Rev hang issue

[eaglescout526]

You dont have AC do you?

[CheepComanche]

no, I don't

[CheepComanche]

It hangs the worst between 1st and 2nd. It also gets much worse going up hill.

[eaglescout526]

Unplug the power steering pressure switch. 

[CheepComanche]

Unplugging it made it hang worse but nothing else changed. At least we have a little more information now

[eaglescout526]

Interesting….that rules out the power steering switch from being bad. 
 

You don’t have an REM do you? 

[CheepComanche]

no, I’ve really wanted to get it but it’s been on backorder 

[eaglescout526]

Damn. I’m curious as to what the read out would be. Well drive it without the ISA plugged in and hopefully we can solve the issue. I’ll rack my brain and think what else would cause this before looking at the ECU. 
 

So let’s see MAP is fine

TPS adjusted?

ISA rebuilt and replaced

Power steering switch operating

Vac lines, inspected

manifold bolts, tight

O2? 

That leaves the MAT and the CTS on the manifold. 
 

[cruiser54]

MAT and CTS can be tested with a meter.

 

Firewall ground all refreshed?

 

 

[Ωhm]

Cruise Control maybe, if equipped ?????

[eaglescout526]

2 hours ago, Ωhm said:

Cruise Control maybe, if equipped ?????

That would rev it out unless the cable from the servo is caught. That’s a good one Ωhm. 

[cruiser54]

Always good to consider mechanical issues as a possibility!!

[CheepComanche]

I don’t have cruise so think the most likely possibility is the mat sensor because the problem isn’t quite as bad in warmer weather 

[eaglescout526]

Could be it. ECU could be getting false readings and the high rev would be to help warm it up to go into closed loop. 

[cruiser54]

1 hour ago, CheepComanche said:

I don’t have cruise so think the most likely possibility is the mat sensor because the problem isn’t quite as bad in warmer weather 

Can be tested!!

[CheepComanche]

I backprobed the mat sensor with the engine running but no matter how much I tried, all I would get was 0 ohms. Could this mean the sensor is bad? 

[cruiser54]

Unplug it and check the ohms to ground. 

[CheepComanche]

So I have removed the mat sensor and got an ohm reading. It does seem to be working but it responds to temperature change super slowly. After a few minutes in the freezer it barely got to 6000 ohms. Is it supposed to be slow? 

[eaglescout526]

It should be pretty instant and responsive to temp change. 

[cruiser54]

I wouldn't think it would be that slow. 

[CheepComanche]

I cleaned it with MAF cleaner and that didn’t make any difference. If I need to get a new sensor, where can I get one? 

[eaglescout526]

I’ve got some. I’d have to test them first. 
 

FYI. They can’t really be had new but there’s a GM one that’s close that would do but you’d have to modify the wiring. 

[CheepComanche]

So tested my sensor again today and it’s working perfectly. Do they just need to stay clean? If so how clean should it be? 

[cruiser54]

[CheepComanche]

I cleaned it with a whole can of maf cleaner and couldn’t get it any cleaner. I figured it was responded to temp fine so I reinstalled it. Now I’m only left with the coolant temp sensor as a possible problem