remove the o2 sensor and see if it'll rev
CK5
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Revived ‘91 TBI running poorly
- Thread starter 76k5blazerr
- Start date
Would unplugging it accomplish the same thing?
not if the point was to see if the Cat is all clogged up?
Yeah we want to use the O2 bung as a temporary tail pipe
on my k5... small chance the cat is boogered. it just got a new muffler, and i no longer want to drill holes in the pipes for diagnostic purposes. if I need to second guess the cat soon, i will be pulling the o2 sensor (when its cold)
Yes you can measure back pressure there. Iirc the spec is 2.5psi at 2500rpm.
Just based off of how it sounds when it does run, I don’t think the cat is plugged. It also has an aftermarket dual exhaust so not the original pipe anymore either. 90% sure the problem is a crap fuel pump based on how wheezy it sounded and the symptoms from the engine. I have the tank out again now waiting for my new pump to come Friday.
Oh yeah. 10 gallons. Filter is new, tank is new. Everything is clean. I guess maybe the filter could be faulty too but it’s a cheap Amazon pump/sending unit combo and that’s why I suspect it.
pulled the tank without pressure testing? not with MY back thank you very much
Guess we’ll find out whose hunch is correct in a couple days. Since I hadn’t put the bumper or anything back on yet I had it out in 15 mins
Well, neither of us were right... Turns out the fuel supply line had a major clog in it between the tank and filter. I thought I had it cleaned out well the first time I dropped the tank but I guess a chunk of something dislodged once gas was flowing. Got it blown out good and reinstalled the tank, the pump sounds normal now and it revs as it should. Still not idling right once it gets warmed up. Cold starts are ok. A little stumbly right off the bat but within 10 seconds it sounds good on a normal high idle. Once it warms up and the idle drops is when it really starts stumbling. I have replaced several rotten vacuum hoses already that seemingly had no effect on it. I have sprayed brake clean around the TB and intake gaskets looking for vacuum leaks and found no obvious ones.
Yesterday I thought maybe the thermostat was stuck open and it wasn't warming up all the way, so I changed the stat and topped off the coolant. Also threw on a new rad cap. Now I guess since the coolant is full and pressurizing like it should, a small coolant leak has surfaced from the water jacket between 1 and 3 on the intake. Great! It is possible the old stat was ok because the temp gauge still doesn't get higher than about 140, so I think the sender is bad now.
One thing I did yesterday was unplug the IAC while it was running and it immidieatly jumped to a higher more normal sounding idle and didn't stumble as bad. I don't know if this was because the higher idle was covering it up or if it was actually running better. Maybe it is bad.
I know i still probably need to replace the o2 sensor and make sure the cat isn't plugged. What else might could be causing this rough idle when warm?
Yesterday I thought maybe the thermostat was stuck open and it wasn't warming up all the way, so I changed the stat and topped off the coolant. Also threw on a new rad cap. Now I guess since the coolant is full and pressurizing like it should, a small coolant leak has surfaced from the water jacket between 1 and 3 on the intake. Great! It is possible the old stat was ok because the temp gauge still doesn't get higher than about 140, so I think the sender is bad now.
One thing I did yesterday was unplug the IAC while it was running and it immidieatly jumped to a higher more normal sounding idle and didn't stumble as bad. I don't know if this was because the higher idle was covering it up or if it was actually running better. Maybe it is bad.
I know i still probably need to replace the o2 sensor and make sure the cat isn't plugged. What else might could be causing this rough idle when warm?
What's the injector spray pattern look like? It wouldnt hurt to ensure it looks decent.
I had a ton of black crud in the filter on the tank side in mine. No idea what it was, it was a new tank. Perhaps material from a failed pump. Luckily it didn't affect operation, just happened to pop the line off and see it pour out with the leftover fuel.
I had a ton of black crud in the filter on the tank side in mine. No idea what it was, it was a new tank. Perhaps material from a failed pump. Luckily it didn't affect operation, just happened to pop the line off and see it pour out with the leftover fuel.
Since there was debris before the filter, did you get a new filter installed?
