Misfire/stalling issues

[Chris_Guthrie]

Hey guys,

1990 R32 GTS-T sedan with the RB20DET in it.
Mostly stock, has an apexi air filter, ti catback, coilovers and wheels. ~67k miles

Just bought this about a month ago. The past 2 weeks I've been having some issues. On cold start ups, there's a bit of a hanging idle at around 1700rpm. Once it warms up a little it drops to a normal idle. When I drive the car and come to a stop light, the idle hangs for a little while then returns to normal.

On idle I have an intermittent misfire. Cold, hot, doesn't matter. Unrhythmatic.

Go out for a drive and until the engine is warmed up it drives perfectly fine. Hits boost fine, feels strong fir a mostly stock car.

Once warm, under a load especially when hitting boost there's a heavy misfire, feels a lot like spark blowout but it's as if the car is cutting off. Eventually, it gets worse and worse until the engine completely cuts off. First time it happened, it bump started itself before I stopped. Got home fine no issues (about 8m). 2nd time it happened, came to a complete stop, turned the key off, primed the pump, started up fine made it home fine (about 5m).

So, investigation commenced. So far, I started with putting some BG 44K in the fuel. That didn't help at all so I started by replacing the spark plugs with the same NGK BCPR6ES gapped at .8mm. I've installed slpitfire coils and a wiring specialties coil harness. I popped the fuel sender up and checked the tank for rust, very minimal if any. The fuel filter was brand new when I got the car. Cleaned the MAF with MAF cleaner. In the US and run the highest octane available to me - 93. 

I've done a ton of research in the last 2 weeks and sort of narrowed it down to a few things. The problem is I'm having a difficult time finding clear information on how to test these things. The list of things I have left are

1- MAF
2- Ignitor/ ignition control module
3- fuel pump losing pressure when hot (happens at all levels of fuel in the tank)
4- fuel pressure regulator
5- TPS
6- CAS
7- fuel injectors
8- ECU
9- Turbo - maybe blown?

I'm new to RBs, skylines in general. Really been enjoying driving this car when I can. I'm pretty good with most things automotive. Any help much appreciated. Keep in mind I don't know a single other R chassis owner or have access to known good parts to test... and I'm broke so there's that but I'm handy with a multimeter and pretty much everything but soldering.

Thanks guys

[joshuaho96]

39 minutes ago, Chris_Guthrie said:

Hey guys,

1990 R32 GTS-T sedan with the RB20DET in it.
Mostly stock, has an apexi air filter, ti catback, coilovers and wheels. ~67k miles

Just bought this about a month ago. The past 2 weeks I've been having some issues. On cold start ups, there's a bit of a hanging idle at around 1700rpm. Once it warms up a little it drops to a normal idle. When I drive the car and come to a stop light, the idle hangs for a little while then returns to normal.

On idle I have an intermittent misfire. Cold, hot, doesn't matter. Unrhythmatic.

Go out for a drive and until the engine is warmed up it drives perfectly fine. Hits boost fine, feels strong fir a mostly stock car.

Once warm, under a load especially when hitting boost there's a heavy misfire, feels a lot like spark blowout but it's as if the car is cutting off. Eventually, it gets worse and worse until the engine completely cuts off. First time it happened, it bump started itself before I stopped. Got home fine no issues (about 8m). 2nd time it happened, came to a complete stop, turned the key off, primed the pump, started up fine made it home fine (about 5m).

So, investigation commenced. So far, I started with putting some BG 44K in the fuel. That didn't help at all so I started by replacing the spark plugs with the same NGK BCPR6ES gapped at .8mm. I've installed slpitfire coils and a wiring specialties coil harness. I popped the fuel sender up and checked the tank for rust, very minimal if any. The fuel filter was brand new when I got the car. Cleaned the MAF with MAF cleaner. In the US and run the highest octane available to me - 93. 

I've done a ton of research in the last 2 weeks and sort of narrowed it down to a few things. The problem is I'm having a difficult time finding clear information on how to test these things. The list of things I have left are

1- MAF
2- Ignitor/ ignition control module
3- fuel pump losing pressure when hot (happens at all levels of fuel in the tank)
4- fuel pressure regulator
5- TPS
6- CAS
7- fuel injectors
8- ECU
9- Turbo - maybe blown?

I'm new to RBs, skylines in general. Really been enjoying driving this car when I can. I'm pretty good with most things automotive. Any help much appreciated. Keep in mind I don't know a single other R chassis owner or have access to known good parts to test... and I'm broke so there's that but I'm handy with a multimeter and pretty much everything but soldering.

Thanks guys

Multimeter isn't going to be super helpful when a lot of these signals need to be probed dynamically. If you suspect it's a MAF try tapping or jiggling the harness connector while the car is idling to see if it stutters. Also, 1700 RPM cold start idle is super high. You can try ohming the ignitor when cold and then again when hot to see if heat is killing the module for some reason. Fuel pressure requires a tee after the fuel filter to measure with a gauge.

My advice is get a Consult cable and you can monitor basically all the ECU I/O and also do some kind of sanity check of the ECU as well. If Consult logging craps out when the engine misfires then you should probably suspect the ECU. If you see weird TPS behavior, either not smoothly following real throttle position or dropping out then diagnose that further. If RPM doesn't make sense then suspect the CAS. If you want to test the CAS further you really need a timing light.

If you suspect lean-out and not just a dead misfire under boost stop going into boost immediately until you can be confident the fuel system is trustworthy. You can easily kill the engine doing this.

[GTSBoy]

The cold idle problems will be dirty AAC and IACV. Need thorough cleaning with carby cleaner. The cold idle up valve is also electrically heated, so you need to make sure that's working.

The stalling when it gets warm will be the igniter. No ifs or buts.

[Chris_Guthrie]

Thanks guys that gives me at least a place to start tomorrow. I was debating on the consult cable but that solidifies it for me. Ran the ecu diagnostic and got a 55 figured nothing stored should mean okay but would really like to see the inputs when the issue is happening. I'll get that fuel Guage asap and will probably order an igniter but want to give it a check cold and hot to see if there's any difference. I really appreciate the quick replies and experience fellas

[Chris_Guthrie]

Also forgot to mention this but I've also noticed that my speedo doesn't move smoothly like normal and it's only sometimes but it's kind of Skippy, up, down, up a lot, down a little. Not sure if that makes a difference but thought I'd mention it just in case. 

[GTSBoy]

The R32 ECU won't know why it is misfiring.

1 hour ago, Chris_Guthrie said:

Also forgot to mention this but I've also noticed that my speedo doesn't move smoothly like normal and it's only sometimes but it's kind of Skippy, up, down, up a lot, down a little. Not sure if that makes a difference but thought I'd mention it just in case. 

This is likely to be a problem with the speedo drive cable. it could be broken and still driving, but lets go from time to time (which is unlikely, but possible). You could have damage at the plastic connector between it and the input to the speedo head. That's where mine broke. You could have gearbox oil creeping up the drive cable from a failed seal in the speedo drive at the gearbox. This is able to climb all the way up and gunk up the inside of the speedo. I had this too, and had to dismantle everything and very very gingerly clean the speedo out.

[Chris_Guthrie]

It won't know it's misfiring but I'm thinking if I can compare the values of things like tps and maf then at least I can rule them out if they are within range when it's acting up. 

That speedo cable sounds like a bit of a drag. But hey, worth a try to see if I can fix it. Going to focus more on the stalling issue for now and come back to that once that part is sorted. Thank again for all of your help!

[GTSBoy]

3 hours ago, Chris_Guthrie said:

tps and maf then at least I can rule them out if they are within range when it's acting up

They will be (within normal range) and they won't be causing the misfiring.

Edited April 16, 2024 by GTSBoy

[Duncan]

I agree with GTSBoy's earlier post, an increasing missfire when hot is a good description of an issue I've previously had with the ignitor module. I understand these days you can get coil kits which do away with it (noting you have just spend on the loom and coils which is a pain).

[Chris_Guthrie]

21 hours ago, Duncan said:

I agree with GTSBoy's earlier post, an increasing missfire when hot is a good description of an issue I've previously had with the ignitor module. I understand these days you can get coil kits which do away with it (noting you have just spend on the loom and coils which is a pain).

Facts but it's okay I've ordered a new ignitor based on GTSBoy's confidence. In the meantime I did the ole jiggle tap on the maf connector with no change. Seems like the warmer it gets outside the worse the issues get. Hoping it's the ignitor. Also going to pick up some carb cleaner and try to get that iacv cleaned out real good. I'll report back once I've gathered more data. I really appreciate the feedback though guys keep it coming. Trying to learn everything I can about this car want to keep this thing for a long time.

[Chris_Guthrie]

So latest update. I replaced the ignitor with a jspec unit from enjuku. It felt a lot better at first although it is a little bit cooler of a day than it has been. Warming up didn't have as much misfire sputtering as before. Went on a 10m test drive. Felt good, a lot stronger though I was taking it easy on the boost. On the return trip started getting the cutting out at higher rpm again and was getting worse the longer I was driving. Took it easy the rest of the way home. Before turning the car off was getting the normal idle sputtering I was getting before. 

So where I'm at now, entire ignition system has been replaced with upgraded components. Plugs still gapped at .8mm. Removed the fuel cap in case it was building too much reverse pressure I'm the tank, didn't help at all. Now I'm still on the same tank of gas the fuel treatment was in, I'm thinking if I can run that out and then refill with fresh 93 maybe  the treatment is too concentrated in some areas but doesn't explain that it only does it once the car is warm. I'm leaning towards fuel pump or injectors but if the injector was clogging I don't think it would make it shut off like it has but then fire right back up like nothing happened. So my current guess would be the pump. Without a fuel pressure guage no way to test or check it while it's running. 

So that's kind of where I'm at. Need to start testing fuel components and ecu/wiring but I'm at a loss of what's the next logical step and procedure for testing it. 

[Chris_Guthrie]

I do think it's weird I had it for 2 weeks then the issue came up out of nowhere and progressively got worse. I would've imagined changing everything in the ignition system would've resolved any ignition related misfires but still has the high rpm and idle misfires that seem unchanged. I would've thought if it was fuel related it would happen all the time unless it's the pump losing pressure when it gets hot. If it was the ecu I would think it would do it all of the time. 

Something I noticed when I had it all apart was a pretty decent coating of oil in the J pipe coming from the throttle body. The weird thing about that is the pcv that goes to the intake is blocked off. So that has me wondering if the oil is coming from the turbo because that's the only thing that could get oil in there. This thing does sound like it spools like a mofo like I'm a former dsm guy and the only stock turbo I've ever heard spool this loud (to only go up to about 5psi) is on a diesel truck. And the recirculated bov is really loud too I had a TurboXS RFL and this thing is just as loud and being so low on psi seems a little weird. I don't know if any of this is or isn't related but just trying to make sure I'm not leaving any potentially helpful information out. 

[Duncan]

well, to check fuel pressure all you need is a gauge and a 8mm joiner with a gauge port in the inlet fuel line; if it stalls at idle when hot you can open the bonnet and check pressure at that time; the fuel pump is a potential cause for what you are describing but it could also be wiring to the pump getting hot. You haven't mentioned that the factory fuel flow control on the fuel pump earth is removed.

So either way, it is worth running a suitably sized and fused wire from the battery to pin 30 in a new relay in the boot.  Use the ECU trigger wire into the standard fuel relay to pin 86. Earth relay pin 85 and the Fuel Pump negative (nice big wire for the latter too). Run relay pin 86 pin to Fuel Pump +. That will remove multiple possible fuel pump wiring issues in a 30+ year old car

[Chris_Guthrie]

Actually I did the fuel pump rewire 2 days after the issues started. Grinded away the paint and grounded it to the chassis behind the right panel in the trunk. 

[Chris_Guthrie]

It has a separate fused 10ga wire running from the battery to the relay in the trunk. 10ga on the ground also. 

[Chris_Guthrie]

I'll rent a fuel pressure tester soon and report back. 

[joshuaho96]

I would not trust whatever J Replace ignitor you bought personally, just searching them up on Zilvia their parts are basically complete shot in the dark alibaba crap: https://zilvia.net/f/showpost.php?p=6422907&postcount=15

This is a hard lesson to learn with these cars. Almost always these aftermarket parts are a false economy. I bet the power transistors are not able to keep up once they get hot enough which is not helping with your misfires. At least with the RB26 the OEM ignitor + Hitachi coils are so expensive now that it's not even worth it to bother with OEM much of the time, R35 coilpack conversions are the same price initially and then any replacement afterwards ends up cheaper because there is no separate ignitor, if one coil fails you replace that coil only.

If there is oil in the intake and the PCV is not venting to the intake then pull apart the intake and verify the turbo is ok. Do not drive the car if the turbo has shaft play. It will shed metal and debris into the rest of the engine and make things go from bad to worse.

Edited April 21, 2024 by joshuaho96

[Chris_Guthrie]

Well considering I have the exact same problem with that as the original one I don't think that the ignitor is the problem. I would imagine that this being such an uncommon problem the possibility of getting a new ignitor that is bad in the same way as the old one has to be very slim. I'll definitely pull everything apart this weekend and check the turbo out. Got quite a bit of things to check out Saturday like fuel pressure and the pcv so I'll report back once I do that. 

Thanks everyone for all the replies this is all really helpful

 

[Chris_Guthrie]

So I checked the turbo out today. Very minimum play at all just enough for the oil to take up when it's running. I did find an exhaust leak at the manifold. 1 stud all the way in the front is missing and the one all the way in the back is broken off. Front has visible signs of an exhaust leak. I'll fix that soon but that's not my problem still. 

I also found that the nipple coming off the turbo had the hose capped off and a hose ran from the j-pipe by the bov going to the wastegate. I removed that hose and capped that nipple and put the turbo nipple hose back on the wastegate. 

There was a ton of oil residue all through the charge side of the intercooler piping going to the throttle bodg. I'm thinking that's from the pcv. Doesn't seem to be coming from the turbo that was all clean on the pipes side. 

Haven't had a chance to check fuel pressure yet, haven't had time been having to pull a lot of doubles at work. I did pick up some carb cleaner to clean the iacv but wanted to make sure I had a fresh gasket in case the old one rips when I pull it off. 

I'm waiting on a MAF that was supposed to be here today but delayed to Monday. Have a double Monday and Friday and work all of next weekend so going to try to find some time in the middle of the week to try that out. Did about a 10m trip around the block today and towards the end the issues were coming back. Fingers crossed on this MAF but if not just going to throw a fuel pressure gauge in and see where I'm at. 

Did notice today that I can definitely hear the injectors pulsing. Very audible clicking coming from them. Assuming that's normal? Should also mean CAS is functioning somewhat properly. After it warmed up when I started it the intermittent misfires came in again. Did start doing that before it was fully warmed up. 

[Chris_Guthrie]

Any recommendations on a decent replacement manifold that doesnt break the bank or require additional mods for the stock turbo setup? I figure if I'm going to pull the manifold off anyway to fix the studs might as well replace it.