condition. I went through the WSM and ran multiple LH tests. Here are the results. I would appreciate any help in deciphering and other recommendations. Thanks!!

Testing done @ Multiple Pin Plug at LH air flow sensor
skipping to...

TP#3 - LH Air Flow Sensor
3. Pins 4 & 2 - 12.3v @ spec
4. Pins 6 & 3 idle mixture position (spec. 0-1000 ohms) =411
c. Pins 5 & 3 (3.6-4.1) =4.3

TP#4 - Temp Sensor II
1. Prong 1 @ temp sensor = 648 - Engine Temp = 44C/111F degrees // Ambient temp is 83 degrees F
2. Prong 2 @ temp sensor = 657 - Engine Temp = 44C/111F degrees // Ambient temp is 83 degrees F
Spec:

• 0 C / 32 F: 4.4k to 6.0k Ohms
  
• 15 - 30 C / 59 - 86 F: 1.4k to 3.6k Ohms
  
• 40 C / 104 F: 0.9 to 1.3k Ohm
  
• 60 C / 140 F: 480 to 720 Ohms
  
• 80 C / 176 F: 250 to 390 Ohm

TP#7 - Auxillary Air valve
2. Voltage = 12.7v in spec
3. 26.1 Ohms @ plug (specification 10-45 Ohms)

TP#10 - Fuel Pressure
3. Fuel Pressure @ idle = 2bar (spec 2 bar)
4. Fuel Pressure with vacuum hose removed = 2.5bar (spec 2.3-2.7 bar)

Thanks!

Rich9928p

The 1984 - 1985 Euro 928s require air/fuel mixture to be manually set at the MAF. The CO spec is 0.5 to 1.5% with intake at 59 -95 F and oil temp at 80C (176F). The CO% is measure pre-catalytic converter if in stalled.

The EURO 928s are sensitive to an out of calibrated MAF.


Rich
928 OC Membership Chairman
1993 928 GTS Cover Girl
1987 928 S4
1979 928 5-speed rescue cover girl too
1979 928 Euro 5-liter track beast

checkmate1996

Rich - I sent you an email. Thanks!

checkmate1996

Does the Temp 2 readings give anyone heartburn? They seem very low to me as well.

byrdman454

The 84-86 Euros were always on the lean side from the factory. I had a lean condition (bucking sometimes) even with a new MAF and sorted engine. Back in the day, we would swap in an adjustable fuel reg and the S3 damper in order to richen it up. That worked pretty good. This was before John Speake offered his S2 Euro performance chips several years ago. These things worked flawless for my Dad's '84. It has never ran as good as it does with those chips. You will have to swap out the '84 LH for the '85 or newer one. The S3 LH will also work. That is what my Dad's 84 is using with John's chips.

checkmate1996

Replaced Temp 2 sensor. Atleast that is reading correctly now. It helped my idle as well.

checkmate1996

To follow up - I started checking all things vacuum. Please correct me, but from the WSM the vacuum line coming off the spider goes to the ignition control unit in the car next to the CE Panel. (The other vacuum on spider goes to AC idle valve).

1) There is only one vacuum line from spider entering the firewall to goto the ignition unit, correct?

I ask because I found something strange. The vacuum line coming off the spider as intended (small hard vacuum hose with the rubber curved connector), it wrapped down under some wires and then back up near the air tube to connect to a slightly larger vacuum hose. That hose looks to run down the fender area and I presume goes to the ignition unit in the ce panel. The part that has me scratching my head is where the hose enters the larger hose somebody previously put a screw in the hard tube which seems to me effectively cutting off vacuum to controller. Is there a reason why somebody would have done this? This can't be right.

Thoughts??

byrdman454

This thread has a copy of the vacuum diagram that comes with Roger's replacement kit. It is good for the 85-86 US and 84-86 Euro according to the pic. Maybe this will help...

https://rennlist.com/forums/928-foru...uum-lines.html

AO

Not that I have this, but there might be a line for vapor recovery. I don't think the RoW cars had this, but perhaps as part of the federalization, it was added? Just a thought.

checkmate1996

Good point andy. Thanks. I'm going to snap a picture later...it definately looks like an after thought.

Great to see you again at SIH!

checkmate1996

Very helpful. Thanks. Here's a thread you posted along time ago. https://rennlist.com/forums/928-foru...ting-help.html Does that euro wiring diagram hold true. Also, did you mean ignition control unit for LH?

Thanks!

checkmate1996

heres some more pictures of my wacky vacuum setup. I did find one hose providing false air. The ac idle valve hose coming off the spider was hard as a rock and a smoke test confirm a crack in the middle of the hose on the underneath side.
Black vacuum line coming off spider. In wsm this is suppose to go to Ecu.
A smoke test revealed false air leakin out of the screwed in end . I have no idea why it's capped off.
The hose runnin down the fender of which the black hose was connected too.

checkmate1996

Case closed. The 84 euro does have a vacuum hose that connects from the front of the spider to the ecu. I had found the "other half" of the vacuum hose tucked under the wires near the t14 connector just sucking in unmetered air. I reconnected the two hose and voila air was passing through as expected. I put vacuum on the line and it held perfectly. I started the car and the hesitation, choppiness, lean feeling between 0-2000 rpms was gone. Why someone capped this hose will probably be forever a mystery.

Thanks for for all the responses.

checkmate1996

I wanted to follow-up with this thread. The the case was not fully closed upon further review. After finding the initial vacuum leak, yes the hesitation went away in neutral but ended up rearing its head again under load. Additional vacuum leaks were found since this post and resolved. I also realized the MAF was not fully seated also increasing unmetered air. Once I got the vacuum leaks sorted, I also got the fuel injectors flowed and tested (thank you withchunter) and got new spark plug wires (thank you Roger) as they had several ends corroded. At this point, I narrowed the hesitation between 1700-2100 RPMS. Pressing on the gas and it would smooth out, just like many others have posted. However, one thing I didn't see posted anywhere else but was recommended to me by Stan (MRMERLIN) at Frenzy this year was to clean the two hidden grounds that connect to the passenger camtower under the fuel rail. Two 10mm bolts support the ground rings for the the fuel injectors. The bolts are somewhat difficult to get to but after removing them, they were not shiny at all. I took the dremel and ground the dirt and corrosion off the rings till they were a shiny gold again. I also replaced the washer with a fresh one that was correct for 10mm. I also sanded down the contact points on the cam towers as well. Finally, for good measure, sprayed everything down with deoxit. I put everything back and took if a test drive today. The surging between the RPM range was gone! I truly was shocked. The RPM range was silky smooth.

Possible theory??: LH Computer is getting signal from MAF, signal is downgraded at the fuel injectors more than normal and running leaner due to corroded grounds making MAF work harder by having to increase AF mixture causing faster MAF burnout??

Anyways, here's to adding to the list of items to fix 84-86 Euro hesitation, stumbling, surging, bucking:

1. Verify all vacuums lines, elbows, hoses are not leaking.
2. Verify fuel regulators and dampers hold vacuum and fuel pressure
3. Verify timing belt on twin dizzy is in good shape and rotors are aligned to notches
4. Verify spark plugs are in good shape
5. Verify spark plug wires measure 3k OHM (resistance) from end to end.
6. Verify current MAF resistance
7. Verify Rotors and Caps are good condition.
8. CLEAN all Grounds as mentioned above!

Potential solutions if that doesn't work

1. S3 damper and Adjustable fuel regulator
2. Update LH with new S3 and get Johns chips
3. Roger Tyson also suggested getting Greg's adaptors and running higher powered injectors e.g. 24 lb Type IIs...
4. Test and or replace MAF after having exhaust analyzed and making sure itis' in spec and all the other things above have checked out

Please add to this list! After reading a lot of rennlist posts on this subject it would be nice to have definitive place for resolving this issue.