Tbi rough cold starts

[tayto]

I do have an EGR valve still installed. The diaphragm seems to hold pressure as it should with the old finger holding test lol.

At one point I did disconnect the vac lines to it and plugged them off, that made no difference in cold engine operation.

blocking off the vac lines only eliminates the vac lines as a problem. the EGR valve in the '91 passed the diaphragm test too, but it wasn't seating fully all the time.

 

[JPVortex]

blocking off the vac lines only eliminates the vac lines as a problem. the EGR valve in the '91 passed the diaphragm test too, but it wasn't seating fully all the time.

Okay thanks! I may try making a block off plate out of some sheet metal with a gasket under it.

 

[JPVortex]

Just updating yall. Was looking at different TBI cold start videos, my truck almost sounds exactly like this one on cold start. Stumbly with a pop out the exhaust which sounds like a misfire.

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[JPVortex]

Well folks might've found something. Replaced the ECT in 5 minutes, truck ran the same as always.

However, I used the throttle on the tbi to rev the engine under the hood, and thats when I got zapped by what felt like a spark.

My plug wires run right next to the tbi, and I think one of them has ripped rubber somewhere and grounded against the tbi unit, shocking me.

Time to get some new plug wires!

 

[tayto]

open the hood at night or in a dark garage, makes it easy to spot if you have bad wires

 

[JPVortex]

open the hood at night or in a dark garage, makes it easy to spot if you have bad wires

Yeah definitely going to do that tonight, going to get the wires now but am going to check that before touching them.

99% sure it’s the wires though, they look old and worn

 

[tayto]

Yeah definitely going to do that tonight, going to get the wires now but am going to check that before touching them.

99% sure it’s the wires though, they look old and worn

i've also spotted cracked spark plugs this way too

 

[JPVortex]

Well working at Napa is nice lol, new wires and retainers originally $50 for $27!

 

[JPVortex]

Yeah definitely the wires, no night test needed. Just looked at the one next to the tbi unit and its ripped in multiple spots.

 

[JPVortex]

well new wires are in, routing is pretty terrible but its not going to hit the headers or anything hot, so good enough for now. 5 & 7 wires are also not right on top of each other.

Just cold started it again, its still a bit stumbly when cold but am happy to report the popping misfire out of the exhaust is gone now!

The lengths of the wires from NAPA weren't exact, so there's only so much I can do. I matched up the old lengths the best I could and put them in the same spot.

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