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Discussion Starter · #1 · (Edited)
Hi all, new owner and first post, hopefully this is a reasonable place to put this.

As a bit of a backstory and even more of a vent, I bought the car (an '89 R32 GTR) about 6-7 months ago now and, after it's arrival in the UK shortly after Christmas, went to pick it up in late February. Driving the car home it ran great for about 100 miles and then, quite suddenly, decided to throw a dashboard disco on the M62. Engine died and I had to rapidly make my way from the outside lane to the hard shoulder with no engine, brakes or power steering :eek:

Fortunately, this turned out to just be a MAF sensor giving up and, true to their word, the importer fixed it for free about a week later (including towing it from my parents house where it'd been taken after the breakdown, honestly great service :thumbsup:). The car then made it back to my parents under its own power and seemingly ran fine for about another 150 miles. However, when I tried to drive make the longer drive from from there to my place (about 145 miles further south), it started to misfire quite heavily under any sort of boost, it almost felt like I was driving over rumble strip if I took it over ~4k rpm - I promptly dropped the rpm, turned round and, being closest, took it back to my parents at granny like speeds.

Diagnosing the problem as likely being faulty coil packs, the importer once again sent me free replacements (again, excellent service) and, after installing them this weekend, I tried for a third time to get it home. The change of coil packs cleared the misfire up nicely; it now revved cleanly, built power strongly and, predictably, ran beautifully for about another 120 miles.

This brings us to few hours ago where, in 30-50mph traffic on the M4, the car started to very slightly lose power. At the time I thought my mind was playing tricks.... soul crushing bank holiday traffic seems to alter your sense of time :D, but in hindsight it started with that very slight power loss. About 5 min later, the dash once again lights up, this time it's the cat overhead light and the power loss is quite severe, coming on and off in spurts. The light itself was only on for about 10 seconds but the power losses kept on going until I found a safe spot to park up and cool down. It's probably important to note that as this was happening, all the other pressure/temperature gauges looked normal.

Upon restarting the car the exhaust was noticeably louder than when I'd set off and instead of a nice smooth idle there there was a slight vibration coming though the car and what I can best describe as an irregular exhaust beat (more misfire?). I thought about driving carefully down the quieter backroads into Cardiff but the car just didn't feel right so after about 1/2 a mile I gave up and had a friend pick me up on his flatbed (always good to have friends with nice toys :D).

So, my question for you if you've survived my block of text so far is what do you think?

My thoughts are the following:

Firstly, I'll wait until I cool down. I don't really want to work on it in the mood that it's put me in.

Secondly, I'll try and get the cat off. If it's genuinely melted I guess the exhaust restrictions will form a big part of the power loss, but that then leaves the causes. From my understanding it'll either have been caused by excess fuel in the cat (misfires/over fueling) or very hot exhaust gasses (one or more cylinders running lean?). So I think I'll recheck the coils (for signs of failure) and try and get a read on the spark plugs for rich/lean/mechanical failure etc.

From there, does anything else obviously stand out?

I suppose the increased exhaust volume could also mean failed gaskets/cracked manifolds (it's quite loud in the bay) so I'll look out for those. There's also possibly the chance that a plug's come loose (although I don't hear the tick that I'd associate with that and I deliberately left them alone when I did the coils since from what I was told they'd only recently been done).

For additional information, it's an 1989 model r32 gtr. Engine is, as far as I can tell, stock. Turbos look stock. The boost restrictor seems to be in the yellow banded pipe - so again hopefully the boost is stock boost. The exhaust itself is also an original Nissan example. Basically, bar some interior wear and tear (and frequent breakdowns :p) it seems to be a nice stock example.

Finally, I'd just like to make it clear I don't blame the importer for this at all, I knew what I was getting into when I bought an old japanese car (previous was a MR2 turbo of similar vintage and reliability) and so far they've seen me right each time (and thus will be unnamed to protect their good reputation). I just want to be able to either fix it myself if possible - the car's a hobby for me after all - or call up in a few days and give them the information that matters.

Cheers,
Greg.
 

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I would start with basics, re-soldier the MAF's (there are write ups on google), compression check (important) and change spark plugs. It does sound like the cat is clogged up
 

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Discussion Starter · #4 · (Edited)
Ok, I've already noticed something potentially strange. The plugs are NGK R7436-8's, not only are they fairly expensive racing iridiums (£25-30 a plug), but at heat range 8 they strike me as being too cold for a stock engine. I'm starting to wonder if they were put in there by mistake or whether this engine once saw some tuning.
 

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Discussion Starter · #6 ·
I would start with the plugs and gap them to 0.8 a missfire would send raw fuel from 1 cylinder to the cat where it would ignite and cause your temp issue. It would also sound louder and explain the power loss.
I had a quick look again this morning before going to work. My 0.8 feeler gauge is a no-go, they currently seem to be gapped something closer to 0.7mm. They're also older than I though they were supposed to be, the cylinder 5 plug even has what looks like the early stages of rust. I'll order some new ones today, perhaps a set of bcpr7eix's?

Cheers,
Greg.
 

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I had a quick look again this morning before going to work. My 0.8 feeler gauge is a no-go, they currently seem to be gapped something closer to 0.7mm. They're also older than I though they were supposed to be, the cylinder 5 plug even has what looks like the early stages of rust. I'll order some new ones today, perhaps a set of bcpr7eix's?

Cheers,
Greg.
Greg I have the same issue on my R33 GTR. What caused the clogged cat? And was there any engine damage?
 
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