Fuel Cut?

[Neil W]

Hello! I bought an 87 a few weeks ago, and have been driving it for about a week. Tonight, halfway through a drive, on the highway, the car stumbled going up a hill. It was like I turned the key off, paused and turned it back on. After that whenever I tried to accelerate, even "normally" or gently, the same would happen. if I left the throttle part way down, it would cut in and out until I let off the throttle. The car is still driveable, but only barely.

I have done some reading on this, and I understand that there is a fuel cut, that may or may not also cut the ignition.

From what I know about NA cars, this sounds like a dirty fuel filter.

Any insight would be great...

The car is completely stock, 141000 kms.

 

[jdub]

Sounds like a boost leak...one of your IC pipes split or came loose at the connector.

 

[forcefedsupra]

^^^^true dat

 

[antman]

Probably a waste, but... I'll third that!

 

[CajunKenny]

He He...I'll fourth it!

Can we get a 5th!?!?!?!?!?

 

[Neil W]

Alright, I'll fifth it. heh heh

Thanks folks, I'll report back.

I guess if there is an air leak after the MAS, the car will have the wrong info for mixture.

If I unplug my MAS, will the car use the O2 sensor? That would be an easy way to confirm... not that looking at the IC hoses is hard.

Neil

 

[jdub]

The 7M doesn't have a MAS, it's an AFM...unplugging it will do the same thing, just worse
It doesn't use the O2 sensor that way.

 

[forcefedsupra]

Mine won't even run without the AFM.

 

[jdub]

Mine does...it's not pretty though

 

[Neil W]

Ok, thanks for the replies, and thanks for the patience.

 

[Poodles]

Up hill = higher load = higher boost pressure = 20 year old pipes can't take it

 

[sneakypete]

From what I know about NA cars, this sounds like a dirty fuel filter.

Dont you have an NA? If so, then you posted in the wrong section and you shouldnt have a problem with a boost leak. You might have unmetered air getting past the AFM.
If you are a turbo, then i will agree with the boost leak

-pete

 

[Neil W]

Sorry if I wasn't clear, it is a turbo.

 

[Orangeracer]

i bought my car and it had that problem. needed a fuel filter. although i replaced the new pump anyway. lol if i were you i would drop a walbro in and a new fuel filter. its a pita.

 

[suprafanatic]

i had the same problem when the coupler poped off my turbo! sounds like boost leak

 

[Neil W]

Thanks for the help. It turns out that when I replaced the exhaust manifold gasket, and repaired all the stripped threads, I did not tighten the hose clamp on the outlet side of the turbo. It's tight now, and the car boosts to ~5-6 psi. Under full throttle on the highway it seems to hesitate a little. Not quite stumble, but the power is not smooth.

From the difference with that hose clamp, I am thinging I am looking for a smaller leak in the induction side, after the turbo. Not too worried, as a litte rich won't hurt.

Or maybe the plugs are all fouled from the week of driving around rich!

 

[jdub]

Do you have any codes?

 

[Neil W]

Nope, but the CEL lights if I forget to connect the AFS (so I think it works)...

Is there a code for a leak in the IC pipes?

 

[jdub]

You mean the AFM?

Some codes do not illuminate the CEL and can have a pretty big impact on how well the car runs. You need to check for codes:
http://www.cygnusx1.net/supra/TechTips/engine_error_codes.aspx

Code 34 is fairly common with a boost leak...not from the leak itself per say, but from the increased volume of charge air (going no where) flowing past the AFM.

 

[Neil W]

OK, I'll do that. Thanks for the tip.