finnystew Posted 23March, 2019 Author Report Share Posted 23March, 2019 Bad news. Misfiring is happening again. But intermediately. Sometime on a cold start it just takes about 5 mins of running to get it to clear up and it'll run perfectly. Other times it just misfires a little but (Drivable). Then today it was misfiring so badly that I drove home after a test drive with several stalls and a huge amount of unburnt fuel coming out the back. Something I've also noticed is that if the engine starts to misfire, I can change the calibration for the AFM to make it run leaner and it sometimes magically comes good! Also in the last couple days it has developed a problem that was there when I first got the car, but seemed to have gone away. This is that after the driving the car for 5-10 minutes it will start shuddering back and forth violently. Particularly on acceleration. It does this until it cant take it and the engine dies. However if shuffle through the gears I can stave off the engine dying (switching back and forth between 3rd and 4th) To update, i've replaced recently: Spark plugs, Leads, injectors seals, filter baskets and hats (which seemed to solve the issue but alas). I also have the injectors a DIY clean and tested the spray which looked perfect. Quote Link to comment Share on other sites More sharing options...
tazzieman Posted 23March, 2019 Report Share Posted 23March, 2019 Are you sure you haven't got a split vacuum hose somewhere? Quote Link to comment Share on other sites More sharing options...
finnystew Posted 23March, 2019 Author Report Share Posted 23March, 2019 2 hours ago, tazzieman said: Are you sure you haven't got a split vacuum hose somewhere? Cant be sure no. Ill look into doing a bubble spray test tomorrow. Is this characteristic of this behaviour? Seems like it could explain the intermittent nature of the problem. (sometimes sealed, sometimes not, sometimes sorta) Thanks Quote Link to comment Share on other sites More sharing options...
944s2cab Posted 23March, 2019 Report Share Posted 23March, 2019 "I will be investigating the idle control valve and a couple sensors mentioned earlier in this thread" How did you get on with the, TPS? have you tried running without it, if the TPS WOT switch (or it's wiring) was shorted it would bring in a different (richer) map, and ultimately I reckon that's what's causing your issues, over fuelling causing fouled plugs, check your (DME) coolant temp sender as well, with these tests it's best if you test at the DME plug, so you test the wiring as well. List of things which effect (over) fuelling Engine temp. AFM, inc. air temp TPS Fuel regulator injectors Have you checked you FQS on the DME? https://www.google.com/search?q=PORSCHE+968+FQS&source=lnms&tbm=isch&sa=X&ved=0ahUKEwis_4y-x5LhAhXCAnIKHWcaAKsQ_AUIDigB&biw=1215&bih=666#imgrc=TIi78SqLe-SnFM: I know how frustrating and demoralising it can be when you have engine issues but you'll get there finnystew 1 Quote Link to comment Share on other sites More sharing options...
tazzieman Posted 23March, 2019 Report Share Posted 23March, 2019 After the vac line checks which you need to do anyway (splits can be hard to diagnose , sometimes wiggling/pushing on each hose can affect the idle by opening up a split). There are some awkward to get at spots. Fuel pressure regulator? What about your ECU? Intermittent problems are often electrical. The soldered joints get brittle after all these years + vibrations. They can be reflowed. Easy to pull and inspect the board for obvious burns etc. Can you borrow an ECU - quick efficient way to test if your is faulty? Bloody annoying all of this , but at the end of the day you will have a fine car that runs as nature intended. finnystew and firstone 1 1 Quote Link to comment Share on other sites More sharing options...
finnystew Posted 24March, 2019 Author Report Share Posted 24March, 2019 15 hours ago, 944s2cab said: "I will be investigating the idle control valve and a couple sensors mentioned earlier in this thread" How did you get on with the, TPS? have you tried running without it, if the TPS WOT switch (or it's wiring) was shorted it would bring in a different (richer) map, and ultimately I reckon that's what's causing your issues, over fuelling causing fouled plugs, check your (DME) coolant temp sender as well, with these tests it's best if you test at the DME plug, so you test the wiring as well. I didnt end up looking at the sensors since my mechanic said those are 'trimming devices' and thus wouldnt be causing the misfiring. However, the TPS diagnostic page on clarks garage seems to fit my issue almost perfectly. Poor idle - particularly a high idle condition Engine cuts out to an idle condition during acceleration Poor power at various RPMs (various throttle positions) Surging idle Misfire Stumble during acceleration So i've got the DME out and my multimeter. Only seem to be reading OL for it all though. Im probably missing something obvious. Quote Link to comment Share on other sites More sharing options...
944s2cab Posted 24March, 2019 Report Share Posted 24March, 2019 19 hours ago, finnystew said: I didnt end up looking at the sensors since my mechanic said those are 'trimming devices' and thus wouldnt be causing the misfiring. However, the TPS diagnostic page on clarks garage seems to fit my issue almost perfectly. Poor idle - particularly a high idle condition Engine cuts out to an idle condition during acceleration Poor power at various RPMs (various throttle positions) Surging idle Misfire Stumble during acceleration So i've got the DME out and my multimeter. Only seem to be reading OL for it all though. Im probably missing something obvious. https://www.manualslib.com/manual/392533/Porsche-944-Volume-5-Electrical.html?page=158#manual Quote Link to comment Share on other sites More sharing options...
finnystew Posted 1April, 2019 Author Report Share Posted 1April, 2019 Did some inspection of the throttle body and TPS. Looks fine but I was getting strange multimeter readings. I didn’t wanna backprod the boot without knowing which wire was which so I just put it all back together to get it off to a local European specialist shop. However during this I noticed some of the pintel caps on the injectors had dropped down and were covering the terminal. One completely fell off again after I pulled the fuel rail a second time. So I’m now thinking this is the misfiring issue once again. Perhaps the seal kits are not the proper once’s after all. Or at least one of the parts isn’t. So I will buy either the rennbay or bosche OEM kit. Thoughts on which? I’ve heard negative things about the Bosch kit and it is remarkably more $$$ https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.au%2Fulk%2Fitm%2F312525787030 http://rennbay.com/944-Fuel-Injector-Seal-Kit.html Quote Link to comment Share on other sites More sharing options...
944s2cab Posted 1April, 2019 Report Share Posted 1April, 2019 I bought these https://www.ebay.com.au/itm/Fuel-Injector-Service-Kit-Ford-Falcon-XE-XF-4-1L-EA-EB-3-9L-ED-EF-EL-XG-XH-4-0L/112410089759?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 the pintel cap went on with a satisfying click, only reservation I've got is that the O ring were quite hard, Are you sure you pressed the caps on far enough? Quote Link to comment Share on other sites More sharing options...
finnystew Posted 2April, 2019 Author Report Share Posted 2April, 2019 @944s2cabThe caps were pressed on with a drill press and a special tool that protects the nozzle. I think it made a click. Done by a retired injection specialist. He says he’s never heard of them coming off so easily without being broken first. And it’s happened to me 4 times at this point! perhaps the o-ring is too wide. Or maybe I need more engine oil on the o ring so it slides out of the cylinder chamber easier? Quote Link to comment Share on other sites More sharing options...
finnystew Posted 18May, 2019 Author Report Share Posted 18May, 2019 So... I have another lead. The fuel pressure is reading 6 bar after the regulator instead of 3. That would explain the; misfiring, unburnt fuel, running rich, shuddering once plugs foul, etc. Ive ordered at replacement from 3 different places in America only to be told days afterward that it isn’t available. Apparently it’s only available for $500+ from Porsche themselves. I assume because they’ve stopped being produced like the dampeners. Im now considering buying an aftermarket one from Lindsey Racing. Or even buying their fuel rail kit with replacement braided fuel lines, adjustable regulator and pressure gauge. My fuel lines have cracks so this might be the go to nullify the fire risk. Does anyone have experience with these LS parts? Know of any better alternatives? Quote Link to comment Share on other sites More sharing options...
Zelrik911 Posted 18May, 2019 Report Share Posted 18May, 2019 Just read through your thread. I havent ever had a 944 but I had a similar problem on my Mercedes SL. It had high fuel pressure and this was traced to the return fuel line into the tank which was blocked by rust in the tank. That caused flooding in the cylinders & rich running. You could test for this by undoing the return line, after the FPR, and blowing air back into the tank. Make sure you take the petrol cap off & listen for 'gurgling' There should be no restriction for return fuel. Otherwise it maybe a bad FPR. finnystew 1 Quote Link to comment Share on other sites More sharing options...
Redracn Posted 18May, 2019 Report Share Posted 18May, 2019 The FPR regulates the pressure going to it not after it. So if there is 6 bar after the FPR then you have a restriction in the return. Return pressure should never be more than half the regulated pressure. finnystew 1 Quote Link to comment Share on other sites More sharing options...
Rob Posted 19May, 2019 Report Share Posted 19May, 2019 If you decide you want to try another FPR, I have 2x 3bar ones from 944Ts that I upgraded to 4bar. One is from an '86, the other from a '90. Free to you if you're interested... finnystew 1 Quote Link to comment Share on other sites More sharing options...
finnystew Posted 21May, 2019 Author Report Share Posted 21May, 2019 On 20/05/2019 at 09:43, Rob said: If you decide you want to try another FPR, I have 2x 3bar ones from 944Ts that I upgraded to 4bar. One is from an '86, the other from a '90. Free to you if you're interested... How did you upgrade them? I assumed they were a non serviceable part. is there any benefit in running it at 4 bar without forced intake? Or could I reverse the mod if not? Im very interested considering my luck so far... Quote Link to comment Share on other sites More sharing options...
Rob Posted 21May, 2019 Report Share Posted 21May, 2019 Hey Finny Maybe I wasn't clear enough. The FPRs I have are 3bar ones, because I replaced them with 4 bar ones when I ungraded my 944Ts boost. 0 280 160 286 (has screw-on fuel line) From '90 944T 0 280 160 227 (has barb and clamp connection for fuel line) This is from '86 944T Check if yours has either number and you can have one or both... finnystew 1 Quote Link to comment Share on other sites More sharing options...
finnystew Posted 22May, 2019 Author Report Share Posted 22May, 2019 15 hours ago, Rob said: Hey Finny Maybe I wasn't clear enough. The FPRs I have are 3bar ones, because I replaced them with 4 bar ones when I ungraded my 944Ts boost. 0 280 160 286 (has screw-on fuel line) From '90 944T 0 280 160 227 (has barb and clamp connection for fuel line) This is from '86 944T Check if yours has either number and you can have one or both... Ah I see. Both of those should fit perfectly given which fuel line I’m running (braided or rubber). Thankyou! I’ll pm you Quote Link to comment Share on other sites More sharing options...
finnystew Posted 22May, 2019 Author Report Share Posted 22May, 2019 On 18/05/2019 at 18:51, Zelrik911 said: You could test for this by undoing the return line, after the FPR, and blowing air back into the tank. Make sure you take the petrol cap off & listen for 'gurgling' There should be no restriction for return fuel. Otherwise it maybe a bad FPR. Checked for blockage on the return. All good on that front Quote Link to comment Share on other sites More sharing options...
finnystew Posted 6June, 2019 Author Report Share Posted 6June, 2019 Update New FPR (courtesy of Rob) has lowered the fuel pressure to the 3 bar spec. I have replaced the injector pintle caps with rennline re-seal kit ones. They are slightly shorter than the blue ford ones i had fitted before. These ford ones would come off and fall into the engine each time I pulled the fuel rail as well as covering the nozzle. It is now running MUCH better (even more so after blowing out some carbon buildup). I suspect the spray was hitting the cap and dripping down. Now its actually idling after being given some gas immediately after cranking. However its still missing in no particular cylinder. It also hesitates before revving and the engine dies after you rev it and quickly get off the throttle. There is no more thick black smoke out the exhaust but the spark plugs are still indicating rich mixture. Although that could just because i'm mostly running it at idle. - I have blown smoke machine fog into the airline to check for vacuum leaks. No obvious leaks. Also wouldn't the engine be lean not rich with a vacuum leak? - I have replaced the intake manifold gasket - Cleaned and gapped plugs Previous work - Checked distributor - New plug leads - New ignition coil - Alternator rebuild - Injectors cleaned DIY with carb cleaner and 12v battery + new filter baskets + spray inspected Suspects: - better vacuum leak test with compressed air - TPS - AFM - valve spring? Quote Link to comment Share on other sites More sharing options...
tazzieman Posted 7June, 2019 Report Share Posted 7June, 2019 What have you done to check the AFM? Quote Link to comment Share on other sites More sharing options...
finnystew Posted 7June, 2019 Author Report Share Posted 7June, 2019 1 hour ago, tazzieman said: What have you done to check the AFM? Just inspected the contact point and checked that the valve is freely opening. Next should probably be the connection to DME Quote Link to comment Share on other sites More sharing options...
tazzieman Posted 7June, 2019 Report Share Posted 7June, 2019 3 minutes ago, finnystew said: Just inspected the contact point and checked that the valve is freely opening. Next should probably be the connection to DME Yep. A good sensor is one thing - but the message has to flow! Is the "brain" OK? Quote Link to comment Share on other sites More sharing options...
finnystew Posted 7June, 2019 Author Report Share Posted 7June, 2019 3 hours ago, tazzieman said: Yep. A good sensor is one thing - but the message has to flow! Is the "brain" OK? The connector has a 2nd rigid boot so looks like might have to strip the wires a tad to test it. As for the brain, I’m not sure I can know tts condition without swapping in another? Quote Link to comment Share on other sites More sharing options...
tazzieman Posted 7June, 2019 Report Share Posted 7June, 2019 2 hours ago, finnystew said: As for the brain, I’m not sure I can know tts condition without swapping in another? I did suggest this. Shouldn't be too hard to find a kind buddy! finnystew 1 Quote Link to comment Share on other sites More sharing options...
finnystew Posted 11June, 2019 Author Report Share Posted 11June, 2019 Did a better vacuum line test with a compressor and this diy jboot adapter found at least one leak at the intake manifold gasket. (Pictured) tightened the bolts but still getting small bubbles. I just replaced this so I’m wondering what I’ve done wrong. I think I can hear some hissing near the firewall too but could just be this. Zelrik911 1 Quote Link to comment Share on other sites More sharing options...
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