Hi everybody,
i've got a problem and i can't get it fixed.
a half year ago i bought a new tbi engine with some modifications.
the chip in the ecm wasn't good and i bouht a custom chip.
after 3 months there appears a problem while logging in a wot run.after it the car has lots of vibrations and shakes on lower rpm and idle.
around 1500rpm it's the most shake.
i've replaced the parts but it become really expensive over here in Europe:ignition-module,pickup-coil,fuelfilter,ignition-coil,egr-valve,map-sensor,knock-sensor,esc-module.
for more specs on the engine check: http://www.cardomain.com/id/tomc1500
i hope you can help me
Tom

have you checked the engine mounts lately. it could be the harmonic balancer.

is it possible that the engine mounts get stuck within 2 secons?
how can i check the harmonic balancer?
sometimes i think it miss a cilinder but it's hard to find out the problem
Tom

Does it only do it after a wot run or anytime in that rpm range. Does the data log show anything that looks out of place?

Steve

it do it whole the time in the rpm-range(idle-2000rpm).
the most shake is around the 1500rpm

i can datalog it but i can't understand the data.
Tom

Recheck your plug wires to make sure there on correctly. The easist way to find the cyclinder(s) that are missfiring is to start the engine when it's cold (get a spray bottle with water or window cleaner) then just start spraying the exshaust manifolds untill the water starts to steam up. The faulty cyclinder(s) will not steam up as quickly as the ones firing correctly. If you have tube headers the the missfiring cyclinder(s) won't even evaporate the water at all. If all cyclinders are firing then you may have an ignition problem in the distributor or ecm. Check you base timing first. Or you could have other issues like a mechanical problem.

Steve

Does it shake all the time at that rpm range, or only after a WOT run?

hi,

i'm sorry for the late reply but i was on a holiday in Ibiza

it shake all the time at that rpm range

Tom
tomorrow i check some other parts.

hi,

today i checked my plugwires.
i also put in new sparkplugs(acdelco-gap-0.45)(rapidfire-1)

i found out that cil:8 was not getting spark.
i pull the plugwire from the cap and no difference in the enginesound(with the other wires the sound changed)
also the old spark plug was really black.
i put on another cable but no change.
what can i do??
i think tomorrow when the engine is cold i get the plug out of cil-8 and look if he's got the spark.

anybody have some advice?

thanks tom

I am assuming that this combination ran with out shaking for three months and then immediately after a WOT run suddenly had this problem.

several possibilities come to mind.

Could something suddenly be physically out of balance? Torque converter or flexplate/ flywheel becoming uninstalled?

Something happen to the valve trian when at high RPMs durring the WOT run?

Run lean durring the WOT run and burn a hole threw a piston ?

A compression check may be helpful. Or at least comforting.

I am assuming that this combination ran with out shaking for three months and then immediately after a WOT run suddenly had this problem.----
this is correct

i pull the sparkplug from cil#8 and when i ground it to something he's give spark out of the cylinder.

flexplate looks good.
maybe indeed something in the valvetrain?

Tom

hi,
I’m not so happy.i found the problem

I took off the valve cover en looked at cil#8.(I’ve got spark there but no detonation)

It turned out that the pushrod from the intake valve was bent en broken!

I have no more than 2000 miles driven with this engine.


What must I do now?

The piece pushrod that was fallen into the engine I got out and the 2 parts directly fit to each other.(so no metal or so is in the engine)?

Thanks Tom

What heads did they use on the rebuild? Sounds like they either didn't use the right pushrods, or there was serious coil bind which caused the demise of the pushrod.

hi,

64cc heads with 1.940"Int/1.500"Exh valves and 1.250" high performance springs setup to match cam
High temperature valve seals
Spiral-type valve guides
1.6 steel rocker arms with ***** and nuts
Hardened push rods

what is coil bind?(my english is not so good)

Tom

Can you take the car back to the shop that did your engine work? Is there a warranty, guarantee on the parts and labor? I would take it back to whoever did the engine work, and make them fix it. Motor should last at least 200 000 miles, not 2000! Good luck.

Also, I have heard it's good to "break in" a motor, before really getting on it. At least wait 10,000 miles.

There is an oil additive for new engines*, you can get at GM Parts. Apparently, an additive that protects against scuffing, wear in new motors, is no longer added to regular motor oil. Specifically protects metal on metal areas, like pushrods.

*Article on this in CarQuest magazine, I forget the name of the GM oil additive. But it is highly recommended. (It's not Assembly Lube, but same idea.)