theastronaut Posted August 30, 2014 Report Share Posted August 30, 2014 I've had a problem to develop on my '87 TSi. It is all stock except for a gutted pre-cat, and full 2.5" exhaust from there back. I have a MBC adjusted to 11-12 psi (judging by the stock boost gauge). It ran fine with this combination for around 1500 miles before the problem started. Problem- it runs perfect except it won't tolerate boost under about 3500 rpm. It will idle and drive perfectly at any rpm as long as I stay below 1-2 psi. Over 3500 I can punch it and it bucks once as it builds boost quickly and pulls normally like it should. If I slowly roll into at any rpm it stumbles and sounds just like anti-lag. It feels like it's retarding the timing substantially. It will free-rev in neutral normally as long as I'm smoothly pressing the gas; if I press the gas hard enough to spool the turbo it'll stumble/buck and won't go over about 4500; again just like if it had anti-lag. I've replaced the cap, rotor, vacuum advance can, plug wires, and I bought new injector clips and soldered them on. The injector prongs were cleaned with sandpaper and I applied dielectric grease before plugging the new clips in. The TPS passed a sweep test, no dead spots. I also checked for error codes once it was up to full temp and the light was on steadily; no error codes present. I pulled the distributor out and checked to make sure the vacuum advance/retard assembly wasn't binding. It did have a groove worn in the body where the arm was riding; I smoothed that out with sandpaper, cleaned it, and applied grease. Also smoothed out the arm while it was out so it wouldn't cut a new groove. The ring that the arm attaches to seems to be rotating freely and I can suck on the vacuum line and it advances like it should. I do have another use distributor I can try out but haven't had a chance yet. What do I check next? I really feel like it is overly retarding the timing as it starts to build boost. Even after replacing the vacuum advance can and checking the advance/retard mechanism for free movement, I still don't think that it's retarding properly. It feels like the distributor never retards, and the knock sensor(?) is kicking in and over-retarding the timing- similar to how anti-lag works. It's still getting fuel as this happens; it'll continue to build boost as it's stumbling and it'll pop and blow flames out the exhaust just like anti-lag. I think if it was a fuel problem then it would just lean out, and wouldn't be able to build boost. I'm really at a loss on this one, I've tried everything I know to check but I'm not that familiar with these cars and could be overlooking something. Link to comment Share on other sites More sharing options...
scott87star Posted August 30, 2014 Report Share Posted August 30, 2014 I really feel like it is overly retarding the timing as it starts to build boost. Even after replacing the vacuum advance can and checking the advance/retard mechanism for free movement, I still don't think that it's retarding properly. It feels like the distributor never retards, and the knock sensor(?) is kicking in and over-retarding the timing- similar to how anti-lag works. ?? It's overly retarding timing yet it never retards? Can't do that. The timing advance/retard is totally linear assuming its working properly, I have seen some seriously sticky grease in dizzys sent to me so I would start by taking yours apart and cleaning it really well. Link to comment Share on other sites More sharing options...
TexasQuest Posted August 30, 2014 Report Share Posted August 30, 2014 I'm having similar problems too. Have you checked the maf sensor? Link to comment Share on other sites More sharing options...
theastronaut Posted August 30, 2014 Author Report Share Posted August 30, 2014 It's overly retarding timing yet it never retards? Can't do that. The timing advance/retard is totally linear assuming its working properly, I have seen some seriously sticky grease in dizzys sent to me so I would start by taking yours apart and cleaning it really well. It seems like it has no vacuum retard, so it senses that there is too much advance for boost and it massively pulls timing out. Maybe with the extra advance the knock sensor kicks in? Link to comment Share on other sites More sharing options...
theastronaut Posted August 30, 2014 Author Report Share Posted August 30, 2014 I'm having similar problems too. Have you checked the maf sensor? No, how is it checked? Link to comment Share on other sites More sharing options...
TexasQuest Posted August 30, 2014 Report Share Posted August 30, 2014 There is an air temp sensor built into the maf sensor.There are two pins and you can check the resistance between them. Link to comment Share on other sites More sharing options...
theastronaut Posted August 30, 2014 Author Report Share Posted August 30, 2014 2 ohms at about 80-85 degrees, testing as the service manual instructs. I'll test it again to see if resistance goes down with added heat as it should. Link to comment Share on other sites More sharing options...
TexasQuest Posted August 30, 2014 Report Share Posted August 30, 2014 Yeah start by testing it at room temp. Link to comment Share on other sites More sharing options...
theastronaut Posted August 30, 2014 Author Report Share Posted August 30, 2014 Ok, just took the MBC off and drove home with it limited to 7 psi, made it easier to stay out of boost. I noticed that it's fine with up to 3 psi. It's also breaking up in or out of boost over 4500 rpm, like the timing is erratic. It does seem to be smoother and more responsive since I did the injector clips earlier today. Link to comment Share on other sites More sharing options...
theastronaut Posted August 30, 2014 Author Report Share Posted August 30, 2014 Pick up coil in the distribution has more resistance than it should, and has a burnt spot on the harness coming out of the distributor. Going to swap out the one that's in my '89 to see what it does. Link to comment Share on other sites More sharing options...
theastronaut Posted August 31, 2014 Author Report Share Posted August 31, 2014 Swapped the pick up coil out and cleaned/lubed the advance parts. No change. Link to comment Share on other sites More sharing options...
StarquestRescue Posted August 31, 2014 Report Share Posted August 31, 2014 I was checking out your 55 international resto. My brother drove one for years. a neat old truck. Check the wire coming off your knock sensor to see if it maybe broke off. If it did or other wise failed some how, the system would retard timing 8* just off of idle. The sealant on the back of the sensor will likely be missing, but do not worry about that, it does not seem to effect them. Link to comment Share on other sites More sharing options...
doomviillain Posted August 31, 2014 Report Share Posted August 31, 2014 It will free-rev in neutral normally as long as I'm smoothly pressing the gas; if I press the gas hard enough to spool the turbo it'll stumble/buck and won't go over about 4500; again just like if it had anti-lag. Im having somewhat of the same issue here. I'm still trying to diagnose what the problem is. Rebuilt motor, flow tested & cleaned injectors ( new injector clips on the way), walbro fuel pump, etc etc. and when I start it a few times, it will either idle smoothly, or sometimes it idles like crap. I think it might be my 1g mas since I dropped it? Link to comment Share on other sites More sharing options...
theastronaut Posted September 3, 2014 Author Report Share Posted September 3, 2014 Swapped out the coil for a newer/known good coil. No change. I ordered the parts to rebuild the throttle body so I'll do that and tap it so I can check the fuel pressure. Link to comment Share on other sites More sharing options...
theastronaut Posted September 6, 2014 Author Report Share Posted September 6, 2014 Yesterday it started cutting off completely at zero psi at a certain throttle position. If I pushed the gas a little more it would stutter like its been doing. It also started idling uneven and was pulsing when driving out of boost. It's completely undriveable now. I did check the fuel line at the tank, there's no cone filter since it has an aftermarket pump. Still waiting on a TB rebuild kit so I can rebuild it and tap it to check the fuel pressure. Still seems like an ignition problem with it cutting out completely and stuttering? I guess the injectors could be shutting down though. Link to comment Share on other sites More sharing options...
StarquestRescue Posted September 6, 2014 Report Share Posted September 6, 2014 The secondary kicks in around zero boost. So the injector terminals corrosion, injector clips and injectors them self are suspect. The pulsing at low load and idle point to isc problems or possibility the mas. A bad isc nose switch can cause a complete shut off of the injector at about 1800-2000 rpms. Or even if it is good if the engine idles up to that point when the throttle is closed. There are likely a number of problems here, as the lates complaints are different from your original one. Link to comment Share on other sites More sharing options...
theastronaut Posted September 6, 2014 Author Report Share Posted September 6, 2014 I'm leaning towards two problems as well. I checked the fuel pressure just now. Started out at about 50 psi at idle and drops to about 30 as soon as it boost any. Does the same thing when driving. Vid of the fuel pressure check: Link to comment Share on other sites More sharing options...
theastronaut Posted September 6, 2014 Author Report Share Posted September 6, 2014 It did clear out at run fine over 3500 at full throttle like it used to when the problem first started... also idled smooth and ran fine out of boost while I was out testing the fuel pressure. Link to comment Share on other sites More sharing options...
StarquestRescue Posted September 6, 2014 Report Share Posted September 6, 2014 Well there are your two problems. The base pressure is to high for stock mitsu injectors, and the pump can't keep up under load. Start in the tank by changing the in tank filter. It is a dealer item. You can get it from engine machine as well. Base pressure should be 35-37 for stock injectors, and about 40-45 for aftermarket. Link to comment Share on other sites More sharing options...
theastronaut Posted September 9, 2014 Author Report Share Posted September 9, 2014 In tank strainer was squeaky clean, inside of the tank looked new as well. Will check the other filters as I have time. Link to comment Share on other sites More sharing options...
theastronaut Posted September 11, 2014 Author Report Share Posted September 11, 2014 (edited) Filter in the engine compartment at the frame rail changed, still dropping pressure in boost. Should I change the pump next or the fuel pressure regulator? I have a Walbro and an older but unused new made in USA stock replacement pump. Edit- current pump is unknown aftermarket?. Previous owner cut an access panel to change the pump at some point. Edited September 11, 2014 by theastronaut Link to comment Share on other sites More sharing options...
StarquestRescue Posted September 11, 2014 Report Share Posted September 11, 2014 Try the walbro next. Link to comment Share on other sites More sharing options...
theastronaut Posted September 13, 2014 Author Report Share Posted September 13, 2014 Stuck a used fuel pressure regulator on since I had an extra. Fuel pressure isn't dropping like it was, can't really tell if it's rising with boost since it won't boost more than 1-2 psi. FP is still too high, 50 at idle/driving. I checked and the current pump is an Airtex E8000. Still cutting out in boost, I will swap the secondary injector out next. Link to comment Share on other sites More sharing options...
speed racer Posted September 13, 2014 Report Share Posted September 13, 2014 Had an airtex e8000 fuel pump when first put my car back together.wasnt worth the box it come in.bad outta the box.wouldn;t even pull fuel from the tank muchless enough pressure to run properly.and yes....everything else was new.the pump just sucked so took it back for my $.got a different pump...started up in a couple cranks and has ever since.swap the pump for the walbro one and see if it don't help. Link to comment Share on other sites More sharing options...
StarquestRescue Posted September 13, 2014 Report Share Posted September 13, 2014 Stuck a used fuel pressure regulator on since I had an extra. Fuel pressure isn't dropping like it was, can't really tell if it's rising with boost since it won't boost more than 1-2 psi. FP is still too high, 50 at idle/driving. I checked and the current pump is an Airtex E8000. Still cutting out in boost, I will swap the secondary injector out next.Are these stock regulators? If so does the bottom look they were crushed, pushed in with say a socket. That is an old school mod to increase the base fuel pressure. 50 is to much with oem injectors and no tuning system. It will just go pig rich when you try and boost. Link to comment Share on other sites More sharing options...
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