Ok, so i posted this problem here a few months ago and the problem went away on it's own somehow, now it's back and it's haunting me cause I can't figure out what it the problem is. Ok, the problem is that right around 6500 rpms the tach starts bouncing everywhere and will revlimit at 6500 rpm because the tach signal is cutting out, this is what i was told by a tech when I got it looked at. He told me to buy a new dizzy, so I did, didn't fix the problem at all. The problem is the tach signal is somehow dropping our in the higher rpm band and I don't know why it's only at high rpms, loose connection somewhere but I don't know where. I've double checked all my grounds, all connections to the ecu, connectors at the shock tower everywhere they're all good. O and I've also tried a different ecu and same problem! Only cel i'm getting is for EGR because this is a swap. The interesting thing is that when the engine cuts out at 6500 rpms the CEL actually turns off, which is weird it's like the ecu loses power or something, but then will rev back down fine like nothing ever happened, just won't let me go past 6500 rpms.
Info: H22a, replaced dizzy, tried another ecu, no cels that would lead me to the cause of this problem. Grounds are all good. Any ideas? Please any help would be great.

 

are u using aftermarket ignition, i.e. msd? how about coil, what are u using in that department?

 

Nope everything's stock except for bolt ons. Stock p13 ecu too. It's been working fine for months and out of randomness decided to act up today so it's nothing that I changed or did. Replaced oem dizzy with another brand new oem dizzy.

 

i have no idea and i've had so many stupid little problems like that too. if you find out though i'd like to know what the problem was. i know its a stretch but try checking resistance across all of your plug wires and coil wire (if external) and try swapping your MAP sensor (if u have access to a free one).

 

virginia

oh yeah, the post. I had a problem like this in the past, and it was my alternator. It took a while to figure it out. Wouldn't hurt to look?

 

ignition control module.. 99 percent garuntee it. do you have a spare distributor?? if you have to order a new icm they are close to 500 bucks best advice would be find another distributor or if you cant do that, i think i may have a few spare icms laying around i could hook you up with. but yeah ive had it happen before and that is the exact symptoms.. good luck and let me know if you need anything

 

this happend to me, i replaced the p13 and it fixed it... wierd

 

Man I hate to be mean but i'm SICK of ppl not reading my post and posting useless info that doesn't help. Ok, to championwhite, I already said i've tried a brand new dizzy, brand new... and the icm is in the dizzy so that's not the problem plus i've tried swapping out the internals in the dizzy too so i've tried brand new parts and other working used parts and it didn't change anything. Also, to darkbb4, I said i already tried different ecu's, tried a chipped p28 and p13 same problem. The problem is, at higher rpms the tach signal is getting lossed and the ecu isn't getting any tach signal so it revlimits it at 6500 rpm and drops out of vtec, BECAUSE the tach signal is lost. This is what the tech told me and showed me when he was datalogging it. So I'm trying to figure out WHY the tach signal is intermittent only at higher rpms. Thanks for the help so far, and anyother help is appreciated.

 

damn i totally missed all of that. well... what ecu are you running? are you running an aftermarket tuning device, ie hondata, vafc? aftermarket ignition component? did you try replacing the external coil or did you keep the internal coil jdm dizzy? knock sensor maybe?? if im not mistakened when it reads a knock it pulls timing and cuts the limiter at 65k. more info is needed man.

 

It's ok, I'm just frustrated cause this problem is bugging the heck out of me. I'm not using any aftermarket ignition or anything, everything is stock except for basic bolt ons. Also it has an internal coil (h22a). So that's all been replaced when I tried the brand new dizzy. So it's not a problem in the dizzy, also not getting knock code, never have so that shouldn't be the problem. Thanks for the help so far guys keep it comin.
Edit: I think the problem lies within the CEL turning off once it revlimits and cuts out, and that the tach signal is intermittent above 6000 rpms, because not only the tach shows it but the ecu shows it when it was being datalogged. so i'm thinking eather ground (somehow even though I've quadruple checked em all) or loose wire from dizzy to ecu somehow.

 

What harness did you use for the swap?

 

Used the jdm h22 harness sent it into Hasport and they redid it for the swap haven't had any problems yet.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JasonST &raquo;</TD></TR><TR><TD CLASS="quote">haven't had any problems yet.</TD></TR></TABLE>

ehh...kinda sounds like you have had some problems in the past, and are having some right now....

honestly, there are only a few things that can cause a tach signal to bounce like that, they are as follows:
faulty ICM
faulty ICM/tach wiring
faulty ECU
bad ground

now I know you have said that you have checked all this stuff, etc, but thats all there is to it....there is no other reason this would happen

 

Here is a really useful previous thread from the wise men, it's full of things to check and reasons why you could have your problem. One thing I wonder is wether you have a bad wiring run from the ECU to the Vtec solenoid ?

https://honda-tech.com/zerothread?id=830163

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by britishdude &raquo;</TD></TR><TR><TD CLASS="quote">Here is a really useful previous thread from the wise men, it's full of things to check and reasons why you could have your problem. One thing I wonder is wether you have a bad wiring run from the ECU to the Vtec solenoid ?

https://honda-tech.com/zerothread?id=830163</TD></TR></TABLE>

Thats a great writeup for diagnosing problems with vtec, but since his problem deals with a bouncing tach and the engine cutting out, he needs to look elsewhere IMO

the EXACT same thing was happening with my friend's prelude, it would only cut out at high rpm or high load, that is when a bad ground becomes apparent....

If you have a multimeter, test resistance between the ECU's main ground wire and the chassis. Let us know what you get

 

thats what i have a feeling i believe the culprit to be. ill stay tuned as well

 

Call me an idiot, because I am but you said you are getting a CEL for ERG. Can't that put your ECU into limp mode? I know you have other problems, but have you hooked up ERG and cleared your CEL to see if that helped anything? Not trying to be a smart ***, but also not trying to be a dumbass. I had my 99 lude throw a code and it wouldnt rev past 6500 rpm, it would hit a rev limiter, not that I tried to bounce off that wall but it was a shock when it happened because the car felt like it shut off when I hit 6500 rpm.


Modified by Chuckles99SH at 9:33 AM 1/4/2007

 

Ok BB4 I finally had time to work on my car today, and I tried just what u suggessted, and I'm glad because I think I may have finally found the problem. Ok, so I tested the main ground, and all the other grounds just for the heck of it. All the other grounds except for the main one were awesome, no resistance hardly, but the main one, B1 power ground 1 I got a reading of 3.1 resistance on 20K, which I don't know what that all means yet, but I'm sure that means that there's a problem if all my other grounds tested good almost 0.00 and this one tested 3.1 every time. If you or somone else could get back to me on this that would be super awesome! And maybe a specific ground to check because of this, Thanks.

 

Ok, after checking things out, I found that my ground that goes onto the throttle body was completly tight and could slight a from left to right, so I tightened it down really tight, and the problem has gone away, so I'm pretty sure that's what the problem was. I'm really really glad to have finally got it fixed and am posting this here for future reference in case anyone else has this annoying problem, it took me about 4 months to figure out what it was and all the time I didn't think it would be something so simple, so if somone has this problem, tighten down ur grounds, don't just look to make sure they're on , tighten em!

 

damn, glad you got it fixed.