incorrect tachometer reading

New to the site and new Tacoma owner.

Have a few issues with my truck but only addressing one in this thread.

I have a handheld code reader with live data display. When I look at the live data for rpm it is quite different than what is displayed on the tach. The tach seems to be reading high (3200 rpm at 70 mph) which I gathered from reading a post here about people's highway rpms.

This also has been problematic because my truck is idling high and it says it is idling very high (2600 rpm) but it may not actually be idling that high.

Anyway, does anybody have experience with something like this?

 

if you are idling at anything above 1000rpm, then it is too high. I would recommend getting that addressed first. Also, those handheld code readers are not always real accurate on the data. They have a very slow response to changes.

 

I am working on that, I have an IAC fault so I'm starting with that as a possible solution to my idle problem.

While I can't say the reader is correct, when sitting consistently at one rpm the readings are stable but significantly different. When cruising the rpm that the reader displays are consistent with what other people report as a cruising rpm.

 

More info on the truck would be nice
Year?
Model?
Engine?
Tranny?
Miles?

Bone stock?
Modifications?
Stock cluster or upgraded?

 

Of course.

It is a 1999 Tacoma extended cab. 3.4 v6. Factory gauge cluster. Only mods are k&n intake and filter, 33's and lift. Gearing is stock as far as I know and it has an automatic transmission. It has 195k kms.

 

Anybody got any ideas?

 

I assume you got the truck used, so who knows what has been done to it by the previous owners. You've already said there are multiple problems.

If the motor or ECU was swapped out (but not both), there might be a mis-match, causing the bad tach reading (especially if a 4-cyl was swapped to a 6-cyl).

At hot idle, what are your two rpm readings (hand-held and cluster tach) ?

 

That 4 cylinder ecu thing would make sense.

Hot idle the reader says 1800 the cluster tach says 2500

In gear hot idle reader says 1000 cluster tach says 1500

 

Changed the IAC valve and the idle is much better but not perfect. There may be a slight vacuum leak as well.

The rpm on the tach problem remains, which is not surprising as I have done nothing to fix it.