Welcome to the Corvette Forums at the Corvette Action Center!

Help! Hard to start & uphill chatter has become a shake

Where should I start / focus?

  • Check spark plugs

    Votes: 0 0.0%
  • Check motor mounts & subframe

    Votes: 0 0.0%
  • Check CV joints

    Votes: 0 0.0%
  • Check O2 censors for carbon build-up

    Votes: 0 0.0%
  • Change the oil to synthetic

    Votes: 0 0.0%
  • Check & reset engine timing

    Votes: 0 0.0%
  • Have someone check the transmission (over my head)

    Votes: 0 0.0%

  • Total voters


New member
Mar 23, 2009
Greenville, SC
First off, I want to thank all of you that take your time to get on this site, help people diagnose their issues, and give them expert advice on resolving the issues. Without you and this site, I would have already blown thousands with a mechanic... Thank you for what you do!

I have an '85 Vette that I bought a few years ago for my daughter, and have been having a helluva time getting all of the kinks worked out. The previous owner(s) was more abusive than negligent, and I've been dealing with all of the issues to try to get her back in shape. I've been able to fix most of the issues, but have been running around in circles on a couple of issues, and could use your help:

The main issue started over a year ago: Under load going uphill (mainly), the car makes a rattling sound from the engine bay. This usually is more prominent in cold weather, but does the same when the engine is still cold. I've stalked this (phenomenal resource of a) website for quite some time, and have followed a TON of advice. However, I think I probably replaced more than needed, as the problem persists. The previous owner had just replaced the O2/knock sensors, so I ran through the checklist: changed the spark plugs, re-ran the cables to ensure that none were touch metal or eachother, ran fuel system cleaner through for a month or more, etc. The car coded an EGR issue, so I replaced that. No help. Someone mentioned that it was probably a worn out belt tensioner. Replaced that to no avail. Someone here mentioned that it could be valve chatter, so I did a valve adjustment, cold. No help. So I did a valve adjustment, hot. Still no help. I did it again (following another of the numerous methods suggested), and though it seemed to be slightly better by making less of a rattle sound (under load, low RPMs, usually going uphill), I wasn't satisfied, did another valve adjustment, and the problem continues to haunt me. The car became hard to start, so I bought a new "high crank" battery. Still hard to start - always takes 2 tries.

As a guy that had no more experience working on a car than watching my dad's feet under the family car in anticipation of "Hand me a...", I have learned to swim by being thrown into the deep water. I am proud & saddened to say that I can now do a valve job in under an hour, though I still don't know if it's proper, since the original issue continues. :0

Having quarantined the car for a couple of months doing all of this, I'd bought the car for my daughter and she was getting anxious to show up at her high school in her "dream car." Though the issue was annoying to me, she didn't notice it & so I shelved tinkering with it for a while and asked her to let me know if the issue got any worse. For the past 9+ months, she has been driving the car regularly, & being a female, she has neglected to inform me that the issues have gone from slightly annoying to seriously concerning. Yesterday, in passing, she mentioned, "Oh, dad. The Corvette now shakes really badly going uphill between 35-45 MPH..." "How long has it been doing that?" "I don't know. A month or so..." Checking the distributor cap, the connectors looked burned &/or corroded, so I took that opportunity to upgrade my future toy (as soon as my daughter goes to college), and installed an MSD cap & coil. Still hard to start, still bucks like a bull aspiring to be memorialized with his name on a future Lambo.

So, I'm back in the hunt for solutions. I don't know if all of this is related, but my gut tells me that it is. After doing more research on this site and others, I've developed the following action plan:

1. Check spark plugs - though I replaced them a year ago, it's an easy enough first step.
2. Check motor mounts & subframe under engine & transmission. (Won't address the starting issue, but potentially the shuttering.)
3. Check CV joints (like above)
4. Test fuel pressure, injectors & pump. Just bought a compression tool, & looking forward to using my new toy. (Though I'll have to research here on the exact process.)
5. Check for vacuum leaks. Another toy purchased, and like above, will require some guidance.
6. Check O2 censors for carbon build-up. Though they were supposedly replaced 2 years ago, and the rattling sound was happening then, it seems to be a prevalent response.
7. Valve adjustment (#?). I figured that if I'm doing it again, and the wife has agreed to the budgetary constraints of, "just fix it", I might follow the same path I did with the ignition & upgrade to some fairly inexpensive roller rockers (if they exist), new rods & springs. I say this because each time I've gone back to do an adjustment (like an automotive chiropractor), there always seems to be a couple of them that are obviously loose, even though I'd followed the routine to the 'T'. I'm suspecting that it could be bad lock nuts, bent push rods, bad springs, or something along those lines...
8. Change the oil to synthetic.
9. Check & reset engine timing, if necessary. (A tool that I've yet to covet)
10. Transmission?

That's my extended weekend plan, though I'm begging for someone to please enlighten this path by either narrowing my plan or pinpointing another yet-to-be realized source of my frustrations. A quicker fix would make for a happier dad & daughter.

Thanks in advance for any & all advice. (Scratch the "any" - any USEFUL advice.) ;)

John Walsh
85 Corvette
K&N air filter & intake kit
Ported & polished plenum
Hypertech Power Chip
MSD Ignition (cap & coil)
Bilstein shocks
BBS wheels

roger longman

Well-known member
May 13, 2008
southern california
1977 c3 orange ! 1988 c4 kinda purple 1991 'race
Hi John, Sounds to me like it could be small end wear but, others will know better, I hope......Roger.


Well-known member
Dec 18, 2008
87 z-51
I don;t even know how or where to start addressing all this...

I've got to tell you though, that it really bothers me to see a great machine like this abused and unappreciated by a kid that can;t even relate to you that the engine is barely running...

From what you're describing I'd start with fuel pressure and go from there. Next would be MAF relays. Beyond that, isolate each system and go thru it until you are certain that its right....not good 'nuff, or ok, but right.

I'd plan on spending $200 at FIC and end the guess work with the injectors. I KNOW those are bad if they are stock.

When you test fuel pressure also do leakdown and see how long the system will hold its pressure. It should hit 40 and stay near there for a couple hrs and slowly drop to 20ish after a few hrs. If it falls fast, figure out where the fuel is going.

Did you get a real FSM? Thats a MUST HAVE to deal with this amount of diagnostic work.

You should get under it and do a detailed chassis inspection...C-beam bolts, bushings, mounts etc.

The "clicking" may actually be an exhaust leak.

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors


MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Top Bottom