90 LT5 backfire
03-28-2011, 07:33 PM
#1
Racer
Thread Starter
90 LT5 backfire
The car is a stock 90 ZR1 with <26k. It sat for 2 weeks because of the weather. Today I started it and immediate backfire then died. It starts right up but will die if you don't feather the gas. I know I have a vacuum leak I just don't know where to start. I did a search on LT5 backfire and got a thread from 06 saying the LT5 is prone to backfire and vacuum leaks. Is there a list of probable hoses that leak or come off after a backfire? New to LT5.
Thanks for any help,
Bill
Thanks for any help,
Bill
03-28-2011, 07:46 PM
#2
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Map sensor hose at the rear of the plenum. It most likely came off with the backfire. Has it set any codes? May also want to check the lines just under the Throttle body driver’s side.
Last edited by FASTAZU; 03-28-2011 at 07:53 PM.
03-28-2011, 08:28 PM
#3
Racer
Thread Starter
Thanks for the reply. I haven't really started troubleshooting it . I want to get information before I start. The weather is iffy for tomorrow but there will be several good days after that. My shop and garage are full so I have to work "exposed".
There was smoke/exhaust coming from the windshield edge of the hood. This was right after the BF. By the time I opened the hood there was no trace.
Thanks again.
There was smoke/exhaust coming from the windshield edge of the hood. This was right after the BF. By the time I opened the hood there was no trace.
Thanks again.
03-29-2011, 01:15 AM
#4
Drifting
Member Since: Jun 2007
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Yeah, sounds like it's the MAP sensor hose. Here is a picture to help you locate the hose.
Last edited by bdw18_123; 04-01-2011 at 12:01 AM.
03-29-2011, 05:15 PM
#6
Drifting
03-31-2011, 07:14 PM
#7
Racer
Thread Starter
Thanks to all. Yes the hose was off. It seems a very loose fit and I don't see where there was a clamp. Is this normally a slip fit?
Again every body, Thanks,
Bill
Again every body, Thanks,
Bill
03-31-2011, 07:44 PM
#8
Drifting
It's probably gotten loose from heat/oil deterioration. There are no clamps, which is probably a good thing. When backfire occurs, it's better to blow a vacuum hose off that is accessable, like this one, instead of one under the plenum.
Most, if not all, backfires occur on startup because the key is released from the start position too soon. Hold the key on momentarily after start to eliminate starting backfires and the rersultant MAP hose blow-off.
Most, if not all, backfires occur on startup because the key is released from the start position too soon. Hold the key on momentarily after start to eliminate starting backfires and the rersultant MAP hose blow-off.
