gsmarrara

Dear all, I have a 1983 S automatic A28.07, with a 1988 S4 engine swap. The car works mostly as it should. Idles ok, works mostly as it should, but at 2000rpm or 2500rpm's, when I hit the floor the car shifts down but it gains speed slowly. When I hit the gas pedal but keep in the same gear the increase in the speed is really slow. But the car revs until 5000 or more smoothly, just slowly. Probably the most important fact is the 0-60 time that is about 11 seconds at WOT, very very far for the 6.3 it should. So, the car accelerates and drives as a good 140 hp car.... but not 316hp...
What I have done on the car so far:
1- Cleaned and checked the injectors.
2- Checked the ign plugs, ign wires.
3- Adjusted the quadrant (throtle, bowden, pedal)
4- Flappy working ok.
5- No fireflies in the engine bay
6- Fuel filter replaced 1 year ago, 2K miles since them.
7- New oil, oil filter.
8- Thrust bearing checked ok.
9 - Air filter ok.
10- Temp II checked ok
11- MAF - partially checked (resistance of 4.4 ohms between 3 and 5 on the MAF, correct tension at the plug, definitely runs much better with the MAF on, when disconnect the MAF that car stalls or can barely move). I don't have access to a spare MAF to install and check.
12- Checked Idle sensor and WOT in the LH/EZK terminals - ok

What I'm missing? Clogged fuel filter? Coils?
Thanks for the support,
GM.

Hilton

Check the cam timing - first check is to rotate the engine by hand to TDC and then with the left and right belt covers off, make sure the marks line up and the distributor cap bolts are roughly in the center of the slots.

Also check the fuel pressure and delivery rate. You can check the pressure at the fuel rail, and the delivery rate at the fuel-tank sender (pop the hose off the level sender in the tank, and attach a hose to it into a jerry can out the back of the car)

gsmarrara

Dear Hilton,
thanks for the tips. Will try them tomorrow and get back to you! Best, GM.

gsmarrara

Hilton, what would be correct pressure and delivery rate specs for this engine? thanks, gm

Ian S4

Maybe this will help...

gsmarrara

Thanks Ian!!!!

Chalkboss

I think the timing check is great advice. Sounds like a timing issue especially if you don't know the history. Good luck, she should not perform like that.

ALKada

Not that this is a cause, but since you have already done so much at this point, clean all of your ground points. Search on the 928 forum for a schematic of where they are at if you do not have it.

Hope you resolve the issue.

John Speake

How many miles on the car ? If more than 80k miles then get the MAF checked out..... when that's sorted, get a diagnostic tester on the car to see if the knock sensors /Hall sensor are OK.

worf928

The above. Before anything else.

OP's description is a paragon of symptoms of a failed Hall sensor.

gsmarrara

John, the car is 129K miles, but in theory (PO documentation) the MAF was replaced 30K miles and 5 years ago. I will post a picture of the MAF, seems pretty clean (I know this don't means anything in terms of functionality).

Worf, you and John gave me a very good tip. The wires for the knock sensor are very old, and the plastic at the connectors falling apart when I did the last service (injector cleaning), despite I made a continuity test to the wire itself (between the metal area of the wire to the connector, but didn't test the functionality of those sensors), and re-built the connector plastics (the molding plastic). But definitely will give a special look today to the hall sensor.

Thanks guys, I investigate all those and report back.
Best and thanks!
Giuseppe

John Speake

Certainly at 30k miles, the MAF should be fine if it was well calibrated.

Sounds like knock sensors are next on your list !

Mrmerlin

also replace the CPS
the knock sensors,
and the Hall sensor for the cam.

NOTE all of these parts have the same connector material,
and will all fail at the same time, simply fixing connector body isnt the best way to fix these parts as the insulation will also degrade and cause other issues

gsmarrara

Mr merlin and john, i believe those sensors will need to be replaced. Unfortunately i have to import them so the feedback will take a while. Meanwhile the fuel pressure seems to be ok and the engine timing is ok as well. But the knock sensor, for example, lost the plastic shield in some parts and is covered just with a aluminum foil, for sure should under heavy interference.

One question, i read about the bosch tool to read and clean the alarms. I dont think theres a kts 304 around but i have access to a Bosch kts 340 in a Bosch center nearby. Does this units reads the 928 codes? Not sure if this is a obdii only scanner.

Thanks for the help
Gm

victor25

Your in Brazil? What are you using for fuel? Gas or Alcohol?
If your burning Alcohol, you need to adjust for that or your too lean!!