Lost My Boost
#1
Lost My Boost
Drove to work yesterday and the car ran fine. On the way home I pulled out to pass someone and the car wouldn't go. It won't rev above 4000 and doesn't even want to go that high. Boost gauge never goes above 0. I was able to drive it home at reduced power. Looked under the hood and everythig looked O.K. but it was hot and I didn't get a chance to work on it last night.
Any ideas where I should start looking when I get home today? I drove the other car so the Miata will be cool enough to work on as soon as I get home.
Thanx.
Any ideas where I should start looking when I get home today? I drove the other car so the Miata will be cool enough to work on as soon as I get home.
Thanx.
#5
+1 on the check your couplers.
Sometimes, it's just a tear near one of the pulleys b/c the pulley can touch the coupler briefly with engine movement. You won't see the tear sometimes, but if you remove the coupler, you'll see a crack that would open under boost. Also, once I had a loose coupler that leak under boost but on quick inspection of the pipes, everything looked like it was still together as nothing was separated.
Sometimes, it's just a tear near one of the pulleys b/c the pulley can touch the coupler briefly with engine movement. You won't see the tear sometimes, but if you remove the coupler, you'll see a crack that would open under boost. Also, once I had a loose coupler that leak under boost but on quick inspection of the pipes, everything looked like it was still together as nothing was separated.
#12
speedracer, Vacuum at idle is 20. The intercooler has not been installed yet. The reason I'm leaning away from it being a coupler is that the AFR doesn't go to full rich like it has any other time I've had coupler problems. I will pull all couplers and piping as soon as I'm sure it's not the cat. I haven't had time to work on it this week. Life happens.
PAT!, I don't think he has or ever had any affiliation with ISP.
PAT!, I don't think he has or ever had any affiliation with ISP.
#13
What other mods do you have? I mentioned a valve, if it is recirc and it has failed it can kill boost without technically being a leak... don't know what would happen to the AF in the case. What are you using to tell that the AF isn't going rich?
Have you checked the wastegate yet? Could have failed in a number of ways.
Have you checked the wastegate yet? Could have failed in a number of ways.
#14
BOV is vented to atmosphere. If the waste gate was stuck closed I would expect to see an overboost condition. If stuck open the revs would not be limited and the engine should act as if normaly asperated.
Narrow band O2 sensor with gauge. It behaved normaly, bouncing between lean and stoic (sp?) while driving. When I've had coupler failures or blow offs in the past it has gone to full rich if the engine kept running. Such as when this happened.
Narrow band O2 sensor with gauge. It behaved normaly, bouncing between lean and stoic (sp?) while driving. When I've had coupler failures or blow offs in the past it has gone to full rich if the engine kept running. Such as when this happened.
#15
Do you have a cat? Could be clogged.
What other mods? Something that could be effecting timing? Something that alters the rev limiter? Something that could affect fuel?
Other than that all I can think of is something physically limiting the amount of air coming into the motor...
Has anyone seen an AFM fail and cause the rev limit issue?
#19
It was the cat! I was going to hollow it out but it had been replaced once with a generic one and was welded on both ends. I took it to a muffler shop and they put in another generic one, runs fine now. Hopefully in the fall, new down pipe, high flow cat and cat back exaust.
Thanx everybody for your comments and suggestions,
Pete
Thanx everybody for your comments and suggestions,
Pete
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09-30-2018 01:09 PM