Engine and exhaust help - v8 Miata Forum - Home of the v8 Miata Conversion

Engine and exhaust help

Old 01-24-2016, 07:26 PM
  #1  
V8 Miata Noob
Thread Starter
 
Join Date: Oct 2015
Location: chicago, il
Posts: 10
Thanked 0 Times in 0 Posts
Default Engine and exhaust help

Help, I'm a noob who recently bought a 94 monster w a 331 stroker. This was originally owned by GT420hp. With the weather in Chicago I haven't been able to drive it but I took it out for the first time this weekend for a short drive. When it first starts it doesn't like to idle and will stall but once I was driving it seemed to run fine. There was some strange noises that sounded like they were right under me. Sounded like something loose but it was only when moving and in gear (need to investigate more). When I got back i let it idle so I could look under and see if something was out of sorts. It idled great, then I realized there was smoke getting into the cabin and the cats were cherry read. I shut it off immediately and am fearing the worse. After seeing that color, I'm sure they are fried and plugged now. The previous owner said he was having blow by issues and low compression on one cylinder. Maybe oil got into exhaust? Was thinking a rebuild was in order but not sure if that would fix this issue?
94miataM is offline  
Old 01-24-2016, 08:32 PM
  #2  
V8 Miata Noob
 
Join Date: Jan 2016
Location: South Central PA
Posts: 9
Thanks: 0
Thanked 1 Time in 1 Post
Default

Is this a carb or FI set-up? When cats get really hot its because youre running to rich and dumping fuel into the exhaust so the cat is trying to clean up even more gasses. If you have a carb, its pretty normal that it doesnt like cold starts(a lot of FI vehicles dont even like to idle well when cold). The carb could also be jetted improperly (did the car drastically change climates or elevation from the PO?) which could definately cause your cats to get hot. As for oil in the exhaust, that shouldn't cause a cat to get much hotter.

My suggestion, check your fueling and make sure you are aren't restricting intake airflow.

As for your noises under the car, possibly a bad universal joint. You can also listen to the transmission through the shifter with a screwdriver to see if any bearings are bad, the noise in this case would occur with clutch in and out. Having a friend drive the car while you listen is advised.

Keep us updated!

-Jordan
SVTwins is offline  
The Following User Says Thank You to SVTwins For This Useful Post:
94miataM (01-24-2016)
Old 01-24-2016, 08:51 PM
  #3  
V8 Miata Noob
Thread Starter
 
Join Date: Oct 2015
Location: chicago, il
Posts: 10
Thanked 0 Times in 0 Posts
Default

Jordan-

Thanks man, it's a 95 5.0 FI. It was shipped to Chicago when it was in the teens from Arkansas so there would have been a major climate change.
The noise wasn't consistent and popped up when I was going about 25-30+. I'll check the joint since it was intermitten. The transmission was supposedly rebuilt but it ground a bit going into reverse. I'll see what I can find.

Thanks again.
94miataM is offline  
Old 01-24-2016, 09:03 PM
  #4  
V8 Miata Noob
 
Join Date: Jan 2016
Location: South Central PA
Posts: 9
Thanks: 0
Thanked 1 Time in 1 Post
Default

One more thing: To check blowby quickly you can start the engine and remove the oil fill cap, put your hand on the hole, if it pushes your hand outward then you have blowby.

Basically the combustion pressure pushes past the rings into the crankcase and that pressure will push your hand outward. If your hand gets sucked inward thats good, its supposed to.
SVTwins is offline  
Old 01-25-2016, 08:29 AM
  #5  
V8 Miata Participant
 
5.0MX5's Avatar
 
Join Date: Jan 2010
Posts: 261
Thanked 10 Times in 10 Posts
Default

94miata said; was supposedly rebuilt but it ground a bit going into reverse.

That's not that unusual, a lot of us (and Mustang drivers) when needing to hit reverse will go to 4th or 5th, then reverse. No grinding and it's much easier to engage.

On the engine problems, I'd do a compression test first thing. If one or possibly two cylinders (two indicates blown head gasket) have low compression I'd at a minimum pull that head and see what's up. My opinion is the engine had a quality build a few thousand miles ago, the big unknown is what's it been exposed to since then.

Good Luck
Ron
5.0MX5 is offline  
The Following User Says Thank You to 5.0MX5 For This Useful Post:
94miataM (01-25-2016)
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
jonbon88
Ford V8 Discussion
13
02-22-2013 10:45 AM
MiataAndy
V8 Miata Exhaust
4
11-16-2012 10:17 AM
MiataAndy
V8 Miata Safety, Legal, & Emissions
11
07-04-2012 05:47 PM
randy
Wanted to Buy - Parts
10
04-13-2012 07:26 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Rate This Thread
Rate This Thread:
You have already rated this thread Rating: Thread Rating: 0 votes,  average.

Quick Reply: Engine and exhaust help


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.