Erratic tach, terrible idle, hiccup, and hesitation. This happened while I was warming up my car a few weeks ago. It normally doesn't do this when I start the car. This is the worst I've ever seen it and captured it on video.

This issue happens 95% of the time while driving not while warming up and it cuts out so hard I feel like I just hit a brick wall at 10 MPH. Commonly happens around 2,500-4,000 RPMs. Somedays are better than others. Sometimes I can accelerate all the way to redline without a single hiccup. Other times I can get it passed 4,000 RPMs and have it hiccup closer to 6,000 RPMs and up.


Any ideas would be great. I've researched a lot and haven't really found this exact problem.

 

So not a single person on this forum has any idea what could cause this issue? I really thought a video would be super helpful..

 

Did you check the leading coil and trailing coils? Have you checked the grounds. Did you do anything to the car beforehand which might have contributed to this problem? Locate the Black bullet connector wire on the lead coil which connects to nothing and then find the same wire on the trailing coil and jumper these two wires together. This will cause the tach to work off of the leading coil and not the trailing coil. The coils also need to be grounded to the fender via contact so make sure they are both bolted to the fender properly and that the contact is clean between the coil bracket and the fender surface. If the ground is erratic or not present then the coils cannot work.

 

Thank you, I wasn't sure if this was a CAS issue or coil issue. I'll try your method and clean up as many grounds as i can get to.

 

i had a problem where i would give it gas and it felt like the car threw me into the steering wheel. and all the problem was, was the fuel filter was clogged up.

 

I replaced my fuel filter about a month ago, didn't notice any improvement.

I inspected and cleaned all the nuts, bolts, mounts, and brackets for both coils, also tried jumping them to run my tach off the other. Tach still glitches out and my car has no improvement.

I guess next step is to pull the fuel pump and test it... If that's not the issue then I guess I'll be forced to remove my intake manifold and get my injectors cleaned and balanced. And clean my ECU ground.

Anyone have any other ideas?

 

Did you check your spark plugs? Vacuum leaks?

 

Check your AFM and TPS for dead spots along the full sweep.
Did you set your timing with the idle under 1k?
And check for vacuum leaks.

 

My spark plugs are maybe 2 months old. NGK Plantium. I've inspected them recently and they look just fine. All my vacuum lines appear to be in good condition.

 

I jumped the coils and I noticed my car randomly starts to beep at me. So I removed the jumper wire and my tach died. Put the jumper wire back on and my tach came back... Weird thing is, before you told me to try that, my tach always worked....

 

W/the jumper in place, does the tach act sporadically as it did in the video or is that part better? Did you make sure the trailing coil was bolted to a clean fender surface? Did you check to see if the two electrical connectors to the coil were clean and solid?

 

The tach still glitches out. I cleaned all mounts and brackets with a wire blush and degreaser. The electrical connections were good.

 

Go for the ecu ground next. And try to separate the plug wires to minimize cross-talk.

 

I can tell the ECU ground is bolted down... But it does appear to be covered in grease and grime. I'll separate my wire today.

 

A little update, I double checked my ECU ground and was able to get a finger on it.. It turns out its loose and very greasy/oily. Im going to try and clean the sh*t out of this ground and considering adding the pressure sensor ground mod for good measure.

Has anyone added the pressure sensor ground? I've heard it can be very effective.

Thanks

 

The Pressure Sensor ground is easy to do.

 

Issue resolved! All those hiccups and terrible spontaneous hesitation turned out to be just my ECU ground. Cleaned it up, bolted it to the factory location and problem solved!

Is there a detailed write up on the pressure sensor ground mod? I've only read very brief descriptions on what to do.. But nothing with detail or pictures...