Unleaded or leaded

[mitsy]

Hi folks how can you tell if your car should be on lead substitute or unleaded as my car is running rough as a badgers arse

[Danglerb]

Cars about 10 years older than a 928 might have needed lead, but not any 928.

Rough idle or rough under throttle?

[dr bob]

If it's a US car with catalysts and an oxy sensor, leaded fuel will quickly trash both.

[mitsy]

Its rough on idle and wont rev past 3000 without a struggle the car does have quite a loud hiss even with the air intake buttoned up the reason i asked about leaded fuel it has a red fuel cap not green for unleaded

[MPDano]

Originally Posted by mitsy

Its rough on idle and wont rev past 3000 without a struggle the car does have quite a loud hiss even with the air intake buttoned up the reason i asked about leaded fuel it has a red fuel cap not green for unleaded

This is the exact hiss I was asking everyone about last year. I climbed under the car and it sounded like it was coming from the Torque Converter area.

Could also be a big Vac leak on your car though. How is your timing? A/F Ratio? Are you CIS?

[lfausty]

82us never reved past 3000 thought it was all it had, nothing nothing i did changed it. compensated some idle increase lesson the roughness so it was happy idling and driving prob to blow past some hiss too leaks can be as minor as doors/heat. hiss hiss hiss already.

a big hiss was under the intake pass side way WAY down theres a diverter with screen(black clogged not good) in it , the clamped short rubber hose was broken, the tube continues down runs along side the cat, theres a connection there before it goes into cat too check valve? there. I didnt have cvalve was red rubber garden hose connecting them .

the wp/tb job kicked the 3000 out of the ball park. the valves and lifters seat and operate nicely, changed the rough struggle. cam seals,oil seal anything related doing wp/tb check into. Its not all its got you will get there, have you done water pump timing belt yet?

did u already do all new vac line routing? more major vac leaks
fuel lines? run techron bottle of finj cleaner into gas tank
each of those inj have screens in them and pintles on the ends maybe sticky wont spray correctly techron helpful?

Cleaning inj - can send them out they rebuild and pressure test so all working good 100bucks (which hunter co)......
while there out can purchase finj harness kit cut off each one at a time (crimp or solder option to purchase) and will fix the brittle connection to each inj. A SAFETY MUST , Fuel=fire
get noid like (disc, size of a silver dollar, 5bucks) insert into each inj harness turning car on and off each inj make sure each lights. All reassemble make sure each one clicks too

did you clean fuse panel fuses/prongs that hold em?
relays them selves and where there plugging into.

QUICKIEST WAY TO GET IT ON THE ROAD SAFELY AND KEEP WORKING ON IT FROM THERE TOO
PAMELA WILL BE SOOO HAPPY!!!!! FOR ALL YOUR HARD WORK.

[mitsy]

Done wp tb mm [bugger of a job give me the tb anyday] new vac hoses,spider removed,replaced with new gaskits wur cleaned cold start replaced fuses and panel all done,timing done,a/f only done by ear ill check diverter valve and how do i tell if its cis

[dr bob]

Originally Posted by mitsy

Its rough on idle and wont rev past 3000 without a struggle the car does have quite a loud hiss even with the air intake buttoned up the reason i asked about leaded fuel it has a red fuel cap not green for unleaded

I think all 928's start out with red fuel caps.

The variations ROW-vs-US-vs-other specialty markets include different coding plugs for the brains, giving more or less advance and fuel, reading oxy sensor or not, and there's a low-octane jumper that retards the timing some for poor fuel quality when installed.

If you have a US car, forget about using leaded fuel or a lead additive.

Remember that tetraethyl lead was added to motor fuel as an anti-knock agent, and many motors depended on it for valve stem/guide lubrication. Modern unleaded fuels in the US have 'other' ingredients to boost octane now, all of which have lower specific energy than the gasoline they displace in the blend. Adding lead doesn't decrease the amounts of the 'other' ingredients in the leaded fuels today so there's really no advantage for performance. The only purpose for the additives is to allow you to drive your original/unmolested/unrebuilt 1950's Pontiac to the end of its 50,000 mile life without worrying about excessive valve-guide wear. It's almost impossible to buy leaded fuel around here, save soe specialty race fuels and for older airplanes.

----

The oil breather hoses connect to the boot between te MAF and throttle. Any air leaks there mean false air leaking in downstream of the MAF so no fuel is added to make up for the extra air. With the injection controller in closed-loop mode, it reads from the oxy sensor and compensates some. At higher loads (but not necessarily related to RPM's), control changes to open-loop, where the controller looks only at MAF signals; It's in that mode that MAF errors and air leaks mean serious power losses. You can see the oil breather hoses, and get to them with the air cleaner housing removed and the MAF removed. The hoses do get tired.

There's a RL thread worth searching that describes a tester for intake leaks using Home Depot plumbing parts, a natural gas pressure gauge unit used for testing new piping (also from H-D), and a bit of air from your compressor. Roll the engine to 45º before or after top center, add a little air, and it either holds pressure or you'll hear where it's leaking. Roger (928srus) has all the plumbing pieces packaged if you don't want to drive to Home Depot. If your oil system vents are plumbed with original hoses, it's a good idea to renew them anyway. There's an issue with cracking at the plastic oil filler neck too, but that needs the intake and the water bridge removed before you can comfortably replace the filler neck and gasket.

[mitsy]

had a little play about checking vacs should the top hose on the distributor be drawing air mine is not?

[dr bob]

That's "ported vacuum", and increases as velocity and mass through the throttle area increase. Same as higher load on the engine. If you T your gauge into that line, you should see more vacuum at higher RPM's and more throttle, within some limits past half throttle.

And I'm sorry I wasn't careful enough to notice that you are in Scotland rather than the US.

I should also suggest that you start off with common maintenance items if they aren't current. Plugs, ignition wires, distributor caps and rotors top the list.

Also verify that the belt in the distributor is intact if you have the twin-distributor-cap motor. Just pop the forward cap and see if you can turn the rotor any by hand, indicating a failed belt. A failed drive belt will cause four-maybe-five cylinder operation, very rough by any standard. Easy and inexpensive to fix, in the big picture.

[Normy]

Originally Posted by dr bob

That's "ported vacuum", and increases as velocity and mass through the throttle area increase. Same as higher load on the engine. If you T your gauge into that line, you should see more vacuum at higher RPM's and more throttle, within some limits past half throttle.

And I'm sorry I wasn't careful enough to notice that you are in Scotland rather than the US.

I should also suggest that you start off with common maintenance items if they aren't current. Plugs, ignition wires, distributor caps and rotors top the list.

Also verify that the belt in the distributor is intact if you have the twin-distributor-cap motor. Just pop the forward cap and see if you can turn the rotor any by hand, indicating a failed belt. A failed drive belt will cause four-maybe-five cylinder operation, very rough by any standard. Easy and inexpensive to fix, in the big picture.

He doesn't have the twin distributors. It sounds like he has no vacuum advance at the distributor, but I can't believe that this would prevent the engine from revving past 3000 rpm. It sounds like he's got a big vacuum leak somewhere that is most of the problem.

My '85 ran rough for years; turns out it wasn't a single large problem, just lots of little ones that added up. Sound advice to do the plugs, wires, caps and rotors.

N

[mitsy]

sorry forgot to put leads plugs and cap on the done list,could the big seal at the bottom of the spider cause this sort of problem,had another thought the car hasnt been on the road properly for at least 6 years its been running for maybe an hour or so at a time,could it just need a good run,and cheers for all the input its priceless

[lfausty]

does mitsy have cis? or not i didnt think so cis is a whole fuel distribition system in back of eng under intake big heavy disc with many bolts on top of it in a circle
or youd have just intake... and fuel rails inj 16v/32v. maybe someone will post pic of ea.

big seal at the bottom of the spider yeah problem for vac leak

[mitsy]

from your discription lfausty it is cis can it be cleaned or something

[lfausty]

take a pic and post i dont hve cis though familiar ( 78euro parts car does) and thread read. theres talk of peeps going through rebuild very very costly item the part itself i dont think avail. Under each of the bolts there are small (thimble shaped) filters , gunked and varnished gas ? and case itself does split in half (reassembly procedure) and on the bottom it does feeding fuel into system? could be in horrible varnished condition under there. if you have cis this is your fuel system it will need attention.

What did your inj look like varnished? are they clean , equal spray pattern flow coming out of them, did you get rebuild kit for each inj or send them out,

Trying techron bottle first is hopeful may dissolve filter and gunked sprayers. But six yrs setting . Gas tank clean?

[MPDano]

CIS has mechanical fuel injectors, which is your first clue. Is there just a fuel line to the injectors or wires?

[mitsy]

fuel lines on mine leo,reading what lfausty is saying looks like some real fun only good thing is i have two,one on my 78

[MPDano]

Originally Posted by mitsy

fuel lines on mine leo,reading what lfausty is saying looks like some real fun only good thing is i have two,one on my 78

It should look like this then:

[mitsy]

the two engines look the same except for the obvious[show off]mine is minging,so do i pull this fuel distributer apart or get a pro to do it if one exists on this little island of ours

[lfausty]

search threads..... cis fuel distributor too

try 7/15/09 yoni thread engine wont rev over 4500rpm

start a new thread so your not under gasoline topic

ask fuel distrib rebuild or send out
i believe you send your core and they rebuild send back theres thread of some that had rebuild couple things on resealing it and some successfully rebuild some dont

buying one was thousands new ?? rebuild 600 and up ??

diy parts available ? and where to go for procedure to do?

Matbe just a matter of rich/lean mixture and idle and/or related sensors??