Strange Tach

[wkornf]

Hey guys, ive been asking a few questions recently, as you can probably tell because this forums moves like a snail .

Ive been going through all these idle fix techniques but i completely forgot to mention 1 thing.

The tach in my car always , well not always but most of the time registers the wrong RPMs, sometimes it (when the check engine light turns off) actually shows me the correct RPMs. which is rare.

so my point is , i guess i cant really tell if im having idle problems since my Tach always shows 500ish on idle. and even at 70 mph shows like 1.2k.

anyone seen something similiar? i took the car in to a friendly mechanic friend, said he would look at it. anywhere i should start?

93 lx 2.3l A4LD, modded intake, cleaned throttlebody with cleaner, cleaned MAF. cant reset idle or adjust TPS because i cant get a solid RPM reading on the thing. cars got just under 100k miles on it

 

[Dr_EluSivE]

sounds like a bad DIS module. they Are known to effect the tach when they start to go out. I would reccomend replacing it.

Dr.

 

[Shinlee]

i was gonna say ICM myself. mine did that for like 2 years, then my ICM finally hit a brick wall and died, and when i replaced it ( not inexpensive 180ish bucks ) my tach has worked perfect from then on

 

[glowstang93]

Agreed, you can do a search on hear under "icm" and i'm sure you will find a few of my posts and my problems that were solved with a new icm and a couple of coil packs. But as always, checking the engine codes is a good place to start.

 

[Pro-Hawk]

sounds like a bad DIS module. they Are known to effect the tach when they start to go out. I would reccomend replacing it.

Dr.

That is my guess as well. I would think you would have some starting issues as well...like hot starts. Anyways, that part is pretty steep...was around 250.00 I believe but it's been a while.

 

[glowstang93]

I got 2 coil packs, one ICM and a tube of dielectric grease for the plug boots for $300 all together. Borg Warner parts from O'Reilly's.

 

[wkornf]

thanks just got to reading your replies, a code that i came up with when this first started happening was 224, this was over a year ago. but still same problem. every mechanic ive brought the car to hands it back the same way.

code 224, sounds right for what you guys are responding with.

 

[glowstang93]

I know the codes were 223 and 224, sorry I can't tell you which one is what. When my mechanic told me the codes, I knew what was wrong from the help of everyone on here. The first time, I changed the icm and then the problem still came back. Thats when I changed the coil packs. You might get lucky and just be the icm.