15austin

Hi fellas. Me an my bro-in-law has been working on his car (93 coupe) for a few months and I have no other ideas. It has F-cam, 1.6s, TFS intake, full exhaust, 24#inj, cobra mass air/ computer 3.55s, stock bottom end, and most the basic bolt ons. When he first got it it ran a 13.6. It started slowing down (14.1) and kind of popping/cutting out at higher rpms. So I thought valve springs right? It had stock heads and springs so he bought my old heads (ported e7s 1.94 1.6s msn springs) which were fine with my x-cam to the rev limiter my car ran 13.1 with the same heads. It helped alittle it ran 13.8s but still the problem exists.
We stripped my car trying to diagnose the prob-distributer, 3 different comp, coil, mass air, whole gas tank and fuel pump, fuel press regulator and gauge so we can see it through the wind shield, compression is all @ 120-130lbs, plugs wires, injectors, rockers.
What would cause a car to slow down?

mjr46

loss of compression seal....timing chain slack...but in all reality what you have described is a tough one to diagnosis over the net.......A drive/ride along is the first thing i'D WANT TO DO

15austin

It has a timing chain about 1year old we put in with the cam. It pulls just fine ecept it runs slow. It quip popping cutting out , but it runs 13.8 on a perfect run it used to run 13.6 on stock unporter e7s. Is it possible to have a loss of compression under a load, but the compression test to come out fine?

mjr46

MY 92 HAD A SIMILAR PROB.....IT LOST A solid 1.5 mph in the 1/4 and .2 tenths et, it ended up having faulty plug wires, even though you couldn't really feel a heavy hesitation..it was ever so slight

15austin

Yes that is one of the things we've changed. Everything that could be unbolted from my car and bolted to his easily even the TPS and IAC. Also fuel filter, blew out the lines, my battery.

mjr46

well depending on the springs used and the rate of them, to much spring pressure could slow it down, I had an e-cam and stock springs and could never reach full rpm potential and when I swapped to a f-cam i PUT THE A-50 springs and b-50 retainers and solved issue just a thought

Joel5.0

Did you check for the correct PR's length? .... valve train geometry check?..... how much preload are those lifters getting?..... any failure codes showing in the EEC? ..... A/F control codes? .... fuel pressure set at? ..... initial timing?

Unless those valve springs are in the 200# closed and 500# open (SADI cam damage territory)..... a little extra pressure helps in the revs dept.... the low compression test figures might indicate a problem in the valve train dept. LUK

15austin

The car startes runny badly before we put on the heads. We put on the heads trying to fix the problem. Everything heads, pushrods, rockers are from my car which ran strong. We've tried every thing about the fuel pressure from 35psi to 55psi, normally ran at 39-40 psi. Timing at 14*. We've also changed the lifters ran codes with no cods that came up. The geometry was checked, 3 different computers.

15austin

Is it possible for a motor to have a loss of compression under a load but a compression test under no load to be fine? Could it be the bottom end even though the compression test shows 120-130psi?

Portmaster

Anything from a coil wire to a draging caliper could slow it down. Nobody will be able to pin that question down.