Rough Running 88

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
24 Oct 2012 13:27 #11961 by Slave01
Rough Running 88 was created by Slave01
Before I part out my car; any ideas on a rough running engine? Ignition is new, plugs are perfect, idle is smooth. At the start of acceleration and hard acceleration the engine becomes extremely rough. And getting worse. Not driveable anymore.

ECU is 13 years old. Original LH. Problem is about 4 years old and getting worse. Ideas? Opinions? Crude remarks?

Thanks for the help

Please Log in or Create an account to join the conversation.

  • the flying scotsman
  • the flying scotsman's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
More
24 Oct 2012 13:38 #11962 by the flying scotsman
Replied by the flying scotsman on topic Rough Running 88
fuel, fuel filter, fuel injectors?

I'd run a can or 3 of cleaner through the fuel system.......if it runs better you know where to start.

Please Log in or Create an account to join the conversation.

More
24 Oct 2012 13:57 #11963 by srshaw3
Replied by srshaw3 on topic Rough Running 88
MAF issue perhaps, you could have it rebuilt. I had mine done, I think it was $150. As I recall, if you disconnect the wiring to the MAF, and it makes little or now difference, then it is "a" problem, even if not "the" problem.
When you say ignition is new, I am not sure what that means. spark plug wires? coil wires? coils? coil amplifiers?
Any such issue should wear on the plugs at some point.

Please Log in or Create an account to join the conversation.

More
24 Oct 2012 13:59 #11964 by xstepson
Replied by xstepson on topic Rough Running 88
Rough running could be one or more of your cylinders not firing. Can you narrow it down to which cylinders? After you do that, you can find what is preventing those cylinders from firing, ie fuel issues or ignition issues. And as Stan says above, it could be the MAF needing a new connection or needing to be rebuilt.

Please Log in or Create an account to join the conversation.

More
24 Oct 2012 16:00 #11967 by Kiln_Red
Replied by Kiln_Red on topic Rough Running 88
Spark plugs reveal a lot on rough running cars. I'd pull them all to check their condition. Take photos of them and post it here. Coordinate your pictures so that we all will see your plugs in chronological order, from #1 cylinder to #8 cylinder.

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
25 Oct 2012 08:42 #11990 by Slave01
Replied by Slave01 on topic Rough Running 88
First of all, thank all of you for your response to this problem. Outstanding!

MAF disconnect= engine doesn't run, connector looks great

Ignition System= everything replaced to include;coils, wires, caps and rotors, plugs

Spark plugs= all look great

Coil amps= connectors look fine but will swap to see what happens

Fuel Filter & pump= replaced 2 years ago. Will do a fuel pressure check

Injectors= never been out.

Did do a diagnostic with DT999 software. Discovered; Temp II sensor fault, Hall sensor fault, O2 Lambda sensor fault. Car ran with these albeit with vibration at initial acceleration and then again under hard acceleration and above 90 mph. Vibration at speed is felt in steering wheel and console.

Vibration is now continuous, increasing with acceleration.

Thanks for the help!

Please Log in or Create an account to join the conversation.

  • the flying scotsman
  • the flying scotsman's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
More
25 Oct 2012 10:47 #11993 by the flying scotsman
Replied by the flying scotsman on topic Rough Running 88
Does the engine move from side to side when the throttle is blipped? if not, the motor mounts may be shot which has the engine rest on the crossmember and transmit all sorts of unwanted vibes.

Strg wheel vibration are perhaps strg components, wheel brgs and/or brake rotors.

Please Log in or Create an account to join the conversation.

More
25 Oct 2012 14:29 #12001 by xstepson
Replied by xstepson on topic Rough Running 88
Okay,
1)Let's rule out the MAF for now.
2) I'll assume that your distributor cap is seated properly and the screws holding it are tight. Please, please, please check your plug wires. Make sure they go to the proper cylinder. For whatever reason, when I have replaced plug wires, I seem to want to cross #5 and #6 ...or #6 and #7. I dunno why, but the car runs much better when the plug wires go to the right place.:)
3) Coil amps. I suppose you are talking about the secondary ignition amps in the front under the plastic cover? If one was bad, the car would run on only 4 cylinders. You would need to know what 4 cylinders it was running on so when you swapped the amps, you could check to see if it was running on the other 4. But that is possible.
4) If you have insuffiecient fuel pressure, that could cause the symptoms you describe. We'll have to wait for your pressure test to let us know if this is, in fact, part of the problem.
5)The injectors probably do need to be cleaned. They could be gummed up enough that the car will idle but starve for fuel beyond that.
6)Temp 2 sensor can cause all kinds of funky running issues. It communicates with both the LH and EZK, is easy to replace and relatively cheap. Replace it. The Hall sensor fault will retard timing and reduce power, but beyond that, I don't think it will cause the symptoms you describe. The O2 sensor can cause some crazy running issues also. You can unplug the O2 sensor and disconnect your battery for a short time to reset the computers. The computers will reset and look for the O2. When it doesn't find one, it will increase the fuel to the cylinders by a certain amount, but the car will run fine with that additional amount.

And...check your grounds for the injection harness at the back of the engine on either side of the "V" and your coil grounds.

Please Log in or Create an account to join the conversation.

More
25 Oct 2012 20:33 #12015 by Kiln_Red
Replied by Kiln_Red on topic Rough Running 88
Just to add to John's suggestions.. Get a vacuum gauge and verify that you have a good vacuum.

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
27 Oct 2012 14:55 #12040 by Slave01
Replied by Slave01 on topic Rough Running 88
Great stuff!

Plug wires to plug: did it twice with supervision. Correct.

Replaced motor mounts: same symptoms

New O2 sensor enroute.

Problem became what it is now after running the diagnostic program. Car went from a little rough to un-driveable.

EZK replaced with unknown quality EZK (used or refurbished?) don't know which. That was 2001 Vertex Miami. Been working OK for 12 years. Thinking about having it looked at along with LH.

Will check grounds.

Did vacuum check. Surprisingly holds quite well.

Firm user of Techron, and with storage.

Heading for FL for winter. May not get back to car until spring. Thank you all for your help. Will advise.

Please Log in or Create an account to join the conversation.

More
27 Oct 2012 15:37 #12041 by Kiln_Red
Replied by Kiln_Red on topic Rough Running 88
Something else to consider.. Check your temp II sensor and its connection. The MAF and temp II plugs can be common fault points. It's good that you verified that the MAF plug is in good condition.

Please Log in or Create an account to join the conversation.

More
27 Oct 2012 19:19 #12042 by pcar928fan
Replied by pcar928fan on topic Rough Running 88

Heading for FL for winter. May not get back to car until spring. Thank you all for your help. Will advise.


You should have one waiting for you in FL! That would be a GREAT place to drive a 928 in the winter time!!!! Its not like they are all that expensive either! Just gotta find the right one! Some great Regional Reps in FL too!!!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
28 Oct 2012 06:50 #12051 by Slave01
Replied by Slave01 on topic Rough Running 88
Got that right James!

And nice job on those water bottles. Use the all the time.

Thanks!

Please Log in or Create an account to join the conversation.

  • the flying scotsman
  • the flying scotsman's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
More
28 Oct 2012 08:50 #12052 by the flying scotsman
Replied by the flying scotsman on topic Rough Running 88

Problem became what it is now after running the diagnostic program. Car went from a little rough to un-driveable.

EZK replaced with unknown quality EZK (used or refurbished?) don't know which. That was 2001 Vertex Miami. Been working OK for 12 years. Thinking about having it looked at along with LH.


The DT 999 communicates directly with epus one at a time. It is a reader and does not alter the programming although saying that Ive found the epus struggle to maintain integrity when the engine is running and Theos diag system being operated.

It sounds as if the LH is struggling and the easiest test is to remove it and install in a well running car to see if the symptoms travel.......dont do the other way as perhaps the issue with your car corrupts a perfectly good LH.

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
29 Oct 2012 03:08 #12088 by Slave01
Replied by Slave01 on topic Rough Running 88
The LH struggle during diagnosis was expected and confirmed.

Will trying my LH in another car cause that car any trouble? That I can find one is another question.

Thanks Malcolm

Please Log in or Create an account to join the conversation.

More
30 Oct 2012 10:47 #12139 by xstepson
Replied by xstepson on topic Rough Running 88
No, it won't cause the car any trouble. However, if you plug a known good LH into YOUR car could cause the known good LH trouble.

Did you unplug your O2 sensor, reset, and try starting the car?

Did you replace the Temp 2 sensor yet?

Please Log in or Create an account to join the conversation.

  • the flying scotsman
  • the flying scotsman's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
More
30 Oct 2012 12:28 #12142 by the flying scotsman
Replied by the flying scotsman on topic Rough Running 88
It shall cause the other car trouble if your LH is bad.

What we are suggesting is you do not want to put a known good LH into your car where other factors are perhaps corrupting the EPU.

Please Log in or Create an account to join the conversation.

More
30 Oct 2012 16:35 #12150 by wallyp
Replied by wallyp on topic Rough Running 88
Some "back to basics" comments:

Secondary ignition faults (plug wires, plugs, coils - everything from the primary connection at the coils thru the plugs) tend to get worse as combustion chamber pressures increase. This often means that the problems are worse at near the max torque RPMs with full throttle, less noticeable at light throttle openings.

Injection problems can vary. If one or more injectors are partially plugged, the misfire will be worse at full throttle. If one or more are fully plugged or non-functional, the misfire will be very noticeable at idle, and less noticeable at high engine RPMs with light throttle openings.

The S4 cars have two almost-independent ignition systems. If one system fails (two cylinders on each side of the engine) the roughness will be very noticeable at lower engine RPMs and heavy throttle opening, almost not noticeable at high RPMs and light throttle openings.

The electronic/electrical side of the injection is often an off-or-on deal. If an injector connection shorts out, it kills the entire system. If an injector connector opens, only that injector is dead, and it is usually dead at all speeds - not throttle or speed sensitive.

Mixture problems can be caused by vacuum leaks ("false air" - that is, air that is not measured by the MAF); or by sensor problems (Temp II being most common).

If the Temp II sensors (there are two in the sensor - one for injection, one for ignition) fail, the result depends upon which side fails and how it fails. If the LH side fails open, the fuel/air ratio will be very rich, with poor or no running when the engine gets warm, and very, very hard starting when warm. If the LH side fails by shorting, the engine will run very poorly when cold, and will be hard to start cold. If the ignition side fails, there will be a slight loss in power, but much less effect than if the LH side fails.

Oxygen sensor failure can seriously affect running, but if you just unplug the sensor (the connector is the black wire that runs across the floor at the bottom of the Central Electric Panel), the car should go to "open loop", and should run pretty well.

There are, of course, mechanical problems that can affect running. You might need to pull the belt covers and check the camshaft timing - that is, make sure that the crank and both cams are on the timing marks. A compression test will usually let you know if there is a problem with cam timing.

Wally Plumley
928 Specialists
www.928gt.com

Please Log in or Create an account to join the conversation.

More
30 Oct 2012 18:41 #12154 by martinss
Replied by martinss on topic Rough Running 88

Some "back to basics" comments:

Secondary ignition faults (plug wires, plugs, coils - everything from the primary connection at the coils thru the plugs) ....


That is a very useful summary Wally. Perhaps it could be in the Tips section for general use. I will certainly bookmark it for myself, altho I hope I never need it...

Please Log in or Create an account to join the conversation.

More
30 Oct 2012 18:48 #12157 by Kiln_Red
Replied by Kiln_Red on topic Rough Running 88
Martin, I have added tags to this discussion so that it can be accessed easily through search. I will try to do this more often with tech threads. Perhaps the moderators could assist in doing this.

Please Log in or Create an account to join the conversation.

More
30 Oct 2012 21:17 #12189 by mm928
Replied by mm928 on topic Rough Running 88
Be glad to Austin, that is a new one for me. I will try to keep an eye out for these kinds of opportunities. The better the search, the quicker someone is helped.

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

Please Log in or Create an account to join the conversation.

More
30 Oct 2012 23:46 #12199 by 928mac
Replied by 928mac on topic Rough Running 88
+1

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
01 Nov 2012 07:24 #12228 by Slave01
Replied by Slave01 on topic Rough Running 88
For sure will not replace LH for the above reasons.

I resistance checked Temp II sensor and found it to be OK. It is original equipment and may be replaced after the new O2 sensor goes in.

Has anyone heard of harmonic balancers having issues? I heard, don't recall where, that the balancer hub (?) can slip, moving timing marks. Nearly rotated the car on its stands trying to break the crankshaft nut loose. Dr. Scholls Wart Remover was used to freeze shaft threads. Nut broke free but would that harm the balancer?

I think I've asked this question: Are there dynamic balancers on the crank? Don't think so but it feels that way. Stuck dynamic balancer that is.

Timing gears and belts were changed moving the onset of these vibrations by about 500-700 rpms sooner. Will be heading back here after sensors.

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
01 Nov 2012 07:34 #12229 by Slave01
Replied by Slave01 on topic Rough Running 88
One more thing; after the timing belt procedure, the flywheel occasionally makes contact with the starter gear after it disengages from the flywheel. Just a "ching". Nothing more.

Crankshaft nut was pretty tight. 1" drive breaker bar with a 5' pipe on that. Dr Scholls too. Never been up at 290 ft/lbs. That sound right to anyone?

Please Log in or Create an account to join the conversation.

More
01 Nov 2012 07:52 #12230 by Kiln_Red
Replied by Kiln_Red on topic Rough Running 88
The crankshaft bolt is supposed to be torqued to 210 ft/lbs. I prefer to use an impact to remove it. My old IR-231 impact gun turned up all the way has never failed me yet. :D

Your temp II sensor may check out fine but sometimes the concern is with the plug itself. You want to make sure the wires aren't touching and that it is making a good contact.

I am not sure I understand the situation with the flywheel. Unless your starter is worn out and causing your starter pinion to disengage too slowly, then I don't see how it could contact your ring gear after the car is running. :eek:

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
01 Nov 2012 17:53 #12243 by Slave01
Replied by Slave01 on topic Rough Running 88
Kiln,

Thanks for your input.

The flywheel connecting with the starter drive; would, no, I did flex the flywheel with the flywheel tool when breaking the crankshaft bolt free. Would that bit of bend in the flywheel create a vibration like I have?

Back to the amount of force, and technique, required to remove the crankshaft bolt; ever have that in your or anyones experience? I'm just curious about that amount of pressure to break it free.

Bless James Morrison for recommending another 928 in FL. My wife just ordered a flamethrower.

Cheers!

Please Log in or Create an account to join the conversation.

More
01 Nov 2012 19:31 #12244 by wallyp
Replied by wallyp on topic Rough Running 88
I have cleanly sheared a Craftsman 1/2" extension trying to remove the bolt. Got 3/4" pull handle and extensions, no more problem.

Wally Plumley
928 Specialists
www.928gt.com

Please Log in or Create an account to join the conversation.

More
01 Nov 2012 23:58 #12247 by xstepson
Replied by xstepson on topic Rough Running 88
I have used a 3/4" drive breaker bar with a 5' pipe handle to break one loose once. It was a tight mofo for a minute. IIRC, it's a real bad thing to have your crank bolt go spinning off while going down the highway.

Please Log in or Create an account to join the conversation.

More
02 Nov 2012 07:53 #12252 by wallyp
Replied by wallyp on topic Rough Running 88
There have been a couple of reported cases of the crank bolt coming loose - damage can be moderate to severe.

Wally Plumley
928 Specialists
www.928gt.com

Please Log in or Create an account to join the conversation.

  • Slave01
  • Slave01's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
More
29 Jul 2014 13:34 #17422 by Slave01
Replied by Slave01 on topic Rough Running 88
To all who helped: Thank you if I've not already done that. Torque Tube was the problem. All good now.

Please Log in or Create an account to join the conversation.

Moderators: Rich928mm928billvvOC

Don't have an account yet? Register Now!