rotorheadcase

Hi Guys,

Here's the problem...

I installed an aftermarket chip in my '90 C4 and during the post install run it suddenly started making a popping noise from the engine and from that point on hasn't run smoothly or properly.

The car started fine and felt smooth with plenty of urge so I opened the throttle right up for a high speed run. Nothing outrageous and changes well below redline. I had just changed down into at 180km feeling pretty pleased with the difference in power when suddenly it sounded like someone had started an air compressor in the back seat!! Loss of power accompanied with a loud popping noise. The car was able to limp home with lots of popping and farting from the back. It didn't stall or die at any time but it has no power to speak of and sounds like a clapped out VW engine!! I tried restarting when I got it back in the garage and it started fine but again lots of noise and misfiring.

The new chip seemed to be performing faultlessly up until the problem started including a smoother idle so I don't think it is the chip (but hey, I wouldn't really know.)

It's late here so I haven't tried the old chip again to see if it makes a difference but I will do in the morning.

Any ideas? Possible DME relay problem? If so how do I test this? HELP!!!

KirkF

You could guess for a while on this one but:

Perhaps a backfire popped off one or more of your intake manifolds? (Rubber piece between the intake and the engine where the injector is mounted)

???
Kirk

tafkai

take the chip out , put the old one back in . and try again .
kirks answer sounds good ( hopefully ) , but you got to eliminate the cause , not fix the aftermath

rotorheadcase

Thanks guys...that seems to coincide with the kind of noise I was hearing. Lots of air and a real compressor kind of sputtering sound to it.

Not having looked that deeply before....rubber pieces held on with hose clamps? Do I need to remove much to get to the intakes? It's now VERY late so my wife is telling me this is a problem for tomorrow! First the chip and then I'll have a look at the manifolds...

Thanks again

tafkai

you have 6 stubs with injectors on your heads , and 6 branches on the manifold (bottom). these are held together with 6 pieces of hose around 2" long , with a hose-clamp on both ends .
then the 2 halves of the manifold (top) sandwich your throttle body , these 3 pieces are held together in the same way , only the hoses are about 4"

KirkF

Ya and put the old chip back in. Guess I should have mentioned that.
My guess was based on the fact the chip probably played with the timing advance.
Gas quality might have made it backfire & pop on the downshift, (I think alot of the chips assume you get top of the line premium, which isnt necessary available everywhere)

Kirk