TBI rebuild

[tsr2185]

Check timing. Set it back to the base of 0*. Clean the IAC valve. There is plenty of things that could cause a bad idle.

Dude I've damn near done everything.
Compression check
Base timing to 0
New IAC, egr, egr solenoid, CTS, dizzy, wires, plugs, IC, all new vac lines, vac test (-22), rebuilt TBI, fuel filter, fuel pressure test (11.5 psi)...

It didnt run when I bought it in dec, until I put the new spectra dizzy in. Been having rough idle since and nothing made a difference.

Got a ac delco ICM coming in to replace my spectra dizzy one (which is only 6 months old).

Playingwithtbi been helping me a ton. But it's hard to tell anything in the data stream (but I'm a NooB)

 

[Manimal]

is it popping in the exhaust or intake? Have you sprayed brake clean or carb cleaner on the intake? Any vacuum leaks? What were the compression numbers?

 

[tsr2185]

is it popping in the exhaust or intake? Have you sprayed brake clean or carb cleaner on the intake? Any vacuum leaks? What were the compression numbers?

I has like a coughing sound at the exhaust (true duals with cherry bombs) I uses a butane torch around everything and didnt detect anything. Compression numbers:

You must be registered for see images attach

 

[Schurkey]

I uses a butane torch around everything and didnt detect anything.

BUTANE? What do you have that has butane, and can deliver a reasonable quantity of gas? Everything I own that's butane has a tiny little flame, and therefore a minuscule fuel delivery.

Propane, maybe. I prefer aerosol carb cleaner.

 

[Schurkey]

Well idle issue still occurs, rebuild made no difference. Other than starting up much faster.....

Rough idle? That's the only problem?

WHAT VEHICLE IS THIS? WHAT ENGINE?

Have you tried a cylinder balance test, to see which cylinder(s) are misfiring?

V-8? Get eight small nails. Blunt the point on a grinding wheel. Put some silicone grease on them, and SLIDE them between the plug wire and the plug boot. With a little care, you will NOT puncture the insulation, but you will feel when the nail slides up to the metal plug wire end at the distributor cap.

You must be registered for see images attach

With the engine at idle, connect a vacuum gauge to manifold vacuum, and ground a test-light or jumper wire. Touch the other end to each nail in turn. Not more than 5 seconds each, with a pause of 5 seconds between each one. Each time you touch a nail with the test light or jumper wire, the vacuum should drop. Each cylinder should drop the vacuum the same amount. Cylinders that DON'T drop the vacuum are dead. Cylinders that don't drop the vacuum as much as the others are weak. Spend your time working on the dead or weak cylinder(s).

Don't forget to remove the nails when you're done. Some of them may arc to the air cleaner. I found this out the hard way...

 

[tsr2185]

Rough idle? That's the only problem?

WHAT VEHICLE IS THIS? WHAT ENGINE?

Have you tried a cylinder balance test, to see which cylinder(s) are misfiring?

V-8? Get eight small nails. Blunt the point on a grinding wheel. Put some silicone grease on them, and SLIDE them between the plug wire and the plug boot. With a little care, you will NOT puncture the insulation, but you will feel when the nail slides up to the metal plug wire end at the distributor cap.

You must be registered for see images attach

With the engine at idle, connect a vacuum gauge to manifold vacuum, and ground a test-light or jumper wire. Touch the other end to each nail in turn. Not more than 5 seconds each, with a pause of 5 seconds between each one. Each time you touch a nail with the test light or jumper wire, the vacuum should drop. Each cylinder should drop the vacuum the same amount. Cylinders that DON'T drop the vacuum are dead. Cylinders that don't drop the vacuum as much as the others are weak. Spend your time working on the dead or weak cylinder(s).

Don't forget to remove the nails when you're done. Some of them may arc to the air cleaner. I found this out the hard way...

91' 350TBI

If i get to the point where I run outta parts cannon ammo I may try that lol. It seems to be coming from the passenger side mostly but sometimes from drivers side too. I thought it may be valves needed adjustment, but it passed the compression test, and drivability is fine on throttle.

BUTANE? What do you have that has butane, and can deliver a reasonable quantity of gas? Everything I own that's butane has a tiny little flame, and therefore a minuscule fuel delivery.

Propane, maybe. I prefer aerosol carb cleaner.

Sorry propane. Yes a propane torch that I used all around the intake and vac lines. Havent used carb or starter fluid yet. I'll try that tomorrow with carb cleaner. Also, with my vac guage reading -22 at the booster port, I assumed I have no vac leaks aswell?

 

[Manimal]

No bounce on the vac guage? And are those dry compression numbers?

 

[tsr2185]

No bounce on the vac guage? And are those dry compression numbers?

Yes dry and engine hot.

I didnt notice vac guage bouncing, but it wasn't on there long. I did notice the map vac bouncing from 17 - 18 on the data log but I chalked it up the the idle bouncing from 625-675 rpm. Manual gauge read ~22 (harbor freight guage)

 

[tsr2185]

Well new ICM and still same issue.

Rough idle? That's the only problem?

WHAT VEHICLE IS THIS? WHAT ENGINE?

Have you tried a cylinder balance test, to see which cylinder(s) are misfiring?

V-8? Get eight small nails. Blunt the point on a grinding wheel. Put some silicone grease on them, and SLIDE them between the plug wire and the plug boot. With a little care, you will NOT puncture the insulation, but you will feel when the nail slides up to the metal plug wire end at the distributor cap.

You must be registered for see images attach

With the engine at idle, connect a vacuum gauge to manifold vacuum, and ground a test-light or jumper wire. Touch the other end to each nail in turn. Not more than 5 seconds each, with a pause of 5 seconds between each one. Each time you touch a nail with the test light or jumper wire, the vacuum should drop. Each cylinder should drop the vacuum the same amount. Cylinders that DON'T drop the vacuum are dead. Cylinders that don't drop the vacuum as much as the others are weak. Spend your time working on the dead or weak cylinder(s).

Don't forget to remove the nails when you're done. Some of them may arc to the air cleaner. I found this out the hard way...

I may get to that. I'm starting to think I may have a valve or intake/head gasket issue. I dont understand why on throttle and hwy it drives fine (17mpg sometimes) good vacuum and good compression tests. Smh

 

[MIHELA]

Datalogs, especially on a 160 baud computer, are not nearly as useful as a vacuum gauge for these kind of tests. You will only get a couple of data points per second so you really only see trends. The gauge responds instantly.